pt-query-digest: specifying a file that doesn't exist as log causes the tool to wait for STDIN instead of giving an error

[Kenny Gryp]

if you specify a file to process that does not exist, pt-query-digest waits forever. Often you will think that it's just slow to process, until you check and find out that it's not using any CPU at all.
<code>
Pertop:consulting gryp$ pt-query-digest filethatdoesntexist
^C# Caught SIGINT.
</code>

Basically, the tool waits for STDIN data.

The good behavior should be that pt-query-digest exits when the file is not found.

[Muhammad Irfan (muhammad-irfan)]

Verified as described.

# pt-query-digest --version
pt-query-digest 2.2.12

# pt-query-digest dummy-slow.log

Tool runs foreever where dummy-slow.log doesn't exists on disk.

[Frank Cizmich (frank-cizmich)]

Throwing a proper error proved impractical because of possible use case where the tool receives no file but does receive a DSN parameter. This DSN can consist of a single hostname, which is indistiguishable from a filename.

Workaround fix: Tool now announces it is waiting for STDIN , making the situation more obvious to the user.

[Shahriyar Rzayev (rzayev-sehriyar)]

Percona now uses JIRA for bug reports so this bug report is migrated to: https://jira.percona.com/browse/PT-817