Improve exporter metric emission logging

monitoring/docker-exporter/exporter.py

@@ -44,6 +44,29 @@ LAST_CHECK = Gauge(
     "Last time the update check ran (unix timestamp)"
 )
 
+
+def set_container_update_metric(container_name, compose_image, running_image, project_name, update_flag):
+    """Set update metric for a container and log the emitted metric payload."""
+    metric_labels = {
+        "container": container_name,
+        "compose_image": compose_image or "unknown",
+        "running_image": running_image,
+        "com_docker_compose_project": project_name,
+    }
+    CONTAINER_UPDATE.labels(**metric_labels).set(update_flag)
+    logger.info(
+        "Metric emitted: docker_container_update_available=%s labels=%s",
+        update_flag,
+        metric_labels,
+    )
+
+
+def set_last_check_metric():
+    """Set and log the timestamp for the most recent check cycle."""
+    ts = time.time()
+    LAST_CHECK.set(ts)
+    logger.info("Metric emitted: docker_image_update_last_check_timestamp=%s", ts)
+
 # --- Persistent Cache ---
 def load_cache():
     if not os.path.exists(CACHE_FILE):
@@ -380,6 +403,8 @@ def check_containers():
     if client is None:
         logger.error("Docker client is unavailable; skipping check cycle")
         return
+
+    set_last_check_metric()
     CONTAINER_UPDATE.clear()
 
     project_name = parse_project_name_from_script(SERVICES_UP_SCRIPT)
@@ -409,12 +434,13 @@ def check_containers():
         if local_digest and remote_digest and local_digest != remote_digest:
             update_flag = 1
 
-        CONTAINER_UPDATE.labels(
-            container=container.name,
-            compose_image=compose_image or "unknown",
+        set_container_update_metric(
+            container_name=container.name,
+            compose_image=compose_image,
             running_image=running,
-            com_docker_compose_project=proj
-        ).set(update_flag)
+            project_name=proj,
+            update_flag=update_flag,
+        )
 
 def dump_service_image_mapping():
     project_name = parse_project_name_from_script(SERVICES_UP_SCRIPT)