Add interface to customize CreateContainerCmd (#7421)

Add `CreateContainerCmdModifier` interface to customize
`CreateContainerCmd`. Customization is applied after Testcontainers
configuration is set.

Author: eddumelendez

core/src/main/java/org/testcontainers/containers/GenericContainer.java

@@ -48,6 +48,7 @@
 import org.testcontainers.containers.wait.strategy.Wait;
 import org.testcontainers.containers.wait.strategy.WaitStrategy;
 import org.testcontainers.containers.wait.strategy.WaitStrategyTarget;
+import org.testcontainers.core.CreateContainerCmdModifier;
 import org.testcontainers.images.ImagePullPolicy;
 import org.testcontainers.images.RemoteDockerImage;
 import org.testcontainers.images.builder.Transferable;
@@ -88,6 +89,7 @@
 import java.util.Map.Entry;
 import java.util.Objects;
 import java.util.Optional;
+import java.util.ServiceLoader;
 import java.util.Set;
 import java.util.UUID;
 import java.util.concurrent.ExecutionException;
@@ -203,7 +205,6 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
 
     /**
      * Set during container startup
-     *
      */
     @Setter(AccessLevel.NONE)
     @VisibleForTesting
@@ -220,8 +221,6 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
 
     private List<Consumer<OutputFrame>> logConsumers = new ArrayList<>();
 
-    private final Set<Consumer<CreateContainerCmd>> createContainerCmdModifiers = new LinkedHashSet<>();
-
     private static final Set<String> AVAILABLE_IMAGE_NAME_CACHE = new HashSet<>();
 
     private static final RateLimiter DOCKER_CLIENT_RATE_LIMITER = RateLimiterBuilder
@@ -238,6 +237,19 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
 
     private boolean hostAccessible = false;
 
+    private final Set<CreateContainerCmdModifier> createContainerCmdModifiers = loadCreateContainerCmdCustomizers();
+
+    private Set<CreateContainerCmdModifier> loadCreateContainerCmdCustomizers() {
+        ServiceLoader<CreateContainerCmdModifier> containerCmdCustomizers = ServiceLoader.load(
+            CreateContainerCmdModifier.class
+        );
+        Set<CreateContainerCmdModifier> loadedCustomizers = new LinkedHashSet<>();
+        for (CreateContainerCmdModifier customizer : containerCmdCustomizers) {
+            loadedCustomizers.add(customizer);
+        }
+        return loadedCustomizers;
+    }
+
     public GenericContainer(@NonNull final DockerImageName dockerImageName) {
         this.image = new RemoteDockerImage(dockerImageName);
     }
@@ -890,7 +902,9 @@ private void applyConfiguration(CreateContainerCmd createCommand) {
             createCommand.withPrivileged(privilegedMode);
         }
 
-        createContainerCmdModifiers.forEach(hook -> hook.accept(createCommand));
+        for (CreateContainerCmdModifier createContainerCmdModifier : this.createContainerCmdModifiers) {
+            createCommand = createContainerCmdModifier.modify(createCommand);
+        }
 
         Map<String, String> combinedLabels = new HashMap<>();
         combinedLabels.putAll(labels);
@@ -1491,12 +1505,16 @@ public SELF withStartupAttempts(int attempts) {
      * @return this
      */
     public SELF withCreateContainerCmdModifier(Consumer<CreateContainerCmd> modifier) {
-        createContainerCmdModifiers.add(modifier);
+        this.createContainerCmdModifiers.add(cmd -> {
+                modifier.accept(cmd);
+                return cmd;
+            });
         return self();
     }
 
     /**
      * Size of /dev/shm
+     *
      * @param bytes The number of bytes to assign the shared memory. If null, it will apply the Docker default which is 64 MB.
      * @return this
      */
@@ -1507,6 +1525,7 @@ public SELF withSharedMemorySize(Long bytes) {
 
     /**
      * First class support for configuring tmpfs
+     *
      * @param mapping path and params of tmpfs/mount flag for container
      * @return this
      */

core/src/main/java/org/testcontainers/core/CreateContainerCmdModifier.java

@@ -0,0 +1,13 @@
+package org.testcontainers.core;
+
+import com.github.dockerjava.api.command.CreateContainerCmd;
+
+/**
+ * Callback interface that can be used to customize a {@link CreateContainerCmd}.
+ */
+public interface CreateContainerCmdModifier {
+    /**
+     * Callback to modify a {@link CreateContainerCmd} instance.
+     */
+    CreateContainerCmd modify(CreateContainerCmd createContainerCmd);
+}

core/src/test/java/org/testcontainers/custom/TestCreateContainerCmdModifier.java

@@ -0,0 +1,18 @@
+package org.testcontainers.custom;
+
+import com.github.dockerjava.api.command.CreateContainerCmd;
+import org.testcontainers.core.CreateContainerCmdModifier;
+
+import java.util.HashMap;
+import java.util.Map;
+
+public class TestCreateContainerCmdModifier implements CreateContainerCmdModifier {
+
+    @Override
+    public CreateContainerCmd modify(CreateContainerCmd createContainerCmd) {
+        Map<String, String> labels = new HashMap<>();
+        labels.put("project", "testcontainers-java");
+        labels.put("scope", "global");
+        return createContainerCmd.withLabels(labels);
+    }
+}

core/src/test/java/org/testcontainers/junit/GenericContainerRuleTest.java

@@ -264,6 +264,7 @@ public void customLabelTest() {
             final GenericContainer alpineCustomLabel = new GenericContainer<>(TestImages.ALPINE_IMAGE)
                 .withLabel("our.custom", "label")
                 .withCommand("top")
+                .withCreateContainerCmdModifier(cmd -> cmd.getLabels().put("scope", "local"))
         ) {
             alpineCustomLabel.start();
 
@@ -278,6 +279,10 @@ public void customLabelTest() {
                 .containsKey("org.testcontainers.version");
             assertThat(labels).as("our.custom label is present").containsKey("our.custom");
             assertThat(labels).as("our.custom label value is label").containsEntry("our.custom", "label");
+            assertThat(labels)
+                .as("project label value is testcontainers-java")
+                .containsEntry("project", "testcontainers-java");
+            assertThat(labels).as("scope label value is local").containsEntry("scope", "local");
         }
     }
 

core/src/test/resources/META-INF/services/org.testcontainers.core.CreateContainerCmdModifier

@@ -0,0 +1 @@
+org.testcontainers.custom.TestCreateContainerCmdModifier

docs/features/advanced_options.md

@@ -33,6 +33,8 @@ It is possible to specify an Image Pull Policy to determine at runtime whether a
 
 ## Customizing the container
 
+### Using docker-java
+
 It is possible to use the [`docker-java`](https://github.com/docker-java/docker-java) API directly to customize containers before creation. This is useful if there is a need to use advanced Docker features that are not exposed by the Testcontainers API. Any customizations you make using `withCreateContainerCmdModifier` will be applied _on top_ of the container definition that Testcontainers creates, but before it is created.
 
 For example, this can be used to change the container hostname:
@@ -53,6 +55,20 @@ For example, this can be used to change the container hostname:
 
 For what is possible, consult the [`docker-java CreateContainerCmd` source code](https://github.com/docker-java/docker-java/blob/3.2.1/docker-java-api/src/main/java/com/github/dockerjava/api/command/CreateContainerCmd.java).
 
+### Using CreateContainerCmdModifier
+
+Testcontainers provides a `CreateContainerCmdModifier` to customize [`docker-java CreateContainerCmd`](https://github.com/docker-java/docker-java/blob/3.2.1/docker-java-api/src/main/java/com/github/dockerjava/api/command/CreateContainerCmd.java)
+via Service Provider Interface (SPI) mechanism.
+
+<!--codeinclude-->
+[CreateContainerCmd example implementation](../../core/src/test/java/org/testcontainers/custom/TestCreateContainerCmdModifier.java)
+<!--/codeinclude-->
+
+The previous implementation should be registered in `META-INF/services/org.testcontainers.core.CreateContainerCmdModifier` file.
+
+!!! warning
+    `CreateContainerCmdModifier` implementation will apply to all containers created by Testcontainers.
+
 ## Parallel Container Startup
 
 Usually, containers are started sequentially when more than one container is used.