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Serilog.Formatting.Compact

A simple, compact JSON-based event format for Serilog. CompactJsonFormatter significantly reduces the byte count of small log events when compared with Serilog's default JsonFormatter, while remaining human-readable. It achieves this through shorter built-in property names, a leaner format, and by excluding redundant information.

Sample

A simple Hello, {User} event.

{"@t":"2016-06-07T03:44:57.8532799Z","@mt":"Hello, {User}","User":"nblumhardt"}

Getting started

Install from NuGet:

dotnet add package Serilog.Formatting.Compact

The formatter is used in conjunction with sinks that accept ITextFormatter. For example, the file sink:

Log.Logger = new LoggerConfiguration()
  .WriteTo.File(new CompactJsonFormatter(), "./logs/myapp.json")
  .CreateLogger();

XML `<appSettings>` configuration

To specify the formatter in XML <appSettings> provide its assembly-qualified type name:

<appSettings>
  <add key="serilog:using:File" value="Serilog.Sinks.File" />
  <add key="serilog:write-to:File.path" value="./logs/myapp.json" />
  <add key="serilog:write-to:File.formatter"
       value="Serilog.Formatting.Compact.CompactJsonFormatter, Serilog.Formatting.Compact" />

JSON `appsettings.json` configuration

To specify formatter in json appsettings.json provide its assembly-qualified type name:

{
  "Serilog": {
    "WriteTo": [
      {
        "Name": "File",
        "Args": {
          "path": "./logs/myapp.json",
          "formatter": "Serilog.Formatting.Compact.CompactJsonFormatter, Serilog.Formatting.Compact"
        }
      }
    ]
  }
}

Rendered events

CompactJsonFormatter will preserve the message template, properties, and formatting information so that the rendered message can be created at a later point. When the JSON is intended for consumption in an environment without message template rendering, RenderedCompactJsonFormatter can be used instead.

Instead of the message template, RenderedCompactJsonFormatter writes the fully-rendered message, as well as an event id generated from the message template, into the event:

{"@t":"2016-06-07T03:44:57.8532799Z","@m":"Hello, \"nblumhardt\"","@i":"7a8b9c0d","User":"nblumhardt"}

Format details

The format written by the compact formatters is specified generically so that implementations for other logging libraries, including Microsoft.Extensions.Logging, are possible if desired.

Payload

Each event is a JSON object with event data at the top level. Any JSON property on the payload object is assumed to be a regular property of the event, apart from the reified properties below.

Reified properties

The format defines a handful of reified properties that have special meaning:

Property	Name	Description	Required?
`@t`	Timestamp	An ISO 8601 timestamp	Yes
`@m`	Message	A fully-rendered message describing the event
`@mt`	Message Template	Alternative to Message; specifies a message template over the event's properties that provides for rendering into a textual description of the event
`@l`	Level	An implementation-specific level identifier (string or number)	Absence implies "informational"
`@x`	Exception	A language-dependent error representation potentially including backtrace
`@i`	Event id	An implementation specific event id (string or number)
`@r`	Renderings	If `@mt` includes tokens with programming-language-specific formatting, an array of pre-rendered values for each such token	May be omitted; if present, the count of renderings must match the count of formatted tokens exactly
`@tr`	Trace id	The id of the trace that was active when the event was created, if any
`@sp`	Span id	The id of the span that was active when the event was created, if any

The @ sigil may be escaped at the start of a user property name by doubling, e.g. @@name denotes a property called @name.

Batch format

When events are batched into a single payload, a newline-delimited stream of JSON documents is required. Either \n or \r\n delimiters may be used. Batches of newline-separated compact JSON events can use the (unofficial) MIME type application/vnd.serilog.clef.

Versioning

Versioning would be additive only, with no version identifier; implementations should treat any unrecognised reified properties as if they are user data.

Comparison

The output and benchmarks below compare the compact JSON formatter with Serilog's built-in JsonFormatter.

Event

Log.Information("Hello, {@User}, {N:x8} at {Now}",
  new
  {
    Name = "nblumhardt",
    Tags = new[] { 1, 2, 3 }
  },
  123,
  DateTime.Now);

Default JsonFormatter 292 bytes

{"Timestamp":"2016-06-07T13:44:57.8532799+10:00","Level":"Information","MessageT
emplate":"Hello, {@User}, {N:x8} at {Now}","Properties":{"User":{"Name":"nblumha
rdt","Tags":[1,2,3]},"N":123,"Now":"2016-06-07T13:44:57.8532799+10:00"},"Renderi
ngs":{"N":[{"Format":"x8","Rendering":"0000007b"}]}}

CompactJsonFormatter 187 bytes (0.64)

{"@t":"2016-06-07T03:44:57.8532799Z","@mt":"Hello, {@User}, {N:x8} at {Now}","@r
":["0000007b"],"User":{"Name":"nblumhardt","Tags":[1,2,3]},"N":123,"Now":2016-06
-07T13:44:57.8532799+10:00}

Formatting benchmark

See test/Serilog.Formatting.Compact.Tests/FormattingBenchmarks.cs.

Formatter	Median	StdDev	Scaled
`JsonFormatter`	11.2775 µs	0.0682 µs	1.00
`CompactJsonFormatter`	6.0315 µs	0.0429 µs	0.53
`JsonFormatter(renderMessage: true)`	13.7585 µs	0.1194 µs	1.22
`RenderedCompactJsonFormatter`	7.0680 µs	0.0605 µs	0.63

Tools

Several tools are available for working with the CLEF format.

Analogy.LogViewer.Serilog - CLEF parser for Analogy Log Viewer
clef-tool - a CLI application for processing CLEF files
Compact Log Format Viewer - a cross-platform viewer for CLEF files
seqcli - pretty-print CLEF files at the command-line, or ingest CLEF files into Seq for search, and analysis
Serilog.Formatting.Compact.Reader - convert CLEF documents back into Serilog LogEvents

Customizing output

Serilog.Formatting.Compact is not intended to provide customizable formatters. See this blog post for comprehensive Serilog JSON output customization examples.