mirror of https://github.com/status-im/consul.git
consul: Refactor forward to hold RPC when no leader is known
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26ca78936c
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@ -10,6 +10,7 @@ import (
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"time"
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"github.com/armon/go-metrics"
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"github.com/hashicorp/consul/consul/agent"
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"github.com/hashicorp/consul/consul/state"
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"github.com/hashicorp/consul/consul/structs"
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"github.com/hashicorp/consul/lib"
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@ -39,7 +40,8 @@ const (
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// jitterFraction is a the limit to the amount of jitter we apply
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// to a user specified MaxQueryTime. We divide the specified time by
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// the fraction. So 16 == 6.25% limit of jitter
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// the fraction. So 16 == 6.25% limit of jitter. This same fraction
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// is applied to the RPCHoldTimeout
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jitterFraction = 16
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// Warn if the Raft command is larger than this.
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@ -189,6 +191,8 @@ func (s *Server) handleConsulConn(conn net.Conn) {
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// forward is used to forward to a remote DC or to forward to the local leader
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// Returns a bool of if forwarding was performed, as well as any error
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func (s *Server) forward(method string, info structs.RPCInfo, args interface{}, reply interface{}) (bool, error) {
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var firstCheck time.Time
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// Handle DC forwarding
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dc := info.RequestDatacenter()
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if dc != s.config.Datacenter {
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@ -201,20 +205,51 @@ func (s *Server) forward(method string, info structs.RPCInfo, args interface{},
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return false, nil
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}
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// Handle leader forwarding
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if !s.IsLeader() {
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err := s.forwardLeader(method, args, reply)
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CHECK_LEADER:
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// Find the leader
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isLeader, remoteServer := s.getLeader()
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// Handle the case we are the leader
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if isLeader {
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return false, nil
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}
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// Handle the case of a known leader
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if remoteServer != nil {
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err := s.forwardLeader(remoteServer, method, args, reply)
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return true, err
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}
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return false, nil
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// Gate the request until there is a leader
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if firstCheck.IsZero() {
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firstCheck = time.Now()
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}
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if time.Now().Sub(firstCheck) < s.config.RPCHoldTimeout {
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jitter := lib.RandomStagger(s.config.RPCHoldTimeout / jitterFraction)
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select {
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case <-time.After(jitter):
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goto CHECK_LEADER
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case <-s.shutdownCh:
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}
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}
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// No leader found and hold time exceeded
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return true, structs.ErrNoLeader
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}
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// forwardLeader is used to forward an RPC call to the leader, or fail if no leader
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func (s *Server) forwardLeader(method string, args interface{}, reply interface{}) error {
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// getLeader returns if the current node is the leader, and if not
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// then it returns the leader which is potentially nil if the cluster
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// has not yet elected a leader.
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func (s *Server) getLeader() (bool, *agent.Server) {
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// Check if we are the leader
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if s.IsLeader() {
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return true, nil
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}
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// Get the leader
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leader := s.raft.Leader()
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if leader == "" {
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return structs.ErrNoLeader
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return false, nil
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}
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// Lookup the server
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@ -222,6 +257,12 @@ func (s *Server) forwardLeader(method string, args interface{}, reply interface{
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server := s.localConsuls[leader]
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s.localLock.RUnlock()
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// Server could be nil
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return false, server
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}
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// forwardLeader is used to forward an RPC call to the leader, or fail if no leader
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func (s *Server) forwardLeader(server *agent.Server, method string, args interface{}, reply interface{}) error {
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// Handle a missing server
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if server == nil {
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return structs.ErrNoLeader
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