[Bug 1875517] Re: check_http inefficient and sometimes times out

[Rafael David Tinoco]

** Description changed:

  [Impact]
  
-  * check_http nagios plugin module faces timeouts multiple times when
- checking for http health.
+  * Based on the test case numbers, and the numbers provided by the end
+ user, it seems that memory reclaiming for the http buffer, in check_http
+ module, is the real issue here. It turns out that, a heavily overloaded
+ servers might be under big memory pressure and having difficulties
+ trying to reclaim heap memory pages (flushing dirty cache/buffers,
+ swapped_cached pages, or worst) for the check_http network buffer.
  
  [Test Case]
  
-  * not specific clear one. to measure http health in a big environment.
-  * being tested by real user case.
+  * Execute check_http with a 150MB file:
+ 
+ - Unpatched (~ 108 sec)
+ 
+ | $ /usr/lib/nagios/plugins/check_http -H archive.ubuntu.com -j GET -u /ubuntu/pool/main/l/linux-hwe-5.0/linux-hwe-5.0_5.0.0.orig.tar.gz -t 600
+ | HTTP OK: HTTP/1.1 200 OK - 162594115 bytes in 108.216 second response time |time=108.215539s;;;0.000000 size=162594115B;;;0
+ 
+ - Patched (~ 0.5 sec)
+ 
+ | $ /usr/lib/nagios/plugins/check_http -H archive.ubuntu.com -j GET -u /ubuntu/pool/main/l/linux-hwe-5.0/linux-hwe-5.0_5.0.0.orig.tar.gz -t 600
+ | HTTP OK: HTTP/1.1 200 OK - 162594115 bytes in 0.499 second response time 
+ |time=0.498710s;;;0.000000;600.000000 size=162594115B;;;0
  
  [Regression Potential]
  
-  * check_http module might face a regression (only code touched).
-  * we are using realloc instead of a new free/malloc for the http buffer
-  * change is based in an upstream commit and proposed by end-user
+  * Very little but existent for the network receiving buffer logic under check_http module.
+  * Change is based in an bigger upstream commit and only a minor subset of the upstream patch is being backported.
  
  [Other Info]
  
-  * Original Description:
+  * Original Description:
  
  Hi,
  
  We're frequently seeing socket timeouts with some checks using the
  check_http plugin. It seems this is a known issue with some fixes
  upstream:
  
  | https://github.com/nagios-plugins/nagios-plugins/commit/2b38350d546ef9632ccd90e300eeaf6eda0ca32c
  | https://github.com/nagios-plugins/nagios-plugins/commit/fc1bf94655aaed32eeb6fb5c33b6d093f5564bad
  
  Think we can backport these fixes?

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Title:
  check_http inefficient and sometimes times out

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