Serilog: cannot log to MongoDb using MongoDb sink

Question

I have a local MongoDb database instance (created by running mongod from the Windows command line), and a simple console program that tries to log a string to the MongoDb database using Serilog and its MongoDb sink:

        var log = new LoggerConfiguration()
            .MinimumLevel.Debug()
            .WriteTo.ColoredConsole()
            .WriteTo.MongoDB("mongodb://localhost/mydb")
            .CreateLogger();

        log.Fatal("Fatal message");

The "Fatal message" message is written correctly to the console, but not to my MongoDb database.

My current MongoDb database is "mydb". According to "show collections", I only have collections system.indexes and testData, and "db.testData.find()" produces nothing.

The Serilog site says to use connection string "mongo://mydb/log", but that throws an exception "An unhandled exception of type 'System.FormatException' occurred in MongoDB.Driver.dll". The connection string I used in my code is specified on the MongoDb site, at http://docs.mongodb.org/manual/reference/connection-string/

How can I log to MongoDb using Serilog?

Nicholas Blumhardt Nicholas Blumhardt · Accepted Answer · 2014-07-13T00:55:14

It's possible that you're just experiencing the default (two second?) buffering delay - if you close a console app in Windows it hard-terminates the program so buffers can't always be flushed. Waiting a few seconds before closing the app will fix this if so.

Otherwise, the way to tackle all sink debugging in Serilog is to set SelfLog.Out:

SelfLog.Out = Console.Error;

This will print any exceptions raised by the sink, allowing you to zoom in on the error pretty quickly if that's where it is.

Serilog: cannot log to MongoDb using MongoDb sink

3 Answers