How does Openwhisk decide how many runtime containers to create?

I am working on a project that is using Openwhisk. I have created a Kubernetes cluster on Google cloud with 5 nodes and installed OW on it. My serverless function is written in Java. It does some processing based on arguments I pass to it. The processing can last up to 30 seconds and I invoke the function multiple times during these 30 seconds which means I want to have a greater number of runtime containers(pods) created without having to wait for the previous invocation to finish. Ideally, there should be a container for each invocation until the resources are finished.

Now, what happens is that when I start invoking the function, the first container is created, and then after few seconds, another one to serve the first two invocation. From that point on, I continue invoking the function (no more than 5 simultaneous invocation) but no containers are started. Then, after some time, a third container is created and sometimes, but rarely, a fourth one, but only after long time. What is even weirded is that the containers are all started on a single cluster node or sometimes on two nodes (always the same two nodes). The other nodes are not used. I have set up the cluster carefully. Each node is labeled as invoker. I have tried experimenting with memory assigned to each container, max number of containers, I have increased the max number of invocations I can have per minute but despite all this, I haven’t been able to increase the number of containers created. Additionally, I have tried with different machines used for the cluster (different number of cores and memory) but it was in vain.

Since Openwhisk is still relatively a young project, I don’t get enough information from the official documentation unfortunately. Can someone explain how does Openwhisk decide when to start a new container? What parameters can I change in values.yaml such that I achieve greater number of containers?

Source: StackOverflow

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