Enhance application performance

[3dgiordano]

This pull request introduces several important improvements to memory management, resource cleanup, and protocol cache handling in the HTTP plugin. The main changes address memory leaks and resource retention issues by ensuring buffers and caches are properly released or capped, and by adding explicit cache management methods. These updates help prevent excessive memory usage and improve the stability of long-running or high-throughput tests.

Memory and Buffer Management:

• Added logic to release Jetty transport buffers in HTTP2FutureResponseListener to avoid retaining unnecessary copies of response bodies and request graphs, preventing memory leaks after sample materialization, cancellation, or failed/raced requests. [1] [2] [3] [4] [5] [6]
• Updated HTTP2JettyClient to cap the pooled buffer memory by introducing a configurable maximum for the ArrayByteBufferPool, and provided a method to clear the buffer pool. [1] [2] [3]

Protocol Cache Management:

• Introduced soft limits and explicit TTL-based pruning for protocol negotiation caches (Alt-Svc, HTTP/1.1-only, H2C, and HTTP/3 exploration), including static methods to clear or prune expired entries and prevent unbounded cache growth. [1] [2]

Compression and Decoder Resource Handling:

• Added explicit management and capping of the gzip InflaterPool and other compression-related resources to prevent retention of large pools per thread. [1] [2]

Transaction Sample Lifecycle Improvements:

• Ensured that completed parent transaction samples are released from the TestCompiler map after listeners and assertions have run, mirroring upstream JMeter fixes and preventing retention of large sample trees.

Async Sample Cleanup:

• Ensured that pending async HTTP/2 samples are fully cleared, including dropping references to response/request graphs, when an iteration is aborted.