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Re: [Qemu-devel] [PATCH 4/5] iotests: Make 083 less flaky
From: |
Max Reitz |
Subject: |
Re: [Qemu-devel] [PATCH 4/5] iotests: Make 083 less flaky |
Date: |
Thu, 9 Nov 2017 21:29:20 +0100 |
User-agent: |
Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.4.0 |
On 2017-11-09 15:11, Eric Blake wrote:
> On 11/08/2017 07:38 PM, Max Reitz wrote:
>> 083 has (at least) two issues:
>
> I think I hit one of them intermittently yesterday; thanks for
> diagnosing these (and like you say, there may be more lurking, but we'll
> whack them separately if we can reproduce and identify them).
>
>>
>> 1. By launching the nbd-fault-injector in background, it may not be
>> scheduled until the first grep on its output file is executed.
>> However, until then, that file may not have been created yet -- so it
>> either does not exist yet (thus making the grep emit an error), or it
>> does exist but contains stale data (thus making the rest of the test
>> case work connect to a wrong address).
>> Fix this by explicitly overwriting the output file before executing
>> nbd-fault-injector.
>>
>> 2. The nbd-fault-injector prints things other than "Listening on...".
>> It also prints a "Closing connection" message from time to time. We
>> currently invoke sed on the whole file in the hope of it only
>> containing the "Listening on..." line yet. That hope is sometimes
>> shattered by the brutal reality of race conditions, so invoke grep
>> before sed.
>
> Invoking 'grep | sed' is almost always a waste of a process; sed can do
> the job alone.
>
>>
>> Signed-off-by: Max Reitz <address@hidden>
>> ---
>> tests/qemu-iotests/083 | 3 ++-
>> 1 file changed, 2 insertions(+), 1 deletion(-)
>>
>> diff --git a/tests/qemu-iotests/083 b/tests/qemu-iotests/083
>> index 0306f112da..2f6444eeb9 100755
>> --- a/tests/qemu-iotests/083
>> +++ b/tests/qemu-iotests/083
>> @@ -86,6 +86,7 @@ EOF
>>
>> rm -f "$TEST_DIR/nbd.sock"
>>
>> + echo > "$TEST_DIR/nbd-fault-injector.out"
>
> This makes the file contain a blank line. Would it be any better as a
> truly empty file, as in:
>
> : > "$TEST_DIR/nbd-fault-injector.out"
Although ":>" looks funny, I guess I'd rather stay with the echo...
Yes, it may look stupid to you, but I would have to look up what exactly
that will do, whereas the echo is clear.
And in the end, both work equally fine.
>> $PYTHON nbd-fault-injector.py $extra_args "$nbd_addr"
>> "$TEST_DIR/nbd-fault-injector.conf" >"$TEST_DIR/nbd-fault-injector.out" 2>&1
>> &
>>
>> # Wait for server to be ready
>> @@ -94,7 +95,7 @@ EOF
>> done
>>
>> # Extract the final address (port number has now been assigned in tcp
>> case)
>> - nbd_addr=$(sed 's/Listening on \(.*\)$/\1/'
>> "$TEST_DIR/nbd-fault-injector.out")
>> + nbd_addr=$(grep 'Listening on ' "$TEST_DIR/nbd-fault-injector.out"
>> | sed 's/Listening on \(.*\)$/\1/')
>
> Fixing TAB damage while at it - nice.
>
> Here's how to do it using just sed, and with less typing:
>
> nbd_addr=$(sed -n 's/^Listening on //p' \
> "$TEST_DIR/nbd-fault-injector.out")
Oh, nice! Will do, thanks.
Max
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- [Qemu-devel] [PATCH 0/5] iotests: Make some tests less flaky, Max Reitz, 2017/11/08
- [Qemu-devel] [PATCH 1/5] iotests: Make 030 less flaky, Max Reitz, 2017/11/08
- [Qemu-devel] [PATCH 2/5] iotests: Add missing 'blkdebug::' in 040, Max Reitz, 2017/11/08
- [Qemu-devel] [PATCH 3/5] iotests: Make 055 less flaky, Max Reitz, 2017/11/08
- [Qemu-devel] [PATCH 4/5] iotests: Make 083 less flaky, Max Reitz, 2017/11/08
- [Qemu-devel] [PATCH 5/5] iotests: Make 136 less flaky, Max Reitz, 2017/11/08
- Re: [Qemu-devel] [Qemu-block] [PATCH 0/5] iotests: Make some tests less flaky, Stefan Hajnoczi, 2017/11/09