fix(backfill-ci): revert to CQL-log wait and make the c4 logback log to stdout

The host-side CQL-port probe regressed all 9 Kafka backfill jobs (c3/dse4 had
passed with the log wait). A host-side TCP connect to a mapped port is
unreliable: Docker's port forwarding can accept the connection before
Cassandra has bound 9042, so the wait returns prematurely and getCqlSession()
then fails -- across every family.

Revert to the proven "Starting listening for CQL clients" log wait, and fix
the actual c4 outlier: its config-override logback.xml had every root
appender-ref (including STDOUT) commented out, so Cassandra 4.0.4 logged
nothing to the container stdout and the log wait never matched. Re-enable the
STDOUT appender so c4 emits the readiness line like c3/dse4 already do.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

Author: Madhavan

backfill-cli/src/test/resources/c4/logback.xml

@@ -90,7 +90,7 @@ appender reference in the root level section below.
 
     <root level="INFO">
         <!--        <appender-ref ref="SYSTEMLOG" />-->
-        <!--        <appender-ref ref="STDOUT" />-->
+        <appender-ref ref="STDOUT" />
         <!--        <appender-ref ref="DEBUGLOG" /> &lt;!&ndash; Comment this line to disable debug.log &ndash;&gt;-->
         <!--
         <appender-ref ref="LogbackMetrics" />

testcontainers/src/main/java/com/datastax/testcontainers/cassandra/CassandraContainer.java

@@ -30,15 +30,13 @@
 import org.testcontainers.delegate.DatabaseDelegate;
 import org.testcontainers.ext.ScriptUtils;
 import org.testcontainers.ext.ScriptUtils.ScriptLoadException;
-import org.testcontainers.containers.ContainerLaunchException;
-import org.testcontainers.containers.wait.strategy.AbstractWaitStrategy;
+import org.testcontainers.containers.wait.strategy.Wait;
 import org.testcontainers.utility.DockerImageName;
 import org.testcontainers.utility.MountableFile;
 
 import javax.script.ScriptException;
 import java.io.IOException;
 import java.net.InetSocketAddress;
-import java.net.Socket;
 import java.net.URL;
 import java.nio.charset.StandardCharsets;
 import java.time.Duration;
@@ -275,12 +273,13 @@ public static CassandraContainer<?> createCassandraContainer(DockerImageName ima
                 .withEnv("MAX_HEAP_SIZE", "1500m")
                 .withEnv("HEAP_NEWSIZE", "300m")
                 .withEnv("DS_LICENSE", "accept")
-                // Wait only on the CQL port. The default strategy waits for ALL exposed ports,
-                // including the debug port (8000) that the agent-based factories open via the JVM
-                // debug agent but a no-agent node never does. A log-message strategy is also unusable
-                // here because some config-override logback.xml files (e.g. c4) route Cassandra
-                // output to file only, leaving stdout empty.
-                .waitingFor(new CqlPortWaitStrategy().withStartupTimeout(Duration.ofSeconds(180)))
+                // The base container exposes the debug port (8000) alongside CQL (9042) and JMX
+                // (7199); the default strategy waits for ALL exposed ports, but a no-agent node never
+                // opens 8000 (only the JVM debug agent does). Wait on the CQL-readiness log line
+                // instead. This requires the mounted logback.xml to log to stdout (the c3/c4/dse4
+                // config overrides all enable the STDOUT appender).
+                .waitingFor(Wait.forLogMessage(".*Starting listening for CQL clients.*", 1)
+                        .withStartupTimeout(Duration.ofSeconds(180)))
                 .withStartupTimeout(Duration.ofSeconds(180));
         if (nodeIndex > 1) {
             cassandraContainer.withEnv("CASSANDRA_SEEDS", "cassandra-1");   // for Cassandra
@@ -289,36 +288,6 @@ public static CassandraContainer<?> createCassandraContainer(DockerImageName ima
         return cassandraContainer;
     }
 
-    /**
-     * Waits until the CQL native-transport port (9042) accepts TCP connections from the host.
-     * Targets only the CQL port so it does not block on the always-exposed-but-unused debug port
-     * (8000), and does not depend on Cassandra writing to stdout (some config-override logback.xml
-     * files log to file only).
-     */
-    private static class CqlPortWaitStrategy extends AbstractWaitStrategy {
-        @Override
-        protected void waitUntilReady() {
-            final String host = waitStrategyTarget.getHost();
-            final int port = waitStrategyTarget.getMappedPort(CQL_PORT);
-            final long deadline = System.currentTimeMillis() + startupTimeout.toMillis();
-            while (System.currentTimeMillis() < deadline) {
-                try (Socket socket = new Socket()) {
-                    socket.connect(new InetSocketAddress(host, port), 2000);
-                    return;
-                } catch (IOException notReadyYet) {
-                    try {
-                        Thread.sleep(1000);
-                    } catch (InterruptedException ie) {
-                        Thread.currentThread().interrupt();
-                        throw new ContainerLaunchException("Interrupted while waiting for the CQL port", ie);
-                    }
-                }
-            }
-            throw new ContainerLaunchException(
-                    "Timed out waiting for the CQL port (" + CQL_PORT + ") to accept connections");
-        }
-    }
-
     public static CassandraContainer<?> createCassandraContainerWithAgent(DockerImageName image,
                                                                           Network network,
                                                                           int nodeIndex,