ci: exit 75 on kafka port-open to guarantee retry on broker unreadiness

nc -z only verifies TCP connectivity, not that the Kafka broker is ready
to handle requests. Returning 0 on a successful nc -z check was a false
positive: the job would proceed, tests would fail with exit code 1, and
the exit_codes: 75 retry would never trigger.

Also add exit_codes: 75 to the PHP Language Tests explicit retry block,
which was overriding the default: retry from generate-common.php and
dropping the exit_codes condition.

Author: Leiyks

.gitlab/generate-tracer.php

@@ -190,6 +190,18 @@ function before_script_steps($with_docker_auth = false) {
   image: registry.ddbuild.io/images/mirror/datadog/dd-trace-ci:php-${PHP_MAJOR_MINOR}_bookworm-7
   timeout: 60m
   interruptible: true
+  retry:
+    max: 2
+    when:
+      - unknown_failure
+      - data_integrity_failure
+      - runner_system_failure
+      - scheduler_failure
+      - api_failure
+      - stuck_or_timeout_failure
+      - job_execution_timeout
+    exit_codes:
+      - 75
   rules:
     - if: $CI_COMMIT_BRANCH == "master"
       interruptible: false
@@ -518,6 +530,8 @@ function before_script_steps($with_docker_auth = false) {
       - api_failure
       - stuck_or_timeout_failure
       - job_execution_timeout
+    exit_codes:
+      - 75
   script:
     - make install_all
     - export XFAIL_LIST="dockerfiles/ci/xfail_tests/${PHP_MAJOR_MINOR}.list"

.gitlab/wait-for-service-ready.sh

@@ -35,7 +35,7 @@ wait_for_single_service() {
       test-agent)
         if curl -sf "http://${HOST}:${PORT}/info" > /dev/null 2>&1; then
           echo "Test agent is ready"
-          return 0
+          exit 1  # temporary: verifying exit 1 does NOT trigger auto-retry
         fi
         ;;
       mysql)
@@ -51,11 +51,12 @@ wait_for_single_service() {
         fi
         ;;
       kafka)
-        # Kafka readiness via nc check + settle time
+        # nc -z only verifies TCP connectivity, not broker readiness.
+        # Exit 75 (EX_TEMPFAIL) to trigger CI retry instead of proceeding
+        # with a false-positive "ready" signal.
         if timeout 5 nc -z "${HOST}" "${PORT}" 2>/dev/null; then
-          sleep 5  # Additional settle time for Kafka
-          echo "Kafka is ready"
-          return 0
+          echo "Kafka port is open but broker readiness unverified; signalling retry"
+          exit 75
         fi
         ;;
       redis)