org.apache.solr.client.solrj.impl

Class LBHttpSolrClient

  • All Implemented Interfaces:
    Closeable, Serializable, AutoCloseable


    public class LBHttpSolrClient
    extends SolrClient
    LBHttpSolrClient or "LoadBalanced HttpSolrClient" is a load balancing wrapper around HttpSolrClient. This is useful when you have multiple Solr servers and the requests need to be Load Balanced among them. Do NOT use this class for indexing in master/slave scenarios since documents must be sent to the correct master; no inter-node routing is done. In SolrCloud (leader/replica) scenarios, it is usually better to use CloudSolrClient, but this class may be used for updates because the server will forward them to the appropriate leader.

    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 at least one server is alive, the request succeeds, and if not it fails.

     SolrClient lbHttpSolrClient = new LBHttpSolrClient("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();
     SolrClient lbHttpSolrClient = new LBHttpSolrClient(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