Now we can compute the max place depending on the number of servers,
maximum weight and weight scale. The formula has been stored as a
comment so that it's easy to choose between smooth weight ramp up
and high number of servers. The default scale has been set to 16,
which permits 4000 servers with a granularity of 6% in the worst
case (weight=1).
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.
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.
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.
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
It is important to know how your installation performs. Haproxy masks
connection errors, which is extremely good for a client but it is bad for
an administrator (except people believing that "ignorance is a bless").
Attached patch adds retries and redispatches counters, so now haproxy:
1. For server:
- counts retried connections (masked or not)
2. For backends:
- counts retried connections (masked or not) that happened to
a slave server
- counts redispatched connections
- does not count successfully redispatched connections as backend errors.
Errors are increased only when client does not get a valid response,
in other words: with failed redispatch or when this function is not
enabled.
3. For statistics:
- display Retr (retries) and Redis (redispatches) as a "Warning"
information.
Struct server has gathered lots of informations over the time, but
it's better for clarity and performance to group those information
by usage, the most common ones at the top and the least ones at the
bottom.
Patch from Fabrice Dulaunoy. Explanation below, and script
merged in examples/.
This patch allow to put a different address in the check part for each
server (and not only a specific port)
I need this feature because I've a complex settings where, when a specific
farm goes down, I need to switch a set of other farm either if these other
farm behave perfectly well.
For that purpose, I've made a small PERL daemon with some REGEX or PORT
test which allow me to test a bunch of thing.
Using the cttproxy kernel patch, it's possible to bind to any source
address. It is highly recommended to use the 03-natdel patch with the
other ones.
A new keyword appears as a complement to the "source" keyword : "usesrc".
The source address is mandatory and must be valid on the interface which
will see the packets. The "usesrc" option supports "client" (for full
client_ip:client_port spoofing), "client_ip" (for client_ip spoofing)
and any 'IP[:port]' combination to pretend to be another machine.
Right now, the source binding is missing from server health-checks if
set to another address. It must be implemented (think restricted firewalls).
The doc is still missing too.
The files are now stored under :
- include/haproxy for the generic includes
- include/types.h for the structures needed within prototypes
- include/proto.h for function prototypes and inline functions
- src/*.c for the C files
Most include files are now covered by LGPL. A last move still needs
to be done to put inline functions under GPL and not LGPL.
Version has been set to 1.3.0 in the code but some control still
needs to be done before releasing.
