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HAProxy - Load balancer
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Recently, a new allocation mechanism was implemented for Tx buffers used by QUIC MUX. Now, underlying congestion window size is used to determine if it is still possible or not to allocate a new buffer when necessary. This mechanism has render the QUIC stack more flexible. However, it also has brought some performance degradation, with transfer time longer in certain environment. It was first discovered on the measurement results of the interop. It can also easily be reproduced using the following ngtcp2-client example which forces a very small congestion window due to frequent loss : $ ngtcp2-client -q --no-quic-dump --no-http-dump --exit-on-all-streams-close -r 0.1 127.0.0.1 20443 "https://[::]:20443/?s=10m" This performance decrease is caused by the allocator which is now too strict. It may cause buffer underrun frequently at the MUX layer when the congestion window is too small, as new buffers cannot be allocated until the current one is fully acknowledged. This resuls in transfers with very bad throughput utilisation. The objective of this new serie of patches is to relax some restrictions to permit QUIC MUX to allocate new buffers more quickly, while preserving the initial limitation based on congestion window size. An interesting method for this is to notify QUIC MUX about newly available room on individual ACK reception, without waiting for the full bffer acknowledgement. This is easily implemented by adding a new notify_room invokation in QUIC streamdesc layer on ACK reception. However, ACK reception are handled in-order at the stream level. Out of order ACKs are buffered and are not decounted for now. This will be implemented in a future commit. Note that for a single buffer instance, data can in parallel be written by QUIC MUX and removed on ACK reception. This could cause room notification to QUIC MUX layer to report invalid values. As such, ACK reception are only accounted for released buffers. This ensures that such buffers won't received any new data. In the same time, buffer room is notified on release operation as it does not need acknowledgement. This commit has permit to improve performance for the ngtcp2-client scenario above. However, it is not yet sufficient enough for interop goodput test. |
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HAProxy
HAProxy is a free, very fast and reliable reverse-proxy offering high availability, load balancing, and proxying for TCP and HTTP-based applications.
Installation
The INSTALL file describes how to build HAProxy. A list of packages is also available on the wiki.
Getting help
The discourse and the mailing-list are available for questions or configuration assistance. You can also use the slack or IRC channel. Please don't use the issue tracker for these.
The issue tracker is only for bug reports or feature requests.
Documentation
The HAProxy documentation has been split into a number of different files for ease of use. It is available in text format as well as HTML. The wiki is also meant to replace the old architecture guide.
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)
License
HAProxy is licensed under GPL 2 or any later version, the headers under LGPL 2.1. See the LICENSE file for a more detailed explanation.