Dependency Manager - Performance Tuning

To further tune the performance of an application using Dependency Manager and a lot of services, we created the concept of filter indices. They work similarly to the way indices speed up relational database queries and are explained below.

Filter Indices¶

Filter indices allow you to speed up the service resolution process by skipping the services registry, in favor of a fast index on given service properties.

The Dependency Manager will look for a set of filter indices in the org.apache.felix.dependencymanager.filterindex system property. This system property uses the following syntax,

property-index ::= service-property | service-property ',' property-index
index ::= '*aspect*' | '*adapter*' | property-index
indices ::= index | indices ';' index

The implementation ships with three kinds of index implementations.

• Service property indices are based on a set of service properties, like a multi-column index in a database.
• Aspect indices work with Dependency Manager Aspect services, and will provide indexing for the specific filters that they use.
• Adapter indices work like Aspect indices, but for Adapter services.

Performance¶

The index isn't free, but reduces the linear (and wasteful) filter-based lookup to an indexed log(n) lookup. You can expect noticeable speedup if you have at least several hundred services.

Examples¶

-Dorg.apache.felix.dependencymanager.filterindex=objectClass

Sets an index on objectClass, speeding up lookups for any filter that contains an objectClass in its filter (all regular services do).

-Dorg.apache.felix.dependencymanager.filterindex=objectClass,id

This filter helps if you have a lot of similar services, identified by some id.

-Dorg.apache.felix.dependencymanager.filterindex=objectClass,id;objectClass,ipAddress

This is a set of two filter indices, helping when you have one set of services that has an id, and another set that uses an ipAddress for identification.

-Dorg.apache.felix.dependencymanager.filterindex=*aspect*

Provides indexing for all Aspect services.