Added dry-run option. (#181)

Signed-off-by: Peter Štibraný <[email protected]>

Author: pstibrany

cmd/blockscopy/main.go

@@ -42,20 +42,22 @@ type config struct {
 	copyPeriod        time.Duration
 	enabledUsers      flagext.StringSliceCSV
 	disabledUsers     flagext.StringSliceCSV
+	dryRun            bool
 
 	httpListen string
 }
 
 func (c *config) RegisterFlags(f *flag.FlagSet) {
-	f.StringVar(&c.sourceBucket, "source-bucket", "", "Source GCS bucket with blocks")
-	f.StringVar(&c.destBucket, "destination-bucket", "", "Destination GCS bucket with blocks")
-	f.DurationVar(&c.minBlockDuration, "min-block-duration", 24*time.Hour, "If non-zero, ignore blocks that cover block range smaller than this")
+	f.StringVar(&c.sourceBucket, "source-bucket", "", "Source GCS bucket with blocks.")
+	f.StringVar(&c.destBucket, "destination-bucket", "", "Destination GCS bucket with blocks.")
+	f.DurationVar(&c.minBlockDuration, "min-block-duration", 24*time.Hour, "If non-zero, ignore blocks that cover block range smaller than this.")
 	f.IntVar(&c.tenantConcurrency, "tenant-concurrency", 5, "How many tenants to process at once.")
 	f.IntVar(&c.blocksConcurrency, "block-concurrency", 5, "How many blocks to copy at once per tenant.")
 	f.DurationVar(&c.copyPeriod, "copy-period", 0, "How often to repeat the copy. If set to 0, copy is done once, and program stops. Otherwise program keeps running and copying blocks until terminated.")
 	f.Var(&c.enabledUsers, "enabled-users", "If not empty, only blocks for these users are copied.")
 	f.Var(&c.disabledUsers, "disabled-users", "If not empty, blocks for these users are not copied.")
-	f.StringVar(&c.httpListen, "http-listen-address", ":8080", "HTTP listen address")
+	f.StringVar(&c.httpListen, "http-listen-address", ":8080", "HTTP listen address.")
+	f.BoolVar(&c.dryRun, "dry-run", false, "Don't perform copy, only log what would happen.")
 }
 
 type metrics struct {
@@ -139,12 +141,12 @@ func runCopy(ctx context.Context, cfg config, logger log.Logger, m *metrics) boo
 	err := copyBlocks(ctx, cfg, logger, m)
 	if err != nil {
 		m.copyCyclesFailed.Inc()
-		level.Error(logger).Log("msg", "failed to copy blocks", "err", err)
+		level.Error(logger).Log("msg", "failed to copy blocks", "err", err, "dryRun", cfg.dryRun)
 		return false
 	}
 
 	m.copyCyclesSucceeded.Inc()
-	level.Info(logger).Log("msg", "finished copying blocks")
+	level.Info(logger).Log("msg", "finished copying blocks", "dryRun", cfg.dryRun)
 	return true
 }
 
@@ -229,6 +231,11 @@ func copyBlocks(ctx context.Context, cfg config, logger log.Logger, m *metrics)
 				}
 			}
 
+			if cfg.dryRun {
+				level.Info(logger).Log("msg", "would copy block, but skipping due to dry-run")
+				return nil
+			}
+
 			level.Info(logger).Log("msg", "copying block")
 
 			err = copySingleBlock(ctx, tenantID, blockID, sourceBucket, destBucket)