The following table lists the metrics that are gathered as output from Varnish checks. Entries indicated as Featured metrics are high-visibility metrics that are displayed in the Operator Workspace Metric tab after an alert is generated. These metrics provide the operator with additional information to help them further explore the specified issue.

Table 1. Varnish metrics

Metric type	Resource (name of specific database, where relevant)	Units	Metric type description
MAIN_sess_conn (featured metric)		count	Cumulative number of accepted client connections by Varnish Cache.
MAIN_sess_drop (featured metric)		count	Number of connections dropped due to a full queue.
MAIN_client_req (featured metric)		count	Cumulative number of received client requests. Increments after a request is received, but before Varnish responds.
MAIN_cache_hit		count	Cumulative number of times a file was served from Varnish’s cache.
MAIN_cache_hitpass		count	Cumulative number of hits for a “pass” file.
MAIN_cache_miss		count	Cumulative number of times a file was requested but was not in the cache, and was therefore requested from the backend.
MAIN_backend_conn		count	Cumulative number of successful TCP connections to the backend.
MAIN_backend_unhealthy (featured metric)		count	Cumulative number of backend connections which were not attempted because the backend has been marked as unhealthy.
MAIN_backend_busy		count	Cumulative number of times the maximum amount of connections to the backend has been reached.
MAIN_backend_fail (featured metric)		count	Cumulative number of failed connections to the backend.
MAIN_backend_reuse (featured metric)		count	Cumulative number of connections that were reused from the keep-alive pool.
MAIN_backend_recycle		count	Cumulative number of current backend connections which were put back to a pool of keep-alive connections and have not yet been used.
MAIN_threads (featured metric)		count	Number of threads in all pools.
MAIN_threads_limited		count	Number of times a thread needed to be created but couldn't because varnishd maxed out its configured capacity for new threads.
MAIN_threads_created		count	Number of times a thread has been created.
MAIN_threads_failed (featured metric)		count	Number of times that Varnish unsuccessfully tried to create a thread.
MAIN_thread_queue_len		count	Current queue length: number of requests waiting on worker thread to become available.
MAIN_sess_queued		count	Number of times Varnish has been out of threads and had to queue up a request.
MAIN_n_expired (featured metric)		count	Cumulative number of expired objects for example due to TTL.
MAIN_n_lru_nuked (featured metric)		count	Least Recently Used Nuked Objects: Cumulative number of cached objects that Varnish has evicted from the cache because of a lack of space.
MAIN_backend_req (featured metric)		count	Number of requests to the backend.