BufferingWrapper target

A target that buffers log events and sends them in batches to the wrapped target.

Platforms Supported: All

Configuration Syntax

<targets>
  <target xsi:type="BufferingWrapper"
          name="String"
          bufferSize="Integer"
          flushTimeout="Integer"
          slidingTimeout="Boolean"
          overflowAction="Enum">
    <target xsi:type="wrappedTargetType" ...target properties... />
  </target>
</targets>

Parameters

General Options

• name - Name of the target.

Buffering Options

• bufferSize - Number of log events to be buffered. When the limit is reached, then a synchronous flush is performed. Integer Default: 100

• flushTimeout - Timeout (in milliseconds) after a write, until the entire buffer is asynchronously flushed. Use -1 to disable timed flushes. Integer Default: -1

• slidingTimeout - Indicates whether to use sliding flushTimeout. Boolean Default: True
  This value determines how the inactivity period is determined. If sliding timeout is enabled, the inactivity timer is reset after each write, if it is disabled - inactivity timer will count from the first event written to the buffer.

• overflowAction - Action to be taken when the buffer exceeds the set bufferSize. Enum Default: Flush. Introduced in NLog 4.5
  Possible values:

  • Flush - All the log events in the buffer will be written in the wrapped target.
  • Discard - The oldest log event will be removed from the buffer. If this setting is used, the Flush action will need to be triggered manually using another wrapper like the AutoFlushWrapper or by using the flushTimeout option.

Remarks

Buffering and custom targets

When messages are written into the BufferingWrapper, then LogEvents are queued for writing at a later stage. There can be custom NLog targets that requires writing to happen on the main thread for proper context capture (without being queued). When used together with BufferingWrapper then context information can be lost.

By default all standard NLog targets supports use of BufferingWrapper. Custom NLog targets that inherits from TargetWithContext should also by default work correctly with BufferingWrapper.

Buffer and asynchronously writing

If flushTimeout is larger than 0, then the messages are written asynchronously. If the buffer is filled before the flushTimeout fires and triggers the asynchronous flush, then the logging thread will be performing the flush, and be blocked by the operation.

Because the BufferingWrapper is not intended for performance optimization, but for throttling or even discarding LogEvents. Then it can be a good idea to make use of the async attribute or the AsyncWrapper.

Send batch when triggered by event

This will send the last 50 messages to the myTargetType, when an Error occurs:

  <target name="String" xsi:type="AutoFlushWrapper"
          condition="level >= LogLevel.Error"
          flushOnConditionOnly="true">
     <target xsi:type="BufferingWrapper" bufferSize="50" overflowAction="Discard">
         <target xsi:type="myTargetType" ...target properties... />
     </target>
  </target>