Phase 2.5: Deferred activation — connect before enabling EXT_STMT#6
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pronskiy merged 1 commit intophase2-observer-migrationfrom Mar 10, 2026
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At RINIT, when a debug trigger is present, attempt TCP connect to the client before enabling ZEND_COMPILE_EXTENDED_STMT. If no client is listening (ECONNREFUSED), keep observer_active=0 and skip EXT_STMT. This eliminates ~2.3x overhead in the triggered-no-client scenario (e.g. XDEBUG_SESSION=1 but no IDE listening). The extension now stays dormant, matching the untriggered performance (~10% observer floor). Two-stage connection approach: 1. RINIT: TCP connect only (xdebug_early_connect_to_client) 2. First function call: DBGp handshake on the pre-opened socket Also fixes RINIT trigger check to respect start_with_request=no and XDEBUG_IGNORE, matching xdebug_debug_init_if_requested_at_startup behavior. Benchmark (build server, PHP 8.6.0-dev): - Vanilla: ~0.55s - Loaded, no trigger: ~0.56s (~0%) - Loaded, triggered, no client (before): ~1.63s (~2.3x) - Loaded, triggered, no client (after): ~0.55s (~0%) Test results: 54 fail (same as Phase 2 baseline, zero regressions).
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Phase 2.5: Deferred activation — connect before enabling EXT_STMT
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Summary
At RINIT, when a debug trigger is present (e.g.
XDEBUG_SESSION=1), attempt TCP connect to the client before enablingZEND_COMPILE_EXTENDED_STMT. If no client is listening (ECONNREFUSED), keepobserver_active=0and skip EXT_STMT — the extension stays dormant.This eliminates ~2.3× overhead in the triggered-no-client scenario.
Approach: Two-stage connection
xdebug_early_connect_to_client()— no DBGp handshake (needsprogram_namefrom first op_array)xdebug_init_debugger()sees socket already open → skips connect → does DBGp handshakeAlso fixes RINIT trigger check to respect
start_with_request=noandXDEBUG_IGNORE, matchingxdebug_debug_init_if_requested_at_startup()behavior.Files changed
xdebug.c— RINIT early connect + EXT_STMT decisionsrc/debugger/com.c—xdebug_early_connect_to_client(), modifiedxdebug_init_debugger()to reuse pre-opened socketsrc/debugger/com.h— declarationsrc/debugger/debugger.c— initialize socket to -1Benchmarks (build server, PHP 8.6.0-dev)
Tests
54 failures — identical to Phase 2 baseline. Zero regressions.