69 lines
2.5 KiB
Go
69 lines
2.5 KiB
Go
package node
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import (
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"context"
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"errors"
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"github.com/ethereum/go-ethereum/log"
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"github.com/ethereum/go-ethereum/node"
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"github.com/ethereum/go-ethereum/p2p"
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)
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// All general log messages in this package should be routed through this logger.
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var logger = log.New("package", "status-go/metrics/node")
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// SubscribeServerEvents subscribes to server and listens to
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// PeerEventTypeAdd and PeerEventTypeDrop events.
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func SubscribeServerEvents(ctx context.Context, node *node.Node) error {
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server := node.Server()
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if server == nil {
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return errors.New("server is unavailable")
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}
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ch := make(chan *p2p.PeerEvent, server.MaxPeers)
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subscription := server.SubscribeEvents(ch)
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defer subscription.Unsubscribe()
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logger.Debug("Subscribed to server events")
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for {
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select {
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case event := <-ch:
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if isAddDropPeerEvent(event.Type) {
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// We start a goroutine here because updateNodeMetrics
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// is calling a method on the p2p server, which
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// blocks until the server is available:
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// https://github.com/status-im/status-go/blob/e60f425b45d00d3880b42fdd77b460ec465a9f55/vendor/github.com/ethereum/go-ethereum/p2p/server.go#L301
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// https://github.com/status-im/status-go/blob/e60f425b45d00d3880b42fdd77b460ec465a9f55/vendor/github.com/ethereum/go-ethereum/p2p/server.go#L746
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// If there's back-pressure on the peer event feed
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// https://github.com/status-im/status-go/blob/e60f425b45d00d3880b42fdd77b460ec465a9f55/vendor/github.com/ethereum/go-ethereum/p2p/server.go#L783
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// The event channel above might become full while updateNodeMetrics
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// is called, which means is never consumed, the server blocks on publishing on
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// it, and the two will deadlock (server waits for the channel above to be consumed,
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// this code waits for the server to respond to peerCount, which is in the same
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// event loop).
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// Calling it in a different go-routine will allow this code to keep
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// processing peer added events, therefore the server will not lock and
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// keep processing requests.
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go func() {
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if err := updateNodeMetrics(node, event.Type); err != nil {
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logger.Error("failed to update node metrics", "err", err)
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}
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}()
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}
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case err := <-subscription.Err():
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if err != nil {
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logger.Error("Subscription failed", "err", err)
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}
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return err
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case <-ctx.Done():
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return nil
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}
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}
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}
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func isAddDropPeerEvent(eventType p2p.PeerEventType) bool {
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return eventType == p2p.PeerEventTypeAdd || eventType == p2p.PeerEventTypeDrop
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}
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