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The listener supports a "transient error" situation, which corresponds to those situations where accept fails badly but poll() reports an event. This happens for example when a listener is paused, or on out of FD. The same mechanism is used when facing a maxconn or maxsessrate limitation. When this happens, the listener is disabled for up to 100ms and put back into the global listener queue so that it automatically wakes up again as soon as the conditions change from an existing connection releasing one resource, or the system recovers from a transient issue. The listener_accept() function has a bug in its exit path causing a freshly limited listener to be immediately enabled again because all the conditions are met (connection count < max). It doesn't take into account the fact that the listener might have been queued and must first wait for the timeout to expire before doing so. The impact is that upon certain errors, the faulty process will busy loop on the accept code without sleeping. This is the scenario reported and diagnosed by @hedong0411 in issue #382. This commit fixes it by verifying that the global queue's delay is at least expired before deciding to resume the listener. Another approach could consist in having an extra state like LI_DELAY for situations where only a delay is acceptable, but this would probably not bring anything except more complex code. This issue was introduced with the lock-free listener accept code (commits 3f0d02b and 82c9789a) that were backported to 1.8.20+ and 1.9.7+, so this fix must be backported to the relevant branches.
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)