✨ Refactor NATS consumer management by introducing a dedicated ConsumerManager and StreamManager for lifecycle management. Enhance error handling with a new ErrorHandler to streamline message processing and recovery logic. Update consumer initialization to utilize the new managers, improving code organization and maintainability. Add comprehensive tests for the new components to ensure reliability and robustness in handling NATS operations.
This commit is contained in:
windyboy
@@ -4,7 +4,6 @@ import (
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"caatsm/internal/app"
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obsmetrics "caatsm/internal/infra/metrics"
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"context"
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"errors"
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"fmt"
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"strings"
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"time"
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@@ -15,17 +14,7 @@ import (
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// ensureConsumer creates the consumer if it doesn't exist; if it already exists, it is reused.
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func (c *Consumer) ensureConsumer() error {
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consumerConfig := &nats.ConsumerConfig{
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Durable: c.consumerName,
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DeliverPolicy: mapDeliverPolicy(c.cfg.NATS.ConsumerRules.DeliverPolicy),
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AckPolicy: nats.AckExplicitPolicy,
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AckWait: c.ackWait,
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ReplayPolicy: mapReplayPolicy(c.cfg.NATS.ConsumerRules.ReplayPolicy),
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MaxDeliver: c.cfg.NATS.ConsumerRules.MaxDeliver,
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MaxAckPending: c.cfg.NATS.ConsumerRules.MaxAckPending,
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FilterSubject: c.subject,
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BackOff: c.cfg.NATS.ConsumerRules.Backoff,
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}
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consumerConfig := c.buildConsumerConfig()
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if consumerConfig.DeliverPolicy == nats.DeliverByStartSequencePolicy && c.cfg.NATS.ConsumerRules.StartSequence > 0 {
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consumerConfig.OptStartSeq = c.cfg.NATS.ConsumerRules.StartSequence
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}
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@@ -41,35 +30,7 @@ func (c *Consumer) ensureConsumer() error {
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}
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}
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// First check if the consumer already exists to make this initialization idempotent.
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info, err := c.js.ConsumerInfo(c.streamName, c.consumerName)
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if err == nil && info != nil {
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c.logger.Info("Using existing JetStream consumer",
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zap.String("consumer", c.consumerName),
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zap.String("stream", c.streamName),
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zap.String("subject", c.subject),
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)
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return nil
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}
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if err != nil && !errors.Is(err, nats.ErrConsumerNotFound) {
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return fmt.Errorf("failed to fetch consumer info: %w", err)
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}
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// Consumer does not exist; create it.
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if _, err := c.js.AddConsumer(c.streamName, consumerConfig); err != nil {
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return fmt.Errorf("failed to create consumer: %w", err)
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}
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c.logger.Info("Created JetStream consumer",
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zap.String("consumer", c.consumerName),
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zap.String("stream", c.streamName),
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zap.String("subject", c.subject),
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zap.Duration("ack_wait", c.ackWait),
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zap.String("deliver_policy", c.cfg.NATS.ConsumerRules.DeliverPolicy),
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zap.String("replay_policy", c.cfg.NATS.ConsumerRules.ReplayPolicy),
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)
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return nil
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return c.consumerManager.EnsureConsumer(consumerConfig)
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}
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// recoverJetStreamResources attempts to recreate the stream and consumer in
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@@ -82,46 +43,16 @@ func (c *Consumer) recoverJetStreamResources() error {
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return fmt.Errorf("config is nil")
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}
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// Ensure stream exists (dev/test may auto-create, prod will error).
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if err := EnsureStream(c.js, c.cfg, c.logger); err != nil {
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return fmt.Errorf("ensure stream %s: %w", c.streamName, err)
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}
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// Ensure durable consumer exists and is properly bound.
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if err := c.ensureConsumer(); err != nil {
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return fmt.Errorf("ensure consumer %s: %w", c.consumerName, err)
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}
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return nil
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consumerConfig := c.buildConsumerConfig()
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return c.consumerManager.RecoverResources(c.streamManager, consumerConfig)
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}
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// createPullSubscriptionWithRecovery creates a pull subscription and, in
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// dev/test environments, attempts to self-heal missing stream/consumer
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// by recreating them once.
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func (c *Consumer) createPullSubscriptionWithRecovery() (*nats.Subscription, error) {
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sub, err := c.js.PullSubscribe(c.subject, c.consumerName, nats.Bind(c.streamName, c.consumerName))
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if err == nil {
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return sub, nil
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}
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if isJetStreamResourceNotFound(err) && isDevLikeEnv() && shouldBootstrapStream() {
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c.logger.Warn("PullSubscribe failed due to missing JetStream resources; attempting to recreate",
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zap.Error(err),
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zap.String("stream", c.streamName),
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zap.String("consumer", c.consumerName),
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)
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if recErr := c.recoverJetStreamResources(); recErr != nil {
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return nil, fmt.Errorf("failed to recover JetStream resources: %w", recErr)
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}
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// Retry subscription after successful recovery.
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sub, err = c.js.PullSubscribe(c.subject, c.consumerName, nats.Bind(c.streamName, c.consumerName))
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if err != nil {
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return nil, fmt.Errorf("failed to create pull subscription after recovery: %w", err)
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}
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return sub, nil
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}
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return nil, fmt.Errorf("failed to create pull subscription: %w", err)
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consumerConfig := c.buildConsumerConfig()
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return c.consumerManager.CreatePullSubscriptionWithRecovery(c.streamManager, consumerConfig)
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}
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// nakWithStrategy sends a NAK with appropriate delay based on retry attempt.
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@@ -166,7 +97,6 @@ func sleepWithContext(ctx context.Context, duration time.Duration) bool {
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}
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}
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// fetchBatch fetches a batch of messages from the subscription.
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func (c *Consumer) fetchBatch(sub *nats.Subscription) ([]*nats.Msg, error) {
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return sub.Fetch(c.batchSize, nats.MaxWait(c.batchTimeout))
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@@ -175,156 +105,112 @@ func (c *Consumer) fetchBatch(sub *nats.Subscription) ([]*nats.Msg, error) {
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// handleFetchError handles errors during message fetching, including recovery logic.
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// Returns true if the error was handled and consumption should continue, false otherwise.
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func (c *Consumer) handleFetchError(ctx context.Context, err error, sub **nats.Subscription, fetchErrorStreak *int) (bool, error) {
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if errors.Is(err, nats.ErrTimeout) {
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// Timeout is expected when no messages are available.
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return true, nil
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}
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// JetStream API is currently unavailable (e.g., NATS just restarted or JetStream not ready).
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if errors.Is(err, nats.ErrNoResponders) {
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*fetchErrorStreak++
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backoff := time.Duration(*fetchErrorStreak) * time.Second
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if backoff > 30*time.Second {
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backoff = 30 * time.Second
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result := c.errorHandler.HandleFetchError(ctx, err, sub, fetchErrorStreak, c.streamName, c.consumerName, func() (*nats.Subscription, error) {
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if recErr := c.recoverJetStreamResources(); recErr != nil {
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return nil, recErr
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}
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c.logger.Warn("JetStream not available, will retry with backoff",
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zap.Error(err),
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zap.String("stream", c.streamName),
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zap.String("consumer", c.consumerName),
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zap.Duration("backoff", backoff),
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)
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// Use context-aware sleep instead of blocking time.Sleep
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if !sleepWithContext(ctx, backoff) {
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return false, ctx.Err()
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}
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return true, nil
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(*sub).Unsubscribe()
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return c.createPullSubscriptionWithRecovery()
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})
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if result.RecoveredSub != nil {
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*sub = result.RecoveredSub
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*fetchErrorStreak = 0
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}
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// Underlying consumer/stream removed while app is running.
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if isJetStreamResourceNotFound(err) {
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if isDevLikeEnv() && shouldBootstrapStream() {
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c.logger.Warn("JetStream consumer or stream missing; attempting to recreate",
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zap.Error(err),
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zap.String("stream", c.streamName),
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zap.String("consumer", c.consumerName),
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)
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if recErr := c.recoverJetStreamResources(); recErr != nil {
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return false, recErr
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}
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// Recreate subscription after successful recovery.
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(*sub).Unsubscribe()
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newSub, subErr := c.createPullSubscriptionWithRecovery()
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if subErr != nil {
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return false, subErr
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}
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*sub = newSub
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*fetchErrorStreak = 0
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return true, nil
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}
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// Production: treat as configuration/operational error.
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c.logger.Error("JetStream consumer or stream missing; not auto-recreating in this environment",
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zap.Error(err),
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zap.String("stream", c.streamName),
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zap.String("consumer", c.consumerName),
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)
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return false, err
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}
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// Generic error path with modest backoff.
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*fetchErrorStreak++
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backoff := time.Duration(*fetchErrorStreak) * time.Second
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if backoff > 10*time.Second {
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backoff = 10 * time.Second
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}
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c.logger.Error("Failed to fetch messages; backing off",
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zap.Error(err),
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zap.Duration("backoff", backoff),
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)
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// Use context-aware sleep instead of blocking time.Sleep
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if !sleepWithContext(ctx, backoff) {
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return false, ctx.Err()
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}
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return true, nil
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return result.ShouldContinue, result.Error
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}
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// processBatch processes a batch of messages, handling errors and applying backpressure.
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func (c *Consumer) processBatch(ctx context.Context, msgs []*nats.Msg) {
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for _, msg := range msgs {
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start := time.Now()
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c.processSingleMessage(ctx, msg)
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}
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}
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if err := c.processMessage(ctx, msg); err != nil {
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isPermanent := app.IsPermanent(err)
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elapsed := time.Since(start)
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// processSingleMessage processes a single message with error handling and backpressure.
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func (c *Consumer) processSingleMessage(ctx context.Context, msg *nats.Msg) {
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start := time.Now()
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c.logger.Error("Failed to process message",
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zap.String("subject", msg.Subject),
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zap.Error(err),
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zap.Bool("permanent", isPermanent),
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)
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if err := c.processMessage(ctx, msg); err != nil {
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c.handleMessageError(ctx, msg, err, time.Since(start))
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return
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}
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result := obsmetrics.ResultFail
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if isPermanent {
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result = obsmetrics.ResultPermanentFail
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}
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c.telemetry.RecordMessageHandled(ctx, c.streamName, c.consumerName, result, elapsed)
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// Successful processing resets the error streak.
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if c.consecutiveProcessErrors > 0 {
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c.consecutiveProcessErrors = 0
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}
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if isPermanent {
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c.consecutiveProcessErrors = 0
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// Poison/permanent message: route to DLQ if configured, then ACK
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if err := c.routeToDLQ(ctx, msg, err); err != nil {
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c.logger.Error("Failed to route permanent-error message to DLQ", zap.Error(err))
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}
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if ackErr := msg.Ack(); ackErr != nil {
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c.logger.Error("Failed to ACK permanent-error message", zap.Error(ackErr))
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}
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continue
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}
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// ACK the message
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if ackErr := msg.Ack(); ackErr != nil {
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c.logger.Error("Failed to ACK message", zap.Error(ackErr))
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} else {
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elapsed := time.Since(start)
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c.telemetry.RecordMessageHandled(ctx, c.streamName, c.consumerName, "ok", elapsed)
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}
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}
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// Transient error: increment error streak and apply simple backpressure if needed.
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if c.consecutiveProcessErrors < 0 {
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c.consecutiveProcessErrors = 0
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}
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c.consecutiveProcessErrors++
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if c.consecutiveProcessErrors >= 10 {
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// Apply a brief sleep to slow down consumption when the system
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// is failing many messages in a row (e.g. DB unavailable).
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backoff := time.Duration(c.consecutiveProcessErrors) * 100 * time.Millisecond
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if backoff > 5*time.Second {
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backoff = 5 * time.Second
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}
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c.logger.Warn("Applying backpressure due to consecutive processing errors",
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zap.Int("consecutive_errors", c.consecutiveProcessErrors),
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zap.Duration("sleep", backoff),
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)
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// Use context-aware sleep instead of blocking time.Sleep
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if !sleepWithContext(ctx, backoff) {
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// Context canceled, stop processing batch
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return
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}
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}
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// handleMessageError handles errors that occur during message processing.
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func (c *Consumer) handleMessageError(ctx context.Context, msg *nats.Msg, err error, elapsed time.Duration) {
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c.logger.Error("Failed to process message",
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zap.String("subject", msg.Subject),
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zap.Error(err),
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zap.Bool("permanent", app.IsPermanent(err)),
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)
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// Transient error: request redelivery with optional delay
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c.telemetry.RecordRetry(ctx, c.streamName, c.consumerName, obsmetrics.RetryReasonProcessorError)
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if nakErr := c.nakWithStrategy(msg); nakErr != nil {
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c.logger.Error("Failed to NAK message", zap.Error(nakErr))
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}
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continue
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result := obsmetrics.ResultFail
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if app.IsPermanent(err) {
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result = obsmetrics.ResultPermanentFail
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}
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c.telemetry.RecordMessageHandled(ctx, c.streamName, c.consumerName, result, elapsed)
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processingResult := c.errorHandler.HandleProcessingError(c.consecutiveProcessErrors, err, c.logger, msg.Subject)
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if processingResult.IsPermanent {
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c.handlePermanentError(ctx, msg, err)
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return
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}
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c.handleTransientError(ctx, msg, processingResult)
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}
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// handlePermanentError handles permanent/poison messages.
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func (c *Consumer) handlePermanentError(ctx context.Context, msg *nats.Msg, err error) {
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c.consecutiveProcessErrors = 0
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// Poison/permanent message: route to DLQ if configured, then ACK
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if dlqErr := c.routeToDLQ(ctx, msg, err); dlqErr != nil {
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c.logger.Error("Failed to route permanent-error message to DLQ", zap.Error(dlqErr))
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}
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if ackErr := msg.Ack(); ackErr != nil {
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c.logger.Error("Failed to ACK permanent-error message", zap.Error(ackErr))
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}
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}
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// handleTransientError handles transient errors with backpressure and redelivery.
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func (c *Consumer) handleTransientError(ctx context.Context, msg *nats.Msg, processingResult ProcessingErrorResult) {
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// Increment error streak
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if c.consecutiveProcessErrors < 0 {
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c.consecutiveProcessErrors = 0
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}
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c.consecutiveProcessErrors++
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if processingResult.ShouldApplyBackpressure {
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c.logger.Warn("Applying backpressure due to consecutive processing errors",
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zap.Int("consecutive_errors", c.consecutiveProcessErrors),
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zap.Duration("sleep", processingResult.BackpressureDelay),
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)
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// Use context-aware sleep instead of blocking time.Sleep
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if !sleepWithContext(ctx, processingResult.BackpressureDelay) {
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// Context canceled, stop processing
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return
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}
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}
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// Successful processing resets the error streak.
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if c.consecutiveProcessErrors > 0 {
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c.consecutiveProcessErrors = 0
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}
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// ACK the message
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if ackErr := msg.Ack(); ackErr != nil {
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c.logger.Error("Failed to ACK message", zap.Error(ackErr))
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} else {
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elapsed := time.Since(start)
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c.telemetry.RecordMessageHandled(ctx, c.streamName, c.consumerName, "ok", elapsed)
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}
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// Transient error: request redelivery with optional delay
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c.telemetry.RecordRetry(ctx, c.streamName, c.consumerName, obsmetrics.RetryReasonProcessorError)
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if nakErr := c.nakWithStrategy(msg); nakErr != nil {
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c.logger.Error("Failed to NAK message", zap.Error(nakErr))
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}
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}
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Reference in New Issue
Block a user