Docker for local development with multiple environment

Docker for local development with multiple environment - docker

I'm looking for using docker to emulate the minimum of our current cloud environment. We have about 10 services (each with your own MySQL8 database, redis, php-fpm and nginx). Currently they have a docker-compose.yml per repository, but they cant talk to each other, if I want to test a feature where a service needs to talk to another I'm out of luck.
My first approach was to create a Dockerfile per service (and run all together using a new docker-compose.yml), using Debian, but i didn't got too far, was able to install nginx, (php-fpm and dependencies), but when I got to the databases it got weird and I had a feeling that this isn't the right way of doing this.
Is there a way to one docker-compose.yml "include" each of docker-compose.yml from the services?
Is there a better approach to this? Or should I just keep with the Dockerfile and run them all on the same network using docker-compose?

TL;DR;
You can configure docker-compose using external networks to communicate with services from other projects or (depending on your project) use the -f command-line option / COMPOSE_FILE environment variable to specify the path of the compose file(s) and bring all of the services up inside the same network.
Using external networks
Given the below tree with project a and b:
.
├── a
│   └── docker-compose.yml
└── b
└── docker-compose.yml
Project a's docker-compose sets a name for the default network:
version: '3.7'
services:
nginx:
image: 'nginx'
container_name: 'nginx_a'
expose:
- '80'
networks:
default:
name: 'net_a'
And project b is configured to using the named network net_b and the pre-existing net_a external network:
version: '3.7'
services:
nginx:
image: 'nginx'
container_name: 'nginx_b'
expose:
- '80'
networks:
- 'net_a'
- 'default'
networks:
default:
name: 'net_b'
net_a:
external: true
... exec'ing into the nginx_b container we can reach the nginx_a container:
Note: this is a minimalist example. The external network must exist before trying to bring up an environment that is configured with the pre-existing network. Rather than modifying the existing projects docker-compose.yml I'd suggest using overrides.
The configuration gives the nginx_b container a foot inside both networks:
Using the -f command-line option
Using the -f command-line option acts as an override. It will not work with the above compose files as both specify an nginx service (docker-compose will override / merge the first nginx service with the second).
Using the modified docker-compose.yml for project a:
version: '3.7'
services:
nginx_a:
container_name: 'nginx_a'
image: 'nginx'
expose:
- '80'
... and for project b:
version: '3.7'
services:
nginx_b:
image: 'nginx'
container_name: 'nginx_b'
expose:
- '80'
... we can bring both of the environments up inside the same network: docker-compose -f a/docker-compose.yml:b/docker-compose.yml up -d:

Related

Docker compose networking between pods [duplicate]

I have two separate docker-compose.yml files in two different folders:
~/front/docker-compose.yml
~/api/docker-compose.yml
How can I make sure that a container in front can send requests to a container in api?
I know that --default-gateway option can be set using docker run for an individual container, so that a specific IP address can be assigned to this container, but it seems that this option is not available when using docker-compose.
Currently I end up doing a docker inspect my_api_container_id and look at the gateway in the output. It works but the problem is that this IP is randomly attributed, so I can't rely on it.
Another form of this question might thus be:
Can I attribute a fixed IP address to a particular container using docker-compose?
But in the end what I'm looking after is:
How can two different docker-compose projects communicate with each other?

You just need to make sure that the containers you want to talk to each other are on the same network. Networks are a first-class docker construct, and not specific to compose.
# front/docker-compose.yml
version: '2'
services:
front:
...
networks:
- some-net
networks:
some-net:
driver: bridge
...
# api/docker-compose.yml
version: '2'
services:
api:
...
networks:
- front_some-net
networks:
front_some-net:
external: true
Note: Your app’s network is given a name based on the “project name”, which is based on the name of the directory it lives in, in this case a prefix front_ was added
They can then talk to each other using the service name. From front you can do ping api and vice versa.

UPDATE: As of compose file version 3.5:
This now works:
version: "3.5"
services:
proxy:
image: hello-world
ports:
- "80:80"
networks:
- proxynet
networks:
proxynet:
name: custom_network
docker-compose up -d will join a network called 'custom_network'. If it doesn't exist, it will be created!
root#ubuntu-s-1vcpu-1gb-tor1-01:~# docker-compose up -d
Creating network "custom_network" with the default driver
Creating root_proxy_1 ... done
Now, you can do this:
version: "2"
services:
web:
image: hello-world
networks:
- my-proxy-net
networks:
my-proxy-net:
external:
name: custom_network
This will create a container that will be on the external network.
I can't find any reference in the docs yet but it works!

Just a small adittion to #johnharris85's great answer,
when you are running a docker compose file, a "default" network is created
so you can just add it to the other compose file as an external network:
# front/docker-compose.yml
version: '2'
services:
front_service:
...
...
# api/docker-compose.yml
version: '2'
services:
api_service:
...
networks:
- front_default
networks:
front_default:
external: true
For me this approach was more suited because I did not own the first docker-compose file and wanted to communicate with it.

All containers from api can join the front default network with following config:
# api/docker-compose.yml
...
networks:
default:
external:
name: front_default
See docker compose guide: using a pre existing network (see at the bottom)

The previous posts information is correct, but it does not have details on how to link containers, which should be connected as "external_links".
Hope this example make more clear to you:
Suppose you have app1/docker-compose.yml, with two services (svc11 and svc12), and app2/docker-compose.yml with two more services (svc21 and svc22) and suppose you need to connect in a crossed fashion:
svc11 needs to connect to svc22's container
svc21 needs to connect to svc11's container.
So the configuration should be like this:
this is app1/docker-compose.yml:
version: '2'
services:
svc11:
container_name: container11
[..]
networks:
- default # this network
- app2_default # external network
external_links:
- container22:container22
[..]
svc12:
container_name: container12
[..]
networks:
default: # this network (app1)
driver: bridge
app2_default: # external network (app2)
external: true
this is app2/docker-compose.yml:
version: '2'
services:
svc21:
container_name: container21
[..]
networks:
- default # this network (app2)
- app1_default # external network (app1)
external_links:
- container11:container11
[..]
svc22:
container_name: container22
[..]
networks:
default: # this network (app2)
driver: bridge
app1_default: # external network (app1)
external: true

Everybody has explained really well, so I'll add the necessary code with just one simple explanation.
Use a network created outside of docker-compose (an "external" network) with docker-compose version 3.5+.
Further explanation can be found here.
First docker-compose.yml file should define network with name giveItANamePlease as follows.
networks:
my-network:
name: giveItANamePlease
driver: bridge
The services of first docker-compose.yml file can use network as follows:
networks:
- my-network
In second docker-compose file, we need to proxy the network by using the network name which we have used in first docker-compose file, which in this case is giveItANamePlease:
networks:
my-proxy-net:
external:
name: giveItANamePlease
And now you can use my-proxy-net in services of a second docker-compose.yml file as follows.
networks:
- my-proxy-net

Since Compose 1.18 (spec 3.5), you can just override the default network using your own custom name for all Compose YAML files you need. It is as simple as appending the following to them:
networks:
default:
name: my-app
The above assumes you have version set to 3.5 (or above if they don't deprecate it in 4+).
Other answers have pointed the same; this is a simplified summary.

UPDATE: As of docker-compose file version 3.5:
I came across a similar problem and I solved it by adding a small change in one of my docker-compose.yml project.
For instance, we have two API's scoring and ner. Scoring API needs to send a request to the ner API for processing the input request. In order to do that they both are supposed to share the same network.
Note: Every container has its own network which is automatically created at the time of running the app inside docker. For example ner API network will be created like ner_default and scoring API network will be named as scoring default. This solution will work for version: '3'.
As in the above scenario, my scoring API wants to communicate with ner API then I will add the following lines. This means Whenever I create the container for ner API then it automatically added to the scoring_default network.
networks:
default:
external:
name: scoring_default
ner/docker-compose.yml
version: '3'
services:
ner:
container_name: "ner_api"
build: .
...
networks:
default:
external:
name: scoring_default
scoring/docker-compose.yml
version: '3'
services:
api:
build: .
...
We can see this how the above containers are now a part of the same network called scoring_default using the command:
docker inspect scoring_default
{
"Name": "scoring_default",
....
"Containers": {
"14a6...28bf": {
"Name": "ner_api",
"EndpointID": "83b7...d6291",
"MacAddress": "0....",
"IPv4Address": "0.0....",
"IPv6Address": ""
},
"7b32...90d1": {
"Name": "scoring_api",
"EndpointID": "311...280d",
"MacAddress": "0.....3",
"IPv4Address": "1...0",
"IPv6Address": ""
},
...
}

You can add a .env file in all your projects containing COMPOSE_PROJECT_NAME=somename.
COMPOSE_PROJECT_NAME overrides the prefix used to name resources, as such all your projects will use somename_default as their network, making it possible for services to communicate with each other as they were in the same project.
NB: You'll get warnings for "orphaned" containers created from other projects.

So many answers!
First of all, avoid hyphens in entities names such as services and networks. They cause issues with name resolution.
Example: my-api won't work. myapi or api will work.
What worked for me is:
# api/docker-compose.yml
version: '3'
services:
api:
container_name: api
...
ports:
- 8081:8080
networks:
- mynetwork
networks:
mynetwork:
name: mynetwork
and
# front/docker-compose.yml
version: '3'
services:
front:
container_name: front
...
ports:
- 81:80
networks:
- mynetwork
networks:
mynetwork:
name: mynetwork
NOTE: I added ports to show how services can access each other, and how they are accessible from the host.
IMPORTANT: If you don't specify a network name, docker-compose will craft one for you. It uses the name of the folder the docker_compose.yml file is in. In this case: api_mynetwork and front_mynetwork. That will prevent communication between containers since they will by on different network, with very similar names.
Note that the network is defined exactly the same in both file, so you can start either service first and it will work. No need to specify which one is external, docker-compose will take care of managing that for you.
From the host
You can access either container using the published ports defined in docker-compose.yml.
You can access the Front container: curl http://localhost:81
You can access the API container: curl http://localhost:8081
From the API container
You can access the Front container using the original port, not the one you published in docker-compose.yml.
Example: curl http://front:80
From the Front container
You can access the API container using the original port, not the one you published in docker-compose.yml.
Example: curl http://api:8080

For using another docker-compose network you just do these(to share networks between docker-compose):
Run the first docker-compose project by up -d
Find the network name of the first docker-compose by: docker network ls(It contains the name of the root directory project)
Then use that name by this structure at below in the second docker-compose file.
second docker-compose.yml
version: '3'
services:
service-on-second-compose: # Define any names that you want.
.
.
.
networks:
- <put it here(the network name that comes from "docker network ls")>
networks:
- <put it here(the network name that comes from "docker network ls")>:
external: true

I would ensure all containers are docker-compose'd to the same network by composing them together at the same time, using:
docker compose --file ~/front/docker-compose.yml --file ~/api/docker-compose.yml up -d

If you are
trying to communicate between two containers from different docker-compose projects and don't want to use the same network (because let's say they would have PostgreSQL or Redis container on the same port and you would prefer to not changing these ports and not use it at the same network)
developing locally and want to imitate communication between two docker compose projects
running two docker-compose projects on localhost
developing especially Django apps or Django Rest Framework (drf) API and running app inside container on some exposed port
getting Connection refused while trying to communicate between two containers
And you want to
container api_a communicate to api_b (or vice versa) without the same "docker network"
(example below)
you can use "host" of the second container as IP of your computer and port that is mapped from inside Docker container. You can obtain IP of your computer with this script (from: Finding local IP addresses using Python's stdlib):
import socket
def get_ip():
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
# doesn't even have to be reachable
s.connect(('10.255.255.255', 1))
IP = s.getsockname()[0]
except:
IP = '127.0.0.1'
finally:
s.close()
return IP
Example:
project_api_a/docker-compose.yml:
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_a
image: api_a:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_a container you are running Django app:
manage.py runserver 0.0.0.0:8000
and second docker-compose.yml from other project:
project_api_b/docker-compose-yml :
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_b
image: api_b:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_b container you are running Django app:
manage.py runserver 0.0.0.0:8001
And trying to connect from container api_a to api_b then URL of api_b container will be:
http://<get_ip_from_script_above>:8001/
It can be especially valuable if you are using even more than two(three or more) docker-compose projects and it's hard to provide common network for all of it - it's good workaround and solution

To connect two docker-compose you need a network and putting both docker-composes in that network,
you could create netwrok with docker network create name-of-network,
or you could simply put network declaration in networks option of docker-compose file and when you run docker-compose (docker-compose up) the network would be created automatically.
put the below lines in both docker-compose files
networks:
net-for-alpine:
name: test-db-net
Note: net-for-alpine is internal name of the network and it will be used inside of the docker-compose files and could be different,
test-db-net is external name of the network and must be same in two docker-compose files.
Assume we have docker-compose.db.yml and docker-compose.alpine.yml
docker-compose.apline.yml would be:
version: '3.8'
services:
alpine:
image: alpine:3.14
container_name: alpine
networks:
- net-for-alpine
# these two command keeps apline container running
stdin_open: true # docker run -i
tty: true # docker run -t
networks:
net-for-alpine:
name: test-db-net
docker-compose.db.yml would be:
version: '3.8'
services:
db:
image: postgres:13.4-alpine
container_name: psql
networks:
- net-for-db
networks:
net-for-db:
name: test-db-net
To test the network, go inside alpine container
docker exec -it alpine sh
then with following commands you could check the network
# if it returns 0 or see nothing as a result, network is established
nc -z psql (container name)
or
ping pgsql

I'm running multiple identical docker-compose.yml files in different directories, using .env files to make a slight difference. And use Nginx Proxy Manage to communicate with other services. here is my file:
make sure you have created a public network
docker network create nginx-proxy-man
/domain1.com/docker-compose.yml, /domain2.com/docker-compose.yml, ...
version: "3.9"
services:
webserver:
build:
context: ./bin/${PHPVERSION}
container_name: "${COMPOSE_PROJECT_NAME}-${PHPVERSION}"
...
networks:
- default # network outside
- internal # network internal
database:
build:
context: "./bin/${DATABASE}"
container_name: "${COMPOSE_PROJECT_NAME}-${DATABASE}"
...
networks:
- internal # network internal
networks:
default:
external: true
name: nginx-proxy-man
internal:
internal: true
.env file just change COMPOSE_PROJECT_NAME
COMPOSE_PROJECT_NAME=domain1_com
.
.
.
PHPVERSION=php56
DATABASE=mysql57
webserver.container_name: domain1_com-php56 - will join the default network (name: nginx-proxy-man), previously created for Nginx Proxy Manager to be accessible from the outside.
Note: container_name is unique in the same network.
database.container_name: domain1_com-mysql57 - easier to distinguish
In the same docker-compose.yml, the services will connect to each other via the service name because of the same network domain1_com_internal. And to be more secure, set this network with the option internal: true
Note, if you don't explicitly specify networks for each service, but just use a common external network for both docker-compose.yml, then it's likely that domain1_com will use domain2_com's database.

Another option is just running up the first module with the 'docker-compose' check the ip related with the module, and connect the second module with the previous net like external, and pointing the internal ip
example
app1 - new-network created in the service lines, mark as external: true at the bottom
app2 - indicate the "new-network" created by app1 when goes up, mark as external: true at the bottom, and set in the config to connect, the ip that app1 have in this net.
With this, you should be able to talk with each other
*this way is just for local-test focus, in order to don't do an over complex configuration
** I know is very 'patch way' but works for me and I think is so simple some other can take advantage of this

Answer for Docker Compose '3' and up
By default Docker Compose uses a bridge network to provision inter-container communication. Read this article for more info about inter-container networking.
What matters for you, is that by default Docker Compose creates a hostname that equals the service name in the docker-compose.yml file. Consider the following docker-compose.yml:
version: '3.9'
services:
server:
image: node:16.9.0
container_name: server
tty: true
stdin_open: true
depends_on:
- mongo
command: bash
mongo:
image: mongo
environment:
MONGO_INITDB_DATABASE: my-database
When you run docker-compose up, Docker will create a default network and assigns the service name as hostname for both mongo and server.
You can now access the backend container via:
docker exec -it server bash
And now you can ping the mongo container using Dockers internal network (default on port 27017 in this case):
curl -v http://mongo:27017/my-database
That's it. The same applies for your setup.

I have had a similar example where I was working with separate docker-compose files working on a docker swarm with an overlay network to do that all I had to do is change the networks parameters as so:
first docker-compose.yaml
version: '3.9'
.
.
.
networks:
net:
driver: overlay
attachable: true
docker-compose -p app up
since I have specified the app name as app using -p the initial network will be app_net.
Now in order to run another docker-compose with multiple services that will use the same network you will need to set these as so:
second docker-compose.yaml
version: '3.9'
.
.
.
networks:
net-ref:
external: true
name: app_net
docker stack deploy -c docker-compose.yml mystack
No matter what name you give to the stack the network will not be affected and will always refer to the existing external network called app_net.
PS: It's important to make sure to check your docker-compose version.

version: '2'
services:
bot:
build: .
volumes:
- '.:/home/node'
- /home/node/node_modules
networks:
- my-rede
mem_limit: 100m
memswap_limit: 100m
cpu_quota: 25000
container_name: 236948199393329152_585042339404185600_bot
command: node index.js
environment:
NODE_ENV: production
networks:
my-rede:
external:
name: name_rede_externa

Follow up of JohnHarris answer, just adding some more details which may be useful to someone: Lets take two docker-compose file and connect them through networks:
1st foldername/docker-compose.yml:
version: '2'
services:
some-contr:
container_name: []
build: .
...
networks:
- somenet
ports:
- "8080:8080"
expose:
# Opens port 8080 on the container
- "8080"
environment:
PORT: 8080
tty: true
networks:
boomnet:
driver: bridge
2nd docker-compose.yml:
version: '2'
services:
pushapiserver:
container_name: [container_name]
build: .
command: "tail -f /dev/null"
volumes:
- ./:/[work_dir]
working_dir: /[work dir]
image: [name of image]
ports:
- "8060:8066"
environment:
PORT: 8066
tty: true
networks:
- foldername_somenet
networks:
foldername_somenet:
external: true
Now you can make api calls to one another services(b/w diff containers)like:
http://pushapiserver:8066/send_push call from some code in files for 1st docker-compose.yml
Two common mistakes (atleast i made them few times):
take note of [foldername] in which your docker-compose.yml file is present. Please see above in 2nd docker-compose.yml i have added foldername in network bc docker create network by [foldername]_[networkname]
Port: this one is very common. Please note i have used 8066 when trying to make connection i.e. http://pushapiserver:8066/... 8066 is port of docker container(2nd docker-compose.yml) so when trying to talk with different docker compose.
docker will use docker container port[8066] and not host machine mapped port
[8060]

Docker-Compose binding volumes, file sharing issue

I am new to docker and had a problem that hope you could help.
I have defined multiple services (HTTPSERV, IMED, etc...) in my docker-compose file and these services have a python code inside and a docker file for running them. The dockerfile also copies the required files into a host path defined in docker-compose. The HTTPSERV and IMED must share a text file and expose it to an external user sending a GET request to HTTPSERV.
In docker-compose I have defined a local host directory and bind it to a named volume. The services and docker files are meant to share each service files and run.
As soon as I run the docker-compose, the files related to the first service copies files in the PATH directory where "src" and change the permission right of the "src" folder not letting the other services copy their files. This causes the next services to fail to find the appropriate files and the whole orchestration process fails.
version: "3.9"
networks:
default:
ipam:
config:
- subnet: 172.28.0.2/20
services:
httpserv:
user: root
container_name: httpserver
build: ./HTTPSERV
volumes:
- myapp:/httpApp:rw
networks:
default:
ipv4_address: 172.28.0.5
ports:
- "8080:3000"
rabitQ:
user: root
container_name: rabitQ
image: rabbitmq:3.8-management
networks:
default:
ipv4_address: 172.28.0.4
ports:
- "9000:15672"
imed:
user: root
container_name: IMED-Serv
build: ./IMED
volumes:
- myapp:/imed:rw
networks:
- default
# restart: on-failure
orig:
user: root
container_name: ORIG-Serv
build: ./ORIG
volumes:
- myapp:/orig:rw
networks:
- default
# restart: on-failure
obse:
container_name: OBSE-Serv
build: ./OBSE
volumes:
- myapp:/obse:rw
networks:
- default
# restart: on-failure
depends_on:
- "httpserv"
links:
- httpserv
volumes:
myapp:
driver: local
driver_opts:
type: none
o: bind
device: /home/dockerfiles/hj/a3/src
The content of the docker file is similar for most of the services and is as follow:
FROM python:3.8-slim-buster
WORKDIR /imed
COPY . .
RUN pip install --no-cache-dir -r imed-requirements.txt
RUN chmod 777 ./imed.sh
CMD ["./imed.sh"]
The code has root access and the UserID and GroupID are set
I also used the anonymously named volumes but the same issue happens.

In Docker it's often better to avoid "sharing files" as a first-class concept. Imagine running this in a clustered system like Kubernetes; if you have three copies of each service, and they're running in a cloud of a hundred systems, "sharing files" suddenly becomes difficult.
Given the infrastructure you've shown here, you have a couple of straightforward options:
Add an HTTP endpoint to update the file. You'd need to protect this endpoint in some way, since you don't want external callers accessing it; maybe filter it in an Nginx reverse proxy, or use a second HTTP server in the same process. The service that has the updated content would then call something like
r = requests.post('http://webserv/internal/file.txt', data=contents)
r.raise_for_status()
Add an HTTP endpoint to the service that owns the file. When the Web server service starts up, and periodically after that, it makes a request
r = requests.get('http://imed/file.txt')
You already have RabbitMQ in this stack; add a RabbitMQ consumer in a separate thread, and post the updated file content to a RabbitMQ topic.
There's some potential trouble with the "push" models if the Web server service restarts, since it won't be functional until the other service sends it the current version of file.
If you really do want to do this with a shared filesystem, I'd recommend creating a dedicated directory and dedicated volume to do this. Do not mount a volume over your entire application code. (It will prevent docker build from updating the application, and in the setup you've shown, you're mounting the same application-code volume over every service, so you're running four copies of the same service instead of four different services.)
Adding in the shared volume, but removing a number of other unnecessary options, I'd rewrite the docker-compose.yml file as:
version: '3.9'
services:
httpserv:
build: ./HTTPSERV
ports:
- "8080:3000"
volumes:
- shared:/shared
rabitQ:
image: rabbitmq:3.8-management
hostname: rabitQ # (RabbitMQ specifically needs this setting)
ports:
- "9000:15672"
imed:
build: ./IMED
volumes:
- shared:/shared
orig:
build: ./ORIG
obse:
build: ./OBSE
depends_on:
- httpserv
volumes:
shared:
I'd probably have the producing service unconditionally copy the file into the volume on startup, and have the consuming service block on it being present. (Don't depend on Docker to initialize the volume; it doesn't work on Docker bind mounts, or on Kubernetes, or if the underlying image has changed.) So long as the files are world-readable the two services' user IDs don't need to match.

CURL different docker-compose [duplicate]

I have two separate docker-compose.yml files in two different folders:
~/front/docker-compose.yml
~/api/docker-compose.yml
How can I make sure that a container in front can send requests to a container in api?
I know that --default-gateway option can be set using docker run for an individual container, so that a specific IP address can be assigned to this container, but it seems that this option is not available when using docker-compose.
Currently I end up doing a docker inspect my_api_container_id and look at the gateway in the output. It works but the problem is that this IP is randomly attributed, so I can't rely on it.
Another form of this question might thus be:
Can I attribute a fixed IP address to a particular container using docker-compose?
But in the end what I'm looking after is:
How can two different docker-compose projects communicate with each other?

You just need to make sure that the containers you want to talk to each other are on the same network. Networks are a first-class docker construct, and not specific to compose.
# front/docker-compose.yml
version: '2'
services:
front:
...
networks:
- some-net
networks:
some-net:
driver: bridge
...
# api/docker-compose.yml
version: '2'
services:
api:
...
networks:
- front_some-net
networks:
front_some-net:
external: true
Note: Your app’s network is given a name based on the “project name”, which is based on the name of the directory it lives in, in this case a prefix front_ was added
They can then talk to each other using the service name. From front you can do ping api and vice versa.

UPDATE: As of compose file version 3.5:
This now works:
version: "3.5"
services:
proxy:
image: hello-world
ports:
- "80:80"
networks:
- proxynet
networks:
proxynet:
name: custom_network
docker-compose up -d will join a network called 'custom_network'. If it doesn't exist, it will be created!
root#ubuntu-s-1vcpu-1gb-tor1-01:~# docker-compose up -d
Creating network "custom_network" with the default driver
Creating root_proxy_1 ... done
Now, you can do this:
version: "2"
services:
web:
image: hello-world
networks:
- my-proxy-net
networks:
my-proxy-net:
external:
name: custom_network
This will create a container that will be on the external network.
I can't find any reference in the docs yet but it works!

Just a small adittion to #johnharris85's great answer,
when you are running a docker compose file, a "default" network is created
so you can just add it to the other compose file as an external network:
# front/docker-compose.yml
version: '2'
services:
front_service:
...
...
# api/docker-compose.yml
version: '2'
services:
api_service:
...
networks:
- front_default
networks:
front_default:
external: true
For me this approach was more suited because I did not own the first docker-compose file and wanted to communicate with it.

All containers from api can join the front default network with following config:
# api/docker-compose.yml
...
networks:
default:
external:
name: front_default
See docker compose guide: using a pre existing network (see at the bottom)

The previous posts information is correct, but it does not have details on how to link containers, which should be connected as "external_links".
Hope this example make more clear to you:
Suppose you have app1/docker-compose.yml, with two services (svc11 and svc12), and app2/docker-compose.yml with two more services (svc21 and svc22) and suppose you need to connect in a crossed fashion:
svc11 needs to connect to svc22's container
svc21 needs to connect to svc11's container.
So the configuration should be like this:
this is app1/docker-compose.yml:
version: '2'
services:
svc11:
container_name: container11
[..]
networks:
- default # this network
- app2_default # external network
external_links:
- container22:container22
[..]
svc12:
container_name: container12
[..]
networks:
default: # this network (app1)
driver: bridge
app2_default: # external network (app2)
external: true
this is app2/docker-compose.yml:
version: '2'
services:
svc21:
container_name: container21
[..]
networks:
- default # this network (app2)
- app1_default # external network (app1)
external_links:
- container11:container11
[..]
svc22:
container_name: container22
[..]
networks:
default: # this network (app2)
driver: bridge
app1_default: # external network (app1)
external: true

Everybody has explained really well, so I'll add the necessary code with just one simple explanation.
Use a network created outside of docker-compose (an "external" network) with docker-compose version 3.5+.
Further explanation can be found here.
First docker-compose.yml file should define network with name giveItANamePlease as follows.
networks:
my-network:
name: giveItANamePlease
driver: bridge
The services of first docker-compose.yml file can use network as follows:
networks:
- my-network
In second docker-compose file, we need to proxy the network by using the network name which we have used in first docker-compose file, which in this case is giveItANamePlease:
networks:
my-proxy-net:
external:
name: giveItANamePlease
And now you can use my-proxy-net in services of a second docker-compose.yml file as follows.
networks:
- my-proxy-net

Since Compose 1.18 (spec 3.5), you can just override the default network using your own custom name for all Compose YAML files you need. It is as simple as appending the following to them:
networks:
default:
name: my-app
The above assumes you have version set to 3.5 (or above if they don't deprecate it in 4+).
Other answers have pointed the same; this is a simplified summary.

UPDATE: As of docker-compose file version 3.5:
I came across a similar problem and I solved it by adding a small change in one of my docker-compose.yml project.
For instance, we have two API's scoring and ner. Scoring API needs to send a request to the ner API for processing the input request. In order to do that they both are supposed to share the same network.
Note: Every container has its own network which is automatically created at the time of running the app inside docker. For example ner API network will be created like ner_default and scoring API network will be named as scoring default. This solution will work for version: '3'.
As in the above scenario, my scoring API wants to communicate with ner API then I will add the following lines. This means Whenever I create the container for ner API then it automatically added to the scoring_default network.
networks:
default:
external:
name: scoring_default
ner/docker-compose.yml
version: '3'
services:
ner:
container_name: "ner_api"
build: .
...
networks:
default:
external:
name: scoring_default
scoring/docker-compose.yml
version: '3'
services:
api:
build: .
...
We can see this how the above containers are now a part of the same network called scoring_default using the command:
docker inspect scoring_default
{
"Name": "scoring_default",
....
"Containers": {
"14a6...28bf": {
"Name": "ner_api",
"EndpointID": "83b7...d6291",
"MacAddress": "0....",
"IPv4Address": "0.0....",
"IPv6Address": ""
},
"7b32...90d1": {
"Name": "scoring_api",
"EndpointID": "311...280d",
"MacAddress": "0.....3",
"IPv4Address": "1...0",
"IPv6Address": ""
},
...
}

You can add a .env file in all your projects containing COMPOSE_PROJECT_NAME=somename.
COMPOSE_PROJECT_NAME overrides the prefix used to name resources, as such all your projects will use somename_default as their network, making it possible for services to communicate with each other as they were in the same project.
NB: You'll get warnings for "orphaned" containers created from other projects.

For using another docker-compose network you just do these(to share networks between docker-compose):
Run the first docker-compose project by up -d
Find the network name of the first docker-compose by: docker network ls(It contains the name of the root directory project)
Then use that name by this structure at below in the second docker-compose file.
second docker-compose.yml
version: '3'
services:
service-on-second-compose: # Define any names that you want.
.
.
.
networks:
- <put it here(the network name that comes from "docker network ls")>
networks:
- <put it here(the network name that comes from "docker network ls")>:
external: true

I would ensure all containers are docker-compose'd to the same network by composing them together at the same time, using:
docker compose --file ~/front/docker-compose.yml --file ~/api/docker-compose.yml up -d

If you are
trying to communicate between two containers from different docker-compose projects and don't want to use the same network (because let's say they would have PostgreSQL or Redis container on the same port and you would prefer to not changing these ports and not use it at the same network)
developing locally and want to imitate communication between two docker compose projects
running two docker-compose projects on localhost
developing especially Django apps or Django Rest Framework (drf) API and running app inside container on some exposed port
getting Connection refused while trying to communicate between two containers
And you want to
container api_a communicate to api_b (or vice versa) without the same "docker network"
(example below)
you can use "host" of the second container as IP of your computer and port that is mapped from inside Docker container. You can obtain IP of your computer with this script (from: Finding local IP addresses using Python's stdlib):
import socket
def get_ip():
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
# doesn't even have to be reachable
s.connect(('10.255.255.255', 1))
IP = s.getsockname()[0]
except:
IP = '127.0.0.1'
finally:
s.close()
return IP
Example:
project_api_a/docker-compose.yml:
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_a
image: api_a:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_a container you are running Django app:
manage.py runserver 0.0.0.0:8000
and second docker-compose.yml from other project:
project_api_b/docker-compose-yml :
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_b
image: api_b:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_b container you are running Django app:
manage.py runserver 0.0.0.0:8001
And trying to connect from container api_a to api_b then URL of api_b container will be:
http://<get_ip_from_script_above>:8001/
It can be especially valuable if you are using even more than two(three or more) docker-compose projects and it's hard to provide common network for all of it - it's good workaround and solution

To connect two docker-compose you need a network and putting both docker-composes in that network,
you could create netwrok with docker network create name-of-network,
or you could simply put network declaration in networks option of docker-compose file and when you run docker-compose (docker-compose up) the network would be created automatically.
put the below lines in both docker-compose files
networks:
net-for-alpine:
name: test-db-net
Note: net-for-alpine is internal name of the network and it will be used inside of the docker-compose files and could be different,
test-db-net is external name of the network and must be same in two docker-compose files.
Assume we have docker-compose.db.yml and docker-compose.alpine.yml
docker-compose.apline.yml would be:
version: '3.8'
services:
alpine:
image: alpine:3.14
container_name: alpine
networks:
- net-for-alpine
# these two command keeps apline container running
stdin_open: true # docker run -i
tty: true # docker run -t
networks:
net-for-alpine:
name: test-db-net
docker-compose.db.yml would be:
version: '3.8'
services:
db:
image: postgres:13.4-alpine
container_name: psql
networks:
- net-for-db
networks:
net-for-db:
name: test-db-net
To test the network, go inside alpine container
docker exec -it alpine sh
then with following commands you could check the network
# if it returns 0 or see nothing as a result, network is established
nc -z psql (container name)
or
ping pgsql

Another option is just running up the first module with the 'docker-compose' check the ip related with the module, and connect the second module with the previous net like external, and pointing the internal ip
example
app1 - new-network created in the service lines, mark as external: true at the bottom
app2 - indicate the "new-network" created by app1 when goes up, mark as external: true at the bottom, and set in the config to connect, the ip that app1 have in this net.
With this, you should be able to talk with each other
*this way is just for local-test focus, in order to don't do an over complex configuration
** I know is very 'patch way' but works for me and I think is so simple some other can take advantage of this

Answer for Docker Compose '3' and up
By default Docker Compose uses a bridge network to provision inter-container communication. Read this article for more info about inter-container networking.
What matters for you, is that by default Docker Compose creates a hostname that equals the service name in the docker-compose.yml file. Consider the following docker-compose.yml:
version: '3.9'
services:
server:
image: node:16.9.0
container_name: server
tty: true
stdin_open: true
depends_on:
- mongo
command: bash
mongo:
image: mongo
environment:
MONGO_INITDB_DATABASE: my-database
When you run docker-compose up, Docker will create a default network and assigns the service name as hostname for both mongo and server.
You can now access the backend container via:
docker exec -it server bash
And now you can ping the mongo container using Dockers internal network (default on port 27017 in this case):
curl -v http://mongo:27017/my-database
That's it. The same applies for your setup.

I have had a similar example where I was working with separate docker-compose files working on a docker swarm with an overlay network to do that all I had to do is change the networks parameters as so:
first docker-compose.yaml
version: '3.9'
.
.
.
networks:
net:
driver: overlay
attachable: true
docker-compose -p app up
since I have specified the app name as app using -p the initial network will be app_net.
Now in order to run another docker-compose with multiple services that will use the same network you will need to set these as so:
second docker-compose.yaml
version: '3.9'
.
.
.
networks:
net-ref:
external: true
name: app_net
docker stack deploy -c docker-compose.yml mystack
No matter what name you give to the stack the network will not be affected and will always refer to the existing external network called app_net.
PS: It's important to make sure to check your docker-compose version.

version: '2'
services:
bot:
build: .
volumes:
- '.:/home/node'
- /home/node/node_modules
networks:
- my-rede
mem_limit: 100m
memswap_limit: 100m
cpu_quota: 25000
container_name: 236948199393329152_585042339404185600_bot
command: node index.js
environment:
NODE_ENV: production
networks:
my-rede:
external:
name: name_rede_externa

Follow up of JohnHarris answer, just adding some more details which may be useful to someone: Lets take two docker-compose file and connect them through networks:
1st foldername/docker-compose.yml:
version: '2'
services:
some-contr:
container_name: []
build: .
...
networks:
- somenet
ports:
- "8080:8080"
expose:
# Opens port 8080 on the container
- "8080"
environment:
PORT: 8080
tty: true
networks:
boomnet:
driver: bridge
2nd docker-compose.yml:
version: '2'
services:
pushapiserver:
container_name: [container_name]
build: .
command: "tail -f /dev/null"
volumes:
- ./:/[work_dir]
working_dir: /[work dir]
image: [name of image]
ports:
- "8060:8066"
environment:
PORT: 8066
tty: true
networks:
- foldername_somenet
networks:
foldername_somenet:
external: true
Now you can make api calls to one another services(b/w diff containers)like:
http://pushapiserver:8066/send_push call from some code in files for 1st docker-compose.yml
Two common mistakes (atleast i made them few times):
take note of [foldername] in which your docker-compose.yml file is present. Please see above in 2nd docker-compose.yml i have added foldername in network bc docker create network by [foldername]_[networkname]
Port: this one is very common. Please note i have used 8066 when trying to make connection i.e. http://pushapiserver:8066/... 8066 is port of docker container(2nd docker-compose.yml) so when trying to talk with different docker compose.
docker will use docker container port[8066] and not host machine mapped port
[8060]

docker-compose: Sharing container between multiple projects by using the same container_name

I want to use a MySQL docker container for multiple projects running on the same server.
Using docker-compose v3 files, I simply have the same mysql container configuration in each of the projects, and they have the same container_name:
version: "3"
services:
app1:
image: foo
links:
- mysql
mysql:
image: mysql/mysql:5.7
container_name: shared_mysql
The second application has a similar docker-compose.yml file, but with app2 instead of app1.
When running docker-compose up --no-recreate for app2, I get an error:
Creating shared_mysql ... error
ERROR: for shared_mysql
Cannot create container for service mysql: Conflict.
The container name "/shared_mysql" is already in use by container "deadbeef".
You have to remove (or rename) that container to be able to reuse that name.
What can I do to share the MySQL container between multiple docker projects?

You can simply avoid redefining the mysql in one of the two docker-compose.yml files and connect mysql and the other containers to the same network.
In order to do so, create a network:
docker network create shared
Assign your network to your mysql container:
version: '3'
services:
mysql:
...
networks:
- shared
networks:
shared:
external:
name: shared
For any other container that has need to access mysql, just add the same network definition as above:
version: '3'
services:
app1:
...
networks:
- shared
app2:
...
networks:
- shared
...
networks:
shared:
external:
name: shared

If your container is only created from other compose file you can use the external links feature in docker-compose.
If you want both docker compose files to be able to create the mysql container, I suggest you look into Share Compose configurations between files and projects. In this case, you can create a base file that only defines mysql and extend/merge it in both apps compose files.

We solve it by using a third project including all the shared services our micro-services are using like mysql, kafka and redis.
in each one of our docker-compose files, we added a external links to those services.
Its a little bit dirty but it working well.
You can follow this issue on github, https://github.com/docker/compose/issues/2075
that is talking about the same issue you struggling with.

Communication between multiple docker-compose projects

I have two separate docker-compose.yml files in two different folders:
~/front/docker-compose.yml
~/api/docker-compose.yml
How can I make sure that a container in front can send requests to a container in api?
I know that --default-gateway option can be set using docker run for an individual container, so that a specific IP address can be assigned to this container, but it seems that this option is not available when using docker-compose.
Currently I end up doing a docker inspect my_api_container_id and look at the gateway in the output. It works but the problem is that this IP is randomly attributed, so I can't rely on it.
Another form of this question might thus be:
Can I attribute a fixed IP address to a particular container using docker-compose?
But in the end what I'm looking after is:
How can two different docker-compose projects communicate with each other?

You just need to make sure that the containers you want to talk to each other are on the same network. Networks are a first-class docker construct, and not specific to compose.
# front/docker-compose.yml
version: '2'
services:
front:
...
networks:
- some-net
networks:
some-net:
driver: bridge
...
# api/docker-compose.yml
version: '2'
services:
api:
...
networks:
- front_some-net
networks:
front_some-net:
external: true
Note: Your app’s network is given a name based on the “project name”, which is based on the name of the directory it lives in, in this case a prefix front_ was added
They can then talk to each other using the service name. From front you can do ping api and vice versa.

UPDATE: As of compose file version 3.5:
This now works:
version: "3.5"
services:
proxy:
image: hello-world
ports:
- "80:80"
networks:
- proxynet
networks:
proxynet:
name: custom_network
docker-compose up -d will join a network called 'custom_network'. If it doesn't exist, it will be created!
root#ubuntu-s-1vcpu-1gb-tor1-01:~# docker-compose up -d
Creating network "custom_network" with the default driver
Creating root_proxy_1 ... done
Now, you can do this:
version: "2"
services:
web:
image: hello-world
networks:
- my-proxy-net
networks:
my-proxy-net:
external:
name: custom_network
This will create a container that will be on the external network.
I can't find any reference in the docs yet but it works!

Just a small adittion to #johnharris85's great answer,
when you are running a docker compose file, a "default" network is created
so you can just add it to the other compose file as an external network:
# front/docker-compose.yml
version: '2'
services:
front_service:
...
...
# api/docker-compose.yml
version: '2'
services:
api_service:
...
networks:
- front_default
networks:
front_default:
external: true
For me this approach was more suited because I did not own the first docker-compose file and wanted to communicate with it.

All containers from api can join the front default network with following config:
# api/docker-compose.yml
...
networks:
default:
external:
name: front_default
See docker compose guide: using a pre existing network (see at the bottom)

The previous posts information is correct, but it does not have details on how to link containers, which should be connected as "external_links".
Hope this example make more clear to you:
Suppose you have app1/docker-compose.yml, with two services (svc11 and svc12), and app2/docker-compose.yml with two more services (svc21 and svc22) and suppose you need to connect in a crossed fashion:
svc11 needs to connect to svc22's container
svc21 needs to connect to svc11's container.
So the configuration should be like this:
this is app1/docker-compose.yml:
version: '2'
services:
svc11:
container_name: container11
[..]
networks:
- default # this network
- app2_default # external network
external_links:
- container22:container22
[..]
svc12:
container_name: container12
[..]
networks:
default: # this network (app1)
driver: bridge
app2_default: # external network (app2)
external: true
this is app2/docker-compose.yml:
version: '2'
services:
svc21:
container_name: container21
[..]
networks:
- default # this network (app2)
- app1_default # external network (app1)
external_links:
- container11:container11
[..]
svc22:
container_name: container22
[..]
networks:
default: # this network (app2)
driver: bridge
app1_default: # external network (app1)
external: true

Everybody has explained really well, so I'll add the necessary code with just one simple explanation.
Use a network created outside of docker-compose (an "external" network) with docker-compose version 3.5+.
Further explanation can be found here.
First docker-compose.yml file should define network with name giveItANamePlease as follows.
networks:
my-network:
name: giveItANamePlease
driver: bridge
The services of first docker-compose.yml file can use network as follows:
networks:
- my-network
In second docker-compose file, we need to proxy the network by using the network name which we have used in first docker-compose file, which in this case is giveItANamePlease:
networks:
my-proxy-net:
external:
name: giveItANamePlease
And now you can use my-proxy-net in services of a second docker-compose.yml file as follows.
networks:
- my-proxy-net

Since Compose 1.18 (spec 3.5), you can just override the default network using your own custom name for all Compose YAML files you need. It is as simple as appending the following to them:
networks:
default:
name: my-app
The above assumes you have version set to 3.5 (or above if they don't deprecate it in 4+).
Other answers have pointed the same; this is a simplified summary.

UPDATE: As of docker-compose file version 3.5:
I came across a similar problem and I solved it by adding a small change in one of my docker-compose.yml project.
For instance, we have two API's scoring and ner. Scoring API needs to send a request to the ner API for processing the input request. In order to do that they both are supposed to share the same network.
Note: Every container has its own network which is automatically created at the time of running the app inside docker. For example ner API network will be created like ner_default and scoring API network will be named as scoring default. This solution will work for version: '3'.
As in the above scenario, my scoring API wants to communicate with ner API then I will add the following lines. This means Whenever I create the container for ner API then it automatically added to the scoring_default network.
networks:
default:
external:
name: scoring_default
ner/docker-compose.yml
version: '3'
services:
ner:
container_name: "ner_api"
build: .
...
networks:
default:
external:
name: scoring_default
scoring/docker-compose.yml
version: '3'
services:
api:
build: .
...
We can see this how the above containers are now a part of the same network called scoring_default using the command:
docker inspect scoring_default
{
"Name": "scoring_default",
....
"Containers": {
"14a6...28bf": {
"Name": "ner_api",
"EndpointID": "83b7...d6291",
"MacAddress": "0....",
"IPv4Address": "0.0....",
"IPv6Address": ""
},
"7b32...90d1": {
"Name": "scoring_api",
"EndpointID": "311...280d",
"MacAddress": "0.....3",
"IPv4Address": "1...0",
"IPv6Address": ""
},
...
}

You can add a .env file in all your projects containing COMPOSE_PROJECT_NAME=somename.
COMPOSE_PROJECT_NAME overrides the prefix used to name resources, as such all your projects will use somename_default as their network, making it possible for services to communicate with each other as they were in the same project.
NB: You'll get warnings for "orphaned" containers created from other projects.

For using another docker-compose network you just do these(to share networks between docker-compose):
Run the first docker-compose project by up -d
Find the network name of the first docker-compose by: docker network ls(It contains the name of the root directory project)
Then use that name by this structure at below in the second docker-compose file.
second docker-compose.yml
version: '3'
services:
service-on-second-compose: # Define any names that you want.
.
.
.
networks:
- <put it here(the network name that comes from "docker network ls")>
networks:
- <put it here(the network name that comes from "docker network ls")>:
external: true

I would ensure all containers are docker-compose'd to the same network by composing them together at the same time, using:
docker compose --file ~/front/docker-compose.yml --file ~/api/docker-compose.yml up -d

If you are
trying to communicate between two containers from different docker-compose projects and don't want to use the same network (because let's say they would have PostgreSQL or Redis container on the same port and you would prefer to not changing these ports and not use it at the same network)
developing locally and want to imitate communication between two docker compose projects
running two docker-compose projects on localhost
developing especially Django apps or Django Rest Framework (drf) API and running app inside container on some exposed port
getting Connection refused while trying to communicate between two containers
And you want to
container api_a communicate to api_b (or vice versa) without the same "docker network"
(example below)
you can use "host" of the second container as IP of your computer and port that is mapped from inside Docker container. You can obtain IP of your computer with this script (from: Finding local IP addresses using Python's stdlib):
import socket
def get_ip():
s = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
try:
# doesn't even have to be reachable
s.connect(('10.255.255.255', 1))
IP = s.getsockname()[0]
except:
IP = '127.0.0.1'
finally:
s.close()
return IP
Example:
project_api_a/docker-compose.yml:
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_a
image: api_a:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_a container you are running Django app:
manage.py runserver 0.0.0.0:8000
and second docker-compose.yml from other project:
project_api_b/docker-compose-yml :
networks:
app-tier:
driver: bridge
services:
api:
container_name: api_b
image: api_b:latest
depends_on:
- postgresql
networks:
- app-tier
inside api_b container you are running Django app:
manage.py runserver 0.0.0.0:8001
And trying to connect from container api_a to api_b then URL of api_b container will be:
http://<get_ip_from_script_above>:8001/
It can be especially valuable if you are using even more than two(three or more) docker-compose projects and it's hard to provide common network for all of it - it's good workaround and solution

To connect two docker-compose you need a network and putting both docker-composes in that network,
you could create netwrok with docker network create name-of-network,
or you could simply put network declaration in networks option of docker-compose file and when you run docker-compose (docker-compose up) the network would be created automatically.
put the below lines in both docker-compose files
networks:
net-for-alpine:
name: test-db-net
Note: net-for-alpine is internal name of the network and it will be used inside of the docker-compose files and could be different,
test-db-net is external name of the network and must be same in two docker-compose files.
Assume we have docker-compose.db.yml and docker-compose.alpine.yml
docker-compose.apline.yml would be:
version: '3.8'
services:
alpine:
image: alpine:3.14
container_name: alpine
networks:
- net-for-alpine
# these two command keeps apline container running
stdin_open: true # docker run -i
tty: true # docker run -t
networks:
net-for-alpine:
name: test-db-net
docker-compose.db.yml would be:
version: '3.8'
services:
db:
image: postgres:13.4-alpine
container_name: psql
networks:
- net-for-db
networks:
net-for-db:
name: test-db-net
To test the network, go inside alpine container
docker exec -it alpine sh
then with following commands you could check the network
# if it returns 0 or see nothing as a result, network is established
nc -z psql (container name)
or
ping pgsql

Another option is just running up the first module with the 'docker-compose' check the ip related with the module, and connect the second module with the previous net like external, and pointing the internal ip
example
app1 - new-network created in the service lines, mark as external: true at the bottom
app2 - indicate the "new-network" created by app1 when goes up, mark as external: true at the bottom, and set in the config to connect, the ip that app1 have in this net.
With this, you should be able to talk with each other
*this way is just for local-test focus, in order to don't do an over complex configuration
** I know is very 'patch way' but works for me and I think is so simple some other can take advantage of this

Answer for Docker Compose '3' and up
By default Docker Compose uses a bridge network to provision inter-container communication. Read this article for more info about inter-container networking.
What matters for you, is that by default Docker Compose creates a hostname that equals the service name in the docker-compose.yml file. Consider the following docker-compose.yml:
version: '3.9'
services:
server:
image: node:16.9.0
container_name: server
tty: true
stdin_open: true
depends_on:
- mongo
command: bash
mongo:
image: mongo
environment:
MONGO_INITDB_DATABASE: my-database
When you run docker-compose up, Docker will create a default network and assigns the service name as hostname for both mongo and server.
You can now access the backend container via:
docker exec -it server bash
And now you can ping the mongo container using Dockers internal network (default on port 27017 in this case):
curl -v http://mongo:27017/my-database
That's it. The same applies for your setup.

I have had a similar example where I was working with separate docker-compose files working on a docker swarm with an overlay network to do that all I had to do is change the networks parameters as so:
first docker-compose.yaml
version: '3.9'
.
.
.
networks:
net:
driver: overlay
attachable: true
docker-compose -p app up
since I have specified the app name as app using -p the initial network will be app_net.
Now in order to run another docker-compose with multiple services that will use the same network you will need to set these as so:
second docker-compose.yaml
version: '3.9'
.
.
.
networks:
net-ref:
external: true
name: app_net
docker stack deploy -c docker-compose.yml mystack
No matter what name you give to the stack the network will not be affected and will always refer to the existing external network called app_net.
PS: It's important to make sure to check your docker-compose version.

version: '2'
services:
bot:
build: .
volumes:
- '.:/home/node'
- /home/node/node_modules
networks:
- my-rede
mem_limit: 100m
memswap_limit: 100m
cpu_quota: 25000
container_name: 236948199393329152_585042339404185600_bot
command: node index.js
environment:
NODE_ENV: production
networks:
my-rede:
external:
name: name_rede_externa

Follow up of JohnHarris answer, just adding some more details which may be useful to someone: Lets take two docker-compose file and connect them through networks:
1st foldername/docker-compose.yml:
version: '2'
services:
some-contr:
container_name: []
build: .
...
networks:
- somenet
ports:
- "8080:8080"
expose:
# Opens port 8080 on the container
- "8080"
environment:
PORT: 8080
tty: true
networks:
boomnet:
driver: bridge
2nd docker-compose.yml:
version: '2'
services:
pushapiserver:
container_name: [container_name]
build: .
command: "tail -f /dev/null"
volumes:
- ./:/[work_dir]
working_dir: /[work dir]
image: [name of image]
ports:
- "8060:8066"
environment:
PORT: 8066
tty: true
networks:
- foldername_somenet
networks:
foldername_somenet:
external: true
Now you can make api calls to one another services(b/w diff containers)like:
http://pushapiserver:8066/send_push call from some code in files for 1st docker-compose.yml
Two common mistakes (atleast i made them few times):
take note of [foldername] in which your docker-compose.yml file is present. Please see above in 2nd docker-compose.yml i have added foldername in network bc docker create network by [foldername]_[networkname]
Port: this one is very common. Please note i have used 8066 when trying to make connection i.e. http://pushapiserver:8066/... 8066 is port of docker container(2nd docker-compose.yml) so when trying to talk with different docker compose.
docker will use docker container port[8066] and not host machine mapped port
[8060]

Develop Reference

ios ruby-on-rails asp.net-mvc docker delphi jenkins grails google-sheets machine-learning dart