Boost Tomcat Performance: Essential Configurations for Faster Servers

Tomcat this old cat has reached version 10.0.2.

Tomcat has many configuration parameters, but focusing on the key ones can make it run faster.

Changing the server port is done in the server.xml file’s Connector section.

1. Three parameters for concurrency

Tomcat supports NIO; adjust thread and connection settings for best performance. maxThreads – maximum request processing threads, default 200, often set to around 1000 for high concurrency. maxConnections – maximum simultaneous connections; default 10000 for NIO, usually left unchanged. acceptCount – max queue size when threads are busy, often set equal to maxThreads.

Relationship: system can maintain connections = maxConnections + acceptCount (maxConnections are dispatchable, acceptCount are queued). System can process requests = maxThreads.

Deprecated parameters maxProcessors and minProcessors were removed after Tomcat 5.

Reference for Tomcat 8 configuration:

https://tomcat.apache.org/tomcat-8.0-doc/config/http.html

2. Thread configuration

In Connector, thread pool settings include: namePrefix – thread name prefix. maxThreads – maximum threads in pool. minSpareThreads – always active threads. maxIdleTime – idle time before thread termination. threadPriority – thread priority, default 5.

Reference:

https://tomcat.apache.org/tomcat-8.0-doc/config/executor.html

3. JVM configuration

Tomcat runs on Java, so JVM settings affect performance.

3.1 Memory region sizes

-XX:+UseG1GC

– select G1 garbage collector. -Xmx – maximum heap size, typically two‑thirds of OS memory. -Xms – initial heap size, usually same as Xmx. -Xmn – young generation size; under G1 it is auto‑adjusted. -XX:MaxMetaspaceSize – metaspace limit, e.g., 256M. -XX:MaxDirectMemorySize – max direct memory. -XX:ReservedCodeCacheSize – JIT code cache size. -Xss – thread stack size, default 1M.

3.2 Memory tuning

-XX:+AlwaysPreTouch

– pre‑touch memory at startup. -XX:SurvivorRatio – ratio of Eden to survivor space, default 8. -XX:MaxTenuringThreshold – object promotion age threshold. PretenureSizeThreshold – allocate large objects directly in old generation.

3.3 Garbage collector tuning (G1)

-XX:MaxGCPauseMillis

– target GC pause time. -XX:G1HeapRegionSize – size of G1 heap regions. -XX:InitiatingHeapOccupancyPercent – heap occupancy threshold to start concurrent marking. -XX:ConcGCThreads – number of GC threads, usually left default.

4. Other important Connector settings

enableLookups

– whether to perform DNS lookup for remote host. URIEncoding – character encoding for URLs, default ISO‑8859‑1. connectionTimeout – connection timeout in milliseconds. redirectPort – port for SSL redirection.

5. Summary

Tomcat is a widely used web container with hundreds of configuration options; focusing on the most important parameters—concurrency, thread pool, JVM, and key Connector settings—yields significant performance improvements without needing to master every option.