perf(runner): stat a marker instead of scanning the shared temp dir - #1270
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Every test's EXIT trap expanded
matches=("$BASHUNIT_TEMP_DIR/${BASHUNIT_CURRENT_TEST_ID}"_*)
which makes bash read all of BASHUNIT_TEMP_DIR. That directory is shared
(${TMPDIR:-/tmp}/bashunit/tmp), survives between runs and nothing reaps it, so
every file an interrupted run left there was re-examined by every test of every
later run. It could never match one: the id carries the run's own $$.
Profiling a 200-test run against a real 4242-file directory, this single call
was 3.16ms of an 8.5ms per-test total -- larger than the test body, both hooks,
mock teardown and result encoding combined. A 100-test file:
leftovers 0 500 2000 5000
before 498ms 513ms 635ms 978ms
after 520ms - 520ms 542ms
temp_file/temp_dir now write a <id>_.mark marker (a redirect, not a fork) and
the trap returns early when it is absent -- the common case, since most tests
create no temp file. The marker shares the <id>_ prefix, so the existing rm
takes it along with the rest.
Behaviour change: a file a test writes into BASHUNIT_TEMP_DIR by hand, named
with its own id, is no longer removed for it. Finding one is exactly the
directory scan being removed. The guard test plants such a file and asserts it
survives, which no timing assertion could pin deterministically.
Closes #1269
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🤔 Background
Related #1269
Every test's EXIT trap expanded a glob over
BASHUNIT_TEMP_DIR, which makes bash read the whole directory. That directory is shared, survives between runs and nothing reaps it — so every file an interrupted run left behind was re-examined by every test of every later run, and could never match, since the test id carries the run's own$$.Profiling a 200-test run against a real 4,242-file directory, this one call was 3.16 ms of an 8.5 ms per-test total — larger than the test body, both hooks, mock teardown and result encoding combined.
💡 Changes
temp_file/temp_dirwrite a<id>_.markmarker (a redirect, not a fork); the trap stats it and returns early when absent, which is the common case since most tests create no temp file. The marker shares the<id>_prefix, so the existingrmtakes it along with the rest