WSO2 ESB Passthrough Transport in a nutshell

If you have ever used WSO2 ESB, you might already know that it is one of the highest performing open source ESB solutions in the integration space. The secret behind its performance is the so-called Pass Through Transport (PTT) implementation which handles the HTTP requests. If you are interested in learning about PTT from scratch, you can refer the fololwing article series written by Kasun Indrasiri.

If you read through the above mentioned posts, you can get a good understanding about the concepts and the implementation. But one thing which is harder to do is remember all the diagrams in your memory. It is not impossible, but little bit harder for a person with average brain. I have tried to draw a picture to capture all the required information related to the PTT. Here is my drawing on WSO2 ESB PTT.

WSO2 ESB Passthrough Transport

If you look at the above picture, it contains 3 main features of the PTT.

  1. The green boxes at the edges of the middle box contains the different methods executed from http-core library towards the Source handler of the ESB when there is any new events
  2. The orange boxes represents the internal state transition of the PTT starting from REQUEST_READY up until RESPONSE_DONE.
  3. Light blue boxes depicts the objects created within a lifecycle of a single message execution flow and how those objects interacted and at which time they get created.

In addition to above 3 main features, axis2 engine and synapse engine also depicted with purple and shiny purple boxes. These components were depicted as black boxes without considering the actual operations happen within those components.