A flow control mechanism in Cloud Data Fusion prevents you from submitting
too many requests, which can cause stuck or failed pipeline runs. This mechanism
applies to start (
Launch) requests for the following pipelines and jobs in all
editions of Cloud Data Fusion, versions 6.6 and later:
- Batch pipelines
- Real-time pipelines
- Replication jobs
To control the number of outstanding start requests in Cloud Data Fusion, flow control relies on two thresholds:
- Launch threshold
- Limits the number of launch requests being made. If the
number of launch requests received by Cloud Data Fusion that are not yet in
Runningstate is greater than the launch threshold (number of launch requests that aren't running yet > launch threshold), the request is rejected. The number includes batch pipelines, real-time pipelines, and Replication jobs.
- Runs threshold
- Limits the number of outstanding launch requests in the system. If the number of outstanding launch requests received by Cloud Data Fusion that have not yet finished is greater than a specified runs threshold (number of outstanding requests that aren't finished yet > runs threshold), the request is rejected.
If either threshold is met, every new start request gets rejected. For example,
a rejected batch pipeline has a
Rejected status in the logs, and a dialog in
the UI describes why the launch was rejected.
The number of launching and running pipelines along with the number of rejected pipelines in the system can be accessed through the metrics service as follows.
Reports the number of launching requests in the system. That is, it reports the
number of launch requests that are in
Reports the number of running pipelines and jobs in the system. The run
threshold is based on the sum of the
Running metrics values.
Reports the number of rejected runs due to the flow control mechanism.
- For examples of providing tags and aggregating the
Rejectedmetric for different pipelines, see CDAP Metrics Microservices.