Writing structured logs with Serilog

Question

I tried the following log with Serilog:

this.logger.Debug("Incoming metrics data {ClientId}", new { clientid = 54732 });

Serilog produced this output:

Incoming metrics data "{ clientid = 54732 }"

Serilog being a structured logger I've expected it to produce something like this:

Incoming metrics data {ClientId}, {clientId: 54732}

Am I doing something wrong or am I understanding Serilog/structured-logging wrong?

Answer 1

Two things; first, to serialize a structure like this you need to use the structure-capturing operator @ :

this.logger.Debug("Incoming metrics data {@Client}", new { ClientId = 54732 });

This will capture the individual properties of the object passed in, so the event in the rewritten example will have a Client property with ClientId sub-property.

This will give you output like:

Incoming metrics data {"ClientId": 54732}

(Assuming you are using the latest Serilog console sink with the default template; other configurations may not print the embedded data JSON-style.)

The second consideration is that the full structure of the event isn't shown in Serilog's text output - it's the "human-friendly" face of Serilog. If you want to record structure, you might plug in CompactJsonFormatter like so (again assuming the console sink):

.WriteTo.Console(new CompactJsonFormatter())

This works for files etc., too - details at https://github.com/serilog/serilog-formatting-compact .