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A Serilog sink that writes events to Microsoft Azure Application Insights

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A sink for Serilog that writes events to Microsoft Application Insights.

Build status NuGet Version

This Sink comes with several defaults that send Serilog

messages to Application Insights as either


The simplest way to configure Serilog to send data to a ApplicationInsights dashboard via Instrumentation key is to use current active telemetry configuration which is already initialised in most application types like ASP.NET Core, Azure Functions etc.:

var log = new LoggerConfiguration()
    .ApplicationInsights(TelemetryConfiguration.Active, TelemetryConverter.Traces)

.. or as

var log = new LoggerConfiguration()
    .ApplicationInsights(TelemetryConfiguration.Active, TelemetryConverter.Events)

You can also pass an instrumentation key and this sink will create a new

based on it, however it's actively discouraged compared to using already initialised telemetry configuration, as your telemetry won't be properly correlated.

Note: Whether you choose

, if the LogEvent contains any exceptions it will always be sent as

Configuring with ReadFrom.Configuration()

The following configuration shows how to create an ApplicationInsights sink with ReadFrom.Configuration(configuration) - the telemetry converter has to be specified with the full type name and the assembly name:

  "Serilog": {
    "Using": [
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft": "Information"
    "WriteTo": [
        "Name": "ApplicationInsights",
        "Args": {
          "restrictedToMinimumLevel": "Information",
          "telemetryConverter": "Serilog.Sinks.ApplicationInsights.Sinks.ApplicationInsights.TelemetryConverters.TraceTelemetryConverter, Serilog.Sinks.ApplicationInsights"
    "Enrich": [ "FromLogContext" ],
    "Properties": {
      "Application": "Sample"

As mentioned above you can also pass an instrumentation key but it's actively discouraged

Note: restrictedToMinimumLevel can be omitted since it is defaulted to LevelAlias.Minimum.

What do we submit?

By default, trace telemetry submits: - rendered message in trace's standard message property. - severity in trace's standard severityLevel property. - timestamp in trace's standard timestamp property. - messageTemplate in customDimensions. - custom log properties as customDimensions.

Event telemetry submits: - message template as event name. - renderedMessage in customDimensions. - timestamp in event's standard timestamp property. - custom log properties as customDimensions.

Exception telemetry submits: - exception as standard AI exception. - severity in trace's standard severityLevel property. - timestamp in trace's standard timestamp property. - custom log properties as customDimensions.

Note that log context properties are also included in customDimensions when Serilog is configured with


How custom properties are logged?

By default custom properties are converted to compact JSON, for instance:

var position = new { Latitude = 25, Longitude = 134 };
var elapsedMs = 34;
var numbers = new int[] { 1, 2, 3, 4 };

Logger.Information("Processed {@Position} in {Elapsed:000} ms., str {str}, numbers: {numbers}", position, elapsedMs, "test", numbers);

will produce the following properties in customDimensions:

|Property|Value| |--------|-----| |Elapsed|34| |Position|{"Latitude":25,"Longitude":134}| |numbers|[1,2,3,4]|

This is a breaking change from v2 which was producing these properties:

|Property|Value| |--------|-----| |Elapsed|34| |Position.Latitude|25| |Position.Longitude|134| |numbers.0|1| |numbers.1|2| |numbers.2|3| |numbers.3|4|

You can revert the old behavior by overriding standard telemetry formatter, for instance:

private class DottedOutTraceTelemetryConverter : TraceTelemetryConverter
    public override IValueFormatter ValueFormatter => new ApplicationInsightsDottedValueFormatter();


Additionally, you can also customize whether to send the LogEvents at all, if so which type(s) of Telemetry to send and also what to send (all or no LogEvent properties at all) by passing your own

instead of
by either implementing your own
or deriving from
and overriding specific bits.
var log = new LoggerConfiguration()
    .ApplicationInsights(configuration, new CustomConverter())
// ...

private class CustomConverter : TraceTelemetryConverter { public override IEnumerable Convert(LogEvent logEvent, IFormatProvider formatProvider) { // first create a default TraceTelemetry using the sink's default logic // .. but without the log level, and (rendered) message (template) included in the Properties foreach (ITelemetry telemetry in base.Convert(logEvent, formatProvider)) { // then go ahead and post-process the telemetry's context to contain the user id as desired if (logEvent.Properties.ContainsKey("UserId")) { telemetry.Context.User.Id = logEvent.Properties["UserId"].ToString(); } // post-process the telemetry's context to contain the operation id if (logEvent.Properties.ContainsKey("operation_Id")) { telemetry.Context.Operation.Id = logEvent.Properties["operation_Id"].ToString(); } // post-process the telemetry's context to contain the operation parent id if (logEvent.Properties.ContainsKey("operation_parentId")) { telemetry.Context.Operation.ParentId = logEvent.Properties["operation_parentId"].ToString(); } // typecast to ISupportProperties so you can manipulate the properties as desired ISupportProperties propTelematry = (ISupportProperties)telemetry;

        // find redundent properties
        var removeProps = new[] { "UserId", "operation_parentId", "operation_Id" };
        removeProps = removeProps.Where(prop => propTelematry.Properties.ContainsKey(prop)).ToArray();

        foreach (var prop in removeProps)
            // remove redundent properties

        yield return telemetry;


If you want to skip sending a particular LogEvent, just return

from your own converter method.

Customising included properties

The easiest way to customise included properties is to subclass one of the

implementations. For instance, let's include
in event telemetry:
private class IncludeRenderedMessageConverter : EventTelemetryConverter
    public override void ForwardPropertiesToTelemetryProperties(LogEvent logEvent, ISupportProperties telemetryProperties, IFormatProvider formatProvider)
        base.ForwardPropertiesToTelemetryProperties(logEvent, telemetryProperties, formatProvider,
            includeLogLevel: false,
            includeRenderedMessage: true,
            includeMessageTemplate: false);

How, When and Why to Flush Messages Manually

Or: Where did my Messages go?

As explained by the Application Insights documentation, the default behaviour of the AI client is to buffer messages and send them to AI in batches whenever the client seems fit. However, this may lead to lost messages when your application terminates while there are still unsent messages in said buffer.

You can control when AI shall flush its messages, for example when your application closes:

1) Create a custom

and hold on to it in a field or property:
// private TelemetryClient _telemetryClient;

// ... _telemetryClient = new TelemetryClient() { InstrumentationKey = "" };

2) Use that custom

to initialize the Sink:
var log = new LoggerConfiguration()
    .ApplicationInsights(_telemetryClient, TelemetryConverter.Events)

3) Call .Flush() on the TelemetryClient whenever you deem necessary, i.e. Application Shutdown:


// The AI Documentation mentions that calling .Flush() can be asynchronous and non-blocking so // depending on the underlying Channel to AI you might want to wait some time // specific to your application and its connectivity constraints for the flush to finish.

await Task.Delay(1000);

// or


Including Operation ID

Application Insight's Operation ID is pushed out if you set

LogEvent property. If it's present, AI's operation ID will be overriden by the value from this property.

This can be set like so:

public class OperationIdEnricher : ILogEventEnricher
    public void Enrich(LogEvent logEvent, ILogEventPropertyFactory propertyFactory)
        if (logEvent.Properties.TryGetValue("RequestId", out var requestId))
            logEvent.AddPropertyIfAbsent(new LogEventProperty("operationId", requestId));

Including Version

Application Insight supports component version and is pushed out if you set

LogEvent property. If it's present, AI's operation version will include the value from this property.

Using with Azure Functions

Azure functions has out of the box integration with Application Insights, which automatically logs functions execution start, end, and any exception. Please refer to the original documenation on how to enable it.

This sink can enrich AI messages, preserving operation_Id and other context information which is already provided by functions runtime. The easiest way to configure Serilog in this case is to use TelemetryConfiguration.Active which is already properly configured. You can, for instance, initialise logging in the static constructor:

public static class MyFunctions
        static MyFunctions()
            var config = TelemetryConfiguration.Active;
            if (config != null)
                Log.Logger = new LoggerConfiguration()
                    .WriteTo.ApplicationInsights(config, TelemetryConverter.Traces)

Copyright © 2019 Serilog Contributors - Provided under the Apache License, Version 2.0.

See also: Serilog Documentation

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