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|  <span id="projectnumber">0.32.0</span> |
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| <div class="title">Logging </div> </div> |
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| <div class="textblock"><p><a class="anchor" id="md__tmp_rgemmell_transom_qpid-proton-0"></a>.32.0_c_docs_logging</p> |
| <h2><a class="anchor" id="autotoc_md13"></a> |
| Backward compatible logging control</h2> |
| <p>Proton has always supported some control over its internal logging using environment variables. The one that has seen the most use is <code>PN_TRACE_FRM</code> which when set to '1', 'on' or 'true' turns on logging of protocol frame traces. This is commonly used on a Unix shell command line like so: </p><pre class="fragment">PN_TRACE_FRM=1 ./proton_program |
| </pre><p>Setting <code>PN_TRACE_FRM</code> is equivalent to using the <a class="el" href="group__logger.html#ggacff7629aa49e187a5e6182b80febabf1a07ed98e7988f169c5c7282bfd3a82c63">PN_LEVEL_FRAME</a> log level setting in the proton <a class="el" href="group__logger.html">Logger</a> API.</p> |
| <p>There are several other (less used) environment variables which are supported:</p> |
| <ul> |
| <li><code>PN_TRACE_RAW</code> - This turns on raw protocol frame tracing and is equivalent to <a class="el" href="group__logger.html#ggacff7629aa49e187a5e6182b80febabf1a6a26f859bdc36ee208a7594067219b27">PN_LEVEL_RAW</a>.</li> |
| <li><code>PN_TRACE_EVT</code> - This is useful for tracing events, but has no direct equivalent in the Logger API.</li> |
| <li><code>PN_TRACE_DRV</code> - This turns on very verbose miscellaneous tracing, again it has no direct equivalent in the Logger API.</li> |
| </ul> |
| <p>The last two variables are still supported, but their effect may not be to turn on exactly the same logging messages as prior to the introduction of the Logger API.</p> |
| <h2><a class="anchor" id="autotoc_md14"></a> |
| Logger control introduced with the logger API</h2> |
| <p>The <a class="el" href="group__logger.html">Logger</a> API uses a single environment variable to control the default logging state - <code>PN_LOG</code>. This can include a number of strings which correspond to log levels to turn on, these are in descending order of importance (case is not significant):</p> |
| <ul> |
| <li>Error</li> |
| <li>Warning</li> |
| <li>Info</li> |
| <li>Debug</li> |
| <li>Trace</li> |
| </ul> |
| <p>These strings can also be suffixed with '+' to mean this level and all the ones above. So specifying 'Info+' means turn on 'Error', 'Warning' and 'Info' levels. For example: </p><pre class="fragment">PN_LOG='info+' ./broker |
| </pre><ul> |
| <li>Frame</li> |
| <li>Raw</li> |
| </ul> |
| <p>These strings are equivalent to the frame and raw frame protocol traces from <code>PN_TRACE_FRM</code> and <code>PN_TRACE_RAW</code>, they will ignore any '+' appended to them. For example: </p><pre class="fragment">PN_LOG='frame' ./proton_program |
| </pre><p>will have the same effect as the first example in this document.</p> |
| <ul> |
| <li>All</li> |
| </ul> |
| <p>This will turn all known logging levels on. This is probably hardly ever useful as it will produce huge amounts of output. Appending '+' will again have no effect as all logging is already turned on!</p> |
| <p>Multiple specifiers can be in the string for more logging levels: </p><pre class="fragment">PN_LOG='error frame' ./proton_program |
| </pre><p>this would be useful to see the frame trace logged together with any errors. </p> |
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