This topic describes common issues and their solutions when you use Knative in Alibaba Cloud Container Service for Kubernetes (ACS) clusters.
Index
Differences between Alibaba Cloud Knative and open source Knative
Alibaba Cloud Knative is compatible with open source Knative. It also provides enhanced features for operations and maintenance (O&M), usability, elasticity, gateways, event-driven architecture, and monitoring and alerting. For more information, see Comparison between Alibaba Cloud Knative and open source Knative.
Gateway selection for Knative installation
Alibaba Cloud Knative supports three types of gateways: Application Load Balancer (ALB), Alibaba Cloud Service Mesh (ASM), and Kourier. ALB specializes in application layer load balancing. ASM provides a service mesh based on Istio. You can choose Kourier if you only need basic gateway features. For more information, see Knative gateway selection guide.
Required permissions for Resource Access Management (RAM) users or roles to use Knative
You must have permissions to access all namespaces in the cluster. To grant the permissions, perform the following steps:
Log on to the ACS console. In the left navigation pane, choose Authorizations.
Click the RAM Users tab. In the list of RAM users, find the target RAM user and click Manage Permissions.
In the Add Permissions section, select the cluster, set Namespace to All namespaces, and follow the prompts to complete the authorization.
Time required for a pod to scale in to zero
The time it takes for a pod to scale in to 0 depends on three parameters:
stable-window: The stable window. Before a pod scales in, Knative observes and evaluates metrics during this period instead of taking immediate action.scale-to-zero-grace-period: The scale-to-zero grace period. During this period, the system does not immediately stop or delete the last pod even if there are no new requests. This prevents issues with burst traffic.scale-to-zero-pod-retention-period: The retention period for the last pod before scaling in to zero. This allows the pod to quickly respond to burst traffic without starting a new pod from scratch.
A pod scales in to zero only if the following three conditions are met:
No requests are received within the
stable-window.The retention period specified by
scale-to-zero-pod-retention-periodhas elapsed.The pod starts to scale in after the time since Serverless Kubernetes Service (SKS) switched to proxy mode exceeds the
scale-to-zero-grace-period.
The retention period before a pod scales in to zero does not exceed stable-window + Max["scale-to-zero-grace-period", "scale-to-zero-pod-retention-period" ]. To enforce a retention period before a pod scales in to zero, you can configure the scale-to-zero-pod-retention-period parameter.
Is the Activator component of ACS Knative billed
The Activator component is a data plane component. It runs as a pod and consumes your instance resources, which are billable.
Configure the listening port for a Knative service
The application's listening port must match the containerPort in the Knative Service. The default port is 8080. To configure a custom listening port, see Configure a custom listening port in Knative.