Preserve container logs after startup failure

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

@@ -56,6 +56,7 @@
 import org.testcontainers.utility.DockerLoggerFactory;
 import org.testcontainers.utility.DockerMachineClient;
 import org.testcontainers.utility.DynamicPollInterval;
+import org.testcontainers.utility.LogUtils;
 import org.testcontainers.utility.MountableFile;
 import org.testcontainers.utility.PathUtils;
 import org.testcontainers.utility.ResourceReaper;
@@ -135,6 +136,15 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
 
     private int startupAttempts = 1;
 
+    /**
+     * Log output captured from the container when it failed to start. Kept so that callers can still
+     * inspect it after the failed container has been removed.
+     */
+    @Getter(AccessLevel.NONE)
+    @Setter(AccessLevel.NONE)
+    @Nullable
+    private String logsFromFailedStartup = null;
+
     @Nullable
     private String workingDirectory = null;
 
@@ -302,6 +312,20 @@ public String getContainerId() {
         return containerId;
     }
 
+    /**
+     * {@inheritDoc}
+     * <p>
+     * If the container failed to start it will already have been removed, so the log output that was
+     * captured during the failure is returned instead.
+     */
+    @Override
+    public String getLogs() {
+        if (getContainerId() == null) {
+            return this.logsFromFailedStartup != null ? this.logsFromFailedStartup : "";
+        }
+        return LogUtils.getOutput(getDockerClient(), getContainerId());
+    }
+
     /**
      * Starts the container using docker, pulling an image if necessary.
      */
@@ -539,6 +563,8 @@ private void tryStart() {
             if (containerId != null) {
                 // Log output if startup failed, either due to a container failure or exception (including timeout)
                 final String containerLogs = getLogs();
+                // Keep the logs around: stop() below removes the container, making them unreachable afterwards
+                this.logsFromFailedStartup = containerLogs;
 
                 if (containerLogs.length() > 0) {
                     logger().error("Log output from the failed container:\n{}", containerLogs);

core/src/test/java/org/testcontainers/containers/LogsAfterStartupFailureTest.java

@@ -0,0 +1,30 @@
+package org.testcontainers.containers;
+
+import org.junit.jupiter.api.Test;
+import org.testcontainers.TestImages;
+import org.testcontainers.containers.wait.strategy.Wait;
+
+import java.time.Duration;
+
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
+class LogsAfterStartupFailureTest {
+
+    @Test
+    void shouldKeepLogsAfterStartupFailure() {
+        try (
+            GenericContainer<?> container = new GenericContainer<>(TestImages.TINY_IMAGE)
+                .withCommand("sh", "-c", "echo 'something went wrong'; exit 1")
+                .waitingFor(
+                    Wait.forLogMessage(".*this will never appear.*", 1).withStartupTimeout(Duration.ofSeconds(10))
+                )
+        ) {
+            assertThatThrownBy(container::start).isInstanceOf(ContainerLaunchException.class);
+
+            assertThat(container.getLogs())
+                .as("log output of the failed container is still available after startup failed")
+                .contains("something went wrong");
+        }
+    }
+}