Wednesday, January 16, 2008

BizTalk 2006 / R2 Publishing Throttling State #2 (imbalanced message publishing rate, input rate exceeds output rate)

Our next destination in BizTalk Throttling exploration drive is inbound Throttling states, publishing throttling state #2 Throttling due to imbalanced message publishing rate (input rate exceeds output rate).

Throttling state # 2, due to imbalanced message publishing rate, input rate exceeds output rate:

This is the most simple scenario to understand, here imbalanced message publishing rate means the ratio of the incoming messages by outgoing messages or vice versa.

The following is the condition of the Throttling state:
- (Message publishing incoming rate / Message publishing outgoing rate) * Rate overdrive factor in %

This condition belong to rate base throttling, For inbound (published) messages, BizTalk Server throttles publishing of messages if The Message publishing incoming rate for the host instance exceeds the Message publishing outgoing rate * the specified Rate overdrive factor (percent) value. The Rate overdrive factor (percent) parameter is configurable on the Message Publishing Throttling Settings dialog box. Rate based throttling for inbound messages is accomplished primarily by inducing a delay before publishing the batch of messages into the MessageBox database. No other action is taken to accomplish rate based throttling for inbound messages.

In following general scenario, I found the the throttling state can be possible in environment.

- very high demand to process messages and less available resources to process those messages.
- high use of co-related messages and self-correlated ports, and multiple subscribers for single received message.
- Slow outbound adapters.
- imbalance between host configured for inbound adapter and host configuration for XLANG / host configuration for outbound adapter.
- high processing complexity.

Understanding about Publishing throttling threshold parameter,

Minimum number of samples: Minimum number of messages BizTalk Server will sample for the Sampling window duration before considering rate-based throttling. If the actual number of samples in a sampling window fall below this value then the samples are discarded and throttling is not applied. This value should be consistent with a rate at which messages can be published under a medium load. For example, if your system is expected to handle 1,000 documents per second under a medium load, then this parameter should be set to 1,000 * Sample window duration in seconds (or more precisely, 1 * Sample window duration (milliseconds)). If the value is set too low, then the system may experience a throttling condition under low load. If the value is set too high, then there may not be enough samples for this technique to be effective.
Enter a value of zero to disable rate based inbound throttling.
The default value is 100.

Sampling window duration (milliseconds): The time-window measured in milliseconds, which is used to calculate the publishing rate based on the samples collected. The duration should be increased if the latency required for publishing a single message is high.
Enter a value of zero to disable rate based inbound throttling.
The default value is 15,000.

Rate overdrive factor (percent): This controls how much higher you allow the request rate to be than the completion rate before a throttling condition occurs. For example, if messages are being published at a rate of 200 per second and this parameter is set to 125, then the system will allow the publication of up to 250 messages per second (125% * 200 = 250) before applying throttling. Specifying too small a value for this parameter will cause the system to throttle more aggressively and could lead to over-throttling. Specifying too large a value for this parameter will cause under throttling and prevent the throttling mechanism from recognizing a legitimate throttling condition.
The default value is 125.

Maximum throttling delay (milliseconds): This is the maximum delay BizTalk Server will impose on a message instance due to throttling. The actual delay depends on the severity of the throttling condition.
Enter a value of zero to disable inbound throttling.
The default value is 300,000.

Triggering Mechanism of State #2 publishing throttling: In the sampling window duration, if the incoming/outgoing ratio excceds the configured parameter "Rate overdrive factor" value then BizTalk will be in throttling state.

Throttling Action: Block the publishing thread for a dynamically computed time period until the Message Publishing Incoming Rate is at par with the Message Publishing Outgoing Rate * the specified Rate overdrive factor (percent) value. By blocking the publishing thread, BizTalk can reduce the queued up messages, I have noticed many time the queued up inbound messages has very bad impact on the memory as well as the processing on the BizTalk artifacts. And the impact of the queued up messages is showing exponential memory & utilization which can also impact indirectly overall to every processing in BizTalk. So by blocking publishing thread, BizTalk is reducing incoming message flow and keeping flow healthy.

Sample collection of BizTalk Perfmon data and Graph: You can view in below graph that when the publishing throttling rate condition is setisfying the system in throttling mode #2, also you can analyze as per the sample window state through it.

If you would like to have the perfmon logs data, biztalk throttling configuration snap and graph in compress file for studying or analyzing it further for study which I have simulate for study, please write me to

Hope this article helped you to understand state#2 of throttling for you.

Related articles posted by me on the same blog:
BizTalk 2006 R2 - Throttling - Perfmon Parameters - My Experience (Tuesday, January 15, 2008)
BizTalk Server 2006 / R2 Throttling Mechanisms (Friday, January 4, 2008)

MSDN Resource Link:

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