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main.go
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main.go
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package main
import (
"context"
"time"
"log"
"github.com/matthagenbuch/followtheleader/physical"
"github.com/matthagenbuch/followtheleader/spanner"
)
const (
bucketName = "matth-follow-the-leader"
leadershipKey = "shard-0"
)
func main() {
logger := log.Default()
// b, err := gcs.NewBackend(map[string]string{
// "bucket": bucketName,
// "ha_enabled": "true",
// }, logger)
b, err := spanner.NewBackend(map[string]string{
"database": "projects/lightstep-dev/instances/development/databases/dev-matth",
"ha_table": "alertevaluator_elections_ha",
"ha_enabled": "true",
}, logger)
if err != nil {
panic(err)
}
haBackend, ok := b.(physical.HABackend)
if !ok {
panic("type casting failed")
}
ctx, cancel := context.WithCancel(context.Background())
defer cancel()
for {
lock, err := haBackend.LockWith(leadershipKey, "follow-the-leader")
if err != nil {
panic(err)
}
logger.Println("running for leadership")
doneCh, err := lock.Lock(ctx.Done())
if err != nil {
panic(err)
}
logger.Println("elected as leader")
select {
case <-doneCh:
logger.Println("lost leadership")
case <-time.After(20 * time.Second):
logger.Println("finished work, ceding leadership")
if err := lock.Unlock(); err != nil {
panic(err)
}
}
}
}