The service crashes every few hours with OutOfMemoryError. Where would you start analyzing the problem?

The first step in troubleshooting an OutOfMemoryError in a Java service is to collect and analyze a heap dump — a snapshot of memory at the time of the error. This helps understand which objects occupy most of the memory and are not being released.

Next, check the JVM settings, especially parameters related to heap size, and ensure they match the load and server resources.

It is also useful to enable garbage collection (GC) logs for analysis of the frequency and efficiency of memory cleanup.

In the code, look for potential memory leaks: for example, collections that grow constantly, unbounded caches, static references to objects, listeners that are not removed.

An example of running the JVM with parameters for collecting heap dump and GC logs:

java -Xmx2g -XX:+HeapDumpOnOutOfMemoryError -XX:HeapDumpPath=/path/to/dumps \
     -Xlog:gc*:file=/path/to/gc.log:time,uptime,level,tags
     -jar yourapp.jar

After collecting the heap dump, it can be analyzed using tools such as VisualVM, Eclipse MAT, or YourKit.