felipegasper298/mongo-provision repository overview

⁠Mongo Provision

This tool provisions a MongoDB cluster for testing. All nodes of the cluster run in a single container.

⁠Example Usage - Docker Hub

# Start a 3-node replica set:
docker run -it --rm -p27017-27019:27017-27019 felipegasper298/mongo-provision 8.0 --replicaset --nodes 3

# … or, for a sharded cluster:
docker run -it --rm -p27017:27017 felipegasper298/mongo-provision 8.0 --replicaset --sharded 3 --nodes 3

The above will hang indefinitely until you kill it, e.g., via CTRL-C.

Then, in another terminal, run:

# for the replset:
mongosh mongodb://localhost:27017,localhost:27018,localhost:27019

# … or, for sharded:
mongosh mongodb://localhost:27017

… and you’re in!

⁠Example Usage - Local

Build the container:

docker build . -t mongo-provision

… then it’s the same as the above but with a local mongo-provision image instead of felipegasper298/mongo-provision.

⁠Syntax

The arguments to the container are:

• a version number (e.g., 8.0) to give to m⁠
• args for mtools⁠’s init subcommand

⁠Preserving state

This container stores its state (e.g., mongod data files) under /data. To introspect that state outside the container, mount a volume to that path in the container.

⁠Pre-downloaded binaries

The container will, on startup, check whether /data/bin/mongod exists. If it does, and if its version matches the one given in the container’s arguments, that binary will be used rather than downloading a new one.

If the supplied binary’s version mismatches the container’s arguments, the container will exit in error.

To use pre-downloaded binaries to start a sharded cluster, provide both /data/bin/mongod and /data/bin/mongos. (The given mongos must match its mongod.)

⁠Readiness checks

To check whether the cluster is ready, exec into the container and check if the ready file exists. For example:

while ! docker exec my-container-name [ -e ready ]; do
    echo "Still waiting for cluster to be ready …"
    sleep 1
done

The ready file is a JSON file with the following data points:

• connection_string (mongoses for sharded clusters)
• shards: a dictionary of shard name to connection string

⁠Caveats

• You MUST anticipate the bound ports and export them.
• The container’s platform will dictate server version availability. For example, you can’t create pre-v5 clusters on Linux/ARM64 because no official builds were made for that version/platform combination. (Try --platform linux/amd64 on multi-platform container engines.)

⁠Acknowledgements

This uses:

• mtools⁠
• m⁠