chore: prom count task retry in celery (#17635)

posthog/celery.py

@@ -6,7 +6,15 @@
 
 from celery import Celery
 from celery.schedules import crontab
-from celery.signals import setup_logging, task_postrun, task_prerun, worker_process_init, task_success, task_failure
+from celery.signals import (
+    setup_logging,
+    task_postrun,
+    task_prerun,
+    worker_process_init,
+    task_success,
+    task_failure,
+    task_retry,
+)
 from django.conf import settings
 from django.db import connection
 from django.dispatch import receiver
@@ -43,6 +51,12 @@
     labelnames=["task_name"],
 )
 
+CELERY_TASK_RETRY_COUNTER = Counter(
+    "posthog_celery_task_retry",
+    "task retry signal is dispatched when a task will be retried.",
+    labelnames=["task_name"],
+)
+
 # Using a string here means the worker doesn't have to serialize
 # the configuration object to child processes.
 # - namespace='CELERY' means all celery-related configuration keys
@@ -242,6 +256,11 @@ def failure_signal_handler(sender, **kwargs):
     CELERY_TASK_FAILURE_COUNTER.labels(task_name=sender.name).inc()
 
 
+@task_retry.connect
+def retry_signal_handler(sender, **kwargs):
+    CELERY_TASK_RETRY_COUNTER.labels(task_name=sender.name).inc()
+
+
 @task_postrun.connect
 def teardown_instrumentation(task_id, task, **kwargs):
     from posthog.clickhouse.query_tagging import reset_query_tags