Use less subshells and tees in running tests with bazel run.
#17846
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Fixes #17754. What we have seen prior to this change was that sometimes for quick tests the output was swallowed. After a lot of poking it became clear that the culprit is the use of subshell and `tee`, e.g. if you remove `tee` completely from the picture the behavior never shows up. The issue is that with a fast test, `tee` seems to be killed (or its parent subshell) before the printing the output to stdout. With this change, we reduce the number of subshells and processes to set up and reduce the chance of the race condition but not remove it. However, for practical purposes, the race condition is gone. With the reproduction steps in #17754, and this command ``` for i in {1..10000}; do /tmp/bazel run :foo &> /tmp/log ; grep -q "useful echo" /tmp/log ; if [ $? -eq 0 ]; then echo -n '+'; else echo -n '-'; fi; done ``` a bazel from head fails ~3900 out of 10000 times. After this commit, it never failed.
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Fixes bazelbuild#17754. What we have seen prior to this change was that sometimes for quick tests the output was swallowed. After a lot of poking it became clear that the culprit is the use of subshell and `tee`, e.g. if you remove `tee` completely from the picture the behavior never shows up. The issue is that with a fast test, `tee` seems to be killed (or its parent subshell) before the printing the output to stdout. With this change, we reduce the number of subshells and processes to set up and reduce the chance of the race condition but not remove it. However, for practical purposes, the race condition is gone. With the reproduction steps in bazelbuild#17754, and this command ``` for i in {1..10000}; do /tmp/bazel run :foo &> /tmp/log ; grep -q "useful echo" /tmp/log ; if [ $? -eq 0 ]; then echo -n '+'; else echo -n '-'; fi; done ``` a bazel from head fails ~3900 out of 10000 times. After this commit, it never failed. Closes bazelbuild#17846. PiperOrigin-RevId: 518794237 Change-Id: I8c1862d3a274799b864f0f5f42b85d6df5af78c7
ShreeM01
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) Fixes #17754. What we have seen prior to this change was that sometimes for quick tests the output was swallowed. After a lot of poking it became clear that the culprit is the use of subshell and `tee`, e.g. if you remove `tee` completely from the picture the behavior never shows up. The issue is that with a fast test, `tee` seems to be killed (or its parent subshell) before the printing the output to stdout. With this change, we reduce the number of subshells and processes to set up and reduce the chance of the race condition but not remove it. However, for practical purposes, the race condition is gone. With the reproduction steps in #17754, and this command ``` for i in {1..10000}; do /tmp/bazel run :foo &> /tmp/log ; grep -q "useful echo" /tmp/log ; if [ $? -eq 0 ]; then echo -n '+'; else echo -n '-'; fi; done ``` a bazel from head fails ~3900 out of 10000 times. After this commit, it never failed. Closes #17846. PiperOrigin-RevId: 518794237 Change-Id: I8c1862d3a274799b864f0f5f42b85d6df5af78c7 Co-authored-by: Tobias Werth <twerth@google.com>
fweikert
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May 25, 2023
Fixes bazelbuild#17754. What we have seen prior to this change was that sometimes for quick tests the output was swallowed. After a lot of poking it became clear that the culprit is the use of subshell and `tee`, e.g. if you remove `tee` completely from the picture the behavior never shows up. The issue is that with a fast test, `tee` seems to be killed (or its parent subshell) before the printing the output to stdout. With this change, we reduce the number of subshells and processes to set up and reduce the chance of the race condition but not remove it. However, for practical purposes, the race condition is gone. With the reproduction steps in bazelbuild#17754, and this command ``` for i in {1..10000}; do /tmp/bazel run :foo &> /tmp/log ; grep -q "useful echo" /tmp/log ; if [ $? -eq 0 ]; then echo -n '+'; else echo -n '-'; fi; done ``` a bazel from head fails ~3900 out of 10000 times. After this commit, it never failed. Closes bazelbuild#17846. PiperOrigin-RevId: 518794237 Change-Id: I8c1862d3a274799b864f0f5f42b85d6df5af78c7
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Fixes #17754.
What we have seen prior to this change was that sometimes for quick tests the output was swallowed. After a lot of poking it became clear that the culprit is the use of subshell and
tee, e.g. if you removeteecompletely from the picture the behavior never shows up.The issue is that with a fast test,
teeseems to be killed (or its parent subshell) before the printing the output to stdout.With this change, we reduce the number of subshells and processes to set up and reduce the chance of the race condition but not remove it.
However, for practical purposes, the race condition is gone.
With the reproduction steps in #17754, and this command
a bazel from head fails ~3900 out of 10000 times.
After this commit, it never failed.