0

I want to unit-test my app which uses a postgres database inside a docker.

EDIT: based on the suggested answer I modified the Dockerfile:

FROM postgres
USER postgres
RUN sleep 2 # remark 1
RUN initdb  # remark 2
RUN sleep 3 # remark 1
RUN psql --host=localhost -l

The remarks are:

Try putting a sleep in there and see if it's still a problem

The default postgres user and database are created in the entrypoint with initdb.

Here is the Dockerfile from the original question:

FROM postgres
COPY input.json .
RUN createdb -h localhost -p 7654 -U moish myLovelyAndTemporaryDb
#
# [ 1 ] run application on input.json
# [ 2 ] check db content after run
#

When I use the above Dockerfile I seem to be missing something: (The errors from the edited version are the same)

$ docker build --tag host --file Dockerfile .
[+] Building 0.3s (7/7) FINISHED                                                                                                       
 => [internal] load build definition from Dockerfile                                                                              0.0s
 => => transferring dockerfile: 125B                                                                                              0.0s
 => [internal] load .dockerignore                                                                                                 0.0s
 => => transferring context: 2B                                                                                                   0.0s
 => [internal] load metadata for docker.io/library/postgres:latest                                                                0.0s
 => [internal] load build context                                                                                                 0.0s
 => => transferring context: 40B                                                                                                  0.0s
 => CACHED [1/3] FROM docker.io/library/postgres                                                                                  0.0s
 => [2/3] COPY input.json .                                                                                                       0.0s
 => ERROR [3/3] RUN createdb -h localhost -p 7654 -U moish myLovelyAndTemporaryDb                                                                0.2s
------
 > [3/3] RUN createdb -h localhost -p 7654 -U moish myLovelyAndTemporaryDb:
#7 0.188 createdb: error: connection to server at "localhost" (127.0.0.1), port 7654 failed: Connection refused
#7 0.188    Is the server running on that host and accepting TCP/IP connections?
#7 0.188 connection to server at "localhost" (::1), port 7654 failed: Cannot assign requested address
#7 0.188    Is the server running on that host and accepting TCP/IP connections?
------
Improve this question
7
  • 1
    A Dockerfile normally constructs a reusable image that you can run containers from; it's not intended as a general-purpose script runner. In the context of a Dockerfile RUN statement, the normal main container process won't be running, and you can't connect to other services. Do you want to run this integration (not unit) test from somewhere else, maybe a test framework entirely outside of Docker? Commented Jan 5, 2023 at 15:31
  • @DavidMaze how would you run a CI/CD pipeline that needs to test such a thing? a docker image isn't always reusable ... Commented Jan 5, 2023 at 16:18
  • I'd write that logic in, say, a Jenkinsfile that plugs into the CI system. Commented Jan 5, 2023 at 17:34
  • @OrenIshShalom It either looks like you are running behind a firewall which block the connection, or the server is actually not running .. Commented Jan 8, 2023 at 13:13
  • @Jib I am trying to access the postgres server from within the docker itself Commented Jan 8, 2023 at 13:55

3 Answers 3

Reset to default
1
+100

Postgres database starts only after you create a container based on postgres image. docker build process doesn't start entrypoint script. You might need a bash script or CI pipeline where you firstly start postgres container and then use it in your unit tests

$ docker run --name mypg -p 5432:5432 -e POSTGRES_PASSWORD=mypgpass -d postgres:9
# copy a script to the mypg container
$ docker cp run.sh mypg:/root/run.sh
# run the script
$ docker exec mypg bash /root/run.sh
...
# use postgres client on your host to connect to mypg container
$ PGPASSWORD="mypgpass" psql -U postgres -p 5432 -h localhost -c "select version()"
                                                               version
--------------------------------------------------------------------------------------------------------------------------------------
 PostgreSQL 9.6.24 on x86_64-pc-linux-gnu (Debian 9.6.24-1.pgdg90+1), compiled by gcc (Debian 6.3.0-18+deb9u1) 6.3.0 20170516, 64-bit
(1 row)

Postgres container docs

Postgres client authentication

EDIT:

By trying to run initdb, psql etc directly in Dockerfile, you are reinventing the docker-entrypoint.sh

Improve this answer
Sign up to request clarification or add additional context in comments.

3 Comments

I want to connect to the dockerized postgres from within the docker image, not from the host.
You can connect to the dockerized postgres (container A) either from a none-dockerized environment (your host system, remote host) or from within another docker container B with you unit test runner. docker build command creates an image, docker run command starts containers based on an image.
what about using docker build up to initdb, then to the rest inside some script that runs in a consecutive docker run? that should work, right?
1

During the build step of the postgres Docker you cannot run postgres commands. Postgres database will only be available after you run the Docker. As specified in the postgres Docker documentation you can add customization to your postgres instance through scripts placed in docker-entrypoint-initdb.d directory.

Alternatively you could use a RUN directive to start the postgres database and after that run the postgres commands you want (making sure to wait for the DB to accept connections), as mentioned here.

Another side note, I personally avoid using real databases for unit testing applications. To me, it's always better to mock the database for unit tests, in python you can do this with unittest.mock.

Improve this answer

2 Comments

I edited the question and tried multiple ways - none worked. I keep getting the same error
This is the proper answer to the question, use docker-entrypoint-initdb.d scripts or switch to proper in memory DB for testing.
0

Here is a complete answer based on the concepts of slava-kuravsky and mello:

$ docker build --tag host --file Dockerfile .
$ docker run -d -t --name pg host
$ docker exec pg bash run.sh

The script can do what I want, currently it only lists the databases:

$ cat run.sh # <--- copied during docker build                                 
echo "Hello Postgres World"
psql --host=localhost -l

The Dockerfile does only initialization:

$ cat Dockerfile 
FROM postgres
USER postgres
COPY run.sh . # <--- the testing script
RUN sleep 2   # <--- probably not needed anymore
RUN initdb
RUN sleep 3   # <--- probably not needed anymore

When I perform the three commands above I get what I expect 🙂 :

$ docker build --tag host --file Dockerfile .
[+] Building 7.2s (10/10) FINISHED                                                                                                     
# ... omitted for brevity ...
$ docker run -d -t --name pg host       
608ac7324e838924c9a5d0cfe65c8000e33350b86faf9df4511ef5fcf7440597
$ docker exec pg bash run.sh                 
Hello Postgres World
                                                List of databases
   Name    |  Owner   | Encoding |  Collate   |   Ctype    | ICU Locale | Locale Provider |   Access privileges   
-----------+----------+----------+------------+------------+------------+-----------------+-----------------------
 postgres  | postgres | UTF8     | en_US.utf8 | en_US.utf8 |            | libc            | 
 template0 | postgres | UTF8     | en_US.utf8 | en_US.utf8 |            | libc            | =c/postgres          +
           |          |          |            |            |            |                 | postgres=CTc/postgres
 template1 | postgres | UTF8     | en_US.utf8 | en_US.utf8 |            | libc            | =c/postgres          +
           |          |          |            |            |            |                 | postgres=CTc/postgres
(3 rows)
Improve this answer

4 Comments

You don't need initdb in your dockerfile, initdb is a part of entrypoint of postgres image and will be executed as soon you start a pg container
Actually you can copy run.sh from the host directly to the running container pg: docker cp run.sh pg:/root/run.sh. So you don't need your dockerfile at all.
@SlavaKuravsky would you like to edit your original answer to have the 1 liner you just suggested? I'd be happy to accept that !
beseder, kvar asiti ;-)

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Start asking to get answers

Find the answer to your question by asking.

Ask question

Explore related questions

See similar questions with these tags.