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• Pros: Reduce the duplicated work that all coordinators implement the same logic.
• Cons:
  1. Introduce the dependency between etcd and Proxy.
  2. Not easy to get resource usage of nodes, such as memory usage, cpu usage and etc.

Detailed Implementation of Plan 1

Every component in Milvus should have an interface GetMetrics to expose their metrics. As the user access layer, Proxy connects to other coordinators directly, such as RootCoord, DataCoord, QueryCoord and IndexCoord. Taking QueryCoord as an example, how could Proxy get topology metrics between QueryCoord and Query Nodes? The answer is that Proxy get these metrics from QueryCoord. QueryCoord manages all the Query Nodes, so the metrics of Query Nodes can be easily reported to QueryCoord and then QueryCoord an summary these metrics to Proxy.

We should add GetMetrics interface to rpc service of coordinator and related node:

service QueryCoord {
  rpc GetMetrics(milvus.GetMetricsRequest) returns (milvus.GetMetricsResponse) {}
}

service QueryNode {
  rpc GetMetrics(milvus.GetMetricsRequest) returns (milvus.GetMetricsResponse) {}
}

How to use GetMetrics interface?

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