Inheritance of Properties
All destination properties are inheritable for both topics and queues. This means that a property set for a "wildcarded" destination is inherited by all destinations with matching names.
For example, if you have the following in your topics.conf file:
foo.* secure
foo.bar
foo.bob
Topics foo.bar and foo.bob are secure topics because they inherit secure from their parent, foo.*. If your EMS server were to dynamically create a foo.new topic, it too would have the secure property.
The properties inherited from a parent are in addition to the properties defined for the child destination.
For example, if you have the following in your topics.conf file:
foo.* secure foo.bar sender_name
Then foo.bar has both the secure and sender_name properties.
In the above example, there is no way to make topic foo.* secure without making foo.bar secure. In other words, EMS does not offer the ability to remove inherited properties. However, for properties that are assigned values, you can override the value established in a parent.
For example, if you have the following in your queues.conf file:
foo.* maxbytes=200 foo.bar maxbytes=2000
The foo.bar queue has a maxbytes value of 2000.
When there are multiple ancestors for a destination, the destination inherits the properties from all of the parents. For example:
> sender_name foo.* secure foo.bar trace
The foo.bar topic has the sender_name, secure and trace properties.
When there are multiple parents for a destination that contain conflicting property values, the destination inherits the smallest value. For example:
> maxbytes=2000 foo.* maxbytes=200 foo.bar
The foo.bar topic has a maxbytes value of 200.
Property inheritance is powerful, but can be complex to understand and administer. You must plan before assigning properties to topics and queues. Using wildcards to assign properties must be used carefully. For example, if you enter the following line in the topics.conf file:
> store=mystore
you make every topic store messages, regardless of additional entries. This might require a great deal of memory for storage and greatly decrease the system performance.