org.apache.solr.client.solrj.impl

Class LBHttpSolrServer

java.lang.Object

org.apache.solr.client.solrj.SolrServer

org.apache.solr.client.solrj.impl.LBHttpSolrServer

All Implemented Interfaces:

Serializable

public class LBHttpSolrServer
extends SolrServer

LBHttpSolrServer or "LoadBalanced HttpSolrServer" is a load balancing wrapper around HttpSolrServer. This is useful when you have multiple SolrServers and the requests need to be Load Balanced among them. This should NOT be used for indexing. Also see the wiki page.

It offers automatic failover when a server goes down and it detects when the server comes back up.

Load balancing is done using a simple round-robin on the list of servers.

If a request to a server fails by an IOException due to a connection timeout or read timeout then the host is taken off the list of live servers and moved to a 'dead server list' and the request is resent to the next live server. This process is continued till it tries all the live servers. If atleast one server is alive, the request succeeds, and if not it fails.

 SolrServer lbHttpSolrServer = new LBHttpSolrServer("http://host1:8080/solr/","http://host2:8080/solr","http://host2:8080/solr");
 //or if you wish to pass the HttpClient do as follows
 httpClient httpClient =  new HttpClient();
 SolrServer lbHttpSolrServer = new LBHttpSolrServer(httpClient,"http://host1:8080/solr/","http://host2:8080/solr","http://host2:8080/solr");
 

This detects if a dead server comes alive automatically. The check is done in fixed intervals in a dedicated thread. This interval can be set using setAliveCheckInterval(int) , the default is set to one minute.

When to use this?
This can be used as a software load balancer when you do not wish to setup an external load balancer. Alternatives to this code are to use a dedicated hardware load balancer or using Apache httpd with mod_proxy_balancer as a load balancer. See Load balancing on Wikipedia

Since:

solr 1.4

See Also:

Serialized Form

Nested Class Summary

Nested Classes

Modifier and Type	Class and Description
static class	LBHttpSolrServer.Req
static class	LBHttpSolrServer.Rsp

Constructor Summary

Constructors

Constructor and Description
LBHttpSolrServer(org.apache.http.client.HttpClient httpClient, ResponseParser parser, String... solrServerUrl) The provided httpClient should use a multi-threaded connection manager
LBHttpSolrServer(org.apache.http.client.HttpClient httpClient, String... solrServerUrl) The provided httpClient should use a multi-threaded connection manager
LBHttpSolrServer(String... solrServerUrls)

Method Summary

Methods

Modifier and Type	Method and Description
void	addSolrServer(String server)
protected void	finalize()
org.apache.http.client.HttpClient	getHttpClient()
protected HttpSolrServer	makeServer(String server)
static String	normalize(String server)
String	removeSolrServer(String server)
LBHttpSolrServer.Rsp	request(LBHttpSolrServer.Req req) Tries to query a live server from the list provided in Req.
NamedList<Object>	request(SolrRequest request) Tries to query a live server.
void	setAliveCheckInterval(int interval) LBHttpSolrServer keeps pinging the dead servers at fixed interval to find if it is alive.
void	setConnectionTimeout(int timeout)
void	setSoTimeout(int timeout) set soTimeout (read timeout) on the underlying HttpConnectionManager.
void	shutdown() Release allocated resources.

Methods inherited from class org.apache.solr.client.solrj.SolrServer

add, add, add, add, addBean, addBean, addBeans, addBeans, commit, commit, commit, deleteById, deleteById, deleteById, deleteById, deleteByQuery, deleteByQuery, getBinder, optimize, optimize, optimize, ping, query, query, queryAndStreamResponse, rollback

Methods inherited from class java.lang.Object

clone, equals, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

LBHttpSolrServer

public LBHttpSolrServer(String... solrServerUrls)
                 throws MalformedURLException

Throws:

MalformedURLException

LBHttpSolrServer

public LBHttpSolrServer(org.apache.http.client.HttpClient httpClient,
                String... solrServerUrl)
                 throws MalformedURLException

The provided httpClient should use a multi-threaded connection manager

Throws:

MalformedURLException

LBHttpSolrServer

public LBHttpSolrServer(org.apache.http.client.HttpClient httpClient,
                ResponseParser parser,
                String... solrServerUrl)
                 throws MalformedURLException

The provided httpClient should use a multi-threaded connection manager

Throws:

MalformedURLException

Method Detail

normalize

public static String normalize(String server)

makeServer

protected HttpSolrServer makeServer(String server)
                             throws MalformedURLException

Throws:

MalformedURLException

request

public LBHttpSolrServer.Rsp request(LBHttpSolrServer.Req req)
                             throws SolrServerException,
                                    IOException

Tries to query a live server from the list provided in Req. Servers in the dead pool are skipped. If a request fails due to an IOException, the server is moved to the dead pool for a certain period of time, or until a test request on that server succeeds. Servers are queried in the exact order given (except servers currently in the dead pool are skipped). If no live servers from the provided list remain to be tried, a number of previously skipped dead servers will be tried. Req.getNumDeadServersToTry() controls how many dead servers will be tried. If no live servers are found a SolrServerException is thrown.

Parameters:

req - contains both the request as well as the list of servers to query

Returns:

the result of the request

Throws:

IOException - If there is a low-level I/O error.

SolrServerException

addSolrServer

public void addSolrServer(String server)
                   throws MalformedURLException

Throws:

MalformedURLException

removeSolrServer

public String removeSolrServer(String server)

setConnectionTimeout

public void setConnectionTimeout(int timeout)

setSoTimeout

public void setSoTimeout(int timeout)

set soTimeout (read timeout) on the underlying HttpConnectionManager. This is desirable for queries, but probably not for indexing.

shutdown

public void shutdown()

Description copied from class: SolrServer

Release allocated resources.

Specified by:

shutdown in class SolrServer

request

public NamedList<Object> request(SolrRequest request)
                          throws SolrServerException,
                                 IOException

Tries to query a live server. A SolrServerException is thrown if all servers are dead. If the request failed due to IOException then the live server is moved to dead pool and the request is retried on another live server. After live servers are exhausted, any servers previously marked as dead will be tried before failing the request.

Specified by:

request in class SolrServer

Parameters:

request - the SolrRequest.

Returns:

response

Throws:

IOException - If there is a low-level I/O error.

SolrServerException

setAliveCheckInterval

public void setAliveCheckInterval(int interval)

LBHttpSolrServer keeps pinging the dead servers at fixed interval to find if it is alive. Use this to set that interval

Parameters:

interval - time in milliseconds

getHttpClient

public org.apache.http.client.HttpClient getHttpClient()

finalize

protected void finalize()
                 throws Throwable

Overrides:

finalize in class Object

Throws:

Throwable