key.go

package concurrency

import (

    "fmt"

    v3 "github.com/coreos/etcd/clientv3"

    "github.com/coreos/etcd/mvcc/mvccpb"

    "golang.org/x/net/context"

)

func waitDelete(ctx context.Context, client *v3.Client, key string, rev int64) error {

    cctx, cancel := context.WithCancel(ctx)

    defer cancel()

    var wr v3.WatchResponse

    wch := client.Watch(cctx, key, v3.WithRev(rev))

    for wr = range wch {

        for _, ev := range wr.Events {

            if ev.Type == mvccpb.DELETE {

                return nil

            }

        }

    }

    if err := wr.Err(); err != nil {

        return err

    }

    if err := ctx.Err(); err != nil {

        return err

    }

    return fmt.Errorf("lost watcher waiting for delete")

}

// waitDeletes efficiently waits until all keys matching the prefix and no greater

// than the create revision.

func waitDeletes(ctx context.Context, client *v3.Client, pfx string, maxCreateRev int64) error {

    getOpts := append(v3.WithLastCreate(), v3.WithMaxCreateRev(maxCreateRev))

    for {

        resp, err := client.Get(ctx, pfx, getOpts...)

        if err != nil {

            return err

        }

        if len(resp.Kvs) == 0 {

            return nil

        }

        lastKey := string(resp.Kvs[0].Key)

        if err = waitDelete(ctx, client, lastKey, resp.Header.Revision); err != nil {

            return err

        }

    }

}