[Feature] Transactions Counter for Gateway

[dulanjalidilmi]

Related Issue: wso2/api-manager#2007

Problem

It is required to count the number of transactions processed through the Gateway to develop a transaction-based pricing model. Currently there is no transaction counting mechanism is implemented.

Solution

Developing a synapse handler based transaction counting mechanism.

Implementation

A synapse handler-based methodology needs to be developed to count the following transactions.

Transaction Type	Counting mechanism
Request Response Pairs	Needs to be counted at request outflow
Incoming messages via WebSockets	Can be counted at request inflow by checking the transport name.

Distributed architecture

Component architecture