mirror of
https://github.com/tstack/lnav
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190 lines
9.4 KiB
ReStructuredText
190 lines
9.4 KiB
ReStructuredText
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.. _data-ext:
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Extracting Data
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===============
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**Note**: This feature is still in **BETA**, you should expect bugs and
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incompatible changes in the future.
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Log messages contain a good deal of useful data, but it's not always easy to get
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at. The log parser built into **lnav** is able to extract data as described by
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:ref:`log-formats` as well as discovering data in plain text messages. This data
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can then be queried and processed using the SQLite front-end that is also
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incorporated into **lnav**. As an example, the following Syslog message from
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:cmd:`sudo` can be processed to extract several key/value pairs::
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Jul 31 11:42:26 Example-MacBook-Pro.local sudo[87024]: testuser : TTY=ttys004 ; PWD=/Users/testuser/github/lbuild ; USER=root ; COMMAND=/usr/bin/make install
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The data that can be extracted by the parser is viewable directly in **lnav**
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by pressing the 'p' key. The results will be shown in an overlay like the
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following::
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Current Time: 2013-07-31T11:42:26.000 Original Time: 2013-07-31T11:42:26.000 Offset: +0.000
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Known message fields:
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├ log_hostname = Example-MacBook-Pro.local
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├ log_procname = sudo
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├ log_pid = 87024
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Discovered message fields:
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├ col_0 = testuser
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├ TTY = ttys004
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├ PWD = /Users/testuser/github/lbuild
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├ USER = root
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└ COMMAND = /usr/bin/make install
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Notice that the parser has detected pairs of the form '<key>=<value>'. The data
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parser will also look for pairs separated by a colon. If there are no clearly
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demarcated pairs, then the parser will extract anything that looks like data
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values and assign them keys of the form 'col_N'. For example, two data values,
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an IPv4 address and a symbol, will be extracted from the following log
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messsage::
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Apr 29 08:13:43 sample-centos5 avahi-daemon[2467]: Registering new address record for 10.1.10.62 on eth0.
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Since there are no keys for the values in the message, the parser will assign
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'col_0' for the IP address and 'col_1' for the symbol, as seen here::
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Current Time: 2013-04-29T08:13:43.000 Original Time: 2013-04-29T08:13:43.000 Offset: +0.000
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Known message fields:
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├ log_hostname = sample-centos5
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├ log_procname = avahi-daemon
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├ log_pid = 2467
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Discovered message fields:
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├ col_0 = 10.1.10.62
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└ col_1 = eth0
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Now that you have an idea of how the parser works, you can begin to perform
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queries on the data that is being extracted. The SQLite database engine is
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embedded into **lnav** and its `Virtual Table
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<http://www.sqlite.org/vtab.html>`_ mechanism is used to provide a means to
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process this log data. Each log format has its own table that can be used to
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access all of the loaded messages that are in that format. For accessing log
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message content that is more free-form, like the examples given here, the
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**logline** table can be used. The **logline** table is recreated for each
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query and is based on the format and pairs discovered in the log message at
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the top of the display.
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Queries can be performed by pressing the semi-colon (;) key in **lnav**. After
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pressing the key, the overlay showing any known or discovered fields will be
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displayed to give you an idea of what data is available. The query can be any
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`SQL query <http://sqlite.org/lang.html>`_ supported by SQLite. To make
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analysis easier, **lnav** includes many extra functions for processing strings,
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paths, and IP addresses. See :ref:`sql-ext` for more information.
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As an example, the simplest query to perform initially would be a "select all",
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like so::
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select * from logline
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When this query is run against the second example log message given above, the
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following results are received::
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log_line log_part log_time log_idle_msecs log_level log_hostname log_procname log_pid col_0 col_1
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292 p.0 2013-04-11T16:42:51.000 0 info localhost avahi-daemon 2480 fe80::a00:27ff:fe98:7f6e eth0
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293 p.0 2013-04-11T16:42:51.000 0 info localhost avahi-daemon 2480 10.0.2.15 eth0
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330 p.0 2013-04-11T16:47:02.000 0 info localhost avahi-daemon 2480 fe80::a00:27ff:fe98:7f6e eth0
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336 p.0 2013-04-11T16:47:02.000 0 info localhost avahi-daemon 2480 10.1.10.75 eth0
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343 p.0 2013-04-11T16:47:02.000 0 info localhost avahi-daemon 2480 10.1.10.75 eth0
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370 p.0 2013-04-11T16:59:39.000 0 info localhost avahi-daemon 2480 10.1.10.75 eth0
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377 p.0 2013-04-11T16:59:39.000 0 info localhost avahi-daemon 2480 10.1.10.75 eth0
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382 p.0 2013-04-11T16:59:41.000 0 info localhost avahi-daemon 2480 fe80::a00:27ff:fe98:7f6e eth0
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401 p.0 2013-04-11T17:20:45.000 0 info localhost avahi-daemon 4247 fe80::a00:27ff:fe98:7f6e eth0
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402 p.0 2013-04-11T17:20:45.000 0 info localhost avahi-daemon 4247 10.1.10.75 eth0
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735 p.0 2013-04-11T17:41:46.000 0 info sample-centos5 avahi-daemon 2465 fe80::a00:27ff:fe98:7f6e eth0
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736 p.0 2013-04-11T17:41:46.000 0 info sample-centos5 avahi-daemon 2465 10.1.10.75 eth0
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781 p.0 2013-04-12T03:32:30.000 0 info sample-centos5 avahi-daemon 2465 10.1.10.64 eth0
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788 p.0 2013-04-12T03:32:30.000 0 info sample-centos5 avahi-daemon 2465 10.1.10.64 eth0
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1166 p.0 2013-04-25T10:56:00.000 0 info sample-centos5 avahi-daemon 2467 fe80::a00:27ff:fe98:7f6e eth0
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1167 p.0 2013-04-25T10:56:00.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.111 eth0
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1246 p.0 2013-04-26T06:06:25.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.49 eth0
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1253 p.0 2013-04-26T06:06:25.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.49 eth0
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1454 p.0 2013-04-28T06:53:55.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.103 eth0
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1461 p.0 2013-04-28T06:53:55.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.103 eth0
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1497 p.0 2013-04-29T08:13:43.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.62 eth0
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1504 p.0 2013-04-29T08:13:43.000 0 info sample-centos5 avahi-daemon 2467 10.1.10.62 eth0
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Note that **lnav** is not returning results for all messages that are in this
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syslog file. Rather, it searches for messages that match the format for the
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given line and returns only those messages in results. In this case, that
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format is "Registering new address record for <IP> on <symbol>", which
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corresponds to the parts of the message that were not recognized as data.
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More sophisticated queries can be done, of course. For example, to find out the
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frequency of IP addresses mentioned in these messages, you can run::
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SELECT col_0,count(*) FROM logline GROUP BY col_0
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The results for this query are::
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col_0 count(*)
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10.0.2.15 1
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10.1.10.49 2
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10.1.10.62 2
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10.1.10.64 2
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10.1.10.75 6
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10.1.10.103 2
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10.1.10.111 1
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fe80::a00:27ff:fe98:7f6e 6
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Since this type of query is fairly common, **lnav** includes a "summarize"
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command that will compute the frequencies of identifiers as well as min, max,
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average, median, and standard deviation for number columns. In this case, you
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can run the following to compute the frequencies and return an ordered set of
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results.
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:summarize col_0
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Recognized Data Types
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---------------------
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When searching for data to extract from log messages, **lnav** looks for the
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following set of patterns:
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Strings
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Single and double-quoted strings. Example: "The quick brown fox."
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URLs
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URLs that contain the '://' separator. Example: http://example.com
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Paths
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File system paths. Examples: /path/to/file, ./relative/path
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MAC Address
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Ethernet MAC addresses. Example: c4:2c:03:0e:e4:4a
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Hex Dumps
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A colon-separated string of hex numbers. Example: e8:06:88:ff
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Date/Time
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Date and time stamps of the form "YYYY-mm-DD" and "HH:MM:SS".
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IP Addresses
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IPv4 and IPv6 addresses. Examples: 127.0.0.1, fe80::c62c:3ff:fe0e:e44a%en0
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UUID
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The common formatting for 128-bit UUIDs. Example:
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0E305E39-F1E9-4DE4-B10B-5829E5DF54D0
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Version Numbers
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Dot-separated version numbers. Example: 3.7.17
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Numbers
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Numbers in base ten, hex, and octal formats. Examples: 1234, 0xbeef, 0777
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E-Mail Address
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Strings that look close to an e-mail address. Example: gary@example.com
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Constants
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Common constants in languages, like: true, false, null, None.
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Symbols
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Words that follow the common conventions for symbols in programming
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languages. For example, containing all capital letters, or separated
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by colons. Example: SOME_CONSTANT_VALUE, namespace::value
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