Make GenericContainer.start() and stop() thread-safe

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

@@ -169,7 +169,7 @@ public class GenericContainer<SELF extends GenericContainer<SELF>>
      */
     @Setter(AccessLevel.NONE)
     @VisibleForTesting
-    String containerId;
+    volatile String containerId;
 
     @Setter(AccessLevel.NONE)
     private InspectContainerResponse containerInfo;
@@ -307,7 +307,7 @@ public String getContainerId() {
      */
     @Override
     @SneakyThrows({ InterruptedException.class, ExecutionException.class })
-    public void start() {
+    public synchronized void start() {
         if (containerId != null) {
             return;
         }
@@ -634,7 +634,7 @@ private void connectToPortForwardingNetwork(String networkMode) {
      * Kill and remove the container.
      */
     @Override
-    public void stop() {
+    public synchronized void stop() {
         if (containerId == null) {
             return;
         }

modules/clickhouse/src/main/java/org/testcontainers/clickhouse/ClickHouseR2DBCDatabaseContainer.java

@@ -24,12 +24,12 @@ public static ConnectionFactoryOptions getOptions(ClickHouseContainer container)
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/junit-jupiter/src/test/java/org/testcontainers/junit/jupiter/ParallelDependsOnTest.java

@@ -0,0 +1,66 @@
+package org.testcontainers.junit.jupiter;
+
+import org.junit.jupiter.api.Test;
+import org.testcontainers.DockerClientFactory;
+import org.testcontainers.containers.GenericContainer;
+import org.testcontainers.lifecycle.Startables;
+import org.testcontainers.utility.DockerImageName;
+
+import java.util.concurrent.atomic.AtomicInteger;
+import java.util.stream.Stream;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+/**
+ * Verifies that concurrent {@link GenericContainer#start()} calls on the same
+ * container do not result in {@link GenericContainer#doStart()} being
+ * called more than once.
+ *
+ * <p>A background thread calls {@code container.start()} during class initialization,
+ * racing with the extension's {@link Startables#deepStart(Stream)} which also starts
+ * the container as part of the {@code @Container} lifecycle.</p>
+ */
+@Testcontainers(parallel = true)
+class ParallelDependsOnTest {
+    static {
+        // Pre-initialize the Docker client to increase the chance of a race
+        // and to emulate a test suite where an earlier test class already
+        // triggered the initialization.
+        DockerClientFactory.instance().client();
+    }
+
+    private static final AtomicInteger doStartCount = new AtomicInteger();
+
+    @Container
+    private static final StartCountingContainer container = new StartCountingContainer(
+        JUnitJupiterTestImages.HTTPD_IMAGE,
+        doStartCount
+    );
+
+    static {
+        // Race with the extension's Startables.deepStart.
+        new Thread(() -> container.start()).start();
+    }
+
+    @Test
+    void containerShouldBeStartedOnlyOnce() {
+        assertThat(container.isRunning()).isTrue();
+        assertThat(doStartCount).as("doStart() invocations").hasValue(1);
+    }
+
+    private static class StartCountingContainer extends GenericContainer<StartCountingContainer> {
+
+        private final AtomicInteger doStartCount;
+
+        StartCountingContainer(DockerImageName image, AtomicInteger doStartCount) {
+            super(image);
+            this.doStartCount = doStartCount;
+        }
+
+        @Override
+        protected void doStart() {
+            doStartCount.incrementAndGet();
+            super.doStart();
+        }
+    }
+}

modules/mariadb/src/main/java/org/testcontainers/mariadb/MariaDBR2DBCDatabaseContainer.java

@@ -42,12 +42,12 @@ public Set<Startable> getDependencies() {
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/mssqlserver/src/main/java/org/testcontainers/mssqlserver/MSSQLR2DBCDatabaseContainer.java

@@ -43,12 +43,12 @@ public Set<Startable> getDependencies() {
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/mysql/src/main/java/org/testcontainers/mysql/MySQLR2DBCDatabaseContainer.java

@@ -42,12 +42,12 @@ public Set<Startable> getDependencies() {
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/oracle-free/src/main/java/org/testcontainers/oracle/OracleR2DBCDatabaseContainer.java

@@ -41,12 +41,12 @@ public Set<Startable> getDependencies() {
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/postgresql/src/main/java/org/testcontainers/postgresql/PostgreSQLR2DBCDatabaseContainer.java

@@ -42,12 +42,12 @@ public Set<Startable> getDependencies() {
     }
 
     @Override
-    public void start() {
+    public synchronized void start() {
         this.container.start();
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         this.container.stop();
     }
 

modules/selenium/src/main/java/org/testcontainers/containers/BrowserWebDriverContainer.java

@@ -351,7 +351,7 @@ public void afterTest(TestDescription description, Optional<Throwable> throwable
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         if (driver != null) {
             try {
                 driver.quit();

modules/selenium/src/main/java/org/testcontainers/selenium/BrowserWebDriverContainer.java

@@ -202,7 +202,7 @@ public void afterTest(TestDescription description, Optional<Throwable> throwable
     }
 
     @Override
-    public void stop() {
+    public synchronized void stop() {
         if (vncRecordingContainer != null) {
             try {
                 vncRecordingContainer.stop();