Upgrade CI Mongo server version

[gencurrent]

When testing async Mongo caching on CI, I end up with this error:

E           pymongo.errors.ConfigurationError: Server at 127.0.0.1:27019 reports wire version 7, but this version of PyMongo requires at least 8 (MongoDB 4.2).

Report example:

• https://github.com/python-cachier/cachier/actions/runs/22005125468/job/63587027714?pr=334

Can we upgrade the Mongo server version in the CI environment?

[shaypal5]

We're using the following code to start MongoDB in Docker:

- name: Start MongoDB in docker
        if: matrix.backend == 'mongodb'
        run: |
          # start MongoDB in a container
          docker run -d -p ${{ env.CACHIER_TEST_PORT }}:27017 --name mongodb mongo:latest
          # wait for MongoDB to start, which is in average 5 seconds
          sleep 5
          # show running containers
          docker ps -a

Doesn't this mean we're already using the latest Docker image for MongoDB?

[gencurrent]

@shaypal5 TY and sorry for a long response.
According to Claude:

Yes, that's very likely the root cause. Here's what's happening:
The mongo:latest trap. Even though the workflow uses mongo:latest, GitHub Actions runners aggressively cache Docker images. If the runner's cached layer for mongo:latest is stale, it won't pull the actual latest from Docker Hub unless the cache is explicitly invalidated or docker pull mongo:latest is called before docker run. So the CI ends up running an old MongoDB version despite the latest tag.

So we can at least try to replace mongo:latest with mongo:8.0.

[gencurrent]

After this is resolved, I can upgrade the tests to work over the newest version of Mongo.

[shaypal5]

Isn't it better to just manually invalidate/refresh the cache explicitly? @gencurrent

[shaypal5]

@copilot what do you think? Can we have something to refresh the docker images used in our CI once a month or something? Like a monthly workflow? Or in the regular CI, something that refreshes the cache on the first of every month?

[shaypal5]

Oh, ok. I get it. We actually WANT to pin MongoDB to 8.0 in the CI.