Check to make sure context isn't expired before doing a raft operation.

changelog/12162.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+storage/raft: Best-effort handling of cancelled contexts.
+```

physical/raft/raft.go

@@ -978,6 +978,10 @@ func (b *RaftBackend) RemovePeer(ctx context.Context, peerID string) error {
 	b.l.RLock()
 	defer b.l.RUnlock()
 
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	if b.disableAutopilot {
 		if b.raft == nil {
 			return errors.New("raft storage is not initialized")
@@ -1034,6 +1038,10 @@ func (b *RaftBackend) GetConfigurationOffline() (*RaftConfigurationResponse, err
 }
 
 func (b *RaftBackend) GetConfiguration(ctx context.Context) (*RaftConfigurationResponse, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	b.l.RLock()
 	defer b.l.RUnlock()
 
@@ -1068,6 +1076,10 @@ func (b *RaftBackend) GetConfiguration(ctx context.Context) (*RaftConfigurationR
 
 // AddPeer adds a new server to the raft cluster
 func (b *RaftBackend) AddPeer(ctx context.Context, peerID, clusterAddr string) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	b.l.RLock()
 	defer b.l.RUnlock()
 
@@ -1096,6 +1108,10 @@ func (b *RaftBackend) AddPeer(ctx context.Context, peerID, clusterAddr string) e
 
 // Peers returns all the servers present in the raft cluster
 func (b *RaftBackend) Peers(ctx context.Context) ([]Peer, error) {
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	b.l.RLock()
 	defer b.l.RUnlock()
 
@@ -1180,6 +1196,10 @@ func (b *RaftBackend) WriteSnapshotToTemp(in io.ReadCloser, access *seal.Access)
 // RestoreSnapshot applies the provided snapshot metadata and snapshot data to
 // raft.
 func (b *RaftBackend) RestoreSnapshot(ctx context.Context, metadata raft.SnapshotMeta, snap io.Reader) error {
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	b.l.RLock()
 	defer b.l.RUnlock()
 
@@ -1214,6 +1234,11 @@ func (b *RaftBackend) RestoreSnapshot(ctx context.Context, metadata raft.Snapsho
 // Delete inserts an entry in the log to delete the given path
 func (b *RaftBackend) Delete(ctx context.Context, path string) error {
 	defer metrics.MeasureSince([]string{"raft-storage", "delete"}, time.Now())
+
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	command := &LogData{
 		Operations: []*LogOperation{
 			{
@@ -1238,9 +1263,17 @@ func (b *RaftBackend) Get(ctx context.Context, path string) (*physical.Entry, er
 		return nil, errors.New("raft: fsm not configured")
 	}
 
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	b.permitPool.Acquire()
 	defer b.permitPool.Release()
 
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	entry, err := b.fsm.Get(ctx, path)
 	if entry != nil {
 		valueLen := len(entry.Value)
@@ -1258,6 +1291,11 @@ func (b *RaftBackend) Get(ctx context.Context, path string) (*physical.Entry, er
 // or if the call to applyLog fails.
 func (b *RaftBackend) Put(ctx context.Context, entry *physical.Entry) error {
 	defer metrics.MeasureSince([]string{"raft-storage", "put"}, time.Now())
+
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	command := &LogData{
 		Operations: []*LogOperation{
 			{
@@ -1284,16 +1322,29 @@ func (b *RaftBackend) List(ctx context.Context, prefix string) ([]string, error)
 		return nil, errors.New("raft: fsm not configured")
 	}
 
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	b.permitPool.Acquire()
 	defer b.permitPool.Release()
 
+	if err := ctx.Err(); err != nil {
+		return nil, err
+	}
+
 	return b.fsm.List(ctx, prefix)
 }
 
 // Transaction applies all the given operations into a single log and
 // applies it.
 func (b *RaftBackend) Transaction(ctx context.Context, txns []*physical.TxnEntry) error {
 	defer metrics.MeasureSince([]string{"raft-storage", "transaction"}, time.Now())
+
+	if err := ctx.Err(); err != nil {
+		return err
+	}
+
 	command := &LogData{
 		Operations: make([]*LogOperation, len(txns)),
 	}
@@ -1330,6 +1381,9 @@ func (b *RaftBackend) applyLog(ctx context.Context, command *LogData) error {
 	if b.raft == nil {
 		return errors.New("raft storage is not initialized")
 	}
+	if err := ctx.Err(); err != nil {
+		return err
+	}
 
 	commandBytes, err := proto.Marshal(command)
 	if err != nil {