pt-sift loses STDIN after pt-diskstats

[Baron Schwartz]

I am unsure of the cause, but the new pt-diskstats seems to cause the 'read' command to fail in pt-sift. The error message is 'resource temporarily unavailable' and the code in question is here:

446 # Capture and handle the interactive key-strokes.
447 KEY=""
448 read -n 1 -s KEY

Note that I have committed a patch to work around this in the fix for bug 945834 so you won't see the problem unless you invoke pt-diskstats correctly and don't catch an error in 'read'. Thus my suspicion that pt-diskstats does something with STDIN and makes it unavailable to pt-sift afterwards.

[Fernando Ipar (fipar)]

Should this be available already?
I have downloaded from percona.com/get (pt-sift, and let it download pt-diskstats again) and it's still not working,.
As a temporary workaround, I have redirected stdin to the keyboard just before that read -n 1 -s KEY on pt-sift.

[Baron Schwartz (baron-xaprb)]

This problem still exists. Fernando, how did you redirect stdin to the keyboard?

[Raghavendra D Prabhu (raghavendra-prabhu)]

Here is the workaround I used (based on what Fernando implied)

--- /mine/bin/site_perl/pt-sift 2012-05-01 10:35:15.008088566 +0530
+++ pt-sift.fixed 2012-05-02 19:42:14.554063131 +0530
@@ -465,6 +465,7 @@

       # Capture and handle the interactive key-strokes.
       tput sgr0
+ exec 0<$(tty)
       KEY=""
       if ! read -n 1 -s KEY 2>/dev/null; then
          echo "Error while trying to read interactive keystroke command. Exiting."

[Baron Schwartz (baron-xaprb)]

Another suggestion was this:

exec </dev/pts/0

Not sure what is the more portable workaround. Of course, pt-diskstats needs to be fixed too.

[Raghavendra D Prabhu (raghavendra-prabhu)]

The /dev/pts/0 may not work because in a master-slave multiplex mode (which is the default now), there are about 16 of them (/dev/pts/1..16), so in tmux/screen, you will have each one of them allocated different /dev/pts/x

[Dave Juntgen (djuntgen)]

Any news on this getting fixed before the next release?

I added "exec </dev/pts/0" line and things seem to be working, although I'm not sure how well.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-492