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Introduction to MOCAng Archtecture September 28, 2009
The Basics -- How We Got Here • Legacy MOCA has a scalability problem > MOCA is Centered around MOCA Server Processes > We spawn mocasrvprc, as needed, to support load > Each mocasrvprc contains • • • • •
Single DB connection (traditionally) The MOCA engine Command configuration (via memory file) Loaded libraries for commands JVM (since 2005.2)
• Loaded Java classes and libraries • Various ad-hoc caches, depending on what commands have been run > Policies > Integrator metadata
> Process startup time has become a problem • We’ve implemented changes to the connection manager process limits to avoid spawning too often.
Side Effects • 64/32-bit capability > C code can still be 32-bit, to avoid risk. > Java VM can run 64-bit, to increase scalability > JVM heap size can be quite large (many GB on server-class hardware)
Performance Overhead - How Slow is Slow? • Two types of overhead should be considered > Calling SQL from C > Calling C components from C
• Generally, SQL overhead is less than initiating C components > SQL execution involves an additional copy of the result data over the native socket. > C component involves potentially many additional copies
SQL Performance Overhead • When calling SQL from C, one extra data copy must be made • Overhead varies with amount of data sent > Note: this test data was from a local database using a very fast single-table SELECT statement. Size (rows)
C Performance Overhead Explained • When a C component initiates another command, it talks to the MOCA server to do it • If that command invocation needs to execute C, it comes back around to the C process MOCA Server
Native Process Call C Function A srvInitiate(...) Call C Function B sqlExec* sqlExec Results C Function B Results srvInitiate(...) Results C Function A Results
C Performance Overhead • Overhead varies with amount of data sent and depth of call stack • Test Case illustrates worst-case situation, but indicates a problem area Call Depth
So What? • Despite appearances, those are not disastrous overheads • If a component is called only few times per day, a few milliseconds of overhead is not a huge problem. • However, when a component gets called several thousand times per hour, it becomes an issue. • Look For > Commands that get run a lot in day-to-day operations > Commands that expect to operate on larger data sets > Commands that initiate a lot of other commands
