[CAMEL-11225] Deadlock in component creation

• Type: Bug
• Status: Resolved
• Priority: Major
• Resolution: Fixed
• Fix Version/s: 2.18.4, 2.19.1, 2.20.0
• Component/s: camel-core, camel-spring
• Estimated Complexity: Unknown
• Assignee: Luca Burgazzoli
• Reporter: Luca Burgazzoli
• Created: 03/May/17 07:45
• Updated: 09/May/17 11:14
• Resolved: 09/May/17 11:14

Description

There are circumstances in which the component creation could enter in a deadlock, let's have a look at the following spring example:

<beans xmlns="http://www.springframework.org/schema/beans"
       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
       xsi:schemaLocation="
         http://www.springframework.org/schema/beans http://www.springframework.org/schema/beans/spring-beans.xsd
         http://camel.apache.org/schema/spring http://camel.apache.org/schema/spring/camel-spring.xsd">
 
  <camelContext id="camel" xmlns="http://camel.apache.org/schema/spring">
    <route id="twitter-route">
      <from id="twitter" uri="twitter://timeline/home?type=polling"/>
      <log id="route-log" message="Got ${body}"/>
    </route>
  </camelContext>
 
</beans>

The critical part is:

  <from id="twitter" uri="twitter://timeline/home?type=polling"/>

What happens is that:

• because there is an id, camel registers a CamelEndpointFactoryBean to the spring application contex
• the endpoint is then resolved which involve the instantiation of the component (twitter in this case) which invoke CamelContext.getComponent
• when the component is being created it then uses the component resolver which goes down to the registry to find out if the requested component is already there
• as in the registry there is a bean factory with the same name as the component we want to create, spring invokes the factory which then goes down to CamelContext.getComponent
• then deadlock