backend_connection failed

[Ashish Nepal]

Hi can anyone suggeset why i get backend connection failed when N-Worker_thread goes anything above default of 100 worker_thread?

While trying to create 491 thread in peak it was unable to connect to backend.whereas, backend servers were not in load or anything.
As i understood, while thread max is 1000 * 2[pools], and varnish server load is below 1, theoritically it should be able to handle that many spikes, And i would not see why backend would fail here.
Also, Due to demand of use, it is designed to cache 1s to 5s at most.

n_worker_thread = 100 , all goodn_worker_thread = 491 , 8 backend_connection failure.

varnishadm
thread_pool_add_delay       2 [milliseconds]thread_pool_add_threshold   2 [requests]thread_pool_fail_delay      200 [milliseconds]thread_pool_max             1000 [threads]thread_pool_min             50 [threads]thread_pool_purge_delay     1000 [milliseconds]thread_pool_stack           unlimited [bytes]thread_pool_timeout         120 [seconds]thread_pool_workspace       65536 [bytes]thread_pools                2 [pools]thread_stats_rate           10 [requests]

varnishstat32+03:45:05Hitrate ratio:        2        2        2Hitrate avg:     0.9404   0.9404   0.9404

backend_conn           4516262         1.63 Backend conn. successbackend_unhealthy            0         0.00 Backend conn. not attemptedbackend_busy                 0         0.00 Backend conn. too manybackend_fail              9562         0.00 Backend conn. failuresbackend_reuse         67350518        24.24 Backend conn. reusesbackend_toolate         361647         0.13 Backend conn. was closedbackend_recycle       67715544        24.38 Backend conn. recyclesbackend_retry             5133         0.00 Backend conn. retryn_backend                    5          .   N backendsbackend_req           71855086        25.87 Backend requests madeLCK.backend.creat              5         0.00 Created locksLCK.backend.destroy            0         0.00 Destroyed locksLCK.backend.locks      149007648        53.64 Lock OperationsLCK.backend.colls              0         0.00 Collisions

RegardsTikejhya
 		 	   		  
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