Linux MySQL command encyclopedia

Maybe you are still in the dynamic content to get 7336.76 reqs/s throughput is excited, and so on, there is a gap between the ideal and the reality, you have to endure the cruelty of reality, don't forget, we stress test dynamic content is in full cache, that is, each request is hit cache, This is often impossible in reality.

First of all, the size of the buffer space is limited, and our site may have a large amount of content to be cached, unlike the previous stress test only one content. Once the buffer is filled, the cache manager eliminates some of the cached content that it deems no longer needed, such as by LRU (the least recent algorithm) to eliminate the cached content that is less frequently used, but it is not strict to judge the "infrequently used" criteria. Maybe the content of the elimination is the next thing you will visit, which affects the hit rate.

Second, the cache expiration time also affects its hit rate, if the validity period is very short, for 10 seconds, then at least 10 seconds will be unable to hit.

Also, some content may not be cached by the proxy server at all, such as the content contains Set-cookie HTTP header information, etc., causing the reverse proxy to not cache them, and will not go to the buffer when the browser requests them. This is an important factor affecting the hit rate, but it is often overlooked by us.

Fortunately, we can easily solve these problems, provided that we need to understand the real-time working state of the reverse proxy cache, such as varnish provides a command line State monitoring Program Varnishstat, we open it, we see the current moment of the state, as follows:

Client_conn 9908723 94.05 Client Connections Accepted

Client_drop 0 0.00 Connection dropped, no sess/wrk

Client_req 16433490 155.99 Client requests received

Cache_hit 8751732 83.07 Cache Hits

Cache_hitpass 42592 0.40 Cache hits for pass

Cache_miss 7573389 71.89 Cache misses

Backend_conn 3889845 36.92 Backend Conn. Success

Backend_unhealthy 0.00 Backend Conn. Not attempted

Backend_busy 0 0.00 Backend Conn. Too many

Backend_fail 4536 0.04 Backend Conn. Failures

Backend_reuse 3780212 35.88 Backend Conn. reuses

Backend_toolate 3866687 36.70 Backend Conn. was closed

Backend_recycle 7646677 72.58 Backend Conn. Recycles

Backend_unused 0 0.00 Backend Conn. Unused

Fetch_head 0.00 Fetch Head

Fetch_length 155097 1.47 Fetch with length

fetch_chunked 7508522 71.27 Fetch chunked

Fetch_eof 0 0.00 Fetch EOF

Fetch_bad 0 0.00 Fetch had bad headers

Fetch_close 3982 0.04 Fetch wanted close

Fetch_oldhttp 0 0.00 Fetch Pre http/1.1 closed

Fetch_zero 0 0.00 Fetch Zero len

Fetch_failed 0 0.00 Fetch Failed

N_sess_mem 1033. N struct SESS_MEM

N_sess 633. N struct Sess

N_object 1016443. N struct Object

N_vampireobject 0. N unresurrected Objects

N_objectcore 1017564. N struct Objectcore

N_objecthead 982903. N struct Objecthead

N_SMF 2647421. N struct SMF

N_smf_frag 622470. N Small Free SMF

N_smf_large 3. N Large Free SMF

N_vbe_conn 12. N struct Vbe_conn

N_wrk 8000. N worker Threads

N_wrk_create 8000 0.08 N worker threads created

N_wrk_failed 0 0.00 N worker Threads not created

N_wrk_max 11021 0.10 N worker Threads Limited

N_wrk_queue 0 0.00 N Queued Work requests

N_wrk_overflow 2441 0.02 N overflowed work requests

N_wrk_drop 0 0.00 N dropped work requests

N_backend 4. N backends

N_expired 6344546. N Expired Objects

N_lru_nuked 183957. N LRU nuked objects

N_lru_saved 0. N LRU saved objects

N_lru_moved 3692170. N LRU moved Objects

N_deathrow 0. N objects on Deathrow

LOSTHDR 0.00 HTTP Header Overflows

N_objsendfile 0 0.00 Objects sent with Sendfile

N_objwrite 15466812 146.81 Objects sent with write

N_objoverflow 0 0.00 Objects Overflowing workspace

S_sess 9906155 94.03 Total Sessions

S_req 16433490 155.99 Total Requests

S_pipe Notoginseng 0.00 Total Pipe

S_pass 108252 1.03 Total Pass

S_fetch 7667658 72.78 Total Fetch

S_hdrbytes 7187255662 68221.35 Total Header bytes

S_bodybytes 111592032839 1059230.32 Total Body bytes

Sess_closed 1905544 18.09 Session closed

Sess_pipeline 0 0.00 Session Pipeline

Sess_readahead 0 0.00 Session Read ahead

Sess_linger 15277717 145.02 Session Linger

Sess_herd 13547370 128.59 Session Herd

Shm_records 1028855796 9765.89 SHM Records

Shm_writes 77957008 739.97 SHM writes

Shm_flushes 131005 1.24 SHM flushes due to overflow

Shm_cont 144281 1.37 SHM MTX contention

Shm_cycles 427 0.00 SHM Cycles through buffer

Sm_nreq 15306717 145.29 Allocator Requests

Sm_nobj 2024948. Outstanding Allocations

Sm_balloc 13595295744. Bytes Allocated

Sm_bfree 40091795456. Bytes free

Sma_nreq 0 0.00 SMA Allocator Requests

Sma_nobj 0. SMA Outstanding Allocations

Sma_nbytes 0. SMA Outstanding bytes

Sma_balloc 0. SMA bytes Allocated

Sma_bfree 0. SMA bytes Free

Sms_nreq 14062 0.13 SMS Allocator requests

Sms_nobj 0. SMS Outstanding Allocations

Sms_nbytes 487. SMS Outstanding bytes

Sms_balloc 6844837. SMS bytes Allocated

Sms_bfree 6846298. SMS bytes Freed

Backend_req 7668789 72.79 Backend requests made

N_VCL 1 0.00 N VCL Total

N_vcl_avail 1 0.00 N VCL Available

N_vcl_discard 0 0.00 N VCL Discarded