Testcontainers-java: Unable to pass --sysctl flag value when starting container

[kdrozd]

Hi,

Some of my containers need to be started with specific --sysctl flags. I don't see any option to pass this values to GenericContainer on creation.

[rnorth]

Unfortunately we'd rely on the docker-java library supporting sysctl flags, but based on a quick search of that library's repo and this issue, I think it's not supported yet: docker-java/docker-java#1078.

If we/you/somebody contribute sysctl flag support to docker-java, then it would be easy to use through testcontainers via the withCreateCmdModifier method (since I think it's niche enough that we shouldn't add sysctl support explicitly to the Testcontainers API.

[kdrozd]

Hi,

I looked at it and... CreateContainerCmd can take HostConfig as one of the parameters. This works for my needs. This is available in 3.1.x version, I tested it with 3.1.0-rc-7.
`
DockerClient dockerClient = DockerClientBuilder.getInstance().build();

    HostConfig hc = new HostConfig();
    Map<String,String> sysctls = new HashMap<>();
    sysctls.put("kernel.msgmnb","1234");
    sysctls.put("kernel.msgmni", "123");
    sysctls.put("kernel.msgmax", "1234");

    ExposedPort tcp1920 = ExposedPort.tcp(1920);

    Ports portBindings = new Ports();
    portBindings.bind(tcp1920, Ports.Binding.bindPort(1920));

    hc.withSysctls(sysctls);
    hc.withPortBindings(portBindings);
    hc.withPublishAllPorts(true);
    CreateContainerResponse container = dockerClient.createContainerCmd("kdappsr")
            .withHostConfig(hc).withExposedPorts(tcp1920).exec();

    dockerClient.startContainerCmd(container.getId()).exec();

`

I'll check how this will work with testcontainers.

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[stale[bot]]

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[nastra]

According to the docs from here and in the context of TestContainers, specifying sysctl settings should be possible via withCreateContainerCmdModifier(..):

HostConfig hc = new HostConfig();
Map<String,String> sysctls = new HashMap<>();
sysctls.put("kernel.msgmnb","1234");
sysctls.put("kernel.msgmni", "123");
sysctls.put("kernel.msgmax", "1234");

public GenericContainer container = new GenericContainer<>(DockerImageName.parse("redis:3.0.2"))
        .withCreateContainerCmdModifier(cmd -> cmd.withHostConfig(hostConfig));

[bsideup]

@nastra precisely! Thanks for posting an example 👍