I have setup docker container with mysql that expose 3306.
I've specified database user, database password and create a test db and give the privileges to new user.
In another container i want to accesso to this db.
So i set up new container with a simply php script that create new table in this db.
I know that mysql container's ip is 172.17.0.2 so :
$mysqli = new mysqli("172.17.0.2", "mattia", "prova", "prova");
Than using mysqli i create new table and all works fine.
But i think that connect to container using his ip address is not good.
Is there another way to specify db host? I tryed with the hostname of the mysql container but it doens't work.
The --link flag is considered a legacy feature, you should use user-defined networks.
You can run both containers on the same network:
docker run -d --name php_container --network my_network my_php_image
docker run -d --name mysql_container --network my_network my_mysql_image
Every container on that network will be able to communicate with each other using the container name as hostname.
You need to link your docker containers together with --link flag in docker run command or using link feature in docker-compose. For instance:
docker run -d -name app-container-name --link mysql-container-name app-image-name
In this way docker will add the IP address of the mysql container into /etc/hosts file of your application container.
For a complete document refer to:
MySQL Docker Containers: Understanding the basics
In your docker-compose.yml file add a link property to your webserver service:
https://docs.docker.com/compose/networking/#links
Then in your query string, the host parameter's value is your database service name:
$mysqli = new mysqli("database", "mattia", "prova", "prova");
If you are using docker-compose, than the database will be accessible under the service name.
version: "3.9"
services:
web:
build: .
ports:
- "8000:8000"
db:
image: postgres
ports:
- "8001:5432"
Then the database is accessible using: postgres://db:5432.
Here the service name is at the same time the hostname in the internal network.
Quote from docker docs:
When you run docker-compose up, the following happens:
A network called myapp_default is created.
A container is created using web’s configuration. It joins the network myapp_default under the name web.
A container is created using db’s configuration. It joins the network myapp_default under the name db.
Source:
https://docs.docker.com/compose/networking/
Related
I've got a Docker image which accepts a DATABASE_URL env and start the container with
docker run -p 3000:3000 -e DATABASE_URL=mysql://root:foobar#localhost:3309/app app_image
On startup the container should run migrations on a database bootstraped from a docker-compose.yml file:
version: '3'
services:
database:
image: mysql:8.0
environment:
- MYSQL_DATABASE=app
- MYSQL_ROOT_PASSWORD=foobar
ports:
- "3309:3306"
volumes:
- db:/var/lib/mysql
volumes:
db:
Unfortunately, I always get Can't reach database at localhost:3309. I assume it has something to do with the network settings - but how to configure these settings in order to make it work?
I've tried many different configurations (e.g. database, 127.0.0.1, etc. instead of localhost) but couldn't make it work and I'm honestly running out of ideas.
Thanks!
Some clarifications:
Unless you specifically bind containers to the same host e.g. --network host or link them together in docker compose using links Links documentation, container A will not be able to reach anything on container B via localhost.
Docker compose, unless specified differently in the docker-compose.yaml file, automatically creates a separate network for all of the containers that are managed by that compose file, its name is usually based on the folder the file is in.
You can view it using docker network ls
that means, any container not managed by that compose file, is not part of the same network by default.
One option easy enough option that you have (among many probably):
Decide on a network name which the compose file and you container will agree on
create this network beforehand (before starting the standalone container and the compose file), the network will probably be in bridge mode
docker network docs docker network create -d bridge my-bridge-network
add it to the compose file so that docker compose uses it instead of the auto-created one
networks:
- my-bridge-network
when starting the stand-alone container, specify which network to attach it to
docker run -p 3000:3000 -e DATABASE_URL=mysql://root:foobar#database:3309/app --network my-bridge-network app_image
notice that the IP/HOSTNAME for the database container is according to the service name in the compose file, you can change that using hostname: some-other-hostname in the yaml.
all containers should now be on the same network, each one has a different IP/Hostname using this method (so cant use localhost for inter-container communication)
Alternative option:
use network: host for both the compose file and the stand-alone container, they can talk to each other using localhost.
i dont recommend this option, and cant find a good enough reason to use it over other options.
I have two docker containers wanted to work as connected. One docker instance(instance1) is connected with the client and another docker(instance2) is wants to connect with instance1. Mainly what it does is when the client sends a request to instance 1, instatnce1 wants to invoke instance2 service and get the response. Then pass it to the client.
Currently, I'm using following docker commands to run the docker images
instance1
docker run --name instance1 -d -p 8290:8290 composite-service
This instance has a service - http://localhost:8290/composite .
This service invokes the service in instance2
instance2
docker run --name instance2 -d -p 8291:8290 service-backend
This instance has a service - http://localhost:8291/service. When this called service response some data to the request. (actually, this service is started on port 8290, but it exposes to externals in 8291 port)
The problem is when the client called to the service in instance1 (http://localhost:8290/composite) it shows an error
Connection refused or failed for : localhost/127.0.0.1:8291
How can I resolve this? I want to connect these 2 containers with existing port mappings passed in the docker run commands.
I tried --link and --net commands to connect these two containers but the result was same.
Building on bellackn’s Answer the easiest way in my opinion is with docker compose.
The dockercompose file would look something like this.
version: "3.7"
services:
service:
image: composite-service:latest
ports:
- 8290:8290
backend:
image: service-backend:latest
expose:
- 8290
Now instead of using docker run … you save the code above in a file called docker-compose.yml, and run docker-compose up from the folder that file is saved in.
Now your composite-service no longer should call http://localhost:8291/service , but instead use something like backend:8290/service.
You can read more about compose-files in the official documentation: https://docs.docker.com/compose/compose-file/
An added benefit is that this way the service-backend is only accessible within the docker compose network (not on your local host).
If you want access to your backend remove the expose statement and add the ports.
localhost inside a container always refers to the container itself (unless you start them with --net host).
If you want containers to communicate, I recommend Docker Compose. The containers can then refer to each other using their service names (if you run them in the same network, of course, but that's the default), i.e. instance1 could reach instance2 via http://instance2:8291/service.
I have two running docker containers. One docker container is calling the other docker container but when it is trying to call application is breaking. When I am giving my hostname of my machine inside the application.Application is working.
This is a really a dependency if i deploy these two containers i again have to find the hostname of that machine and then put inside my application is any other way so that which can remove this dependency.
This url is consumed by my docker container which is failing
http://localhost:8080/userData
Same when i update with my host name then it is working.
http://nl55443lldsfa:8080/userData
But this is really a dependency i cannot change inside my application everytime.Is any work around is there for the same.
You should use docker-compose to run both containers and link them using the link property on your yaml file.
This might be a good example:
web:
image: nginx:latest
ports:
- "8080:8080"
links:
- php
php:
image: php
Then the ip of each container will be associated to its service name on the /etc/hosts file of both containers and you will be able to access them from inside the containers just by using that hostname.
Also be sure to be mapping the ports correctly, using http://localhost:8080 shouldn't fail if you map the ports correctly and the service is running.
Put the two containers inside the same network when running them. Only then you can use hostnames for inter container communication.
Edit: And of course name you containers so you don’t get a random container name each time.
Edit 2: The commands are:
$ docker network create -d bridge my-bridge-network
$ docker run -d \
--name webserver \
--network=my-bridge-network \
nginx:latest
$ docker run -d \
--name dbserver \
--network=my-bridge-network \
mysql:5.7
Containers started both with a specified hostname and a common network can use hostnames internally to communicate with each other.
I created two docker containers based on two different images. One of db and another for webserver. Both containers are running on my mac osx.
I can access db container from host machine and same way can access webserver from host machine.
However, how do I access db connection from webserver?
The way I started db container is
docker run --name oracle-db -p 1521:1521 -p 5501:5500 oracle/database:12.1.0.2-ee
I started wls container as
docker run --name oracle-wls -p 7001:7001 wls-image:latest
I can access db on host by connecting to
sqlplus scott/welcome1#//localhost:1521/ORCLCDB
I can access wls on host as
http://localhost:7001/console
It's easy.
If you have two or more running container, complete next steps:
docker network create myNetwork
docker network connect myNetwork web1
docker network connect myNetwork web2
Now you connect from web1 to web2 container or the other way round.
Use the internal network IP addresses which you can find by running:
docker network inspect myNetwork
Note that only internal IP addresses and ports are accessible to the containers connected by the network bridge.
So for example assuming that web1 container was started with: docker run -p 80:8888 web1 (meaning that its server is running on port 8888 internally), and inspecting myNetwork shows that web1's IP is 172.0.0.2, you can connect from web2 to web1 using curl 172.0.0.2:8888).
Easiest way is to use --link, however the newer versions of docker are moving away from that and in fact that switch will be removed soon.
The link below offers a nice how too, on connecting two containers. You can skip the attach portion, since that is just a useful how to on adding items to images.
https://web.archive.org/web/20160310072132/https://deis.com/blog/2016/connecting-docker-containers-1/
The part you are interested in is the communication between two containers. The easiest way, is to refer to the DB container by name from the webserver container.
Example:
you named the db container db1 and the webserver container web0. The containers should both be on the bridge network, which means the web container should be able to connect to the DB container by referring to its name.
So if you have a web config file for your app, then for DB host you will use the name db1.
if you are using an older version of docker, then you should use --link.
Example:
Step 1: docker run --name db1 oracle/database:12.1.0.2-ee
then when you start the web app. use:
Step 2: docker run --name web0 --link db1 webapp/webapp:3.0
and the web app will be linked to the DB. However, as I said the --link switch will be removed soon.
I'd use docker compose instead, which will build a network for you. However; you will need to download docker compose for your system. https://docs.docker.com/compose/install/#prerequisites
an example setup is like this:
file name is base.yml
version: "2"
services:
webserver:
image: moodlehq/moodle-php-apache:7.1
depends_on:
- db
volumes:
- "/var/www/html:/var/www/html"
- "/home/some_user/web/apache2_faildumps.conf:/etc/apache2/conf-enabled/apache2_faildumps.conf"
environment:
MOODLE_DOCKER_DBTYPE: pgsql
MOODLE_DOCKER_DBNAME: moodle
MOODLE_DOCKER_DBUSER: moodle
MOODLE_DOCKER_DBPASS: "m#0dl3ing"
HTTP_PROXY: "${HTTP_PROXY}"
HTTPS_PROXY: "${HTTPS_PROXY}"
NO_PROXY: "${NO_PROXY}"
db:
image: postgres:9
environment:
POSTGRES_USER: moodle
POSTGRES_PASSWORD: "m#0dl3ing"
POSTGRES_DB: moodle
HTTP_PROXY: "${HTTP_PROXY}"
HTTPS_PROXY: "${HTTPS_PROXY}"
NO_PROXY: "${NO_PROXY}"
this will name the network a generic name, I can't remember off the top of my head what that name is, unless you use the --name switch.
IE docker-compose --name setup1 up base.yml
NOTE: if you use the --name switch, you will need to use it when ever calling docker compose, so docker-compose --name setup1 down this is so you can have more then one instance of webserver and db, and in this case, so docker compose knows what instance you want to run commands against; and also so you can have more then one running at once. Great for CI/CD, if you are running test in parallel on the same server.
Docker compose also has the same commands as docker so docker-compose --name setup1 exec webserver do_some_command
best part is, if you want to change db's or something like that for unit test you can include an additional .yml file to the up command and it will overwrite any items with similar names, I think of it as a key=>value replacement.
Example:
db.yml
version: "2"
services:
webserver:
environment:
MOODLE_DOCKER_DBTYPE: oci
MOODLE_DOCKER_DBNAME: XE
db:
image: moodlehq/moodle-db-oracle
Then call docker-compose --name setup1 up base.yml db.yml
This will overwrite the db. with a different setup. When needing to connect to these services from each container, you use the name set under service, in this case, webserver and db.
I think this might actually be a more useful setup in your case. Since you can set all the variables you need in the yml files and just run the command for docker compose when you need them started. So a more start it and forget it setup.
NOTE: I did not use the --port command, since exposing the ports is not needed for container->container communication. It is needed only if you want the host to connect to the container, or application from outside of the host. If you expose the port, then the port is open to all communication that the host allows. So exposing web on port 80 is the same as starting a webserver on the physical host and will allow outside connections, if the host allows it. Also, if you are wanting to run more then one web app at once, for whatever reason, then exposing port 80 will prevent you from running additional webapps if you try exposing on that port as well. So, for CI/CD it is best to not expose ports at all, and if using docker compose with the --name switch, all containers will be on their own network so they wont collide. So you will pretty much have a container of containers.
UPDATE: After using features further and seeing how others have done it for CICD programs like Jenkins. Network is also a viable solution.
Example:
docker network create test_network
The above command will create a "test_network" which you can attach other containers too. Which is made easy with the --network switch operator.
Example:
docker run \
--detach \
--name db1 \
--network test_network \
-e MYSQL_ROOT_PASSWORD="${DBPASS}" \
-e MYSQL_DATABASE="${DBNAME}" \
-e MYSQL_USER="${DBUSER}" \
-e MYSQL_PASSWORD="${DBPASS}" \
--tmpfs /var/lib/mysql:rw \
mysql:5
Of course, if you have proxy network settings you should still pass those into the containers using the "-e" or "--env-file" switch statements. So the container can communicate with the internet. Docker says the proxy settings should be absorbed by the container in the newer versions of docker; however, I still pass them in as an act of habit. This is the replacement for the "--link" switch which is going away. Once the containers are attached to the network you created you can still refer to those containers from other containers using the 'name' of the container. Per the example above that would be db1. You just have to make sure all containers are connected to the same network, and you are good to go.
For a detailed example of using network in a cicd pipeline, you can refer to this link:
https://git.in.moodle.com/integration/nightlyscripts/blob/master/runner/master/run.sh
Which is the script that is ran in Jenkins for a huge integration tests for Moodle, but the idea/example can be used anywhere. I hope this helps others.
You will have to access db through the ip of host machine, or if you want to access it via localhost:1521, then run webserver like -
docker run --net=host --name oracle-wls wls-image:latest
See here
Using docker-compose, services are exposed to each other by name by default. Docs.
You could also specify an alias like;
version: '2.1'
services:
mongo:
image: mongo:3.2.11
redis:
image: redis:3.2.10
api:
image: some-image
depends_on:
- mongo
- solr
links:
- "mongo:mongo.openconceptlab.org"
- "solr:solr.openconceptlab.org"
- "some-service:some-alias"
And then access the service using the specified alias as a host name, e.g mongo.openconceptlab.org for mongo in this case.
Environment: Windows 10, Docker Desktop version 4.5.1.
Use hostname host.docker.internal to access services running on your host machine from inside a container.
See: https://docs.docker.com/desktop/windows/networking/#use-cases-and-workarounds
I run PostgreSQL in one container and my app in a separate container.
I configure the app database connection to use host.docker.internal as the hostname and it just works.
Consider Example
We Create two containers here PostgreSQL server and pgadmin(for accessing servers like PHPMyAdmin, SQL studio, workbench).
Exposed port
PostgreSql --->5436
Pgadmin --->5050
After adding a server in pgadmin hostname as localhost.It will show a connection error. Because Docker container pgadmin getting localhost as their system instead we need PostgreSQL IP to solve the problem.
docker network create con
docker network connect con app1
docker network connect con app2
This command gets connected container IP address and other details.
docker network inspect con
Now you can see the IP address shown in the network inspect. Choose the Postgres container IP. You can access other exposed ports through this IP. Here postgre 5432 is only exposed.Now set hostname as the container ip and it will work.
You can use the default docker network. If you don't want to go through any docker networking, you can do this:
Copy the ip address in Docker subnet in Resources>Network in Docker Preferences in Mac:
Docker preferences screenshot
As you can see from the screenshot link the ip address is
192.168.65.0
You just need to replace “localhost” in your containers config file with “192.168.65.1" (i.e. IP address picked + 1 ).
You can start your containers and should be set for local development/testing.
For some more details, you can see my article:
Connect Docker containers the easy way
In my case, the host connection in the application to a container from an other container by the IP provide by the bridge didn't work.
But it works with the name of the container (see my screenshot).
So you can replace the IP by the name of the container.
Here's the result when I type docker ps :
I have 3 docker containers: webapps, redis and rabbitmq. I want to link container webapps to container redis and rabbitmq container. In non docker apps, mywebapps can send message to rabbitmq and write/read redis.
I tried using command like this
docker run --name rabbitmq -p 8080:80 --link webapps:nimmis/apache-php7 -d rabbitmq
but it does not work.
Here is my config.php on webapps where I am trying to send messages via rabbitmq:
define('HOST', 'localhost');
define('PORT', 5672);
I tried to change localhost with hostname
define('HOST', 'rabbitmq');
define('PORT', 5672);
Error message says connection refused.
It seems that in my three containers needs to be configured in the same network namespace.
Linking is a legacy feature. Please use "user defined networks":
sudo docker network create mynetwork
Then rerun your containers using this network:
sudo docker run --name rabbitmq -p 8080:80 -d --network mynetwork rabbitmq
Do the same for other containers that you want connected with each other.
Using "user defined networks", you have an "internal name resolution" at your disposal (somewhat like domain name resolution when visiting websites). You can use the names of the container that you want to refer to, in order to resolve the IP addresses of containers, as long as they are running on the same "user defined network". With this, you can resolve the IP address of the rabbitmq container with its name, within other containers, on the same network.
All containters on the same "user defined network" will have network connectivity. There is no need for "legacy linking".
For inter-container dependencies and links, you'll want to use docker-compose where you can define the links between containers.
In your root directory where you store your Docker files, just make a new file called docker-compose.yml and here you can define your containers as services which rely on each other like this:
version: '2'
services:
webapps:
build: .
links:
- "rabbitmq:rabmq"
- "redis"
rabbitmq:
image: rabbitmq
redis:
image: redis
so here in the definition of the webapps service, you see it links the other two services rabbitmq and redis. What this means is that when the webapps container is build, an entry to it's hosts file is made such that the domain name redis is translated to the IP and port number of the actual container.
You have the option to change the name of how this container is address by using the service:alias notation, like how I defined the rabbitmq to
use the alias rabmq inside the container webapps.
To now build and start your containers using docker-compose just type:
docker-compose up -d
So connecting to another container is as simple as using this alias as the name of the host.
Since you are using docker-compose in this case, it creates a docker network automatically to connect all the containers so you shouldn't have to worry about that. But for more information have a look at the docs:
https://docs.docker.com/compose/networking/#/specifying-custom-networks
You need to link rabbitmq and redis to your webapps container and not the other way arround.
#run redis container
docker run --name some-redis -d redis
#run rabbitmq container
docker run -d --hostname my-rabbit --name some-rabbit rabbitmq
#run webapps container
docker run --name webapps -p 8080:80 --link some-redis:redis --link some-rabbit:rabbitmq nimmis/apache-php7
First run redis and rabbitmq containers.
Then run webapps container with links to the 2 containers.
Now, to configure redis host in the webapps - its easy. You can simply use env variable 'REDIS_PORT_6379_TCP_ADDR'. Because once a container is linked you get its env variables. and redis exports that variable.
Regarding the rabbitmq host - you can get the ip after the rabbit container is up by:
RABBITMQ_IP=$(docker inspect --format '{{ .NetworkSettings.IPAddress }}' some-rabbit)
and then pass it in --env when you run the webapps container.
In my experience working with declaratives such as docker-compose.yml is okay, but simply you can use
docker run -d -P -link nimmis/apache-php7 rabbitmq redis
You can define your services to use a user-defined network in your docker-compose.yml
version: "3"
services:
webapps:
image: nimmis/apache-php7
ports:
- "80:8080"
networks:
- my-network
rabbitmq:
image: rabbitmq
networks:
- my-network
redis:
image: redis
networks:
- my-network
networks:
my-network:
driver: overlay
Then do:
docker swarm init
docker stack deploy -c docker-compose.yml my-stack
Check out the full example at https://docs.docker.com/get-started/part3/
You could access the IP Address of your Redis Container.
Start rabbitmq and get the internal IP Adress:
docker inspect -f '{{range.NetworkSettings.Networks}}{{.IPAddress}}{{end}}' rabbitmq > .rabbitmq.ip
Now, you can add an Apache configuration and add the internal IP Address for rabbitmq while starting the webapps container. Or simply add an entry in the Apache container's /etc/hosts like:
// the dynamic internal IP of rabbitmq is known once rabbitmq starts:
172.30.20.10 rabbitmq.redis.local