Merge pull request openyurtio#1864 from rambohe-ch/add-nodebucket-pro…

…posal

proposal: add NodeBucket to reduce cloud-edge traffic spike during rapid node additions.

docs/proposals/20231219-reduce-traffic-spike-during-rapid-node-additions.md

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+|                            title                            | authors     | reviewers | creation-date | last-updated | status      |
+|:-----------------------------------------------------------:|-------------| --------- |---------------| ------------ | ----------- |
+| Reduce cloud-edge traffic spike during rapid node additions | @rambohe-ch |       | 2023-12-19    |    |  |
+
+# Reduce cloud-edge traffic spike during rapid node additions
+
+## Summary
+
+Introducing the NodeBucket resource provides a scalable and efficient way to manage large NodePools in OpenYurt clusters,
+significantly reducing cloud-edge traffic during rapid node additions and maintaining cluster stability.
+
+## Motivation
+
+In OpenYurt, NodePool resources manage a group of nodes, and NodePool.status.nodes hold information about all nodes in the pool.
+YurtHubs rely on NodePool.status.nodes to determine endpoints within the same NodePool, providing service topology capabilities at the node pool level.
+In scenarios where a large NodePool (e.g., with 1000 nodes) experiences rapid growth, such as the addition of 100 edge nodes within a short period of 1 minute,
+the cloud-edge traffic can escalate dramatically. Notably, for each node addition, the NodePool data is updated, resulting in 100 updates for 100 new nodes.
+These updates are then propagated to every YurtHub component. Assuming a NodePool resource with 1000 nodes information is 60KB in size, the average traffic can be calculated as follows:
+
+```
+100 (updates) * 1000 (nodes) * 60KB (size per update) / 60 seconds = 100 MB/s = 800 Mbps.
+```
+
+Such a traffic spike can strain the network and impact cluster stability.
+
+### Goals
+
+- Introduce a scalable solution for managing large-scale NodePools in OpenYurt clusters.
+- Minimize cloud-edge network traffic caused by frequent NodePool updates during rapid node additions.
+- Maintain cluster stability by preventing bandwidth saturation.
+
+### Non-Goals/Future Work
+
+- It does not seek to replace the existing NodePool resource but rather to complement it and optimize it for scalability.
+- Controllers in yurt-manager component that are using NodePool will remain unchanged.
+
+## Proposal
+
+### Solution Introduction
+
+- The proposed solution is the implementation of a NodeBucket resource that holds node information within the NodePool.
+The NodePool to NodeBucket ratio would be 1:N. For example, if one NodeBucket can store information for up to 100 nodes,
+then a NodePool with 1000 nodes could be split into 10 NodeBuckets, each being only 1/10th the size of the original (e.g., 6KB).
+
+- Following the previously described NodeBucket CRD segment, a significant change in design is that YurtHubs will monitor NodeBucket instead of NodePool on all edge nodes.
+This shift is critical for enabling the NodeBucket resource to reduce traffic and increase scalability effectively.
+
+- During the addition of 100 nodes within 1 minute, only the NodeBuckets would be updated and propagated to all YurtHubs. The cloud-edge NodeBucket communication traffic would then be:
+
+```
+100 (updates) * 1000 (nodes) * 6KB (size per update) / 60 seconds = 10 MB/s = 80 Mbps.
+```
+
+This represents a tenfold reduction in cloud-edge traffic compared to the current NodePool approach.
+
+### NodeBucket API
+
+```
+type Node struct {
+    // Name is the name of node
+    Name string `json:"name,omitempty"`
+}
+
+type NodeBucket struct {
+    metav1.TypeMeta   `json:",inline"`
+    metav1.ObjectMeta `json:"metadata,omitempty"`
+    // NumNodes represents the number of nodes in the nodebucket
+    NumNodes int32 `json:"numNodes"`
+    // Nodes represents a subset of nodes in the nodepool
+    Nodes []Node `json:"nodes"`
+}
+
+type NodeBucketList struct {
+    metav1.TypeMeta `json:",inline"`
+    metav1.ListMeta `json:"metadata,omitempty"`
+    Items           []NodeBucket `json:"items"`
+}
+```
+
+1. A label denoted as `openyurt.io/pool-name={nodepool-name}` will be appended to each NodeBucket associated with a NodePool, allowing for the aggregation and retrieval of all relevant NodeBuckets using a LabelSelector based on this specific label.
+
+2. The `OwnerReference` field within NodeBucket will be configured to reference its corresponding NodePool, establishing a clear ownership relationship.
+
+### User Stories
+
+#### Story 1（General）
+
+As a cluster administrator, I manage a large OpenYurt cluster with several node pools, each containing hundreds of edge nodes.
+
+My challenge is to scale the cluster quickly by adding new nodes to the pools without overloading the network bandwidth or affecting the cluster's performance.
+
+With the current NodePool setup, I've noticed cloud-edge traffic spikes and stability issues during rapid node pool expansions.
+
+## Implementation History
+
+- [ ]  12/19/2023: Draft proposal created;