Sunday, March 15, 2009

Performance Optimization in Apache

1. Useful modules which could be used

mod_dbd -> Connection Pooling for other modules

mod_filter -> Dynamic chaing of filters, filters inserted based on request headers and response

mod_dumpio --> Dumps all IO to error log - in case of SSL dumping is done right before encryption and after decryption

mod_log_forensic --> helps in tracking request response , resulting in 2 lines of log for each request

mod_info - helps in giving info about all modules installed


Enabling can improve the performance by reducing IO calls for fetching the content (since all static content are served from apache)

mod_cache --> mod_disk_cache /mod_mem_cache - determines cache implementataion

3. Rewrite rules

a. Since Rewrite rules and regular expression matching are expensive can be replaced with Proxy pass where ever possible

RewriteRule ^/ws/(.*) http://localhost:8080/ws/$1 [P,L] with
ProxyPass ^/ws/ http://localhost:8080/ws/$1 [P,L]

b.Smart order of rewrite rules

The order of rewrite rules needs to be arranged in such a way that the maximum occurring instances should be available at the top , since the entire list is scanned trough for every request


RewriteRule ^/(.*\.jsp) http://localhost:8080/$1 [P]
RewriteRule ^/(.*\.do) http://localhost:8080/$1 [P]

Could be replaced with

RewriteRule ^/(.*\.do) http://localhost:8080/$1 [P]
RewriteRule ^/(.*\.jsp) http://localhost:8080/$1 [P]

Since the maximum number of requests we expect will be .do requests. This will improve performance because there will be only few jsp requests and most of the times execution can stop in the above line.

4. Also other parameters for Operating systems and GC tuning will enhance the performance

5. Graceful shutdown - handle existing request , time limit can be specified in case of long time
consuming request with property GracefulShutdownTime

6. Prefork MPM- Stable but not scalable - one process per request

Worker MPM(Preferred) - more scalable , thread safeness of libs critical - one thread per request

7. Useful Parametres

Controling Idle pool - MinspareServers /MaxspareServers




8. KeepAlives - prevents connections (socket open close for each request)

9.Avoid DNS Lookups

10. On the Fly Compression - deflate - bandwidth reduction and faster response times

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