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:

java.io.Serializable

public class LBHttpSolrServer
extends SolrServer

LBHttpSolrServer or "LoadBalanced HttpSolrServer" is just a wrapper to CommonsHttpSolrServer. 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 roundrobin 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, andif 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. The code is relatively new and the API is currently experimental. 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
private static class	LBHttpSolrServer.ServerWrapper

Field Summary

Fields

Modifier and Type	Field and Description
private java.util.concurrent.ScheduledExecutorService	aliveCheckExecutor
private java.util.concurrent.CopyOnWriteArrayList<LBHttpSolrServer.ServerWrapper>	aliveServers
private static int	CHECK_INTERVAL
private java.util.concurrent.locks.ReentrantLock	checkLock
private java.util.concurrent.atomic.AtomicInteger	counter
private org.apache.commons.httpclient.HttpClient	httpClient
private int	interval
private static SolrQuery	solrQuery
private java.util.concurrent.CopyOnWriteArrayList<LBHttpSolrServer.ServerWrapper>	zombieServers

Constructor Summary

Constructors

Constructor and Description
LBHttpSolrServer(org.apache.commons.httpclient.HttpClient httpClient, ResponseParser parser, java.lang.String... solrServerUrl)
LBHttpSolrServer(org.apache.commons.httpclient.HttpClient httpClient, java.lang.String... solrServerUrl)
LBHttpSolrServer(java.lang.String... solrServerUrls)

Method Summary

Modifier and Type	Method and Description
void	addSolrServer(java.lang.String server)
private void	checkAZombieServer(LBHttpSolrServer.ServerWrapper zombieServer) Takes up one dead server and check for aliveness.
protected void	finalize()
private static java.lang.Runnable	getAliveCheckRunner(java.lang.ref.WeakReference<LBHttpSolrServer> lbHttpSolrServer)
org.apache.commons.httpclient.HttpClient	getHttpClient()
private void	moveAliveToDead(LBHttpSolrServer.ServerWrapper solrServer)
java.lang.String	removeSolrServer(java.lang.String server)
NamedList<java.lang.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	setConnectionManagerTimeout(int timeout) set connectionManagerTimeout on the HttpClient.*
void	setConnectionTimeout(int timeout)
void	setSoTimeout(int timeout) set soTimeout (read timeout) on the underlying HttpConnectionManager.
private void	startAliveCheckExecutor()

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

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

Methods inherited from class java.lang.Object

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

Field Detail

aliveServers

private final java.util.concurrent.CopyOnWriteArrayList<LBHttpSolrServer.ServerWrapper> aliveServers

zombieServers

private final java.util.concurrent.CopyOnWriteArrayList<LBHttpSolrServer.ServerWrapper> zombieServers

aliveCheckExecutor

private java.util.concurrent.ScheduledExecutorService aliveCheckExecutor

httpClient

private org.apache.commons.httpclient.HttpClient httpClient

counter

private final java.util.concurrent.atomic.AtomicInteger counter

checkLock

private java.util.concurrent.locks.ReentrantLock checkLock

solrQuery

private static final SolrQuery solrQuery

interval

private int interval

CHECK_INTERVAL

private static final int CHECK_INTERVAL

See Also:

Constant Field Values

Constructor Detail

LBHttpSolrServer

public LBHttpSolrServer(java.lang.String... solrServerUrls)
                 throws java.net.MalformedURLException

Throws:

java.net.MalformedURLException

LBHttpSolrServer

public LBHttpSolrServer(org.apache.commons.httpclient.HttpClient httpClient,
                        java.lang.String... solrServerUrl)
                 throws java.net.MalformedURLException

Throws:

java.net.MalformedURLException

LBHttpSolrServer

public LBHttpSolrServer(org.apache.commons.httpclient.HttpClient httpClient,
                        ResponseParser parser,
                        java.lang.String... solrServerUrl)
                 throws java.net.MalformedURLException

Throws:

java.net.MalformedURLException

Method Detail

addSolrServer

public void addSolrServer(java.lang.String server)
                   throws java.net.MalformedURLException

Throws:

java.net.MalformedURLException

removeSolrServer

public java.lang.String removeSolrServer(java.lang.String server)

setConnectionTimeout

public void setConnectionTimeout(int timeout)

setConnectionManagerTimeout

public void setConnectionManagerTimeout(int timeout)

set connectionManagerTimeout on the HttpClient.*

setSoTimeout

public void setSoTimeout(int timeout)

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

request

public NamedList<java.lang.Object> request(SolrRequest request)
                                    throws SolrServerException,
                                           java.io.IOException

Tries to query a live server. If no live servers are found it throws a SolrServerException. 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 if available. If all live servers are exhausted then a SolrServerException is thrown.

Specified by:

request in class SolrServer

Parameters:

request - the SolrRequest.

Returns:

response

Throws:

SolrServerException

java.io.IOException

checkAZombieServer

private void checkAZombieServer(LBHttpSolrServer.ServerWrapper zombieServer)

Takes up one dead server and check for aliveness. The check is done in a roundrobin. Each server is checked for aliveness once in 'x' millis where x is decided by the setAliveCheckinterval() or it is defaulted to 1 minute

Parameters:

zombieServer - a server in the dead pool

moveAliveToDead

private void moveAliveToDead(LBHttpSolrServer.ServerWrapper solrServer)

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

startAliveCheckExecutor

private void startAliveCheckExecutor()

getAliveCheckRunner

private static java.lang.Runnable getAliveCheckRunner(java.lang.ref.WeakReference<LBHttpSolrServer> lbHttpSolrServer)

getHttpClient

public org.apache.commons.httpclient.HttpClient getHttpClient()

finalize

protected void finalize()
                 throws java.lang.Throwable

Overrides:

finalize in class java.lang.Object

Throws:

java.lang.Throwable