=== SureAliveD ===
- What is SureAlived?
SureAliveD is a very efective LVS real service tester. We split it on two separated programs - surealived (tester) and ipvssync (kernel ipvs table synchroniser). We deceide to replace keepalived tester functionality (not VRRP)
- it has some bugs and a lack of some features we would like to have.
- Program details:
surealived:
- epoll based
- extensible xml based configuration (module specific)
- real service testers are dynamicaly loaded modules
- currently tcp, http, dns, exec and no-test (virtual tester) tester are implemented
- transparent ssl
- gather and store test statistics
- possibility to dump communication of a tested real
- hosts state are stored in 'offline' and 'override' files honoured when aplication is restarted
- 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)
ipvssync:
- uses configuration stored in ipvsfull.cfg and diffs files
- allows to leave/remove unmanaged reals/virtuals
- synchronize config to ipvs, allows delete/leave unmanaged virtuals (-u option)
- you can check your configuration (-t option)
- Installation
To compile application need development tools and libraries:
- gcc
- cmake
- glib2-dev
- libxml2-dev
- libssl
From src directory (from root account):
cd surealived cmake . make make install cd ../ipvssync cmake . make make install
surealived needn't to be executed from root account, but you need to set apropriate grants for such user. You need following directories created: /var/lib/surealived/ /var/lib/surealived/diffs/ /var/lib/surealived/stats/ /var/log/surealived/ /var/log/surealived/comm/
- Main configuration
4.1 surealived uses configuration files:
- /etc/surealived/surealived.cfg - main config, describes program behaviour and offline.dump, override.dump paths
- xml configuration (set as argument)
4.2 ipvssync uses configuration files:
- /etc/surealived/surealived.cfg really only variables: ipvssync_log, ipvssync_logging, no_sync, lock_sync_file, full_sync_file, full_reload_file, diff_sync_dir are used
- surealived XML configuration file I'll explain semantics on following example:
-
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 ***
a) HTTP
http 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"]
b) DNS dns tester attributes:
- request="string" [mandatory], domain for which soa will be checked
c) TCP No additional attributes are required for this tester.
d) EXEC
- TO DESCRIBE -
e) NO-TEST 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]
- Runtime weight balancing and rstate management
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 Set: 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:
a)
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.
b)
This gives you a lot of debug information (-vvvv) and delete unmanaged virtuals.