Merge pull request #363 from github/interactive-command-question

Interactive commands, question argument for querying staus

Author: Shlomi Noach

doc/interactive-commands.md

@@ -26,9 +26,9 @@ Both interfaces may serve at the same time. Both respond to simple text command,
   - The `critical-load` format must be: `some_status=<numeric-threshold>[,some_status=<numeric-threshold>...]`'
   - For example: `Threads_running=1000,threads_connected=5000`, and you would then write/echo `critical-load=Threads_running=1000,threads_connected=5000` to the socket.
 - `nice-ratio=<ratio>`: change _nice_ ratio: 0 for aggressive (not nice, not sleeping), positive integer `n`:
-  - For any `1ms` spent copying rows, spend `n*1ms` units of time sleeping. 
-  - Examples: assume a single rows chunk copy takes `100ms` to complete. 
-    - `nice-ratio=0.5` will cause `gh-ost` to sleep for `50ms` immediately following. 
+  - For any `1ms` spent copying rows, spend `n*1ms` units of time sleeping.
+  - Examples: assume a single rows chunk copy takes `100ms` to complete.
+    - `nice-ratio=0.5` will cause `gh-ost` to sleep for `50ms` immediately following.
     - `nice-ratio=1` will cause `gh-ost` to sleep for `100ms`, effectively doubling runtime
     - value of `2` will effectively triple the runtime; etc.
 - `throttle-query`: change throttle query
@@ -38,6 +38,10 @@ Both interfaces may serve at the same time. Both respond to simple text command,
 - `unpostpone`: at a time where `gh-ost` is postponing the [cut-over](cut-over.md) phase, instruct `gh-ost` to stop postponing and proceed immediately to cut-over.
 - `panic`: immediately panic and abort operation
 
+### Querying for data
+
+For commands that accept an argumetn as value, pass `?` (question mark) to _get_ current value rather than _set_ a new one.
+
 ### Examples
 
 While migration is running:
@@ -63,6 +67,11 @@ $ echo "chunk-size=250" | nc -U /tmp/gh-ost.test.sample_data_0.sock
 # Serving on TCP port: 10001
 ```
 
+```shell
+$ echo "chunk-size=?" | nc -U /tmp/gh-ost.test.sample_data_0.sock
+250
+```
+
 ```shell
 $ echo throttle | nc -U /tmp/gh-ost.test.sample_data_0.sock
 

go/logic/migrator.go

@@ -761,6 +761,12 @@ func (this *Migrator) printMigrationStatusHint(writers ...io.Writer) {
 			throttleQuery,
 		))
 	}
+	if throttleControlReplicaKeys := this.migrationContext.GetThrottleControlReplicaKeys(); throttleControlReplicaKeys.Len() > 0 {
+		fmt.Fprintln(w, fmt.Sprintf("# throttle-control-replicas count: %+v",
+			throttleControlReplicaKeys.Len(),
+		))
+	}
+
 	if this.migrationContext.PostponeCutOverFlagFile != "" {
 		setIndicator := ""
 		if base.FileExists(this.migrationContext.PostponeCutOverFlagFile) {

go/logic/server.go

@@ -126,7 +126,7 @@ func (this *Server) applyServerCommand(command string, writer *bufio.Writer) (pr
 	if len(tokens) > 1 {
 		arg = strings.TrimSpace(tokens[1])
 	}
-
+	argIsQuestion := (arg == "?")
 	throttleHint := "# Note: you may only throttle for as long as your binary logs are not purged\n"
 
 	if err := this.hooksExecutor.onInteractiveCommand(command); err != nil {
@@ -152,6 +152,7 @@ no-throttle                          # End forced throttling (other throttling m
 unpostpone                           # Bail out a cut-over postpone; proceed to cut-over
 panic                                # panic and quit without cleanup
 help                                 # This message
+- use '?' (question mark) as argument to get info rather than set. e.g. "max-load=?" will just print out current max-load.
 `)
 		}
 	case "sup":
@@ -160,6 +161,10 @@ help                                 # This message
 		return ForcePrintStatusAndHintRule, nil
 	case "chunk-size":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", atomic.LoadInt64(&this.migrationContext.ChunkSize))
+				return NoPrintStatusRule, nil
+			}
 			if chunkSize, err := strconv.Atoi(arg); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -169,6 +174,10 @@ help                                 # This message
 		}
 	case "max-lag-millis":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", atomic.LoadInt64(&this.migrationContext.MaxLagMillisecondsThrottleThreshold))
+				return NoPrintStatusRule, nil
+			}
 			if maxLagMillis, err := strconv.Atoi(arg); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -182,6 +191,10 @@ help                                 # This message
 		}
 	case "nice-ratio":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", this.migrationContext.GetNiceRatio())
+				return NoPrintStatusRule, nil
+			}
 			if niceRatio, err := strconv.ParseFloat(arg, 64); err != nil {
 				return NoPrintStatusRule, err
 			} else {
@@ -191,26 +204,44 @@ help                                 # This message
 		}
 	case "max-load":
 		{
+			if argIsQuestion {
+				maxLoad := this.migrationContext.GetMaxLoad()
+				fmt.Fprintf(writer, "%s\n", maxLoad.String())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadMaxLoad(arg); err != nil {
 				return NoPrintStatusRule, err
 			}
 			return ForcePrintStatusAndHintRule, nil
 		}
 	case "critical-load":
 		{
+			if argIsQuestion {
+				criticalLoad := this.migrationContext.GetCriticalLoad()
+				fmt.Fprintf(writer, "%s\n", criticalLoad.String())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadCriticalLoad(arg); err != nil {
 				return NoPrintStatusRule, err
 			}
 			return ForcePrintStatusAndHintRule, nil
 		}
 	case "throttle-query":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%+v\n", this.migrationContext.GetThrottleQuery())
+				return NoPrintStatusRule, nil
+			}
 			this.migrationContext.SetThrottleQuery(arg)
 			fmt.Fprintf(writer, throttleHint)
 			return ForcePrintStatusAndHintRule, nil
 		}
 	case "throttle-control-replicas":
 		{
+			if argIsQuestion {
+				fmt.Fprintf(writer, "%s\n", this.migrationContext.GetThrottleControlReplicaKeys().ToCommaDelimitedList())
+				return NoPrintStatusRule, nil
+			}
 			if err := this.migrationContext.ReadThrottleControlReplicaKeys(arg); err != nil {
 				return NoPrintStatusRule, err
 			}

localtests/test.sh

@@ -88,7 +88,7 @@ test_single() {
     --throttle-query='select timestampdiff(second, min(last_update), now()) < 5 from _gh_ost_test_ghc' \
     --serve-socket-file=/tmp/gh-ost.test.sock \
     --initially-drop-socket-file \
-    --postpone-cut-over-flag-file="" \
+    --postpone-cut-over-flag-file=/tmp/gh-ost.test.postpone.flag \
     --test-on-replica \
     --default-retries=1 \
     --verbose \