SureAliveD is a very effective LVS service tester that is meant to replace keepalived (but not VRRP). Application is actually two separated programs:

• surealived - tester,
• ipvssync - kernel ipvs table synchroniser.

• epoll based
• extensible xml based configuration (module specific)
• real service testers are dynamically loaded modules
• currently tcp, http, dns, exec and no-test (virtual tester)tester are implemented
• transparent ssl
• surealived restart enforces full ipvs sync
• configuration for ipvssync is saved at start and every minute as main file (ipvssync.cfg), changes are saved in special diffs files
• tests startup are spread in time, decreasing connecting impact and cpu usage
• you can write your own tester for a specified service (see http tester how to do that)
• you can check your config file before you try to restart surealived (-t option)

To compile application need development tools and libraries:

• gcc
• cmake
• libxml2-dev
• libssl-dev
• libpackagekit-glib2-dev
• liblua5.1-0-dev

From src directory (from root account):

mkdir build  
cd build
cmake ..
make           # to biuld binaries or
make package   # to build deb package

SureAliveD can be executed as non-root, but you need to set appropriate grants for such a user. You need following directories created:

/var/lib/surealived/
/var/lib/surealived/diffs/
/var/lib/surealived/stats/
/var/log/surealived/
/var/log/surealived/comm/

• surealived uses configuration files:

  • /etc/surealived/surealived.cfg - main configuration file,
  • xml configuration (set as argument) - test definition

• ipvssync uses only /etc/surealived/surealived.cfg

As an example let's take following config:

<surealived>

<virtual name="onet" addr="192.168.0.1" port="80" proto="tcp" sched="wrr" rt="dr">
  <tester loopdelay="1" timeout="2" retries2fail="1" retries2ok="1"
          proto="http" testport="80" url="/" host="www.onet.pl" />
  <real name="sg" addr="213.180.146.27" port="80" weight="10"/>
</virtual>

</surealived>

• virtual attributes:

  • name="string" [mandatory] (max 31 chars)
  • addr="ip" [mandatory if attribute fwmark is not set, if fwmark is set "0.0.0.0" will be used]
  • port="int16" [0<=port<=65535, mandatory if fwmark is not set, otherwise "0"]
  • proto="tcp|udp|fwmark" [mandatory]
  • sched="string" [mandatory] (such ipvs scheduler will be used)
  • rt="dr|masq|tun" [mandatory]
  • fwmark="int" [optional, if > 0 proto="fwmark" should be set]
  • pers="int" [optional, for persistent connections - this is timeout value]

• tester attributes:

  • loopdelay="int" [optional, default 3] - defines delay in seconds between next testing loop for this virtual
  • timeout="int" [optional, default 5] - each real server must completly respond in this time]
  • retries2ok="int" [optional, default 1] - how much tests must succeed to treat real as online
  • retries2fail="int" [optional, default 1] - how much tests must fail to treat real as offline
  • remove_on_fail="0|1" [optional, default 0 (false)] - if true and real is offline remove it from ipvs
  • debugcomm="0|1" [optional, default 0 (false)] - enable dumping communication details for reals
  • logmicro="0|1"} [optional, default 0 (false)] - do use microseconds resolution while saving the statistics
  • proto="string" [mandatory] - which module is used as tester module
  • testport="int" [mandatory] - which port is tested (can be differ than real port)
  • SSL="0|1" [optional, default 0 - no ssl

  *** other attributes are parsed individual by module specification ***

tester attributes:

• url="string" [mandatory] (max BUFSIZ length, 8192 bytes)
• host="string" [mandatory]
• naive="0|1" [optional], only response code is read in module and compared to retcode
• retcode="string" [optional, default "200"]

dns tester attributes:

• request="string" [mandatory], domain for which soa will be checked

No additional attributes are required for this tester.

?

All hosts in this tester are treated as ONLINE always

• real attributes
  • name="string" [mandatory, max 31 bytes].
  • addr="ip" [mandatory],
  • port="int16" [mandatory]
  • weight="int" [mandatory]
  • uthresh="int" [optional]
  • lthresh="int" [optional]
  • testport="int16" [optional, override tester "testport" attribute]
  • rt="string" [optional, override tester "rt" attribute]

surealived listens at port 1337 by default, you can currently do two important tasks:

• change weight: by setting absolute value or percent of configuration weight. If you'll have weight=20 and you'll set rweight=1% you'll get... 1. We deceide to do that when we want to add a real server which is cache for something and we want to increase its weight depends on cache fill.

• change rstate to: a) DOWN - will remove a real from ipvs b) OFFLINE - will set real weight to 0 c) ONLINE - will bring real to configuration value IF online == ONLINE, otherwise host will be evaluated by (online, remove_on_fail)

To manage real weight you can use commands:

 printf "vlist\n" | nc -q 1 localhost 1337
. vname=onet vproto=tcp vaddr=192.168.0.1 vport=80 vfwmark=0 vrt=dr vsched=wrr
. vname=wp vproto=tcp vaddr=192.168.0.2 vport=80 vfwmark=0 vrt=dr vsched=wrr

 printf "rlist vproto=tcp vaddr=192.168.0.2 vport=80\n" | nc -q 1 localhost 1337
. raddr=212.77.100.101 rport=80 currwgt=11 confwgt=11 ronline=TRUE rstate=ONLINE

 printf "rset vproto=tcp vaddr=192.168.0.2 vport=80 raddr=212.77.100.101 rport=80 rstate=OFFLINE\n" | nc -q 1 localhost 1337
et: rstate=OFFLINE, weight=-1, inpercent=FALSE

 printf "rlist vproto=tcp vaddr=192.168.0.2 vport=80\n" | nc -q 1 localhost 1337
. raddr=212.77.100.101 rport=80 currwgt=0 confwgt=11 ronline=TRUE rstate=OFFLINE

 printf "stats\n" | nc -q 1 localhost 1337
.. useful statistics here ... 

See and try example xml files in examples directory.

Suggested startup when you don't wont to daemonize:

surealived -vvv ./examples/onetwp.xml

This will create /var/lib/surealived/ipvsfull.cfg file which is mandatory for ipvssync. ipvsfull.reload will also be created which enforces ipvssync to reload configuration.

ipvssync -vvvv -u  

This gives you a lot of debug information (-vvvv) and delete unmanaged virtuals.