From af864f7ae5f4ebc531b3bf159fbea83654d80fa4 Mon Sep 17 00:00:00 2001
From: Philip O'Toole <philip.otoole@yahoo.com>
Date: Sun, 29 Sep 2024 18:51:19 -0400
Subject: [PATCH] Node can retrieve commit index of other node

---
 CHANGELOG.md            |  4 ++++
 cluster/client.go       | 20 ++++++++++++++++++++
 cluster/client_test.go  | 36 ++++++++++++++++++++++++++++++++++++
 cluster/service_test.go | 29 +++++++++++++++++++++++++++++
 4 files changed, 89 insertions(+)

diff --git a/CHANGELOG.md b/CHANGELOG.md
index a1a83d996..5c2d4c39d 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -1,3 +1,7 @@
+## v8.31.3 (unreleased)
+### Implementation changes and bug fixes
+- [PR #1923](https://github.com/rqlite/rqlite/pull/1923): Node can retrieve commit index of other node.
+
 ## v8.31.2 (September 28th 2024)
 ### Implementation changes and bug fixes
 - [PR #1915](https://github.com/rqlite/rqlite/pull/1915): Move VACUUM-related testing to its own files.
diff --git a/cluster/client.go b/cluster/client.go
index 341fbcb26..10e3d7c3a 100644
--- a/cluster/client.go
+++ b/cluster/client.go
@@ -125,6 +125,26 @@ func (c *Client) GetNodeAPIAddr(nodeAddr string, retries int, timeout time.Durat
 	return a.Url, nil
 }
 
+// GetCommitIndex retrieves the commit index for the node at nodeAddr
+func (c *Client) GetCommitIndex(nodeAddr string, retries int, timeout time.Duration) (uint64, error) {
+	command := &proto.Command{
+		Type: proto.Command_COMMAND_TYPE_GET_NODE_API_URL,
+	}
+	p, nr, err := c.retry(command, nodeAddr, timeout, retries)
+	stats.Add(numGetNodeAPIRequestRetries, int64(nr))
+	if err != nil {
+		return 0, err
+	}
+
+	a := &proto.NodeMeta{}
+	err = pb.Unmarshal(p, a)
+	if err != nil {
+		return 0, fmt.Errorf("protobuf unmarshal: %w", err)
+	}
+
+	return a.CommitIndex, nil
+}
+
 // Execute performs an Execute on a remote node. If username is an empty string
 // no credential information will be included in the Execute request to the
 // remote node.
diff --git a/cluster/client_test.go b/cluster/client_test.go
index 4140164c3..3eabeb97f 100644
--- a/cluster/client_test.go
+++ b/cluster/client_test.go
@@ -57,6 +57,42 @@ func Test_ClientGetNodeAPIAddr(t *testing.T) {
 	}
 }
 
+func Test_ClientGetCommitIndex(t *testing.T) {
+	srv := servicetest.NewService()
+	srv.Handler = func(conn net.Conn) {
+		var p []byte
+		var err error
+		c := readCommand(conn)
+		if c == nil {
+			// Error on connection, so give up, as normal
+			// test exit can cause that too.
+			return
+		}
+		if c.Type != proto.Command_COMMAND_TYPE_GET_NODE_API_URL {
+			t.Fatalf("unexpected command type: %d", c.Type)
+		}
+		p, err = pb.Marshal(&proto.NodeMeta{
+			CommitIndex: 5678,
+		})
+		if err != nil {
+			conn.Close()
+		}
+		writeBytesWithLength(conn, p)
+	}
+	srv.Start()
+	defer srv.Close()
+
+	c := NewClient(&simpleDialer{}, 0)
+	idx, err := c.GetCommitIndex(srv.Addr(), noRetries, time.Second)
+	if err != nil {
+		t.Fatal(err)
+	}
+	exp, got := uint64(5678), idx
+	if exp != got {
+		t.Fatalf("unexpected addr, got %d, exp: %d", got, exp)
+	}
+}
+
 func Test_ClientExecute(t *testing.T) {
 	srv := servicetest.NewService()
 	srv.Handler = func(conn net.Conn) {
diff --git a/cluster/service_test.go b/cluster/service_test.go
index 023d40410..2cc071354 100644
--- a/cluster/service_test.go
+++ b/cluster/service_test.go
@@ -175,6 +175,35 @@ func Test_NewServiceSetGetNodeAPIAddrTLS(t *testing.T) {
 	}
 }
 
+func Test_NewServiceGetCommitIndex(t *testing.T) {
+	ml := mustNewMockTransport()
+	mgr := mustNewMockManager()
+	s := New(ml, mustNewMockDatabase(), mgr, mustNewMockCredentialStore())
+	if s == nil {
+		t.Fatalf("failed to create cluster service")
+	}
+
+	if err := s.Open(); err != nil {
+		t.Fatalf("failed to open cluster service")
+	}
+	s.EnableHTTPS(true)
+
+	// Test fetch via network.
+	mgr.commitIndex = 1234
+	c := NewClient(ml, 30*time.Second)
+	idx, err := c.GetCommitIndex(s.Addr(), noRetries, 5*time.Second)
+	if err != nil {
+		t.Fatalf("failed to get node API address: %s", err)
+	}
+	if idx != 1234 {
+		t.Fatalf("failed to get correct node commit index, exp %d, got %d", 1234, idx)
+	}
+
+	if err := s.Close(); err != nil {
+		t.Fatalf("failed to close cluster service")
+	}
+}
+
 func Test_NewServiceTestExecuteQueryAuthNoCredentials(t *testing.T) {
 	ml := mustNewMockTransport()
 	db := mustNewMockDatabase()