What"s new for MPX in StarTeam 2009?
The MPX message improvements in StarTeam 2009 are:
With StarTeam 2009, a third parallel substream prefixed with "/STEvent3" has been added. Each update event is broadcast to all three event substreams. "Broadcast" means that the Event Transmitter publishes each message to the root Message Broker (MB). Whether the message goes farther depends on what clients are out there. If there are no StarTeam 2005 R2 clients, the STEvent messages go no farther. If all clients are using the StarTeam 2009 SDK, the STEvent2 messages also go no farther. Technically, all three substreams are always broadcast, which means that the StarTeam server-to-root MB traffic may be higher than before. While this may start out this way as the clients are upgraded to newer SDKs the traffic will decrease to the point where it is less than it would be using pre-2009 StarTeam.
STEvent3 messages - which are only event messages - are always broadcast from the Event Transmitter to the root MB. They are forwarded by the root MB only if and where there are StarTeam 2009 SDK-based clients.
Fine tune client subscriptions to receive fewer messages
Using the StarTeam 2009-based SDK, a client listens to more granular messages than before. In particular, some events that are pertinent to only one view are now broadcast with a subject name that includes the view ID. Hence, a typical StarTeam 2009 client should receive considerably less traffic than its pre-2009 counterparts depending on how many views are being updated. If it were possible for a StarTeam 2009 client to receive all STEvent3 messages (e.g., by opening every view), then the total number of messages it receives would be nearly identical to that received by a pre-2009 client. However, even if it received every message, due to compression and other efficiencies it would use 70% or less of the network bandwidth as its pre-2009 counterpart.
The STEvent3 stream has some new event messages for Change Packages and Traces (initally only presented as StarTeam external links). These are not broadcast to the older substreams since old clients can"t use them. However, we expect the total volume of these messages to be negligible compare to much more common update messages.
Compress event messages
Prior to StarTeam 2009 file content and object caching messages are already compressed before being broadcast. In StarTeam 2009, all event messages, which are currently encrypted, will also be compressed before being encrypted. This will reduce event messages sizes approximately 70%.
Uncompressed/encrypted event messages will continue to be sent to StarTeam 2005 R2 and pre-2009 (STEvent and STEvent2) SDK clients, while the compressed/encrypted event messages will be sent to the 2009 and later SDK clients.
Eliminate unneeded file content messages
Pre-StarTeam 2009, when the File Transmitter gets a "modify" event for a file, it does not know if the file"s content changed or not. So it unconditionally broadcasts the file"s content in the "cache stream" substream. It also broadcasts an object cache message in the "event stream". In StarTeam 2009, the File Transmitter knows if the MD5 changed in file/modify events and it only broadcasts the file content if the MD5 changed. It still broadcasts an object cache message, but, as you would imagine, the file content is the much larger stream. This optimization reduces the traffic between the File Transmitter and all Cache Agents (CA) in the cloud.
When all of the changes have been added together the traffic reduction during load testing has been seen to be reduced by between 80% and 86% for a client subscribed to a single view.
Additional Resulting Improvements in StarTeam 2009
Another important but subtle aspect of the StarTeam 2009 MPX improvements is reduced MB-to-MB traffic. It should be fairly clear that, with StarTeam 2009 servers, MB-to-CA traffic will be less, and with StarTeam 2009 clients, MB-to-client traffic will also be less. However, MB-to-MB traffic could be higher while the customer upgrades old clients. When all clients are upgraded to 2009, STEvent2 traffic goes away.