Mark --snapshot-count as deprecated in v3.6 and will be decommissioned in v3.7

Signed-off-by: Benjamin Wang <benjamin.ahrtr@gmail.com>

server/embed/config.go

@@ -158,6 +158,8 @@ type Config struct {
 	//revive:disable-next-line:var-naming
 	WalDir string `json:"wal-dir"`
 
+	// SnapshotCount is deprecated in v3.6 and will be decommissioned in v3.7.
+	// TODO: remove it in 3.7.
 	SnapshotCount uint64 `json:"snapshot-count"`
 
 	// SnapshotCatchUpEntries is the number of entries for a slow follower
@@ -616,7 +618,7 @@ func (cfg *Config) AddFlags(fs *flag.FlagSet) {
 	fs.UintVar(&cfg.MaxSnapFiles, "max-snapshots", cfg.MaxSnapFiles, "Maximum number of snapshot files to retain (0 is unlimited).")
 	fs.UintVar(&cfg.MaxWalFiles, "max-wals", cfg.MaxWalFiles, "Maximum number of wal files to retain (0 is unlimited).")
 	fs.StringVar(&cfg.Name, "name", cfg.Name, "Human-readable name for this member.")
-	fs.Uint64Var(&cfg.SnapshotCount, "snapshot-count", cfg.SnapshotCount, "Number of committed transactions to trigger a snapshot to disk.")
+	fs.Uint64Var(&cfg.SnapshotCount, "snapshot-count", cfg.SnapshotCount, "Number of committed transactions to trigger a snapshot to disk. Deprecated in v3.6 and will be decommissioned in v3.7.")
 	fs.UintVar(&cfg.TickMs, "heartbeat-interval", cfg.TickMs, "Time (in milliseconds) of a heartbeat interval.")
 	fs.UintVar(&cfg.ElectionMs, "election-timeout", cfg.ElectionMs, "Time (in milliseconds) for an election to timeout.")
 	fs.BoolVar(&cfg.InitialElectionTickAdvance, "initial-election-tick-advance", cfg.InitialElectionTickAdvance, "Whether to fast-forward initial election ticks on boot for faster election.")

server/etcdmain/config.go

@@ -56,6 +56,11 @@ var (
 		"test.coverprofile",
 		"test.outputdir",
 	}
+
+	deprecatedFlags = map[string]string{
+		// TODO: remove in 3.7.
+		"snapshot-count": "--snapshot-count is deprecated in 3.6 and will be decommissioned in 3.7.",
+	}
 )
 
 // config holds the config for a command line invocation of etcd
@@ -165,6 +170,20 @@ func (cfg *config) parse(arguments []string) error {
 		return perr
 	}
 
+	var warningsForDeprecatedFlags []string
+	cfg.cf.flagSet.Visit(func(f *flag.Flag) {
+		if msg, ok := deprecatedFlags[f.Name]; ok {
+			warningsForDeprecatedFlags = append(warningsForDeprecatedFlags, msg)
+		}
+	})
+	if len(warningsForDeprecatedFlags) > 0 {
+		if lg := cfg.ec.GetLogger(); lg != nil {
+			for _, msg := range warningsForDeprecatedFlags {
+				lg.Warn(msg)
+			}
+		}
+	}
+
 	// now logger is set up
 	return err
 }

server/etcdmain/help.go

@@ -58,7 +58,7 @@ Member:
   --wal-dir ''
     Path to the dedicated wal directory.
   --snapshot-count '10000'
-    Number of committed transactions to trigger a snapshot to disk.
+    Number of committed transactions to trigger a snapshot to disk. Deprecated in v3.6 and will be decommissioned in v3.7.
   --heartbeat-interval '100'
     Time (in milliseconds) of a heartbeat interval.
   --election-timeout '1000'

tests/e2e/etcd_config_test.go

@@ -661,3 +661,22 @@ func TestEtcdTLSVersion(t *testing.T) {
 	proc.Wait() // ensure the port has been released
 	proc.Close()
 }
+
+// TestEtcdDeprecatedFlags checks that etcd will print warning messages if deprecated flags are set.
+func TestEtcdDeprecatedFlags(t *testing.T) {
+	e2e.SkipInShortMode(t)
+
+	proc, err := e2e.SpawnCmd(
+		[]string{
+			e2e.BinPath.Etcd,
+			"--name", "e1",
+			"--snapshot-count=100",
+		}, nil,
+	)
+	require.NoError(t, err)
+	require.NoError(t, e2e.WaitReadyExpectProc(context.TODO(), proc, []string{"--snapshot-count is deprecated in 3.6 and will be decommissioned in 3.7"}))
+	require.NoError(t, proc.Stop())
+
+	proc.Wait() // ensure the port has been released
+	proc.Close()
+}