78 lines
2.3 KiB
Go
78 lines
2.3 KiB
Go
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package kafka
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import (
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"context"
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"fmt"
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"github.com/twmb/franz-go/pkg/kgo"
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)
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// Record is a fetched Kafka record relevant to the message plane.
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type Record struct {
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Topic string
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Partition int32
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Offset int64
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Key []byte
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Value []byte
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}
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// Consumer wraps a kgo.Client consuming a queue's shard topics under the
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// shared consumer group (design.md §3 ConsumerGroup). Autocommit is
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// disabled: offset commits are driven by the watermark logic in
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// internal/core/queue, not by the client's own interval commit, so a
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// crash between receive and ack never advances the committed offset past an
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// unacked message (design.md §3's at-least-once guarantee).
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type Consumer struct {
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client *kgo.Client
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}
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// NewConsumer subscribes to the given shard topics as a real consumer-group
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// member: Kafka's group-rebalance protocol handles partition ownership
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// across replicas (design.md §9), and the queue-operator's drain check
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// (internal/kafka.Admin.ConsumerLag) reads this same group's committed
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// offsets to know when a `Closing` shard is safe to delete.
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func NewConsumer(brokers []string, group string, topics ...string) (*Consumer, error) {
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cl, err := kgo.NewClient(
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kgo.SeedBrokers(brokers...),
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kgo.ConsumerGroup(group),
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kgo.ConsumeTopics(topics...),
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kgo.DisableAutoCommit(),
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)
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if err != nil {
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return nil, fmt.Errorf("creating kafka consumer client: %w", err)
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}
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return &Consumer{client: cl}, nil
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}
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// AddTopics subscribes to additional shard topics created by a split,
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// without losing the group membership/offsets already held for existing
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// topics.
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func (c *Consumer) AddTopics(topics ...string) {
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c.client.AddConsumeTopics(topics...)
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}
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func (c *Consumer) Close() {
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c.client.Close()
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}
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// Poll runs one non-blocking fetch iteration and returns whatever records
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// were immediately available. The long-poll wait loop lives in
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// internal/core/queue.ReceiveMessageService, not here.
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func (c *Consumer) Poll(ctx context.Context) ([]Record, error) {
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fetches := c.client.PollFetches(ctx)
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if errs := fetches.Errors(); len(errs) > 0 {
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return nil, fmt.Errorf("poll fetches: %w", errs[0].Err)
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}
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var out []Record
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fetches.EachRecord(func(r *kgo.Record) {
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out = append(out, Record{
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Topic: r.Topic,
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Partition: r.Partition,
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Offset: r.Offset,
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Key: r.Key,
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Value: r.Value,
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})
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})
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return out, nil
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}
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