// findChecker:
// - find a rdonly instance in the keyspace / shard
// - mark it as checker
// - tag it with our worker process
func findChecker(wr *wrangler.Wrangler, cleaner *wrangler.Cleaner, cell, keyspace, shard string) (topo.TabletAlias, error) {
endPoints, err := wr.TopoServer().GetEndPoints(cell, keyspace, shard, topo.TYPE_RDONLY)
if err != nil {
return topo.TabletAlias{}, fmt.Errorf("GetEndPoints(%v,%v,%v,rdonly) failed: %v", cell, keyspace, shard, err)
}
if len(endPoints.Entries) == 0 {
return topo.TabletAlias{}, fmt.Errorf("No endpoint to chose from in (%v,%v/%v)", cell, keyspace, shard)
}
tabletAlias := topo.TabletAlias{
Cell: cell,
Uid: endPoints.Entries[0].Uid,
}
// We add the tag before calling ChangeSlaveType, so the destination
// vttablet reloads the worker URL when it reloads the tablet.
ourURL := servenv.ListeningURL.String()
log.Infof("Adding tag[worker]=%v to tablet %v", ourURL, tabletAlias)
if err := wr.TopoServer().UpdateTabletFields(tabletAlias, func(tablet *topo.Tablet) error {
if tablet.Tags == nil {
tablet.Tags = make(map[string]string)
}
tablet.Tags["worker"] = ourURL
return nil
}); err != nil {
return topo.TabletAlias{}, err
}
// we remove the tag *before* calling ChangeSlaveType back, so
// we need to record this tag change after the change slave
// type change in the cleaner.
defer wrangler.RecordTabletTagAction(cleaner, tabletAlias, "worker", "")
log.Infof("Changing tablet %v to 'checker'", tabletAlias)
wr.ResetActionTimeout(30 * time.Second)
if err := wr.ChangeType(tabletAlias, topo.TYPE_CHECKER, false /*force*/); err != nil {
return topo.TabletAlias{}, err
}
// Record a clean-up action to take the tablet back to rdonly.
// We will alter this one later on and let the tablet go back to
// 'spare' if we have stopped replication for too long on it.
wrangler.RecordChangeSlaveTypeAction(cleaner, tabletAlias, topo.TYPE_RDONLY)
return tabletAlias, nil
}