Spin Up Docker Mongo With Replica Set

Question

For automation tests, both locally and on build servers, I'm trying to spin up a mongo image with a replica set (I need the oplog).

The replica set setup requires me to get into the mongo shell and call "rs.initiate()". I want this all done in code.

public void SpinUpMongoWithReplicaSet()
{
    Process.Start("docker", "run -p 123:27017 --name test_mongo -d mongo:latest mongod --replSet rs0").WaitForExit();

    var replicaSetProcess = new Process
    {
        StartInfo = new ProcessStartInfo
        {
            FileName = "docker",
            Arguments = "exec -it test_mongo mongo",
            UseShellExecute = false,
            RedirectStandardInput = true
        }
    };

    replicaSetProcess.Start();

    using(StreamWriter writer = replicaSetProcess.StandardInput)
    {
        writer.WriteLine("rs.initiate()");
        writer.WriteLine("exit");
    }

    replicaSetProcess.WaitForExit();
}

However, the problem with the docker exec command.

When passing in -it or just -t, I get the following error:

the input device is not a TTY. If you are using mintty, try prefixing the command with 'winpty'

The only solution I could find is to only pass in the -i flag. For whatever reason, this then prevents me from connecting to the mongo container:

MongoDB shell version v3.4.9 connecting to: mongodb://127.0.0.1:27017 2017-10-06T18:25:06.765+0000 W NETWORK [thread1] Failed to connect to 127.0.0.1:27017, in(checking socket for error after poll), reason: Connection refused 2017-10-06T18:25:06.765+0000 E QUERY [thread1] Error: couldn't connect to server 127.0.0.1:27017, connection attempt failed : connect@src/mongo/shell/mongo.js:237:13 @(connect):1:6 exception: connect failed

Does anyone have any experience in executing commands on docker images within C# code?

For reference: this is a good guide to setting up a mongo replica set server with docker, but from the command line. Docker Replica Set Setup

Brenton Hawley Brenton Hawley · Accepted Answer · 2017-10-09T16:39:50

Turns out that Mongo has a way of evaluating text using the --eval flag.

This allows us to avoid using both -i and -t flags. In this manner, the Process.Start() function will be sufficient.

Solution:

Process.Start("docker", "exec test_mongo mongo --eval \"rs.initiate()\"").WaitForExit();

Spin Up Docker Mongo With Replica Set

1 Answers