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[PATCH v2 7/7] test-lib: add the '--stress' option to run a test repeatedly under load

From
SZEDER Gábor <szeder.dev@gmail.com>
Date
Dec 9, 2018, 22:56 UTC
Message-ID
<20181209225628.22216-8-szeder.dev@gmail.com>
In-Reply-To
<20181209225628.22216-1-szeder.dev@gmail.com>

Unfortunately, we have a few flaky tests, whose failures tend to be hard to reproduce. We've found that the best we can do to reproduce such a failure is to run the test repeatedly while the machine is under load, and wait in the hope that the load creates enough variance in the timing of the test's commands that a failure is evenually triggered. I have a command to do that, and I noticed that two other contributors have rolled their own scripts to do the same, all choosing slightly different approaches.

To help reproduce failures in flaky tests, introduce the '--stress' option to run a test script repeatedly in multiple parallel jobs until one of them fails, thereby using the test script itself to increase the load on the machine.

The number of parallel jobs is determined by, in order of precedence: the number specified as '--stress=<N>', or the value of the GIT_TEST_STRESS_LOAD environment variable, or twice the number of available processors (as reported by the 'getconf' utility), or 8.

Make '--stress' imply '--verbose -x --immediate' to get the most information about rare failures; there is really no point in spending all the extra effort to reproduce such a failure, and then not know which command failed and why.

To prevent the several parallel invocations of the same test from interfering with each other:

  - Include the parallel job's number in the name of the trash
    directory and the various output files under 't/test-results/' as
    a '.stress-<Nr>' suffix.
  - Add the parallel job's number to the port number specified by the
    user or to the test number, so even tests involving daemons
    listening on a TCP socket can be stressed.
  - Redirect each parallel test run's output to
    't/test-results/$TEST_NAME.stress-<nr>.out', because dumping the
    output of several parallel running tests to the terminal would
    create a big ugly mess.

For convenience, print the output of the failed test job at the end, and rename its trash directory to end with the '.stress-failed' suffix, so it's easy to find in a predictable path. If, in an unlikely case, more than one jobs were to fail nearly at the same time, then print the output of all failed jobs, and rename the trash directory of only the last one (i.e. with the highest job number), as it is the trash directory of the test whose output will be at the bottom of the user's terminal.

Based on Jeff King's 'stress' script.
Signed-off-by: SZEDER Gábor <szeder.dev@gmail.com>
---
 t/README                |  19 +++++++-
 t/test-lib-functions.sh |   7 ++-
 t/test-lib.sh           | 103 ++++++++++++++++++++++++++++++++++++++--
 3 files changed, 123 insertions(+), 6 deletions(-)
diff --git a/t/README b/t/README
index 28711cc508..11ce7675e3 100644
--- a/t/README
+++ b/t/README
@@ -186,6 +186,22 @@ appropriately before running "make".
 	this feature by setting the GIT_TEST_CHAIN_LINT environment
 	variable to "1" or "0", respectively.
 
+--stress::
+--stress=<N>::
+	Run the test script repeatedly in multiple parallel jobs until
+	one of them fails.  Useful for reproducing rare failures in
+	flaky tests.  The number of parallel jobs is, in order of
+	precedence: <N>, or the value of the GIT_TEST_STRESS_LOAD
+	environment variable, or twice the number of available
+	processors (as shown by the 'getconf' utility),	or 8.
+	Implies `--verbose -x --immediate` to get the most information
+	about the failure.  Note that the verbose output of each test
+	job is saved to 't/test-results/$TEST_NAME.stress-<nr>.out',
+	and only the output of the failed test job is shown on the
+	terminal.  The names of the trash directories get a
+	'.stress-<nr>' suffix, and the trash directory of the failed
+	test job is renamed to end with a '.stress-failed' suffix.
+
 You can also set the GIT_TEST_INSTALLED environment variable to
 the bindir of an existing git installation to test that installation.
 You still need to have built this git sandbox, from which various
@@ -425,7 +441,8 @@ This test harness library does the following things:
  - Creates an empty test directory with an empty .git/objects database
    and chdir(2) into it.  This directory is 't/trash
    directory.$test_name_without_dotsh', with t/ subject to change by
-   the --root option documented above.
+   the --root option documented above, and a '.stress-<N>' suffix
+   appended by the --stress option.
 
  - Defines standard test helper functions for your scripts to
    use.  These functions are designed to make all scripts behave
diff --git a/t/test-lib-functions.sh b/t/test-lib-functions.sh
index 3746327bde..ee3435c6df 100644
--- a/t/test-lib-functions.sh
+++ b/t/test-lib-functions.sh
@@ -1288,8 +1288,6 @@ test_set_port () {
 			# root-only port, use a larger one instead.
 			port=$(($port + 10000))
 		fi
-
-		eval $var=$port
 		;;
 	*[^0-9]*)
 		error >&7 "invalid port number: $port"
@@ -1298,4 +1296,9 @@ test_set_port () {
 		# The user has specified the port.
 		;;
 	esac
+
+	# Make sure that parallel '--stress' test jobs get different
+	# ports.
+	port=$(($port + ${GIT_TEST_STRESS_JOB_NR:-0}))
+	eval $var=$port
 }
diff --git a/t/test-lib.sh b/t/test-lib.sh
index d55d158580..e405191164 100644
--- a/t/test-lib.sh
+++ b/t/test-lib.sh
@@ -87,21 +87,110 @@ do
 		valgrind_only=${opt#--*=} ;;
 	--root=*)
 		root=${opt#--*=} ;;
+	--stress)
+		stress=t ;;
+	--stress=*)
+		stress=${opt#--*=} ;;
 	*)
 		# Other options will be handled later.
 	esac
 done
 
+TEST_STRESS_JOB_SFX="${GIT_TEST_STRESS_JOB_NR:+.stress-$GIT_TEST_STRESS_JOB_NR}"
 TEST_NAME="$(basename "$0" .sh)"
 TEST_RESULTS_DIR="$TEST_OUTPUT_DIRECTORY/test-results"
-TEST_RESULTS_BASE="$TEST_RESULTS_DIR/$TEST_NAME"
-TRASH_DIRECTORY="trash directory.$TEST_NAME"
+TEST_RESULTS_BASE="$TEST_RESULTS_DIR/$TEST_NAME$TEST_STRESS_JOB_SFX"
+TRASH_DIRECTORY="trash directory.$TEST_NAME$TEST_STRESS_JOB_SFX"
 test -n "$root" && TRASH_DIRECTORY="$root/$TRASH_DIRECTORY"
 case "$TRASH_DIRECTORY" in
 /*) ;; # absolute path is good
  *) TRASH_DIRECTORY="$TEST_OUTPUT_DIRECTORY/$TRASH_DIRECTORY" ;;
 esac
 
+# If --stress was passed, run this test repeatedly in several parallel loops.
+if test "$GIT_TEST_STRESS_STARTED" = "done"
+then
+	: # Don't stress test again.
+elif test -n "$stress"
+then
+	if test "$stress" != t
+	then
+		job_count=$stress
+	elif test -n "$GIT_TEST_STRESS_LOAD"
+	then
+		job_count="$GIT_TEST_STRESS_LOAD"
+	elif job_count=$(getconf _NPROCESSORS_ONLN 2>/dev/null) &&
+	     test -n "$job_count"
+	then
+		job_count=$((2 * $job_count))
+	else
+		job_count=8
+	fi
+
+	mkdir -p "$TEST_RESULTS_DIR"
+	stressfail="$TEST_RESULTS_BASE.stress-failed"
+	rm -f "$stressfail"
+
+	stress_exit=0
+	trap '
+		kill $job_pids 2>/dev/null
+		wait
+		stress_exit=1
+	' TERM INT HUP
+
+	job_pids=
+	job_nr=0
+	while test $job_nr -lt "$job_count"
+	do
+		(
+			GIT_TEST_STRESS_STARTED=done
+			GIT_TEST_STRESS_JOB_NR=$job_nr
+			export GIT_TEST_STRESS_STARTED GIT_TEST_STRESS_JOB_NR
+
+			trap '
+				kill $test_pid 2>/dev/null
+				wait
+				exit 1
+			' TERM INT
+
+			cnt=0
+			while ! test -e "$stressfail"
+			do
+				$TEST_SHELL_PATH "$0" "$@" >"$TEST_RESULTS_BASE.stress-$job_nr.out" 2>&1 &
+				test_pid=$!
+
+				if wait $test_pid
+				then
+					printf "OK   %2d.%d\n" $GIT_TEST_STRESS_JOB_NR $cnt
+				else
+					echo $GIT_TEST_STRESS_JOB_NR >>"$stressfail"
+					printf "FAIL %2d.%d\n" $GIT_TEST_STRESS_JOB_NR $cnt
+				fi
+				cnt=$(($cnt + 1))
+			done
+		) &
+		job_pids="$job_pids $!"
+		job_nr=$(($job_nr + 1))
+	done
+
+	wait
+
+	if test -f "$stressfail"
+	then
+		echo "Log(s) of failed test run(s):"
+		for failed_job_nr in $(sort -n "$stressfail")
+		do
+			echo "Contents of '$TEST_RESULTS_BASE.stress-$failed_job_nr.out':"
+			cat "$TEST_RESULTS_BASE.stress-$failed_job_nr.out"
+		done
+		rm -rf "$TRASH_DIRECTORY.stress-failed"
+		# Move the last one.
+		mv "$TRASH_DIRECTORY.stress-$failed_job_nr" "$TRASH_DIRECTORY.stress-failed"
+	fi
+
+	exit $stress_exit
+fi
+
 # if --tee was passed, write the output not only to the terminal, but
 # additionally to the file test-results/$BASENAME.out, too.
 if test "$GIT_TEST_TEE_STARTED" = "done"
@@ -340,7 +429,8 @@ do
 	--va|--val|--valg|--valgr|--valgri|--valgrin|--valgrind|\
 	--valgrind=*|\
 	--valgrind-only=*|\
-	--root=*)
+	--root=*|\
+	--stress|--stress=*)
 		shift ;; # These options were handled already.
 	*)
 		echo "error: unknown test option '$1'" >&2; exit 1 ;;
@@ -379,6 +469,13 @@ then
 	verbose=t
 fi
 
+if test -n "$stress"
+then
+	verbose=t
+	trace=t
+	immediate=t
+fi
+
 if test -n "$color"
 then
 	# Save the color control sequences now rather than run tput

-- 
2.20.0.rc2.156.g5a9fd2ce9c
Previous: SZEDER GáborNext: SZEDER Gábor
Message 43 of 67 in “test-lib: add the '--stress' option to help reproduce occasional failures in flaky tests”
  1. 0/3 test-lib: add the '--stress' option to help reproduce occasional failures in flaky testsSZEDER Gábor, Dec 4, 2018
  2. 1/3 test-lib: consolidate naming of test-results pathsSZEDER Gábor, Dec 4, 2018
  3. Jeff KingDec 5, 2018
  4. 2/3 test-lib-functions: introduce the 'test_set_port' helper functionSZEDER Gábor, Dec 4, 2018
  5. Jeff KingDec 5, 2018
  6. SZEDER GáborDec 5, 2018
  7. Jeff KingDec 5, 2018
  8. 3/3 test-lib: add the '--stress' option to run a test repeatedly under loadSZEDER Gábor, Dec 4, 2018
  9. Ævar Arnfjörð BjarmasonDec 4, 2018
  10. SZEDER GáborDec 4, 2018
  11. Jeff KingDec 5, 2018
  12. Ævar Arnfjörð BjarmasonDec 4, 2018
  13. Jeff KingDec 5, 2018
  14. SZEDER GáborDec 5, 2018
  15. Ævar Arnfjörð BjarmasonDec 5, 2018
  16. SZEDER GáborDec 5, 2018
  17. Ævar Arnfjörð BjarmasonDec 5, 2018
  18. Jeff KingDec 5, 2018
  19. SZEDER GáborDec 5, 2018
  20. Jeff KingDec 5, 2018
  21. Junio C HamanoDec 6, 2018
  22. Jeff KingDec 6, 2018
  23. Junio C HamanoDec 6, 2018
  24. SZEDER GáborDec 6, 2018
  25. Jeff KingDec 7, 2018
  26. SZEDER GáborDec 5, 2018
  27. Jeff KingDec 5, 2018
  28. SZEDER GáborDec 6, 2018
  29. Jeff KingDec 7, 2018
  30. 0/7 test-lib: add the '--stress' option to help reproduce occasional failures in flaky testsSZEDER Gábor, Dec 9, 2018
  31. 2/7 test-lib: parse some --options earlierSZEDER Gábor, Dec 9, 2018
  32. Jeff KingDec 11, 2018
  33. SZEDER GáborDec 11, 2018
  34. Jeff KingDec 17, 2018
  35. SZEDER GáborDec 30, 2018
  36. Jeff KingJan 3, 2019
  37. 1/7 test-lib: translate SIGTERM and SIGHUP to an exitSZEDER Gábor, Dec 9, 2018
  38. Jeff KingDec 11, 2018
  39. 4/7 test-lib: set $TRASH_DIRECTORY earlierSZEDER Gábor, Dec 9, 2018
  40. 5/7 test-lib: extract Bash version check for '-x' tracingSZEDER Gábor, Dec 9, 2018
  41. 3/7 test-lib: consolidate naming of test-results pathsSZEDER Gábor, Dec 9, 2018
  42. 6/7 test-lib-functions: introduce the 'test_set_port' helper functionSZEDER Gábor, Dec 9, 2018
  43. 7/7 test-lib: add the '--stress' option to run a test repeatedly under loadSZEDER Gábor, Dec 9, 2018
  44. fixup! test-lib: add the '--stress' option to run a test repeatedly under loadSZEDER Gábor, Dec 10, 2018
  45. Jeff KingDec 11, 2018
  46. 0/8 test-lib: add the '--stress' option to help reproduce occasional failures in flaky testsSZEDER Gábor, Dec 30, 2018
  47. 1/8 test-lib: translate SIGTERM and SIGHUP to an exitSZEDER Gábor, Dec 30, 2018
  48. 2/8 test-lib: parse options in a for loop to keep $@ intactSZEDER Gábor, Dec 30, 2018
  49. 3/8 test-lib: parse command line options earlierSZEDER Gábor, Dec 30, 2018
  50. 6/8 test-lib: extract Bash version check for '-x' tracingSZEDER Gábor, Dec 30, 2018
  51. Carlo ArenasDec 31, 2018
  52. 7/8 test-lib-functions: introduce the 'test_set_port' helper functionSZEDER Gábor, Dec 30, 2018
  53. 5/8 test-lib: set $TRASH_DIRECTORY earlierSZEDER Gábor, Dec 30, 2018
  54. SZEDER GáborDec 30, 2018
  55. 5/8 test-lib: set $TRASH_DIRECTORY earlierSZEDER Gábor, Dec 30, 2018
  56. 4/8 test-lib: consolidate naming of test-results pathsSZEDER Gábor, Dec 30, 2018
  57. 8/8 test-lib: add the '--stress' option to run a test repeatedly under loadSZEDER Gábor, Dec 30, 2018
  58. 0/8 test-lib: add the '--stress' option to help reproduce occasional failures in flaky testsSZEDER Gábor, Jan 5, 2019
  59. 1/8 test-lib: translate SIGTERM and SIGHUP to an exitSZEDER Gábor, Jan 5, 2019
  60. 2/8 test-lib: extract Bash version check for '-x' tracingSZEDER Gábor, Jan 5, 2019
  61. 3/8 test-lib: parse options in a for loop to keep $@ intactSZEDER Gábor, Jan 5, 2019
  62. 4/8 test-lib: parse command line options earlierSZEDER Gábor, Jan 5, 2019
  63. 5/8 test-lib: consolidate naming of test-results pathsSZEDER Gábor, Jan 5, 2019
  64. 6/8 test-lib: set $TRASH_DIRECTORY earlierSZEDER Gábor, Jan 5, 2019
  65. 8/8 test-lib: add the '--stress' option to run a test repeatedly under loadSZEDER Gábor, Jan 5, 2019
  66. 7/8 test-lib-functions: introduce the 'test_set_port' helper functionSZEDER Gábor, Jan 5, 2019
  67. Jeff KingJan 7, 2019

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