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Compact JSON event format for Serilog
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Serilog.Formatting.Compact Build status NuGet

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:

Install-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();

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

<appSettings>
  <add key="serilog:using:File" value="Serilog.Sinks.RollingFile" />
  <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" />

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

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
RenderedJsonFormatter 13.7585 µs 0.1194 µs 1.22
RenderedCompactJsonFormatter 7.0680 µs 0.0605 µs 0.63

Compiling

Opening serilog-formatting-compact.sln requires VS2015 Update 3 with the .NET Core tooling to be installed.
See: https://www.microsoft.com/net/core#windows

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