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high level overview of the new features contributed to 1.8
(warning, the list is huge) :
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JSON stats (Simon Horman) : the stats socket’s “show stat” and "show info"
output can now be emitted in a structured JSON format which is more
convenient than CSV for some modern data processing frameworks.
-
server templates (Frédéric Lécaille) : servers can be pre-provisionned
in backends using a simple directive (“server-template”). It is then
possible to configure them at runtime over the CLI or DNS, making it
trivial to add/remove servers at run time without restarting. As a side
effect of implementing this, all “server” keywords are now supported on
the “default-server” line and it’s possible to disable any of them using
"no-". All settings changed at runtime are present in the state
file so that upon reload no information is lost.
-
dynamic cookies (Olivier Houchard) : a dynamic cookie can be generated
on the fly based on the transport address of a newly added server. This
is important to be able to use server templates in stateful environments.
-
per-certificate “bind” configuration (Emmanuel Hocdet) : all the SSL
specific settings of the “bind” line may now be set per-certificate in
the crtlist file. A common example involves requiring a client cert for
certain domains only and not for others, all of them running on the same
address:port.
-
pipelined and asynchronous SPOE (Christopher Faulet) : it’s an important
improvement to the Stream Processing Offload Engine that allows requests
to be streamed over existing connections without having to wait for a
previous response. It significantly increases the message rate and reduces
the need for parallel connections. Two example WAFs were introduced as
contributions to make use of this improvement (mod_security and
mod_defender).
-
seamless reloads (Olivier Houchard) : in order to work around some issues
faced on Linux causing a few RST to be emitted for incoming connections
during a reload operations despite SO_REUSEPORT being used, it is now
possible for the new haproxy process to connect to the previous one and
to retrieve existing listening sockets so that they are never closed. Now
no connection breakage will be observed during a reload operation anymore.
-
PCRE2 support (David Carlier) : this new version of PCRE seems to be
making its way in some distros, so now we are compatible with it.
-
hard-stop-after (Cyril Bonté) : this new global setting forces old
processes to quit after a delay consecutive to a soft reload operation.
This is mostly used to avoid an accumulation of old processes in some
environments where idle connections are kept with large timeouts.
-
support for OpenSSL asynchronous crypto engines (Grant Zhang) : this
allows haproxy to defer the expensive crypto operations to external
hardware engines. Not only can it significantly improve the performance,
but it can also reduce the latency impact of slow crypto operations on
all other operations since haproxy switches to other tasks while the
engine is busy. This was successfully tested with Intel’s QAT and with
a home-made software engine. This requires OpenSSL 1.1.x.
-
replacement of the systemd-wrapper with a new master-worker model
(William Lallemand) : this new model allows a master process to stay in
the foreground on top of the multiple worker processes. This process
knows the list of worker processes, can watch them to detect failures,
can broadcast some signals it receives, and has access to the file
system to reload if needed (yes, it even supports seamless upgardes to
newer versions since it reloads using an execve() call). While initially
designed as a replacement for the systemd-wrapper, it also proves useful
in other environments and during development.
-
DNS autonomous resolver (Baptiste Assmann) : the DNS resolution used to
be triggered by health checks. While easy and convenient, it was a bit
limited and didn’t allow to manage servers via the DNS, but only to detect
address changes. With this change the DNS resolvers are now totally
autonomous and can distribute the addresses they’ve received to multiple
servers at once, and if multiple A records are present in a response, the
advertised addresses will be optimally distributed to all the servers
relying on the same record.
-
DNS SRV records (Olivier Houchard) : in order to go a bit further with
DNS resolution, SRV records were implemented. The address, port and weight
attributes will be applied to servers. New servers are automatically added
provided there are enough available templates, and servers which disappear
are automatically removed from the farm. By combining server templates and
SRV records, it is now trivial to perform service discovery.
-
configurable severity output on the CLI : external tools connecting to
haproxy’s CLI had to know a lot of details about the output of certain
actions since these messages were initially aimed at humans, and it was
not envisionned that the socket would become a runtime API. This change
offers an option to emit the severity level on each action’s output so
that external APIs can classify the output between success, information,
warnings, errors etc.
-
TLS 1.3 with support for Early-Data (AKA 0-RTT) on both sides (Olivier
Houchard) : TLS 1.3 introduces the notion of “Early-Data”, which are
data emitted during the handshake. This feature reduces the TLS handshake
time by one round trip. When compiled with a TLS-1.3 compatible TLS
library (OpenSSL 1.1.1-dev for now), haproxy can receive such requests,
process them safely, and even respond before the handshake completes.
Furthermore, when the client opts for this, it is also possible to pass
the request to the server following the same principle. This way it is
technically possible to fully process a client request in a single round
trip.
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multi-thread support (Christopher Faulet, Emeric Brun) : no more need
to choose between having multiple independant processes performing
their own checks or cascading two layers of processes to scale SSL.
With multi-threading we get the best of both : a unified process state
and multi-core scalability. Eventhough this first implementation focuses
on stability over performance, it still scales fairly well, being almost
linear on asymmetric crypto, which is where there’s the most demand.
This feature is enabled by default on platforms where it could be tested,
ie Linux >= 2.6.28, Solaris, FreeBSD, OpenBSD >= 5.7. It is considered
EXPERIMENTAL, which means that if you face a problem with it, you may
be asked to disable it for the time it takes to solve the problem. It is
also possible that certain fixes to come will have some side effects.
-
HTTP/2 (Willy Tarreau) : HTTP/2 is automatically detected and processed
in HTTP frontends negociating the “h2” protocol name based on the ALPN
or NPN TLS extensions. At the moment the HTTP/2 frames are converted to
HTTP/1.1 requests before processing, so they will always appear as 1.1
in the logs (and in server logs). No HTTP/2 is supported for now on the
backend, though this is scheduled for the next steps. HTTP/2 support is
still considered EXPERIMENTAL, so just like for multi-threading, in case
of problem you may end up having to disable it for the time it takes to
solve the issue.
-
small objects cache (William Lallemand) : we’ve been talking about this
so-called “favicon cache” for many years now, so I’m pretty sure it will
be welcome. To give a bit of context, we’ve often been criticized for
not caching trivial responses from the servers, especially some slow
application servers occasionally returning a small object (favicon.ico,
main.css etc). While the obvious response is that installing a cache
there is the best idea, it is sometimes perceived as overkill for just
a few files. So what we’ve done here was to fill exactly that hole :
have a safe, maintenance-free, small objects cache. In practice, if
there is any doubt about a response’s cachability, it will not cache.
Same if the response contains a Vary header or is larger than a buffer.
However this can bring huge benefits for situations where there’s no
argument against trivial caching. The intent is to keep it as simple and
fast as possible so that it can always be faster than retrieving the same
object from the next layer (possibly a full-featured cache). Note that I
purposely asked William not to implement the purge on the CLI so that
it remains maintenance-free and we don’t see it abused where it should
not be installed.
