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57 lines
1.8 KiB
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57 lines
1.8 KiB
Markdown
---
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layout: post
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title: "Support for JSON-encoded logs in v0.6.1"
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date: 2013-09-10 00:00:00
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excerpt: Turning JSON barf into something readable.
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---
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Making logs easily digestible by machines is becoming a concern as tools like
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elasticsearch become more popular. One of the popular strategies is to encode
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the whole log message in JSON and then write that as a single line to a file.
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For example:
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```json
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{"time": "2013-09-04T23:55:09.274041Z", "level" : "INFO", "body" : "Hello, World!" }
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{"time": "2013-09-04T23:56:00.285224Z", "level" : "ERROR", "body" : "Something terrible has happened!", "tb": " foo.c:12\n bar.y:33" }
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```
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Unfortunately, what is good for a machine is not so great for a human. To try to
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improve the situation, the latest release of lnav includes support for parsing
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JSON log messages and transforming them on-the-fly. The display format is
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specified in a log format configuration and can specify which fields should be
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displayed on the main message line. Any unused fields that are found in the
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message will be displayed below the main field so you don't miss anything.
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The above log lines can be transformed using the following format configuration:
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```json
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{
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"json_ex_log": {
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"title": "Example JSON Log",
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"description": "An example log format configuration for JSON logs",
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"json": true,
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"file-pattern": "test-log\\.json.*",
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"level-field": "level",
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"line-format": [
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{
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"field": "time"
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},
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" ",
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{
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"field": "body"
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}
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]
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}
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}
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```
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After copying this config to `~/.lnav/formats/test/format.json`, the log messages
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will look like this when viewed in lnav:
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```
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2013-09-04T23:55:09.274041Z Hello, World!
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2013-09-04T23:56:00.285224Z Something terrible has happened!
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tb: foo.c:12
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tb: bar.y:33
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```
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