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diff --git a/doc/src/sgml/html/logfile-maintenance.html b/doc/src/sgml/html/logfile-maintenance.html new file mode 100644 index 0000000..cf1d2aa --- /dev/null +++ b/doc/src/sgml/html/logfile-maintenance.html @@ -0,0 +1,112 @@ +<?xml version="1.0" encoding="UTF-8" standalone="no"?> +<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><meta http-equiv="Content-Type" content="text/html; charset=UTF-8" /><title>25.3. Log File Maintenance</title><link rel="stylesheet" type="text/css" href="stylesheet.css" /><link rev="made" href="pgsql-docs@lists.postgresql.org" /><meta name="generator" content="DocBook XSL Stylesheets Vsnapshot" /><link rel="prev" href="routine-reindex.html" title="25.2. Routine Reindexing" /><link rel="next" href="backup.html" title="Chapter 26. Backup and Restore" /></head><body id="docContent" class="container-fluid col-10"><div class="navheader"><table width="100%" summary="Navigation header"><tr><th colspan="5" align="center">25.3. Log File Maintenance</th></tr><tr><td width="10%" align="left"><a accesskey="p" href="routine-reindex.html" title="25.2. Routine Reindexing">Prev</a> </td><td width="10%" align="left"><a accesskey="u" href="maintenance.html" title="Chapter 25. Routine Database Maintenance Tasks">Up</a></td><th width="60%" align="center">Chapter 25. Routine Database Maintenance Tasks</th><td width="10%" align="right"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="10%" align="right"> <a accesskey="n" href="backup.html" title="Chapter 26. Backup and Restore">Next</a></td></tr></table><hr /></div><div class="sect1" id="LOGFILE-MAINTENANCE"><div class="titlepage"><div><div><h2 class="title" style="clear: both">25.3. Log File Maintenance</h2></div></div></div><a id="id-1.6.12.12.2" class="indexterm"></a><p> + It is a good idea to save the database server's log output + somewhere, rather than just discarding it via <code class="filename">/dev/null</code>. + The log output is invaluable when diagnosing + problems. + </p><div class="note"><h3 class="title">Note</h3><p> + The server log can contain sensitive information and needs to be protected, + no matter how or where it is stored, or the destination to which it is routed. + For example, some DDL statements might contain plaintext passwords or other + authentication details. Logged statements at the <code class="literal">ERROR</code> + level might show the SQL source code for applications + and might also contain some parts of data rows. Recording data, events and + related information is the intended function of this facility, so this is + not a leakage or a bug. Please ensure the server logs are visible only to + appropriately authorized people. + </p></div><p> + Log output tends to be voluminous + (especially at higher debug levels) so you won't want to save it + indefinitely. You need to <span class="emphasis"><em>rotate</em></span> the log files so that + new log files are started and old ones removed after a reasonable + period of time. + </p><p> + If you simply direct the <span class="systemitem">stderr</span> of + <code class="command">postgres</code> into a + file, you will have log output, but + the only way to truncate the log file is to stop and restart + the server. This might be acceptable if you are using + <span class="productname">PostgreSQL</span> in a development environment, + but few production servers would find this behavior acceptable. + </p><p> + A better approach is to send the server's + <span class="systemitem">stderr</span> output to some type of log rotation program. + There is a built-in log rotation facility, which you can use by + setting the configuration parameter <code class="varname">logging_collector</code> to + <code class="literal">true</code> in <code class="filename">postgresql.conf</code>. The control + parameters for this program are described in <a class="xref" href="runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHERE" title="20.8.1. Where to Log">Section 20.8.1</a>. You can also use this approach + to capture the log data in machine readable <acronym class="acronym">CSV</acronym> + (comma-separated values) format. + </p><p> + Alternatively, you might prefer to use an external log rotation + program if you have one that you are already using with other + server software. For example, the <span class="application">rotatelogs</span> + tool included in the <span class="productname">Apache</span> distribution + can be used with <span class="productname">PostgreSQL</span>. One way to + do this is to pipe the server's + <span class="systemitem">stderr</span> output to the desired program. + If you start the server with + <code class="command">pg_ctl</code>, then <span class="systemitem">stderr</span> + is already redirected to <span class="systemitem">stdout</span>, so you just need a + pipe command, for example: + +</p><pre class="programlisting"> +pg_ctl start | rotatelogs /var/log/pgsql_log 86400 +</pre><p> + </p><p> + You can combine these approaches by setting up <span class="application">logrotate</span> + to collect log files produced by <span class="productname">PostgreSQL</span> built-in + logging collector. In this case, the logging collector defines the names and + location of the log files, while <span class="application">logrotate</span> + periodically archives these files. When initiating log rotation, + <span class="application">logrotate</span> must ensure that the application + sends further output to the new file. This is commonly done with a + <code class="literal">postrotate</code> script that sends a <code class="literal">SIGHUP</code> + signal to the application, which then reopens the log file. + In <span class="productname">PostgreSQL</span>, you can run <code class="command">pg_ctl</code> + with the <code class="literal">logrotate</code> option instead. When the server receives + this command, the server either switches to a new log file or reopens the + existing file, depending on the logging configuration + (see <a class="xref" href="runtime-config-logging.html#RUNTIME-CONFIG-LOGGING-WHERE" title="20.8.1. Where to Log">Section 20.8.1</a>). + </p><div class="note"><h3 class="title">Note</h3><p> + When using static log file names, the server might fail to reopen the log + file if the max open file limit is reached or a file table overflow occurs. + In this case, log messages are sent to the old log file until a + successful log rotation. If <span class="application">logrotate</span> is + configured to compress the log file and delete it, the server may lose + the messages logged in this time frame. To avoid this issue, you can + configure the logging collector to dynamically assign log file names + and use a <code class="literal">prerotate</code> script to ignore open log files. + </p></div><p> + Another production-grade approach to managing log output is to + send it to <span class="application">syslog</span> and let + <span class="application">syslog</span> deal with file rotation. To do this, set the + configuration parameter <code class="varname">log_destination</code> to <code class="literal">syslog</code> + (to log to <span class="application">syslog</span> only) in + <code class="filename">postgresql.conf</code>. Then you can send a <code class="literal">SIGHUP</code> + signal to the <span class="application">syslog</span> daemon whenever you want to force it + to start writing a new log file. If you want to automate log + rotation, the <span class="application">logrotate</span> program can be + configured to work with log files from + <span class="application">syslog</span>. + </p><p> + On many systems, however, <span class="application">syslog</span> is not very reliable, + particularly with large log messages; it might truncate or drop messages + just when you need them the most. Also, on <span class="productname">Linux</span>, + <span class="application">syslog</span> will flush each message to disk, yielding poor + performance. (You can use a <span class="quote">“<span class="quote"><code class="literal">-</code></span>”</span> at the start of the file name + in the <span class="application">syslog</span> configuration file to disable syncing.) + </p><p> + Note that all the solutions described above take care of starting new + log files at configurable intervals, but they do not handle deletion + of old, no-longer-useful log files. You will probably want to set + up a batch job to periodically delete old log files. Another possibility + is to configure the rotation program so that old log files are overwritten + cyclically. + </p><p> + <a class="ulink" href="https://pgbadger.darold.net/" target="_top"><span class="productname">pgBadger</span></a> + is an external project that does sophisticated log file analysis. + <a class="ulink" href="https://bucardo.org/check_postgres/" target="_top"><span class="productname">check_postgres</span></a> + provides Nagios alerts when important messages appear in the log + files, as well as detection of many other extraordinary conditions. + </p></div><div class="navfooter"><hr /><table width="100%" summary="Navigation footer"><tr><td width="40%" align="left"><a accesskey="p" href="routine-reindex.html" title="25.2. Routine Reindexing">Prev</a> </td><td width="20%" align="center"><a accesskey="u" href="maintenance.html" title="Chapter 25. Routine Database Maintenance Tasks">Up</a></td><td width="40%" align="right"> <a accesskey="n" href="backup.html" title="Chapter 26. Backup and Restore">Next</a></td></tr><tr><td width="40%" align="left" valign="top">25.2. Routine Reindexing </td><td width="20%" align="center"><a accesskey="h" href="index.html" title="PostgreSQL 15.5 Documentation">Home</a></td><td width="40%" align="right" valign="top"> Chapter 26. Backup and Restore</td></tr></table></div></body></html>
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