HTTP PassThrough Transport (also referred to as PassThru Transport or PTT) is the default, non-blocking HTTP transport implementation based on HTTP Core NIO and is specially designed for streaming messages. It is similar to the old message relay transport, but it does not care about the content type and simply streams all received messages through. It also has a simpler and cleaner model for forwarding messages back and forth. The HTTP PassThrough Transport uses a single shared buffer instead of the two buffers (shared input buffer and shared output buffer) used by the NHTTP transport, improving performance in pass-through mediation.
The HTTP PassThrough Transport is enabled by default. If you want to use the NHTTP transport instead, uncomment the relevant NHTTP transport entries in axis2.xml and comment out the HTTP PassThrough transport entries. The PassThrough Transport does not require the binary relay builder and expanding formatter.
Connection throttling
With the HTTP PassThrough and HTTP NIO transports, you can enable connection throttling to restrict the number of simultaneous open connections. To enable connection throttling, edit the <ESB_HOME>/repository/conf/nhttp.properties (for the HTTP NIO transport) or <ESB_HOME>/repository/conf/passthru-http.properties (for the PassThrough transport) and add the following line:
max_open_connections = 2
This will restrict simultaneous open incoming connections to 2. To disable throttling, delete the max_open_connections setting or set it to -1.
Connection throttling is never exact. For example, setting this property to 2 will result in roughly two simultaneous open connections at any given time.