Waiting for containers to start or be ready

Wait strategies vs Startup strategies

Wait strategy: is the container in a state that is useful for testing. This is generally approximated as 'can we talk to this container over the network'. However, there are quite a few variations and nuances.

Startup strategy: did a container reach the desired running state. Almost always this just means 'wait until the container is running' - for a daemon process in a container this is the goal. Sometimes we need to wait until the container reaches a running state and then exits - this is the 'one shot startup' strategy, only used for cases where we need to run a one off command in a container but not a daemon.

Wait Strategies

Ordinarily Testcontainers will wait for up to 60 seconds for the container's first mapped network port to start listening.

This simple measure provides a basic check whether a container is ready for use.

public GenericContainer nginx = new GenericContainer("nginx:1.9.4")
    .withExposedPorts(80);

If the default 60s timeout is not sufficient, it can be altered with the withStartupTimeout() method.

If waiting for a listening TCP port is not sufficient to establish whether the container is ready, you can use the waitingFor() method with other WaitStrategy implementations as shown below.

HTTP Wait strategy examples

You can choose to wait for an HTTP(S) endpoint to return a particular status code.

Waiting for 200 OK

public GenericContainer nginxWithHttpWait = new GenericContainer("nginx:1.9.4")
    .withExposedPorts(80)
    .waitingFor(Wait.forHttp("/"));

Variations on the HTTP wait strategy are supported, including:

Waiting for multiple possible status codes

Wait.forHttp("/")
    .forStatusCode(200)
    .forStatusCode(301)

Waiting for a status code that matches a predicate

Wait.forHttp("/all")
    .forStatusCodeMatching(it -> it >= 200 && it < 300 || it == 401)

Using TLS

Wait.forHttp("/all")
    .usingTls()

Healthcheck Wait strategy examples

If the used image supports Docker's Healthcheck feature, you can directly leverage the healthy state of the container as your wait condition:

Wait.forHealthcheck()

Log output Wait Strategy

In some situations a container's log output is a simple way to determine if it is ready or not. For example, we can wait for a `Ready' message in the container's logs as follows:

public GenericContainer containerWithLogWait = new GenericContainer("redis:5.0.3")
    .withExposedPorts(6379)
    .waitingFor(
        Wait.forLogMessage(".*Ready to accept connections.*\\n", 1)
    );

Other Wait Strategies

For further options, check out the Wait convenience class, or the various subclasses of WaitStrategy.

If none of these options meet your requirements, you can create your own subclass of AbstractWaitStrategy with an appropriate wait mechanism in waitUntilReady(). The GenericContainer.waitingFor() method accepts any valid WaitStrategy.

Startup check Strategies

Ordinarily Testcontainers will check that the container has reached the running state and has not exited. In order to do that inspect is executed against the container and state parameter is extracted.

All logic is implemented in StartupCheckStrategy child classes.

Running startup strategy example

This is the strategy used by default. Testcontainers just checks if container is running.

Implemented in IsRunningStartupCheckStrategy class.

One shot startup strategy example

This strategy is intended for use with containers that only run briefly and exit of their own accord. As such, success is deemed to be when the container has stopped with exit code 0.

public GenericContainer bboxWithOneShot = new GenericContainer("busybox:1.31.1")
    .withCommand(String.format("echo %s", HELLO_TESTCONTAINERS))
    .withStartupCheckStrategy(
        new OneShotStartupCheckStrategy().withTimeout(Duration.ofSeconds(3))
    );

Indefinite one shot startup strategy example

Variant of one shot strategy that does not impose a timeout. Intended for situation such as when a long running task forms part of container startup.

It has to be assumed that the container will stop of its own accord, either with a success or failure exit code.

public GenericContainer bboxWithIndefiniteOneShot = new GenericContainer("busybox:1.31.1")
    .withCommand("sh", "-c", String.format("sleep 5 && echo \"%s\"", HELLO_TESTCONTAINERS))
    .withStartupCheckStrategy(
        new IndefiniteWaitOneShotStartupCheckStrategy()
    );

Minimum duration startup strategy example

Checks that the container is running and has been running for a defined minimum period of time.

public GenericContainer bboxWithMinimumDuration = new GenericContainer("busybox:1.31.1")
    .withCommand("sh", "-c", String.format("sleep 5 && echo \"%s\"", HELLO_TESTCONTAINERS))
    .withStartupCheckStrategy(
        new MinimumDurationRunningStartupCheckStrategy(Duration.ofSeconds(1))
    );

Other startup strategies

If none of these options meet your requirements, you can create your own subclass of StartupCheckStrategy with an appropriate startup check mechanism in waitUntilStartupSuccessful(). Or you can leave it as is and just implement the checkStartupState(DockerClient dockerClient, String containerId) if you still want to check state periodically.