Hi all, In Camel, messages can flow between routes through several components like:
1) Direct (Synchronous within CamelContext) 2) Direct-VM (Synchronous within JVM) 3) SEDA (Asynchronous within CamelContext) 4) VM (Asynchronous within JVM) 5) ActiveMQ/AMQP/SJMS/RabbitMQ (Synchronous/Asynchronous between JVM's) 6) Spring Events (invoked the same thread as Spring notifies events) I have several questions regarding these various options. There is a page in the FAQ: https://camel.apache.org/manual/faq/how-do-the-direct-event-seda-and-vm-endpoints-compare.html This page is however not very extensive and only explains it theoretically. Is there a practical guide when to choose which option? Some questions: 1) When to use synchronous or asynchronous? In what use case should we choose synchronous and what use cases asynchronous. For example should I choose "synchronous" when using a request/reply pattern and want to wait for the answer and asynchronous in other use cases? 2) Are the performance issues to take into consideration? I have environments that use 10.000+ routes. Should I take performance considerations when choosing any one of options? 3) When to choose between Direct and Direct-VM? Can't I use "Direct-VM" in all cases for synchronous invocation and "VM" for asynchronous invocation? "VM" work within the CamelContext AND JVM? Is there a performance penalty when choosing "Direct-VM" instead of "Direct"? Or "VM" or "Seda"? 4) Is "Direct" really synchronous? By default "Synchronous" is false. In the documentation: "Whether synchronous processing is forced. If enabled then the producer thread, will be forced to wait until the message has been completed before the same thread will continue processing. If disabled (default) then the producer thread may be freed and can do other work while the message is continued processed by other threads (reactive)." Does reactive mean here it's non-blocking (and can process multiple synchronous calls) or is it asynchronous in disguise? 5) Why the naming of the components? In synchronous it's called direct and direct-vm But asynchronous is called seda and vm Shouldn't be called "seda-vm". Or why are there just these options: sync async reactive 6) Using "Direct" vs "Keeping everything in one route" I ran into this code: <route> <from uri="file:a"/> <setHeader name="headerA"> <constant>testA</constant> </setHeader> <to uri="direct:a"/> </route> <route> <from uri="direct:a"/> <setHeader name="headerB"> <constant>testB</constant> </setHeader> <to uri="direct:b"/> </route> <route> <from uri="file:a"/> <setHeader name="headerC"> <constant>testC</constant> </setHeader> <to uri="http:myendpoint"/> </route> Basically every route contains a "from" and "to" and only one action (in this case a setheader step). I believe this was done, because the routes were generated and the order can be changed easily. How I normally would write this: <route> <from uri="file:a"/> <setHeader name="headerA"> <constant>testA</constant> </setHeader> <setHeader name="headerB"> <constant>testB</constant> </setHeader> <setHeader name="headerC"> <constant>testC</constant> </setHeader> <to uri="http:myendpoint"/> </route> Are there differences between the first three routes and the second (everything in one route)? Is it just a different way of organizing the code or are there actually difference in the way it works? For example, is the second faster than the first (say I send 10 million messages)? Does using direct have advantages in the sense that it for example buffers messages in its "internal queue"? Regards, Raymond
