NLog.Targets.HTTP

NLog.Targets.HTTP is an HTTP POST target for NLog. When combined with JSON formatter it can be used to send events to an instance of Splunk and other HTTP based collectors.

This target is inherently asynchronous, with performance on par or better than with the AsyncWrapper. Remember to Flush and to give it enough time to complete.

Note that the async="true" attribute applied to <targets > will discard by default.

Getting started

Add the library as an extension to nlog:

<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
  <extensions>
    <add assembly="NLog.Targets.Http" />
  </extensions>
  <targets>
    ...

Available Configuration Parameters

Listed below are available configuration parameters with their default values (where applicable)

<target name='target name' 
        type='HTTP' 
        URL='protocol://server:port/path'
        Method='POST'
        Authorization='phrase token' 
        BatchSize='1'
        MaxQueueSize='2147483647'
        IgnoreSslErrors='true'
        FlushBeforeShutdown='true'
        ContentType='application/json'
        Accept='application/json'
        DefaultConnectionLimit='2'
        Expect100Continue='false'
        UseNagleAlgorithm='true'
        ConnectTimeout='30000' 
        InMemoryCompression='true'
        ProxyUrl=''
        ProxyUser=''
        ProxyPassword=''
    >
    <!-- optional additional HTTP Headers -->
    <header name='key' value='value'/>
    <!-- additional headers -->
    <!-- layout element -->
</target>

URL

The URL (Layout element) to send messages to (mandatory).

Method

HTTP method to use (GET,POST).

Authorization

The Authorization Header value to pass.

BatchSize

Number of messages to be sent together in one call.

BatchAsJsonArray

If set to true, messages will be packaged as JSON Array instead of being separated with Environment.NewLine character. Default is false.

MaxQueueSize

Maximum number of messages awaiting to be send. Please note, that if this value is set too low, the logger might be blocking.

IgnoreSslErrors

Some SSL certificates might be invalid or not-trusted.

FlushBeforeShutdown

Force all messages to be delivered before shutting down. Note that by design .Net apps are limited to about 2 seconds to shutdown.
Make sure you leverage LogManager.Flush(TimeSpan.FromHours(24)) in most extreme scenarios.

ContentType

HTTP ContentType Header value. Default is application/json.

Accept

HTTP Accept Header value. Default is application/json.

DefaultConnectionLimit

How many connections might be used at the same time. Changes ServicePointManager.DefaultConnectionLimit, which might affect other parts of your system. Performance improvement was noticeable even with 16 connections, but your application might require more for other functionality. Use with caution.

Expect100Continue

See this article.

UseNagleAlgorithm

The Nagle algorithm is used to buffer small packets of data and transmit them as a single packet. This process, referred to as "nagling," is widely used because it reduces the number of packets transmitted and lowers the overhead per packet. The Nagle algorithm is fully described in IETF RFC 896.

ConnectTimeout

How long should the client wait to connect (default is 30 seconds).

InMemoryCompression

Reduces the amount of memory consumed at the expense of increased CPU usage. Significant performance improvement can be achieved by using default of false.

ProxyUrl

Designates a proxy server to use. Must include protocol (http|https) and port. It is a Layout element so can be dynamic.

ProxyUser

If proxy authentication is needed, you can specify it with a domain prefix, i.e. DOMAIN\USER.

ProxyPassword

Password to use for proxy authentication.

Additional Headers

Additional HTTP Headers can be specified by adding multiple <header name='..' value='..'/> elements. Elements with a blank name or value will not be included.

UnixTimeLayoutRenderer

The "Unix Time" renderer supports universalTime option (boolean), just like the date renderer does.

<attribute name='unixutc' layout='${unixtime:universalTime=true}' />

Sample SPLUNK Configuration

<?xml version="1.0" encoding="utf-8" ?>
<nlog xmlns="http://www.nlog-project.org/schemas/NLog.xsd" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" >
  <targets>
    <target name='splunk' 
            type='HTTP' 
            URL='https://localhost:8088/services/collector/event'
            Authorization='Splunk d758f3fa-740f-4bb7-96be-3da4128708bc' 
            BatchSize='100'>
      <layout type='JsonLayout'>
        <attribute name='sourcetype' layout='_json' />
        <attribute name='host' layout='${machinename}' />
        <attribute name='event' encode='false'>
          <layout type='JsonLayout'>
            <attribute name='level' layout='${level:upperCase=true}' />
            <attribute name='source' layout='${logger}' />
            <attribute name='thread' layout='${threadid}' />
            <attribute name='message' layout='${message}' />
            <attribute name='utc' layout='${date:universalTime=true:format=yyyy-MM-dd HH\:mm\:ss.fff}' />
          </layout>
        </attribute>
      </layout>
    </target>
  </targets>
  <rules>
    <logger name="*" minlevel="Debug" writeTo="splunk" />
  </rules>
</nlog>

Sample stats

On a Lenovo Xeon E3-1505M v6 powered laptop with 64GB of RAM and 3GB/s NVMe storage, this HTTP target was able to consistenlty accept about 125,000 messages per second, and 62,500 per second received and processed by local Dockerized Splunk Enterpise 8.2.4. Please note, that these stats depend heavily on the message size, batch size, and amount of bytes that can be submitted in a single POST message.

Running local Splunk

docker pull splunk/splunk:latest
docker run -d -p 8000:8000 -p 8088:8088 -e "SPLUNK_START_ARGS=--accept-license" -e "SPLUNK_PASSWORD=Pass@W0rd" --name splunk splunk/splunk:latest

After a few moments, depeneding on your systems capacity, login to Splunk at http://localhost:8080/ with admin and Pass@W0rd. The HttpEventCollector (HEC) will listen on port 8088 once created from Settings - Data Inputs menu option.