It is not always handy to manipulate large values exprimed
in milliseconds for timeouts. Also, some values are entered
in seconds (such as the stats refresh interval). This patch
adds support for time units. It knows about 'us', 'ms', 's',
'm', 'h', and 'd'. It automatically converts each value into
the caller's expected unit. Unit-less values are still passed
unchanged.
The unit must be passed as a suffix to the number. For instance:
clitimeout 15m
If any character is not understood, an error is returned.
In order to avoid issues in the future, we want to restrict
the set of allowed characters for identifiers. Starting from
now, only A-Z, a-z, 0-9, '-', '_', '.' and ':' will be allowed
for a proxy, a server or an ACL name.
A test file has been added to check the restriction.
Under certain circumstances, it is very useful to be able to fail some
monitor requests. One specific case is when the number of servers in
the backend falls below a certain level. The new "monitor fail" construct
followed by either "if"/"unless" <condition> makes it possible to specify
ACL-based conditions which will make the monitor return 503 instead of
200. Any number of conditions can be passed. Another use may be to limit
the requests to local networks only.
The new 'slowstart' parameter for a server accepts a value in
milliseconds which indicates after how long a server which has
just come back up will run at full speed. The speed grows
linearly from 0 to 100% during this time. The limitation applies
to two parameters :
- maxconn: the number of connections accepted by the server
will grow from 1 to 100% of the usual dynamic limit defined
by (minconn,maxconn,fullconn).
- weight: when the backend uses a dynamic weighted algorithm,
the weight grows linearly from 1 to 100%. In this case, the
weight is updated at every health-check. For this reason, it
is important that the 'inter' parameter is smaller than the
'slowstart', in order to maximize the number of steps.
The slowstart never applies when haproxy starts, otherwise it
would cause trouble to running servers. It only applies when
a server has been previously seen as failed.
When an HTTP server returns "404 not found", it indicates that at least
part of it is still running. For this reason, it can be convenient for
application administrators to be able to consider code 404 as valid,
but for a server which does not want to participate to load balancing
anymore. This is useful to seamlessly exclude a server from a farm
without acting on the load balancer. For instance, let's consider that
haproxy checks for the "/alive" file. To enable load balancing on a
server, the admin would simply do :
# touch /var/www/alive
And to disable the server, he would simply do :
# rm /var/www/alive
Another immediate gain from doing this is that it is now possible to
send NOTICE messages instead of ALERT messages when a server is first
disable, then goes down. This provides a graceful shutdown method.
To enable this behaviour, specify "http-check disable-on-404" in the
backend.
Hello,
You will find attached an updated release of previously submitted patch.
It polish some part and extend ACL engine to match IP and PORT parsed in
HTTP request. (and take care of comments made by Willy ! ;))
Best regards,
Alexandre
The number of possible options for a proxy has already reached
32, which is the current limit due to the fact that they are
each represented as a bit in a 32-bit word.
It's possible to move the load balancing algorithms to another
place. It will also save some space for future algorithms.
This round robin algorithm was written from trees, so that we
do not have to recompute any table when changing server weights.
This solution allows on-the-fly weight adjustments with immediate
effect on the load distribution.
There is still a limitation due to 32-bit computations, to about
2000 servers at full scale (weight 255), or more servers with
lower weights. Basically, sum(srv.weight)*4096 must be below 2^31.
Test configurations and an example program used to develop the
tree will be added next.
Many changes have been brought to the weights computations and
variables in order to accomodate for the possiblity of a server to
be running but disabled from load balancing due to a null weight.
Under some circumstances, it will be useful to be able to have
a server's effective weight bigger than the user weight, and this
is particularly true for dynamic weight-based algorithms. In order
to support this, we add a "wdiv" member to the lbprm structure
which will always be used to divide the weights before reporting
them.
Since the introduction of server weights, all load balancing algorithms
relied on a pre-computed map. Incidently, quite a bunch of map-specific
parameters were used at random places in order to get the number of
servers or their total weight. It was not architecturally acceptable
that optimizations for the map computation had impact on external parts.
For instance, during this cleanup it was found that a backend weight was
seen as 1 when only the first backup server is used, whatever its weight.
This cleanup consists in differentiating between LB-generic parameters,
such as total weights, number of servers, etc... and map-specific ones.
The struct proxy has been enhanced in order to make it easier to later
support other algorithms. The recount_servers() function now also
updates generic values such as total weights so that it's not needed
anymore to call recalc_server_map() when weights are needed. This
permitted to simplify some code which does not need to know about map
internals anymore.
By default, counters used for statistics calculation are incremented
only when a session finishes. It works quite well when serving small
objects, but with big ones (for example large images or archives) or
with A/V streaming, a graph generated from haproxy counters looks like
a hedgehog.
This patch implements a contstats (continous statistics) option.
When set counters get incremented continuously, during a whole session.
Recounting touches a hotpath directly so it is not enabled by default,
as it has small performance impact (~0.5%).
It is very convenient for SNMP monitoring to have unique process ID,
proxy ID and server ID. Those have been added to the CSV outputs.
The numbers start at 1. 0 is reserved. For servers, 0 means that the
reported name is not a server name but half a proxy (FRONTEND/BACKEND).
A remaining hidden "-" in the CSV output has been eliminated too.
Proxy listeners were very special and not very easy to manipulate.
A proto_tcp file has been created with all that is required to
manage TCPv4/TCPv6 as raw protocols, and provide generic listeners.
The code of start_proxies() and maintain_proxies() now looks less
like spaghetti. Also, event_accept will need a serious lifting in
order to use more of the information provided by the listener.
It's not easy to report useful information to help the user quickly
fix a configuration. This patch :
- removes the word "listener" in favor of "proxy" as it has been
used since the beginning ;
- ensures that the same function (hence the same words) will be
used to report capabilities of a proxy being declared and an
existing proxy ;
- avoid the term "conflicting capabilities" in favor of "overlapping
capabilities" which is more exact.
- just report that the same name is reused in case of warnings
This patch:
- adds proxy_mode_str() similar to proxy_type_str()
- adds a generic findproxy function used with default_backend/setbe/use_backed
- rewrite default_backend/senbe/use_backed to use introduced findproxy()
- relaxes duplicated proxy check
- changes capabilities displaying from "%X" to "%s" with a call to proxy_type_str()
Some applications do not have a strict persistence requirement, yet
it is still desirable for performance considerations, due to local
caches on the servers. For some reasons, there are some applications
which cannot rely on cookies, and for which the last resort is to use
a parameter passed in the URL.
The new 'url_param' balance method is there to solve this issue. It
accepts a parameter name which is looked up from the URL and which
is then hashed to select a server. If the parameter is not found,
then the round robin algorithm is used in order to provide a normal
load balancing across the servers for the first requests. It would
have been possible to use a source IP hash instead, but since such
applications are generally buried behind multiple levels of
reverse-proxies, it would not provide a good balance.
The doc has been updated, and two regression testing configurations
have been added.
A new function "backend_parse_balance" has been created in backend.c,
which is dedicated to the parsing of the "balance" keyword. It will
provide easier methods for adding new algorithms.
In preparation for newer balance algorithms, group the
sparse PR_O_BALANCE_* values into layer4 and layer7-based
algorithms. This will ease addition of newer algorithms.
Currently, there is a hidden line length limit in the haproxy, set
to 256-1 chars. With large acls (for example many hdr(host) matches)
it may be not enough and which is even worse, error message may
be totally confusing as everything above this limit is treated
as a next line:
echo -ne "frontend aqq 1.2.3.4:80\nmode http\nacl e hdr(host) -i X X X X X X X www.xx.example.com stats\n"|
sed s/X/www.some-host-name.example.com/g > ha.cfg && haproxy -c -f ./ha.cfg
[WARNING] 300/163906 (11342) : parsing [./ha.cfg:4] : 'stats' ignored because frontend 'aqq' has no backend capability.
Recently I hit simmilar problem and it took me a while to find why
requests for "stats" are not handled properly.
This patch:
- makes the limit configurable (LINESIZE)
- increases default line length limit from 256 to 2048
- increases MAX_LINE_ARGS from 40 to 64
- fixes hidden assignment in fgets()
- moves arg/end/args/line inside the loop, making code auditing easier
- adds a check that shows error if the limit is reached
- changes "*line++ = 0;" to "*line++ = '\0';" (cosmetics)
With this patch, when LINESIZE is defined to 256, above example produces:
[ALERT] 300/164724 (27364) : parsing [/tmp/ha.cfg:3]: line too long, limit: 255.
[ALERT] 300/164724 (27364) : Error reading configuration file : /tmp/ha.cfg
Hello,
As it is possible to use the same name for two proxies, make sure that
use_backed & friends does not match wrong proxy when used with use_backend/
default_backend/setbe. For example, without this patch, when there is a
backend and frontend with the same name (first backend and then frontend
trying to use specific backend), the application will likely try to use
frontend instead of backend, complaining loudly about a loop.
Best regards,
Krzysztof Oledzki
This patch adds the "maxqueue" parameter to the server. This allows new
sessions to be immediately rebalanced when the server's queue is filled.
It's useful when session stickiness is just a performance boost (even a
huge one) but not a requirement.
This should only be used if session affinity isn't a hard functional
requirement but provides performance boost by keeping server-local
caches hot and compact).
Absence of 'maxqueue' option means unlimited queue. When queue gets filled
up to 'maxqueue' client session is moved from server-local queue to a global
one.
Hello,
This patch implements new statistics for SLA calculation by adding new
field 'Dwntime' with total down time since restart (both HTTP/CSV) and
extending status field (HTTP) or inserting a new one (CSV) with time
showing how long each server/backend is in a current state. Additionaly,
down transations are also calculated and displayed for backends, so it is
possible to know how many times selected backend was down, generating "No
server is available to handle this request." error.
New information are presentetd in two different ways:
- for HTTP: a "human redable form", one of "100000d 23h", "23h 59m" or
"59m 59s"
- for CSV: seconds
I believe that seconds resolution is enough.
As there are more columns in the status page I decided to shrink some
names to make more space:
- Weight -> Wght
- Check -> Chk
- Down -> Dwn
Making described changes I also made some improvements and fixed some
small bugs:
- don't increment s->health above 's->rise + s->fall - 1'. Previously it
was incremented an then (re)set to 's->rise + s->fall - 1'.
- do not set server down if it is down already
- do not set server up if it is up already
- fix colspan in multiple places (mostly introduced by my previous patch)
- add missing "status" header to CSV
- fix order of retries/redispatches in server (CSV)
- s/Tthen/Then/
- s/server/backend/ in DATA_ST_PX_BE (dumpstats.c)
Changes from previous version:
- deal with negative time intervales
- don't relay on s->state (SRV_RUNNING)
- little reworked human_time + compacted format (no spaces). If needed it
can be used in the future for other purposes by optionally making "cnt"
as an argument
- leave set_server_down mostly unchanged
- only little reworked "process_chk: 9"
- additional fields in CSV are appended to the rigth
- fix "SEC" macro
- named arguments (human_time, be_downtime, srv_downtime)
Hope it is OK. If there are only cosmetic changes needed please fill free
to correct it, however if there are some bigger changes required I would
like to discuss it first or at last to know what exactly was changed
especially since I already put this patch into my production server. :)
Thank you,
Best regards,
Krzysztof Oledzki
Currently haproxy accepts a config with duplicated proxies
(listen/fronted/backed/ruleset). This patch fix this, so the application
will complain when there is an error.
With this modification it is still possible to use the same name for two
proxies (for example frontend&backend) as long there is no conflict:
listen backend frontend ruleset
listen - - - -
backend - - OK -
frontend - OK - -
ruleset - - - -
Best regards,
Krzysztof Oledzki
Removed old unused MODE_LOG and MODE_STATS, and replaced the "stats"
keyword in the global section. The new "stats" keyword in the global
section is used to create a UNIX socket on which the statistics will
be accessed. The client must issue a "show stat\n" command in order
to get a CSV-formated output similar to the output on the HTTP socket
in CSV mode.
For people who manage many haproxies, it is sometimes convenient
to be informed of their version. This patch adds this, with the
option to disable this report by specifying "stats hide-version".
Also, the feature may be permanently disabled by setting the
STATS_VERSION_STRING to "" (empty string), or the format can
simply be adjusted.
When one server appears at the same position in multiple backends, it
receives all the checks from all the backends exactly at the same time
because the health-checks are only spread within a backend but not
globally.
Attached patch implements per-server start delay in a different way.
Checks are now spread globally - not locally to one backend. It also makes
them start faster - IMHO there is no need to add a 'server->inter' when
calculating first execution. Calculation were moved from cfgparse.c to
checks.c. There is a new function start_checks() and now it is not called
when haproxy is started in MODE_CHECK.
With this patch it is also possible to set a global 'spread-checks'
parameter. It takes a percentage value (1..50, probably something near
5..10 is a good idea) so haproxy adds or removes that many percent to the
original interval after each check. My test shows that with 18 backends,
54 servers total and 10000ms/5% it takes about 45m to mix them completely.
I decided to use rand/srand pseudo-random number generator. I am aware it
is not recommend for a good randomness but a) we do not need a good random
generator here b) it is probably the most portable one.
The following patch will give the ability to tweak socket linger mode.
You can use this option with "option nolinger" inside fronted or backend
configuration declaration.
This will help in environments where lots of FIN_WAIT sockets are
encountered.
Since the timers have been changed, the timeouts for the default instance
have not been adjusted. This results in unspecified timeouts becoming zero
instead of infinite.
A log chain of if/else prevented many sanity checks from being
performed on TCP listeners, resulting in dangerous configs being
accepted. Removed the offending 'else'.
src/chtbl.c, src/hashpjw.c and src/list.c are distributed under
an obscure license. While Aleks and I believe that this license
is OK for haproxy, other people think it is not compatible with
the GPL.
Whether it is or not is not the problem. The fact that it rises
a doubt is sufficient for this problem to be addressed. Arnaud
Cornet rewrote the unclear parts with clean GPLv2 and LGPL code.
The hash algorithm has changed too and the code has been slightly
simplified in the process. A lot of care has been taken in order
to respect the original API as much as possible, including the
LGPL for the exportable parts.
The new code has not been thoroughly tested but it looks OK now.
Sometimes it may be desirable to automatically refresh the
stats page. Most browsers support the "Refresh:" header with
an interval in seconds. Specifying "stats refresh xxx" will
automatically add this header.
When a very large number of servers is configured (thousands),
shutting down many of them at once could lead to large number
of calls to recalc_server_map() which already takes some time.
This would result in an O(N^3) computation time, leading to
noticeable pauses on slow embedded CPUs on test platforms.
Instead, mark the map as dirty and recalc it only when needed.
The new "use_backend" keyword permits full content switching by the
use of ACLs. Its usage is simple :
use_backend <backend_name> {if|unless} <acl_cond>
It is now possible to read error messages from local files,
using the 'errorfile' keyword. Those files are read during
parsing, so there's no I/O involved. They make it possible
to return custom error messages with custom status and headers.
By default, epoll/kqueue used to return as many events as possible.
This could sometimes cause huge latencies (latencies of up to 400 ms
have been observed with many thousands of fds at once). Limiting the
number of events returned also reduces the latency by avoiding too
many blind processing. The value is set to 200 by default and can be
changed in the global section using the tune.maxpollevents parameter.
ETERNITY is not 0 anymore, so all timeouts will not be initialized
to ETERNITY by a simple calloc(). We have to explictly assign them.
This bug caused random session aborts.
The timeout functions were difficult to manipulate because they were
rounding results to the millisecond. Thus, it was difficult to compare
and to check what expired and what did not. Also, the comparison
functions were heavy with multiplies and divides by 1000. Now, all
timeouts are stored in timevals, reducing the number of operations
for updates and leading to cleaner and more efficient code.
Peter van Dijk contributed this patch which implements the "smtpchk"
option, which is to SMTP what "httpchk" is to HTTP. By default, it sends
"HELO localhost" to the servers, and waits for the 250 message, but it
can also send a specific request.
The new 'block' keyword makes it possible to block a request based on
ACL test results. Block accepts two optional arguments : 'if' <cond>
and 'unless' <cond>.
The request will be blocked with a 403 response if the condition is validated
(if) or if it is not (unless). Do not rely on this one too much, as it's more
of a proof of concept helping in developing other matches.
It is important when parsing configuration file to ensure that at
least one word is empty to mark the end of the line. This will be
required with ACLs in order to avoid reading past the end of line.
The rbtree-based wait queue consumes a lot of CPU. Use the ul2tree
instead. Lots of cleanups and code reorganizations made it possible
to reduce the task struct and simplify the code a bit.
