Serilog.Sinks.ConfluentKafka 0.1.0

serilog-sinks-kafka

A Serilog sink that writes events to Kafka Endpoints (Including Azure Event Hubs).

Dependencies

This sink works with the following packages

• Serilog >v2.9.0
• Serilog.Sinks.PeriodicBatching >v2.3.0
• Confluent.Kafka >v1.6.3

Usage

Log.Logger = new LoggerConfiguration()
    .WriteTo.Kafka()
    .CreateLogger();

Parameters

• bootstrapServers - Comma separated list of Kafka Bootstrap Servers. Defaults to "localhost:9092"
• batchSizeLimit - Maximum number of logs to batch. Defaults to 50
• period - The period in seconds to send batches of logs. Defaults to 5 seconds
• securityProtocol - SecurityProtocol.Plaintext
• saslMechanism - The SASL Mecahnism. Defaults to SaslMechanism.Plain
• topic - Name of the Kafka topic. Defaults to "logs"
• topicDecider - Alternative to a static/constant "topic" value. Function that can be used to determine the topic to be written to at runtime (example below)
• saslUsername - (Optional) Username for SASL. This is required for Azure Event Hubs and should be set to $ConnectionString
• saslPassword - (Optional) Password for SASL. This is required for Azure Event Hubs and is your entire Connection String.
• sslCaLocation - (Optional) Location of the SSL CA Certificates This is required for Azure Event Hubs and should be set to ./cacert.pem as this package includes the Azure carcert.pem file which is copied into your binary output directory.
• formatter - optional ITextFormatter you can specify to format log entries. Defaults to the standard JsonFormatter with renderMessage set to true.

Configuration for a local Kafka instance using appsettings

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft": "Warning",
        "System": "Warning"
      }
    },
    "WriteTo": [
      {
        "Name": "Kafka",
        "Args": {
          "batchSizeLimit": "50",
          "period": "5",
          "bootstrapServers": "localhost:9092",
          "topic": "logs"
        }
      }
    ]
  }
}

Configuration with a topicDecider and a custom formatter

Log.Logger = new LoggerConfiguration()
              .WriteTo.Kafka(GetTopicName, "localhost:9092",
                    formatter: new CustomElasticsearchFormatter("LogEntry"));
              .CreateLogger();

The code above specifies GetTopicName as the topicDecider. Here is a sample implementation:

private static string GetTopicName(LogEvent logEntry)
{
    var logInfo = logEntry.Properties["LogEntry"] as StructureValue;
    var lookup = logInfo?.Properties.FirstOrDefault(a => a.Name == "some_property_name");

    return (string.Equals(lookup, "valueForTopicA")) 
      ? "topicA"
      : "topicB";    
}

The above code also references a CustomElasticSearchFormatter that uses the whole LogEntry as the input to the formatter. This is a custom formatter that inherits from ElasticsearchJsonFormatter in the Serilog.Sinks.Elasticsearch NuGet package, but can be any ITextFormatter that you want to use when sending the log entry to Kafka. Note that if you omit the formatter param (which is fine), the standard JsonFormatter will be used (with the renderMessage parameter set to true).

Configuration for Azure Event Hubs instance

You will need to ensure you have a copy of the Azure CA Certificates and define the location of this cert in the sslCaLocation.

You can download a copy of the Azure CA Certificate here.

Place this in you projects root directory and ensure it is copied to the build output in your csproj.

  <ItemGroup>
    <None Include="cacert.pem">
      <CopyToOutputDirectory>Always</CopyToOutputDirectory>
    </None>
  </ItemGroup>

Configuration for Azure Event Hubs.

Log.Logger = new LoggerConfiguration()
    .WriteTo.Kafka(
      batchSizeLimit: 50,
      period: 5,
      bootstrapServers: "my-event-hub-instance.servicebus.windows.net:9093",
      saslUsername: "$ConnectionString",
      saslPassword: "my-event-hub-instance-connection-string",
      topic: "logs",
      sslCaLocation: "./cacert.pem",
      saslMechanism: SaslMechanism.Plain,
      securityProtocol: SecurityProtocol.SaslSsl)
    .CreateLogger();

Or using appsettings...

{
  "Serilog": {
    "MinimumLevel": {
      "Default": "Debug",
      "Override": {
        "Microsoft": "Warning",
        "System": "Warning"
      }
    },
    "WriteTo": [
      {
        "Name": "Kafka",
        "Args": {
          "batchSizeLimit": "50",
          "period": "5",
          "bootstrapServers": "my-event-hub-instance.servicebus.windows.net:9093",
          "saslUsername": "$ConnectionString",
          "saslPassword": "my-event-hub-instance-connection-string",
          "topic": "logs",
          "sslCaLocation": "./cacert.pem",
          "saslMechanism": "Plain",
          "securityProtocol": "SaslSsl"
        }
      }
    ]
  }
}

Extra Configuration using Environment Variables

You can also specify ProducerConfig configuration using EnvironmentVariables. These settings can be specified as the following EnvironmentVariables...

SERILOG__KAFKA__ProducerConfigPropertyName

or

SERILOG__KAFKA__PRODUCER_CONFIG_PROPERTY_NAME.

SERILOG__KAFKA__ is first stripped from the Environment Variable Name and the remaining name is lowered and single _ is replaced with string.Empty.

The ProducerConfig is first loaded from any specified Environment Variables. Then any of the configuration passed into the KafkaSink constructor will override the Environment Variables. This is to ensure backwards compatability at the moment but passing this configuration into the KafkaSink constructor will be removed in the future.

You can check what properties are supported at the following github https://github.com/confluentinc/confluent-kafka-dotnet/blob/6128bdf65fa79fbb14210d73970fbd4f7940d4b7/src/Confluent.Kafka/Config_gen.cs#L830

Azure EventHubs Recommended Configuration

If you are running against an Azure EventHub, the following configuration is recommended.

https://github.com/Azure/azure-event-hubs-for-kafka/blob/master/CONFIGURATION.md

These EnvironmentVariables can be set...

SERILOG__KAFKA__SocketKeepaliveEnable=true
SERILOG__KAFKA__MetadataMaxAgeMs=180000
SERILOG__KAFKA__RequestTimeoutMs=30000
SERILOG__KAFKA__Partitioner=ConsistentRandom
SERILOG__KAFKA__EnableIdempotence=false
SERILOG__KAFKA__CompressionType=None