// 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) { tabletAlias, err := findHealthyRdonlyEndPoint(wr, cell, keyspace, shard) if err != nil { return topo.TabletAlias{}, err } // We add the tag before calling ChangeSlaveType, so the destination // vttablet reloads the worker URL when it reloads the tablet. ourURL := servenv.ListeningURL.String() wr.Logger().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", "") wr.Logger().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 }