concurrentConsumers not created right away from beginning - apache-camel

Question

I am using Camel in a Spring-Boot application to route from AMQ-Queue. Messages from this queue will be sent to a REST-Webservice. It is already working with this code line:
from("amq:queue:MyQueue").process("jmsToHttpProcessor").to(uri);
My uri looks like this:
http4://localhost:28010/application/createCustomer
Now I have the requirement that the routing to the Webservice should be done parallely:
In order to achive that, I configured concurrentConsumers in JmsConfiguration as follows:
#Bean
public JmsComponent amq(#Qualifier("amqConnectionFactory") ConnectionFactory amqConnectionFactory, AMQProperties amqProperties) {
JmsConfiguration jmsConfiguration = new JmsConfiguration(amqConnectionFactory);
jmsConfiguration.setConcurrentConsumers(50);
jmsConfiguration.setMaxConcurrentConsumers(50);
return new JmsComponent(jmsConfiguration);
}
#Bean
public ConnectionFactory amqConnectionFactory(AMQProperties amqProperties) throws Exception {
ConnectionFactoryParser parser = new ConnectionFactoryParser();
ConnectionFactory returnValue = parser.newObject(parser.expandURI(amqProperties.getUrl()), "amqConnectionFactory");
return returnValue;
}
It is working as expected, BUT not right away from the beginning. I have the phenomenon:
I have 100 messages in the ActiveMQ queue
I start my Spring application
Camel creates only 1 thread consuming 1 message after the previous one gets response
I observe that the amount of messages in queue only decreasing slowly(99.... 98... 97... 96...)
I am filling the queue with new 100 messages
NOW the concurrent consumers are being created as I can observe that the messages decreasing rapidly.
Does someone have any idea, why the concurrentConsumers is not working right away from the beginning?

Answer 1

I tried the advices. Unfortunately they dont change the behaviour. I found out, that the problem is that Camel already starts consuming the messages from the queue before the Spring boot application is startet. I can observe this from the log:
2021-04-01T20:26:33,901 INFO (Camel (CamelBridgeContext) thread #592 - JmsConsumer[MyQueue]) [message]; ...
2021-04-01T20:26:33,902 INFO (Camel (CamelBridgeContext) thread #592 - JmsConsumer[MyQueue]) [message]; ...
2021-04-01T20:26:33,915 INFO (main) [AbstractConnector]; _; Started ServerConnector#5833f5cd{HTTP/1.1,[http/1.1]}{0.0.0.0:23500}
2021-04-01T20:26:33,920 INFO (main) [BridgeWsApplication]; _; Started BridgeWsApplication in 12.53 seconds (JVM running for 13.429)
In this case, only one consumer with thread #592 is consuming all the messages.
In fact, if I start my Spring application first, and then fill the queue with messages, then concurrentConsumers will be used:
2021-04-01T20:30:20,159 INFO (Camel (CamelBridgeContext) thread #594 - JmsConsumer[MyQueue])
2021-04-01T20:30:20,159 INFO (Camel (CamelBridgeContext) thread #599 - JmsConsumer[MyQueue])
2021-04-01T20:30:20,178 INFO (Camel (CamelBridgeContext) thread #593 - JmsConsumer[MyQueue])
2021-04-01T20:30:20,204 INFO (Camel (CamelBridgeContext) thread #564 - JmsConsumer[MyQueue])
In this case, messages are being consumed from concurrentConsumers parallely.
In order to solve the problem, I tried setting autoStartUp to false in my RouteBuilder component:
#Override
public void configure() {
CamelContext context = getContext();
context.setAutoStartup(false);
// My Route
}
In my naive thinking, I let Camel starting after the Spring boot is started and running:
public static void main(String[] args) {
ConfigurableApplicationContext context = SpringApplication.run(BridgeWsApplication.class, args);
SpringCamelContext camel = (SpringCamelContext) context.getBean("camelContext");
camel.start();
try {
camel.startAllRoutes();
} catch (Exception e) {
e.printStackTrace();
}
}
Unfortunately, this does not change the behaviour. There must be a configuration to let Camel starts after Spring is started.