vitess.io/vitess@v0.16.2/go/vt/vttablet/tabletmanager/shard_watcher.go (about)

     1  /*
     2  Copyright 2019 The Vitess Authors.
     3  
     4  Licensed under the Apache License, Version 2.0 (the "License");
     5  you may not use this file except in compliance with the License.
     6  You may obtain a copy of the License at
     7  
     8      http://www.apache.org/licenses/LICENSE-2.0
     9  
    10  Unless required by applicable law or agreed to in writing, software
    11  distributed under the License is distributed on an "AS IS" BASIS,
    12  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    13  See the License for the specific language governing permissions and
    14  limitations under the License.
    15  */
    16  
    17  package tabletmanager
    18  
    19  import (
    20  	"context"
    21  
    22  	"vitess.io/vitess/go/vt/log"
    23  	"vitess.io/vitess/go/vt/topo"
    24  )
    25  
    26  type shardWatcher struct {
    27  	watchChan   <-chan *topo.WatchShardData
    28  	watchCancel context.CancelFunc
    29  }
    30  
    31  func (sw *shardWatcher) active() bool {
    32  	return sw.watchChan != nil
    33  }
    34  
    35  func (sw *shardWatcher) start(ts *topo.Server, keyspace, shard string) error {
    36  	log.Infof("Starting shard watch of %v/%v", keyspace, shard)
    37  
    38  	ctx, cancel := context.WithCancel(context.Background())
    39  	_, c, err := ts.WatchShard(ctx, keyspace, shard)
    40  	if err != nil {
    41  		cancel()
    42  		return err
    43  	}
    44  
    45  	sw.watchChan = c
    46  	sw.watchCancel = cancel
    47  	return nil
    48  }
    49  
    50  func (sw *shardWatcher) stop() {
    51  	if !sw.active() {
    52  		return
    53  	}
    54  
    55  	log.Infof("Stopping shard watch...")
    56  	sw.watchCancel()
    57  
    58  	// Drain all remaining watch events.
    59  	for range sw.watchChan {
    60  	}
    61  	log.Infof("Shard watch stopped.")
    62  
    63  	sw.watchChan = nil
    64  	sw.watchCancel = nil
    65  }