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Bug #1002

lttng snapshot on an empty tracing session results in an unknown error with --mi=xml

Added by Jérémie Galarneau over 4 years ago. Updated over 4 years ago.

Status:
Resolved
Priority:
Normal
Target version:
Start date:
03/14/2016
Due date:
% Done:

100%

Estimated time:

Description

Recording a snapshot on a session which has recorded no events results in the following output in MI output mode:

$ lttng --mi=xml snapshot record | xmllint --format -
Error: Unknown error code
Error: Command error
<?xml version="1.0" encoding="UTF-8"?>
<command xmlns="http://lttng.org/xml/ns/lttng-mi" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:schemaLocation="http://lttng.org/xml/ns/lttng-mi http://lttng.org/xml/schemas/lttng-mi/3/lttng-mi-3.0.xsd" schemaVersion="3.0">
  <name>snapshot</name>
  <output>
    <snapshot_action>
      <name>record</name>
      <output/>
    </snapshot_action>
  </output>
  <success>false</success>
</command>

(Unknown Error Code + Command error)

while the human output results in the following output:

$ lttng snapshot record
Warning: No data available in snapshot

Also, the commands should not result in an error (warning is fine) since the user has no control on whether or not applications (or the kernel) have produced any event between the start of the tracing session and the recording of the snapshot.

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