solr1.4 中SearchHandler使用的httpclient在高并发可能出现的问题
solr 1.4 中使用的分布式搜索，是基于httpclient发出分布结点的请求，主要实现在SearchHandler类，该类里有个内部类

The parameters that can be specified are as follows:socketTimeout. default: 0 (use OS default) - The amount of time in ms that a socket is allowed to wait forconnTimeout. default: 0 (use OS default) - The amount of time in ms that is accepted for binding / connection a socketmaxConnectionsPerHost. default: 20 - The maximum number of connections that is made to each individual shard in a distributed searchcorePoolSize. default: 0 - The retained lowest limit on the number of threads used in coordinating distributed searchmaximumPoolSize. default: Integer.MAX_VALUE - The maximum number of threads used for coordinating distributed searchmaxThreadIdleTime. default: 5 seconds - The amount of time to wait for before threads are scaled back in response to a reduction in loadsizeOfQueue. default: -1 - If specified the thread pool will use a backing queue instead of a direct handoff buffer. This may seem difficult to grasp, essentially high throughput systems will want to configure this to be a direct hand off (with -1). Systems that desire better latency will want to configure a reasonable size of queue to handle variations in requests.fairnessPolicy. default: false - Chooses in the JVM specifics dealing with fair policy queuing, if enabled distributed searches will be handled in a First in First out fashion at a cost to throughput. If disabled throughput will be favoured over latency.

http://blog.csdn.net/duck_genuine/article/details/7839479