Merge pull request #171 from pav-kv/track-inflight-commit

tracker: track in-flight commit index
etcd-io · Mar 7, 2024 · bc285dd · bc285dd
2 parents ed26e90 + 0f9fe52
commit bc285dd
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Showing 11 changed files with 63 additions and 159 deletions.
diff --git a/raft.go b/raft.go
@@ -599,6 +599,10 @@ func (r *raft) sendAppend(to uint64) {
 // argument controls whether messages with no entries will be sent
 // ("empty" messages are useful to convey updated Commit indexes, but
 // are undesirable when we're sending multiple messages in a batch).
+//
+// TODO(pav-kv): make invocation of maybeSendAppend stateless. The Progress
+// struct contains all the state necessary for deciding whether to send a
+// message.
 func (r *raft) maybeSendAppend(to uint64, sendIfEmpty bool) bool {
 	pr := r.trk.Progress[to]
 	if pr.IsPaused() {
@@ -640,7 +644,8 @@ func (r *raft) maybeSendAppend(to uint64, sendIfEmpty bool) bool {
 		Entries: ents,
 		Commit:  r.raftLog.committed,
 	})
-	pr.UpdateOnEntriesSend(len(ents), uint64(payloadsSize(ents)))
+	pr.SentEntries(len(ents), uint64(payloadsSize(ents)))
+	pr.SentCommit(r.raftLog.committed)
 	return true
 }
 
@@ -675,21 +680,21 @@ func (r *raft) maybeSendSnapshot(to uint64, pr *tracker.Progress) bool {
 
 // sendHeartbeat sends a heartbeat RPC to the given peer.
 func (r *raft) sendHeartbeat(to uint64, ctx []byte) {
+	pr := r.trk.Progress[to]
 	// Attach the commit as min(to.matched, r.committed).
 	// When the leader sends out heartbeat message,
 	// the receiver(follower) might not be matched with the leader
 	// or it might not have all the committed entries.
 	// The leader MUST NOT forward the follower's commit to
 	// an unmatched index.
-	commit := min(r.trk.Progress[to].Match, r.raftLog.committed)
-	m := pb.Message{
+	commit := min(pr.Match, r.raftLog.committed)
+	r.send(pb.Message{
 		To:      to,
 		Type:    pb.MsgHeartbeat,
 		Commit:  commit,
 		Context: ctx,
-	}
-
-	r.send(m)
+	})
+	pr.SentCommit(commit)
 }
 
 // bcastAppend sends RPC, with entries to all peers that are not up-to-date
@@ -1480,7 +1485,6 @@ func stepLeader(r *raft, m pb.Message) error {
 				r.sendAppend(m.From)
 			}
 		} else {
-			oldPaused := pr.IsPaused()
 			// We want to update our tracking if the response updates our
 			// matched index or if the response can move a probing peer back
 			// into StateReplicate (see heartbeat_rep_recovers_from_probing.txt
@@ -1517,9 +1521,11 @@ func stepLeader(r *raft, m pb.Message) error {
 					// to respond to pending read index requests
 					releasePendingReadIndexMessages(r)
 					r.bcastAppend()
-				} else if oldPaused {
-					// If we were paused before, this node may be missing the
-					// latest commit index, so send it.
+				} else if r.id != m.From && pr.CanBumpCommit(r.raftLog.committed) {
+					// This node may be missing the latest commit index, so send it.
+					// NB: this is not strictly necessary because the periodic heartbeat
+					// messages deliver commit indices too. However, a message sent now
+					// may arrive earlier than the next heartbeat fires.
 					r.sendAppend(m.From)
 				}
 				// We've updated flow control information above, which may

diff --git a/testdata/confchange_v1_add_single.txt b/testdata/confchange_v1_add_single.txt
@@ -72,7 +72,7 @@ stabilize
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 2 for index 3
   DEBUG 1 decreased progress of 2 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 4] sent snapshot[index: 4, term: 1] to 2 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=1 paused pendingSnap=4]
+  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=5 paused pendingSnap=4]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -94,15 +94,3 @@ stabilize
 > 1 receiving messages
   2->1 MsgAppResp Term:1 Log:0/4
   DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 2 [StateSnapshot match=4 next=5 paused pendingSnap=4]
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 receiving messages
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 handling Ready
-  Ready MustSync=false:
-  Messages:
-  2->1 MsgAppResp Term:1 Log:0/4
-> 1 receiving messages
-  2->1 MsgAppResp Term:1 Log:0/4
diff --git a/testdata/confchange_v2_add_double_auto.txt b/testdata/confchange_v2_add_double_auto.txt
@@ -95,7 +95,7 @@ stabilize 1 2
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 2 for index 3
   DEBUG 1 decreased progress of 2 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 4] sent snapshot[index: 4, term: 1] to 2 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=1 paused pendingSnap=4]
+  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=5 paused pendingSnap=4]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -171,7 +171,7 @@ stabilize 1 3
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 3 for index 3
   DEBUG 1 decreased progress of 3 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 5] sent snapshot[index: 5, term: 1] to 3 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=1 paused pendingSnap=5]
+  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=6 paused pendingSnap=5]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -193,18 +193,6 @@ stabilize 1 3
 > 1 receiving messages
   3->1 MsgAppResp Term:1 Log:0/5
   DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 3 [StateSnapshot match=5 next=6 paused pendingSnap=5]
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->3 MsgApp Term:1 Log:1/5 Commit:5
-> 3 receiving messages
-  1->3 MsgApp Term:1 Log:1/5 Commit:5
-> 3 handling Ready
-  Ready MustSync=false:
-  Messages:
-  3->1 MsgAppResp Term:1 Log:0/5
-> 1 receiving messages
-  3->1 MsgAppResp Term:1 Log:0/5
 
 # Nothing else happens.
 stabilize

diff --git a/testdata/confchange_v2_add_double_implicit.txt b/testdata/confchange_v2_add_double_implicit.txt
@@ -78,7 +78,7 @@ stabilize 1 2
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 2 for index 3
   DEBUG 1 decreased progress of 2 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 4] sent snapshot[index: 4, term: 1] to 2 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=1 paused pendingSnap=4]
+  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=5 paused pendingSnap=4]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:

diff --git a/testdata/confchange_v2_add_single_auto.txt b/testdata/confchange_v2_add_single_auto.txt
@@ -73,7 +73,7 @@ stabilize
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 2 for index 3
   DEBUG 1 decreased progress of 2 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 4] sent snapshot[index: 4, term: 1] to 2 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=1 paused pendingSnap=4]
+  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=5 paused pendingSnap=4]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -95,15 +95,3 @@ stabilize
 > 1 receiving messages
   2->1 MsgAppResp Term:1 Log:0/4
   DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 2 [StateSnapshot match=4 next=5 paused pendingSnap=4]
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 receiving messages
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 handling Ready
-  Ready MustSync=false:
-  Messages:
-  2->1 MsgAppResp Term:1 Log:0/4
-> 1 receiving messages
-  2->1 MsgAppResp Term:1 Log:0/4
diff --git a/testdata/confchange_v2_add_single_explicit.txt b/testdata/confchange_v2_add_single_explicit.txt
@@ -73,7 +73,7 @@ stabilize 1 2
   DEBUG 1 received MsgAppResp(rejected, hint: (index 0, term 0)) from 2 for index 3
   DEBUG 1 decreased progress of 2 to [StateProbe match=0 next=1]
   DEBUG 1 [firstindex: 3, commit: 4] sent snapshot[index: 4, term: 1] to 2 [StateProbe match=0 next=1]
-  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=1 paused pendingSnap=4]
+  DEBUG 1 paused sending replication messages to 2 [StateSnapshot match=0 next=5 paused pendingSnap=4]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -95,18 +95,6 @@ stabilize 1 2
 > 1 receiving messages
   2->1 MsgAppResp Term:1 Log:0/4
   DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 2 [StateSnapshot match=4 next=5 paused pendingSnap=4]
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 receiving messages
-  1->2 MsgApp Term:1 Log:1/4 Commit:4
-> 2 handling Ready
-  Ready MustSync=false:
-  Messages:
-  2->1 MsgAppResp Term:1 Log:0/4
-> 1 receiving messages
-  2->1 MsgAppResp Term:1 Log:0/4
 
 # Check that we're not allowed to change membership again while in the joint state.
 # This leads to an empty entry being proposed instead (index 5 in the stabilize block

diff --git a/testdata/confchange_v2_replace_leader.txt b/testdata/confchange_v2_replace_leader.txt
@@ -143,18 +143,6 @@ stabilize
   4->1 MsgAppResp Term:1 Log:0/4
 > 1 receiving messages
   4->1 MsgAppResp Term:1 Log:0/4
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->4 MsgApp Term:1 Log:1/4 Commit:4
-> 4 receiving messages
-  1->4 MsgApp Term:1 Log:1/4 Commit:4
-> 4 handling Ready
-  Ready MustSync=false:
-  Messages:
-  4->1 MsgAppResp Term:1 Log:0/4
-> 1 receiving messages
-  4->1 MsgAppResp Term:1 Log:0/4
 
 
 # Transfer leadership while in the joint config.
@@ -284,12 +272,10 @@ stabilize
   CommittedEntries:
   2/5 EntryNormal ""
   Messages:
-  4->1 MsgApp Term:2 Log:2/5 Commit:4
   4->1 MsgApp Term:2 Log:2/5 Commit:5
   4->2 MsgApp Term:2 Log:2/5 Commit:5
   4->3 MsgApp Term:2 Log:2/5 Commit:5
 > 1 receiving messages
-  4->1 MsgApp Term:2 Log:2/5 Commit:4
   4->1 MsgApp Term:2 Log:2/5 Commit:5
 > 2 receiving messages
   4->2 MsgApp Term:2 Log:2/5 Commit:5
@@ -302,7 +288,6 @@ stabilize
   2/5 EntryNormal ""
   Messages:
   1->4 MsgAppResp Term:2 Log:0/5
-  1->4 MsgAppResp Term:2 Log:0/5
 > 2 handling Ready
   Ready MustSync=false:
   HardState Term:2 Vote:4 Commit:5
@@ -318,7 +303,6 @@ stabilize
   Messages:
   3->4 MsgAppResp Term:2 Log:0/5
 > 4 receiving messages
-  1->4 MsgAppResp Term:2 Log:0/5
   1->4 MsgAppResp Term:2 Log:0/5
   2->4 MsgAppResp Term:2 Log:0/5
   3->4 MsgAppResp Term:2 Log:0/5

diff --git a/testdata/probe_and_replicate.txt b/testdata/probe_and_replicate.txt
@@ -513,18 +513,6 @@ stabilize 1 2
   2->1 MsgAppResp Term:8 Log:0/21
 > 1 receiving messages
   2->1 MsgAppResp Term:8 Log:0/21
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->2 MsgApp Term:8 Log:8/21 Commit:18
-> 2 receiving messages
-  1->2 MsgApp Term:8 Log:8/21 Commit:18
-> 2 handling Ready
-  Ready MustSync=false:
-  Messages:
-  2->1 MsgAppResp Term:8 Log:0/21
-> 1 receiving messages
-  2->1 MsgAppResp Term:8 Log:0/21
 
 stabilize 1 3
 ----
@@ -579,18 +567,6 @@ stabilize 1 3
   3->1 MsgAppResp Term:8 Log:0/21
 > 1 receiving messages
   3->1 MsgAppResp Term:8 Log:0/21
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->3 MsgApp Term:8 Log:8/21 Commit:18
-> 3 receiving messages
-  1->3 MsgApp Term:8 Log:8/21 Commit:18
-> 3 handling Ready
-  Ready MustSync=false:
-  Messages:
-  3->1 MsgAppResp Term:8 Log:0/21
-> 1 receiving messages
-  3->1 MsgAppResp Term:8 Log:0/21
 
 stabilize 1 4
 ----
@@ -674,18 +650,6 @@ stabilize 1 5
   5->1 MsgAppResp Term:8 Log:0/21
 > 1 receiving messages
   5->1 MsgAppResp Term:8 Log:0/21
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->5 MsgApp Term:8 Log:8/21 Commit:21
-> 5 receiving messages
-  1->5 MsgApp Term:8 Log:8/21 Commit:21
-> 5 handling Ready
-  Ready MustSync=false:
-  Messages:
-  5->1 MsgAppResp Term:8 Log:0/21
-> 1 receiving messages
-  5->1 MsgAppResp Term:8 Log:0/21
 
 stabilize 1 6
 ----
@@ -741,18 +705,6 @@ stabilize 1 6
   6->1 MsgAppResp Term:8 Log:0/21
 > 1 receiving messages
   6->1 MsgAppResp Term:8 Log:0/21
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->6 MsgApp Term:8 Log:8/21 Commit:21
-> 6 receiving messages
-  1->6 MsgApp Term:8 Log:8/21 Commit:21
-> 6 handling Ready
-  Ready MustSync=false:
-  Messages:
-  6->1 MsgAppResp Term:8 Log:0/21
-> 1 receiving messages
-  6->1 MsgAppResp Term:8 Log:0/21
 
 stabilize 1 7
 ----
@@ -816,15 +768,3 @@ stabilize 1 7
   7->1 MsgAppResp Term:8 Log:0/21
 > 1 receiving messages
   7->1 MsgAppResp Term:8 Log:0/21
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->7 MsgApp Term:8 Log:8/21 Commit:21
-> 7 receiving messages
-  1->7 MsgApp Term:8 Log:8/21 Commit:21
-> 7 handling Ready
-  Ready MustSync=false:
-  Messages:
-  7->1 MsgAppResp Term:8 Log:0/21
-> 1 receiving messages
-  7->1 MsgAppResp Term:8 Log:0/21
diff --git a/testdata/snapshot_succeed_via_app_resp.txt b/testdata/snapshot_succeed_via_app_resp.txt
@@ -87,7 +87,7 @@ stabilize 1
 > 1 receiving messages
   3->1 MsgHeartbeatResp Term:1 Log:0/0
   DEBUG 1 [firstindex: 12, commit: 11] sent snapshot[index: 11, term: 1] to 3 [StateProbe match=0 next=11]
-  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=11 paused pendingSnap=11]
+  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=12 paused pendingSnap=11]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -98,7 +98,7 @@ status 1
 ----
 1: StateReplicate match=11 next=12
 2: StateReplicate match=11 next=12
-3: StateSnapshot match=0 next=11 paused pendingSnap=11
+3: StateSnapshot match=0 next=12 paused pendingSnap=11
 
 # Follower applies the snapshot. Note how it reacts with a MsgAppResp upon completion.
 # The snapshot fully catches the follower up (i.e. there are no more log entries it
@@ -127,10 +127,6 @@ stabilize 1
 > 1 receiving messages
   3->1 MsgAppResp Term:1 Log:0/11
   DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 3 [StateSnapshot match=11 next=12 paused pendingSnap=11]
-> 1 handling Ready
-  Ready MustSync=false:
-  Messages:
-  1->3 MsgApp Term:1 Log:1/11 Commit:11
 
 status 1
 ----
@@ -143,16 +139,9 @@ stabilize
 ----
 > 2 receiving messages
   1->2 MsgHeartbeat Term:1 Log:0/0 Commit:11
-> 3 receiving messages
-  1->3 MsgApp Term:1 Log:1/11 Commit:11
 > 2 handling Ready
   Ready MustSync=false:
   Messages:
   2->1 MsgHeartbeatResp Term:1 Log:0/0
-> 3 handling Ready
-  Ready MustSync=false:
-  Messages:
-  3->1 MsgAppResp Term:1 Log:0/11
 > 1 receiving messages
   2->1 MsgHeartbeatResp Term:1 Log:0/0
-  3->1 MsgAppResp Term:1 Log:0/11
diff --git a/testdata/snapshot_succeed_via_app_resp_behind.txt b/testdata/snapshot_succeed_via_app_resp_behind.txt
@@ -124,7 +124,7 @@ stabilize 1
   DEBUG 1 received MsgAppResp(rejected, hint: (index 5, term 1)) from 3 for index 10
   DEBUG 1 decreased progress of 3 to [StateProbe match=0 next=6]
   DEBUG 1 [firstindex: 11, commit: 12] sent snapshot[index: 12, term: 1] to 3 [StateProbe match=0 next=6]
-  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=6 paused pendingSnap=12]
+  DEBUG 1 paused sending replication messages to 3 [StateSnapshot match=0 next=13 paused pendingSnap=12]
 > 1 handling Ready
   Ready MustSync=false:
   Messages:
@@ -152,7 +152,7 @@ stabilize 1
 ----
 > 1 receiving messages
   3->1 MsgAppResp Term:1 Log:0/11
-  DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 3 [StateSnapshot match=11 next=12 paused pendingSnap=12]
+  DEBUG 1 recovered from needing snapshot, resumed sending replication messages to 3 [StateSnapshot match=11 next=13 paused pendingSnap=12]
 > 1 handling Ready
   Ready MustSync=false:
   Messages: