Notes - 6.3

Talend ESB Mediation Developer Guide

EnrichVersion
6.3
EnrichProdName
Talend Data Fabric
Talend Data Services Platform
Talend ESB
Talend MDM Platform
Talend Open Studio for ESB
Talend Real-Time Big Data Platform
task
Design and Development
EnrichPlatform
Talend ESB

Important

If you are using ActiveMQ, note that the JMS component reuses Spring 2's JmsTemplate for sending messages. This is not ideal for use in a non-J2EE container and typically requires some caching in the JMS provider to avoid poor performance .

If you intend to use Apache ActiveMQ as your Message Broker, then we recommend that you either:

  • Use the Camel Component: ActiveMQ component, which is already configured to use ActiveMQ efficiently, or

  • Use the PoolingConnectionFactory in ActiveMQ.

If you are consuming messages and using transactions (transacted=true) then the default settings for cache level can impact performance. If you are using XA transactions then you cannot cache as it can cause the XA transaction not to work properly. If you are not using XA, then you should consider caching as it speeds up performance, such as setting cacheLevelName=CACHE_CONSUMER.

The default setting for cacheLevelName is CACHE_AUTO. This default auto detects the mode and sets the cache level accordingly to:

  • CACHE_CONSUMER = if transacted = false

  • CACHE_NONE = if transacted = true

So you can say the default setting is conservative. Consider using cacheLevelName=CACHE_CONSUMER if you are using non-XA transactions.

If you wish to use durable topic subscriptions, you need to specify both clientId and durableSubscriptionName. The value of the clientId must be unique and can only be used by a single JMS connection instance in your entire network. You may prefer to use Virtual Topics instead to avoid this limitation. More background on durable messaging is available on the ActiveMQ site.

When using message headers, the JMS specification states that header names must be valid Java identifiers. So try to name your headers to be valid Java identifiers. One benefit of doing this is that you can then use your headers inside a JMS Selector (whose SQL92 syntax mandates Java identifier syntax for headers).

A simple strategy for mapping header names is used by default. The strategy is to replace any dots in the header name with the underscore character and to reverse the replacement when the header name is restored from a JMS message sent over the wire. What does this mean? No more losing method names to invoke on a bean component, no more losing the filename header for the File Component, and so on.

The current header name strategy for accepting header names in Camel is as follows:

  • Dots are replaced by _DOT_ and the replacement is reversed when Camel consumes the message. (for example, org.apache.camel.MethodName becomes org_DOT_apache_DOT_camel_DOT_MethodName).

  • Hyphen is replaced by _HYPHEN_ and the replacement is reversed when Camel consumes the message.

Warning

Are you using transactions? If you are consuming messages, and have transacted=true, then the default settings for cache level can impact performance. The default setting is always CACHE_CONSUMER. However, with the CACHE_AUTO setting, when you use transactions the cache level is effectively set to CACHE_NONE, appropriate for transactions.