Implement decreasing health based on observing communication between
HAProxy and servers.
Changes in this version 2:
- documentation
- close race between a started check and health analysis event
- don't force fastinter if it is not set
- better names for options
- layer4 support
Changes in this version 3:
- add stats
- port to the current 1.4 tree
This patch adds health logging so it possible to check what
was happening before a crash. Failed healt checks are logged if
server is UP and succeeded healt checks if server is DOWN,
so the amount of additional information is limited.
I also reworked the code a little:
- check_status_description[] and check_status_info[] is now
joined into check_statuses[]
- set_server_check_status updates not only s->check_status and
s->check_duration but also s->result making the code simpler
Changes in v3:
- for now calculate and use local versions of health/rise/fall/state,
it is a slow path, no harm should be done. One day we may centralize
processing of the checks and remove the duplicated code.
- also log checks that are restoring current state
- use "conditionally succeeded" for 404 with disable-on-404
Collect information about last health check result,
including L7 code if possible (for example http or smtp
return code) and time took to finish last check.
Health check info is provided on both stats pages (html & csv)
and logged when a server is marked UP or DOWN. Currently active
check are marked with an asterisk, but only in html mode.
Currently there are 14 status codes:
UNK -> unknown
INI -> initializing
SOCKERR -> socket error
L4OK -> check passed on layer 4, no upper layers testing enabled
L4TOUT -> layer 1-4 timeout
L4CON -> layer 1-4 connection problem, for example "Connection refused"
(tcp rst) or "No route to host" (icmp)
L6OK -> check passed on layer 6
L6TOUT -> layer 6 (SSL) timeout
L6RSP -> layer 6 invalid response - protocol error
L7OK -> check passed on layer 7
L7OKC -> check conditionally passed on layer 7, for example
404 with disable-on-404
L7TOUT -> layer 7 (HTTP/SMTP) timeout
L7RSP -> layer 7 invalid response - protocol error
L7STS -> layer 7 response error, for example HTTP 5xx
