pt-stalk removes non-empty files that start with empty line

[Robert Wunderer]

pt-stalk 2.2.13
Percona Server version 5.6.21-70.0-log

The code for removing empty files also deletes files that are not empty, but start with an empty line. The behaviour does not depend on any command line options or user settings.

E.g: The output produced by pt-stalk and written to the files

*-innodbstatus[12]

starts with an empty line:

-------------------------------

=====================================
2015-02-24 17:27:52 7eb6d3fc2700 INNODB MONITOR OUTPUT
=====================================
Per second averages calculated from the last 31 seconds
...
-------------------------------

Thus the expression in line 1003

-z "$(grep -v '^TS ' --max-count 1 "$file")"

holds true and the files get deleted even though it holds useful information.

[Frank Cizmich (frank-cizmich)]

Could only partially reproduce but the code seems clear.

When "SHOW INNODB STATUS" fails for some reason, pt-stalk resorts to fetching data from /proc/<mysql_pid>/fd/<N> , where N is the file descriptor that contains innodb status data.
In that case, the first line is indeed empty.

Simplest fix is to increase --max-count to a higher number.

[Frank Cizmich (frank-cizmich)]

Fixed as mentioned in above.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-676