Apache Camel - Synchronicity & Threading (9/250-2016)

A service can be called synchronously as well as asynchronously. 
After the service is invoked - the consumer can use multiple / single thread to complete the operation.

The factors which affect the threading model 

• Component - which starts the process - whether it is fire and forget or request/reply messaging style
• EIP - some support parallel processing (concurrency)
• Configured Synchronicity - some components can be configure to be sync/async
• Transactions - if a route is transacted -- the transactional context is limited to run within one thread only.
• MEP (Message Exchange Pattern) - information in the exchange telling InOnly / OutOnly / InOut

Different scenarios discussed in the book - 

• Async caller - Camel uses only one thread 
• template.sendBody = InOnly Msg
• caller sending InOnly Msg
• single thread - pros
• simple
• support transaction propagation
• cons
• consumer threads can be overloaded by number of incoming messages
• Sync Called - Camel uses multi thread
• template.requestBody = InOutBody
• Async caller - Camel uses only one thread
• Sync caller - Camel uses multi thread

References: 

• pg 335 of   Camel in Action