PingRequestHandler (Solr 4.5.0 API)

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org.apache.solr.handler
Class PingRequestHandler

java.lang.Object
  org.apache.solr.handler.RequestHandlerBase
      org.apache.solr.handler.PingRequestHandler

All Implemented Interfaces:: SolrInfoMBean, SolrRequestHandler, SolrCoreAware

public class PingRequestHandler
extends RequestHandlerBase
implements SolrCoreAware
extends RequestHandlerBase
implements SolrCoreAware

Ping Request Handler for reporting SolrCore health to a Load Balancer.

This handler is designed to be used as the endpoint for an HTTP Load-Balancer to use when checking the "health" or "up status" of a Solr server.

In it's simplest form, the PingRequestHandler should be configured with some defaults indicating a request that should be executed. If the request succeeds, then the PingRequestHandler will respond back with a simple "OK" status. If the request fails, then the PingRequestHandler will respond back with the corrisponding HTTP Error code. Clients (such as load balancers) can be configured to poll the PingRequestHandler monitoring for these types of responses (or for a simple connection failure) to know if there is a problem with the Solr server.

 <requestHandler name="/admin/ping" class="solr.PingRequestHandler">
   <lst name="invariants">
     <str name="qt">/search</str><!-- handler to delegate to -->
     <str name="q">some test query</str>
   </lst>
 </requestHandler>

A more advanced option available, is to configure the handler with a "healthcheckFile" which can be used to enable/disable the PingRequestHandler.

 <requestHandler name="/admin/ping" class="solr.PingRequestHandler">
   <!-- relative paths are resolved against the data dir -->
   <str name="healthcheckFile">server-enabled.txt</str>
   <lst name="invariants">
     <str name="qt">/search</str><!-- handler to delegate to -->
     <str name="q">some test query</str>
   </lst>
 </requestHandler>

If the health check file exists, the handler will execute the delegated query and return status as described above.
If the health check file does not exist, the handler will return an HTTP error even if the server is working fine and the delegated query would have succeeded

This health check file feature can be used as a way to indicate to some Load Balancers that the server should be "removed from rotation" for maintenance, or upgrades, or whatever reason you may wish.

The health check file may be created/deleted by any external system, or the PingRequestHandler itself can be used to create/delete the file by specifying an "action" param in a request:

http://.../ping?action=enable - creates the health check file if it does not already exist
http://.../ping?action=disable - deletes the health check file if it exists
http://.../ping?action=status - returns a status code indicating if the healthcheck file exists ("enabled") or not ("disabled")

Since:: solr 1.3

Nested Class Summary
`protected static class`	`PingRequestHandler.ACTIONS`

Nested classes/interfaces inherited from interface org.apache.solr.core.SolrInfoMBean
`SolrInfoMBean.Category`

Field Summary
`static String`	`HEALTHCHECK_FILE_PARAM`
`static org.slf4j.Logger`	`log`

Fields inherited from class org.apache.solr.handler.RequestHandlerBase
`appends, defaults, httpCaching, initArgs, invariants`

Constructor Summary
`PingRequestHandler()`

Method Summary
`String`	`getDescription()` Simple one or two line description
`String`	`getSource()` CVS Source, SVN Source, etc
`protected void`	`handleEnable(boolean enable)`
`protected void`	`handlePing(SolrQueryRequest req, SolrQueryResponse rsp)`
`void`	`handleRequestBody(SolrQueryRequest req, SolrQueryResponse rsp)`
`void`	`inform(SolrCore core)`
`void`	`init(NamedList args)` Initializes the `SolrRequestHandler` by creating three `SolrParams` named.
`boolean`	`isPingDisabled()` Returns true if the healthcheck flag-file is enabled but does not exist, otherwise (no file configured, or file configured and exists) returns false.

Methods inherited from class org.apache.solr.handler.RequestHandlerBase
`getCategory, getDocs, getInitArgs, getName, getStatistics, getVersion, handleRequest`

Methods inherited from class java.lang.Object
`clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait`

Field Detail

log

public static org.slf4j.Logger log

HEALTHCHECK_FILE_PARAM

public static final String HEALTHCHECK_FILE_PARAM

See Also:: Constant Field Values

Constructor Detail