Fix unbounded StringBuilder retention in ThreadLocal (memory leak)#391
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SylvainJuge merged 1 commit intoelastic:mainfrom Apr 21, 2026
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getMessageStringBuilder() called setLength(0) which resets the logical length but never shrinks the internal char[] buffer. In thread-pool environments, a single large trace permanently bloats the buffer for that thread's lifetime, causing cumulative heap pressure. Add a capacity threshold check (8 KB) that discards oversized buffers and replaces them with fresh instances, while still reusing normally-sized buffers for zero-allocation steady state. Fixes elastic#381
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SylvainJuge
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getMessageStringBuilder() called setLength(0) which resets the logical length but never shrinks the internal char[] buffer. In thread-pool environments, a single large trace permanently bloats the buffer for that thread's lifetime, causing cumulative heap pressure.
Add a capacity threshold check (8 KB) that discards oversized buffers and replaces them with fresh instances, while still reusing normally-sized buffers for zero-allocation steady state.
Fixes #381