On Thu, Apr 27, 2023 at 04:59:24PM +0200, Christopher Faulet wrote:
> Hi,
>
> HAProxy 2.7.7 was released on 2023/04/27. It added 163 new commits
> after version 2.7.6.
>
> This release is pretty huge. In one month, the QUIC team achieved an amazing
> work to improve the stack and make it more stable. A big thanks to Tristan
> for his priceless help. More than half of commits concern the QUIC stack. It
> is hard to sum up all changes. Many bugs were fixed, the most visible are:
>
> * The Congestion algorithms state was shared between connections instead of
>being private.
>
> * HTTP/1.0 responses with an unknown content length and finished on close
>were not properly handled. It was considered as an early close by the
>QUIC multiplexer, leading to a RESET_STREAM emission.
>
> * The streams fairness was improved to prevent timeouts. A stream sending a
>large object could block other streams. With a small client timeout,
>blocked streams could be aborted via a RESET_STREAM.
>
> * Some contradictions in code could lead to very long loops sending empty
>packets (PADDING only packets). One visible effect was a very low
>throughput performance when the client serialized its requests.
>
> * The control window in congestion algorithms could be zero because of a
>wrong calculation and could lead to a SIGFPE crash.
>
> * Padding was missing in very short probe packets
>
> * Possible memory leaks were fixed
>
> And of course, some improvements were brought. The main one is the support
> of the thread loadbalancing on accept. A series of changes allowed to use
> the default mechanism to accept and handle connections. The less loaded
> thread is now selected, improving the global performance of the QUIC
> stack. In addition, a timer was added to delay the acknowledgments.
>
> Recent refactoring about the stream-connector layer introduced a regression
> since the 2.7.4. The read timer was no longer rearmed if the end of the
> message was reached. This change was introduced to avoid server timeouts
> when the server replies before the end of the request. But it revealed
> several bugs, some was fixed, but some others pretty are hard to fix without
> changing some internals. It is too sensitive for a stable version. Thus for
> now we decided to revert this change, waiting for a better solution. Note
> that it is not a big deal because we only restore a behavior that has been
> there for ages.
>
> On soft-stop or reload, idle DNS session are now killed. Since the 2.7.5,
> these sessions were no longer killed, preventing the process to finish. In
> addition, we now force the connect timeout for the DNS resolution. The
> "resolve" timeout is used to set its value. Have no connect timeout was an
> issue for resolution over TCP. Connection failures might take quite long to
> report, leading to an excess of unusable DNS sessions in connecting
> state. It was especially visible on soft-stop because this prevented the
> process to quickly exit. Still on the DNS, errors are now properly handled
> when a response is consumed. This was an issue for truncated responses
> followed by an abort. The applet could ignore the abort and loop waiting for
> more data until a timeout is triggered. A similar issue was fixed in the
> syslog applet.
>
> Several bugs in lua part were fixed. First, except for lua tasks, it is no
> longer possible to register functions at runtime. It was clearly stated in
> the documentation, but nothing forbidden it in the code. An error is now
> triggered if this happens, preventing potential segfaults. Memory leaks on
> references were fixed and the lua locking was simplified to be re-entrant to
> prevent deadlocks.
>
> Aurélien fixed several issues on the servers management. The "visible"
> server list consistency was fixed. It was possible, at least in theory, to
> access an invalid server if several dynamic server deletions were performed
> while the list was accessed. For instance it might happen when the server
> list was dumped in the stats. He also fixed wrong report for tracking
> servers leaving drain state. Finally, he centralized proxy and server stats
> updates on server state transition to be sure to not miss an update on some
> transitions.
>
> The issues that were occasionally met around the use of malloc_trim() that
> had been addressed in 2.8 were finally backported after one month of
> exposure in 2.8. The issue was that not only malloc_trim() could still
> sometimes be used when jemalloc (or any other allocator) was used, but our
> attempts at plugging these special cases didn't work when linking with
> external libs that also explicitly call it. In the end, the opposite was
> done: we redefine our own version of malloc_trim(), which contains the tests
> for the presence of an alternate lib, and call the original if the allocator
> comes from libc, or call the equivalent function from other allocators. This
> way external libs that would use
