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Willy Tarreau bdb86bdaab MEDIUM: server: improve estimate of the need for idle connections 
Starting with commit 079cb9a ("MEDIUM: connections: Revamp the way idle
connections are killed") we started to improve the way to compute the
need for idle connections. But the condition to keep a connection idle
or drop it when releasing it was not updated. This often results in
storms of close when certain thresholds are met, and long series of
takeover() when there aren't enough connections left for a thread on
a server.

This patch tries to improve the situation this way:
  - it keeps an estimate of the number of connections needed for a server.
    This estimate is a copy of the max over previous purge period, or is a
    max of what is seen over current period; it differs from max_used_conns
    in that this one is a counter that's reset on each purge period ;

  - when releasing, if the number of current idle+used connections is
    lower than this last estimate, then we'll keep the connection;

  - when releasing, if the current thread's idle conns head is empty,
    and we don't exceed the estimate by the number of threads, then
    we'll keep the connection.

  - when cleaning up connections, we consider the max of the last two
    periods to avoid killing too many idle conns when facing bursty
    traffic.

Thanks to this we can better converge towards a situation where, provided
there are enough FDs, each active server keeps at least one idle connection
per thread all the time, with a total number close to what was needed over
the previous measurement period (as defined by pool-purge-delay).

On tests with large numbers of concurrent connections (30k) and many
servers (200), this has quite smoothed the CPU usage pattern, increased
the reuse rate and roughly halved the takeover rate.
2020-06-29 16:29:10 +02:00
.github CI: extend spellchecker whitelist 2020-06-26 11:26:52 +02:00
contrib CONTRIB: debug: add missing flags SI_FL_L7_RETRY & SI_FL_D_L7_RETRY 2020-06-28 16:05:39 +02:00
doc MINOR: cli: make "show sess" stop at the last known session 2020-06-28 01:41:56 +02:00
examples CLEANUP: assorted typo fixes in the code and comments 2020-06-26 11:27:28 +02:00
include MEDIUM: server: improve estimate of the need for idle connections 2020-06-29 16:29:10 +02:00
reg-tests REGTEST: ssl: add some ssl_c_* sample fetches test 2020-06-26 12:11:39 +02:00
scripts CI: travis-ci: switch BoringSSL builds to ninja 2020-06-26 11:26:26 +02:00
src MEDIUM: server: improve estimate of the need for idle connections 2020-06-29 16:29:10 +02:00
tests REORG: include: split mini-clist into haproxy/list and list-t.h 2020-06-11 10:18:56 +02:00
.cirrus.yml CI: cirrus-ci: skip reg-tests/connection/proxy_protocol_send_unique_id_alpn.vtc on CentOS 6 2020-05-28 16:51:36 +02:00
.gitignore DOC: create a BRANCHES file to explain the life cycle 2019-06-15 22:00:14 +02:00
.travis.yml CI: travis-ci: switch BoringSSL builds to ninja 2020-06-26 11:26:26 +02:00
BRANCHES DOC: assorted typo fixes in the documentation 2020-03-09 14:45:58 +01:00
CHANGELOG [RELEASE] Released version 2.2-dev11 2020-06-26 22:01:04 +02:00
CONTRIBUTING DOC: assorted typo fixes in the documentation and Makefile 2020-03-06 10:49:55 +01:00
INSTALL BUILD: Makefile: add linux-musl to TARGET 2020-04-16 15:17:13 +02:00
LICENSE LICENSE: add licence exception for OpenSSL 2012-09-07 13:52:26 +02:00
MAINTAINERS REORG: include: split hathreads into haproxy/thread.h and haproxy/thread-t.h 2020-06-11 10:18:56 +02:00
Makefile REORG: buffer: rename buffer.c to dynbuf.c 2020-06-29 09:26:59 +02:00
README DOC: create a BRANCHES file to explain the life cycle 2019-06-15 22:00:14 +02:00
ROADMAP DOC: update the outdated ROADMAP file 2019-06-15 21:59:54 +02:00
SUBVERS BUILD: use format tags in VERDATE and SUBVERS files 2013-12-10 11:22:49 +01:00
VERDATE [RELEASE] Released version 2.2-dev11 2020-06-26 22:01:04 +02:00
VERSION [RELEASE] Released version 2.2-dev11 2020-06-26 22:01:04 +02:00

README 

The HAProxy documentation has been split into a number of different files for
ease of use.

Please refer to the following files depending on what you're looking for :

  - INSTALL for instructions on how to build and install HAProxy
  - BRANCHES to understand the project's life cycle and what version to use
  - LICENSE for the project's license
  - CONTRIBUTING for the process to follow to submit contributions

The more detailed documentation is located into the doc/ directory :

  - doc/intro.txt for a quick introduction on HAProxy
  - doc/configuration.txt for the configuration's reference manual
  - doc/lua.txt for the Lua's reference manual
  - doc/SPOE.txt for how to use the SPOE engine
  - doc/network-namespaces.txt for how to use network namespaces under Linux
  - doc/management.txt for the management guide
  - doc/regression-testing.txt for how to use the regression testing suite
  - doc/peers.txt for the peers protocol reference
  - doc/coding-style.txt for how to adopt HAProxy's coding style
  - doc/internals for developer-specific documentation (not all up to date)