How to connect to the external server from docker container? - docker

I have a redis running on my localhost and the docker container which trying connect to that redis, but it cannot do that. I receive this error in terminal:
AbortError: Stream connection ended and command aborted. It might have been processed.
One way to solve that is to use redis in another container and to link it to my existing container. But I need to have redis running on real host.

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From inside of a Docker container, how do I connect to the endpoint?

I have a cloudwatch agent installed in EC2 instance and also a docker image on the instance.
From the EC2 instance, I could successfully send out logs to endpoint(0.0.0.0:25888) to cloudwatch. But when I get into the docker image using docker exec -it <container id> bash, I tried to publish same logs from inside container but it failed with following error:
2861 2022-07-21 00:11:18,686 ERROR (10.0.1.124,1385:MainThread) aws_embedded_metrics.sinks.tcp_client: Failed to connect to the socket. [Errno 111] Connection refused
2862 2022-07-21 00:11:18,686 INFO (10.0.1.124,1385:MainThread) aws_embedded_metrics.sinks.agent_sink: Parsed agent endpoint (tcp) 0.0.0.0:25888
Wondering if anyone knows the root cause here or any debugging clue? Thanks in advance!
I run into this as well. My solution (workaround?) was to:
Make sure the cloudwatch agent is listening on udp://0.0.0.0:25888 and not 127.0.0.1 (the default). The CWAgent docs I have seen don't have any examples on how to achieve this.
Once inside the container, use the Docker host IP to send messages. For me this was export AWS_EMF_AGENT_ENDPOINT=udp://172.17.0.1:25888, as I was using aws-embedded-metrics-python. YMMV depending on the underlying library that you use.

Enabling Kubernetes on Docker Desktop breaks access to external service

I'm using docker desktop for mac.
I have built a docker image for a Node.js app that connects to an external MongoDB database via URI (the db is running on an AWS instance that I'm connected to over vpn). This works fine - I run the container and the app can connect to the database. Happy days.
Then...
I enable Kubernetes on docker desktop. I apply a deployment.yml to run the container but this deployment fails when trying to connect to the db. From my app's logs (I'm using mongoose):
MongooseServerSelectionError: connect EHOSTUNREACH [MY DB IP] +30005ms
Interestingly...
I can now no longer connect to the db by running my docker container either. I get the same error.
I have to disable kubernetes, restart docker desktop (twice), prune my previous container and network, and re-run my container. Then it will work again.
As soon as I enable kubernetes again, the db becomes unreachable again.
Any ideas why this is and/or how to fix it?
So the issue for us turned out to be an IP range clash. Exactly the same as described in this SO question:
Change Kubernetes docker-for-desktop cluster network ip
Unfortunately, like this user, we haven't been able to find a solution

I want to connect a Docker Superset container to an existing external MySQL database

I am trying to add an existing MySQL database as a source database to a docker container running Apache Superset. The MySQL database that I am trying to add is not running in a docker container. It's an existing MySQL database running on a Windows machine.
I've added mysqlclient==1.4.6 to requirements.txt. The error message seems to indicate that the driver is installed.
I've used mysql://user:password#127.0.0.1:3306/database_name and mysql://user:password#localhost:3306/database_name
The error I get is:
"ERROR: Connection failed, please check your connection settings."
I am using image: apache / 'incubator-superset' v. 0.36.0
Are there any settings or config that needs to be changed to be able to communicate to an external database from within a running docker container?
So I figured it out. For Windows, run ipconfig (maybe ifconfig linux, mac) in terminal/powershell and check what ip address docker ethernet port is using (listed as WSL), let's say ip is: 172.x(x).x(x).x(x). Then configure connection string with ip address on docker ethernet port as follows: 'mysql://user:password#172.x(x).x(x).x(x):3306/database_name'.
Follow-up question if anybody knows: How can I connect my docker container running apache/superset to another server/ip address on my local network running a MySQL server? In other words I want to connect the apache/superset app that is running on my computer in a docker container, to another computer on my local network that is running a MySQL server. The MySQL sever is not in a docker container.
maybe the steps of this blog can help.
If your mysql is in other docker it it is not 127.0.0.1 and in addition if you don't want the requirements to be updated every time that you git pull a new docker, it is better to use the requirements-local.txt
You should be able to do that but your MySQL has to have external IP that you can access from your Supserset Machine. First do a telnet to see if you can listen from port 3306 to that machine and if you can Supserset should work with very similar URI that you have.

Can I connect to remote DB server from inside docker container?

My app is running against a mssql server 2012 or above,
I tried to set up 2 containers - 1 for my app and one to be a DB server.
But I couldn't use the DB container due to mssql server version windows image is not supported by my app.
So I'm want to connect to a remote DB server that I have which is a different server than the Docker host.
How do I get the container to ping the remote DB server?
From the container-
C:\Installation>ping my0134.company.net
Ping request could not find host my0134.company.net. Please check the name and try again.
** NOTE - I am using Docker on windows
Maybe you could try adding <IP of my0134.company.net> my0134.company.net to the etc/hosts file. This way the url can be resolved to a IP address. You can also just use
docker run --add-host 'my0134.company.net':<IP of my0134.company.net> <image>
to spin up your container.
If IPV4 forwarding is enabled then container can connect to DB Server.There is no issue with that.

Connecting to Docker container connection refused - but container is running

I am running 2 spring boot applications: A client and rest-api. The client communicates to the rest-api which communicates to a mongodb database. All 3 tiers are running inside docker containers.
I launch the containers normally specifying the exposed ports in the dockerfile and mapping them to a port on the host machine such as: -p 7070:7070, where 7070 is a port exposed in the Dockerfile.
When I run the applications through the java -jar [application_name.war] command, the application works fine and they all can communicate.
However, when I run the applications in a Docker container I get connection refused error, such as when the client tries to connect to the rest-api I get a connection refused error at http://localhost:7070.
But the command docker ps shows that the containers are all running and listening on the exposed and mapped ports.
I have no clue why the containers aren't recognizing that the other containers are running and listening on their ports.
Does this have anything to do with iptables?
Any help is appreciated.
Thanks
EDIT 1: The applications when ran inside containers work fine on my machine, and they don't throw any connection refused errors. The error only happens on that particular different machine.
I used container linking to solve this problem. Make sure you add --link <name>:<alias> at run-time to the container you want linked. <name> is the name of the container you want to link to and <alias> will be the host/domain of an entry in Spring's application.properties file.
Example:
spring.data.mongodb.host=mongodb if the alias supplied at run-time is 'mongodb':
--link myContainerName:mongodb

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