Filtering for UseSerilogRequestLogging

[cado1982]

It would be handy if I could filter messages that come from the UseSerilogRequestLogging middleware. My use case is to stop logging for my healthcheck path. I'm thinking something along the lines of:

app.UseSerilogRequestLogging(e => e.RequestPath != "/healthcheck");

Maybe this exists but I can't find a way to do that currently. Any ideas?

[cado1982]

I discovered that I can still use a RequestPath filter to remove the condensed logs:

Log.Logger = new LoggerConfiguration() .Filter.ByExcluding((e) => e.Properties.ContainsKey("RequestPath") && e.Properties["RequestPath"].ToString() == "\"/healthcheck\"")

Even though those logs don't contain the RequestPath property in the Properties sent to the log, they are still available in the filters:

[10:25:20.999 INF] HTTP GET /healthcheck responded 200 in 268.6539 ms {"RequestId": "0HLPAQ1TKES3L:00000001", "CorrelationId": null, "ConnectionId": "0HLPAQ1TKES3L"}

[nblumhardt]

Great, thanks for following up, @cado1982 !

The text output you included (starting with [10:...) is based on an "output template" that selects only specific parts of the event to print. Behind the scenes, each event carries a whole lot of other data that you can see by e.g. switching your sink to use JSON formatting (even just for the sake of seeing what's available).

If the Filter.ByExcluding() delegate syntax gets too much, there are two other options to try:

    .Filter.ByExcluding(Matching.WithProperty("RequestPath", "/healthcheck"))

This ☝️ is the same filter as the one you've written longhand (just syntactic sugar).

Alternatively, Serilog.Filters.Expressions enables SQL-like filters written as text:

    .Filter.ByExcluding("RequestPath = '/healthcheck' and StatusCode < 400")

The latter option is easier to work with when things get more complicated :-)

Cheers!

[cado1982]

Brilliant, thanks @nblumhardt.

Serilog is awesome. I love the Matching.WithProperty syntax, it reads better than the lambda I was using. I'll use the second option you provided as I would probably want to log failures based on status code.

Keep up the good work!

[rafamartinsbr]

i was looking for a way of filtering out log entries related to static assets being served from my aspnet core mvc-app (such as .css, .js or image files)

since i've just read many threads/issues and tutorials and could not find such example, i'm sharing one here (just in case someone else is trying the same). the solution i found is based on this github issue (+serilog docs) and seems to work fine.

you can/should of course improve it and make it suitable for your requirements, but this is one way of achieving it:

one could exclude entries of "lib/" content being served (if your webapp stores your client-side dependencies under /lib folder) by adding

.Filter.ByExcluding("RequestPath like '/lib/%'")

or similarly

.Filter.ByExcluding("RequestPath like '/css/%'")

or even by file extension

.Filter.ByExcluding("RequestPath like '/%.png'")

you could of course exclude all 3 examples in one single expression