4d6a85e901
The Checkpoint functionality is an important part of the library and previously it wasn't obvious that the Consumer was defaulting to Redis for this functionality. * Add Checkpoint as required param for new consumer
63 lines
1.5 KiB
Go
63 lines
1.5 KiB
Go
package redis
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import (
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"fmt"
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"os"
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redis "gopkg.in/redis.v5"
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)
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const localhost = "127.0.0.1:6379"
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// New returns a checkpoint that uses Redis for underlying storage
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func New(appName, streamName string) (*Checkpoint, error) {
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addr := os.Getenv("REDIS_URL")
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if addr == "" {
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addr = localhost
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}
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client := redis.NewClient(&redis.Options{Addr: addr})
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// verify we can ping server
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_, err := client.Ping().Result()
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if err != nil {
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return nil, err
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}
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return &Checkpoint{
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appName: appName,
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streamName: streamName,
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client: client,
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}, nil
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}
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// Checkpoint stores and retreives the last evaluated key from a DDB scan
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type Checkpoint struct {
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appName string
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streamName string
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client *redis.Client
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}
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// Get fetches the checkpoint for a particular Shard.
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func (c *Checkpoint) Get(shardID string) (string, error) {
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val, _ := c.client.Get(c.key(shardID)).Result()
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return val, nil
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}
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// Set stores a checkpoint for a shard (e.g. sequence number of last record processed by application).
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// Upon failover, record processing is resumed from this point.
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func (c *Checkpoint) Set(shardID string, sequenceNumber string) error {
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if sequenceNumber == "" {
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return fmt.Errorf("sequence number should not be empty")
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}
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err := c.client.Set(c.key(shardID), sequenceNumber, 0).Err()
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if err != nil {
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return err
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}
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return nil
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}
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// key generates a unique Redis key for storage of Checkpoint.
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func (c *Checkpoint) key(shardID string) string {
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return fmt.Sprintf("%v:checkpoint:%v:%v", c.appName, c.streamName, shardID)
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}
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