What is a ?Poll plugin? ?
Poll plugins have the task of periodically poll the servers in the
server farm, also, this plugins may (or may not) collect stats and
rebuild the servers database (e.g. mark a server as unavailable if
the server can?t be reached, or bring back up a server if it can
be reached by the poll tests). This plugins can be stacked,
this means that you can catenate the tests together, using the
previous result in the following plugin (note that all the
results are stored in the Load Balancer server database).
We have the following poll plugins available in Load Balancer:
| plugin name |
Description |
| poll_generic.so |
This is the generic poll plugin. This plugin trasverses all the servers
in all the clusters, and issues a open/close connection, so it tests that
the machine is alive, and we can connect and close to this port. Also
knows when a server can be marked enable or disabled. At last, this
plugin collects some information about the time spent between the
connection and the close (this allows to stimate the servers? response
time).
configuration options
- server_timeout: the number of seconds required to mark this
server as unrecheable
|
| poll_http.so |
This is a ?smart? plugin that understands the HTTP protocol.
poll_http transverses all the servers in all the clusters,
and issues a HTTP request to the server. Then it processes
the result, and scan the return value to check if it is a hit
(code 2xx or 3xx) or if its an error (4xx or above).
Also knows when a server can be marked enable or disabled. At
last, this plugin collects some information about the time spent
between the connection and the close (this allows to stimate the
servers? response time). This poll plugin is very useful to check
a HTTP server, not only if it is recheable or not, it also test
if the documents are accesible.
configuration options
- server_timeout: the number of seconds required to mark
this server as unrecheable.
- url: the url that the plugin will poll to check
if the HTTP server is returning the data
ok.
|
poll_generic.so
<poll_generic
server_timeout="2"
/>
poll_http.so
<poll_http
server_timeout="2"
url="/"
/>
