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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.