support for 'coordinates' command

Author: Shlomi Noach

doc/interactive-commands.md

@@ -17,6 +17,7 @@ Both interfaces may serve at the same time. Both respond to simple text command,
 - `help`: shows a brief list of available commands
 - `status`: returns a detailed status summary of migration progress and configuration
 - `sup`: returns a brief status summary of migration progress
+- `coordinates`: returns recent (though not exactly up to date) binary log coordinates of the inspected server
 - `chunk-size=<newsize>`: modify the `chunk-size`; applies on next running copy-iteration
 - `max-lag-millis=<max-lag>`: modify the maximum replication lag threshold (milliseconds, minimum value is `100`, i.e. `0.1` second)
 - `max-load=<max-load-thresholds>`: modify the `max-load` config; applies on next running copy-iteration

go/base/context.go

@@ -188,6 +188,8 @@ type MigrationContext struct {
 	MigrationIterationRangeMinValues *sql.ColumnValues
 	MigrationIterationRangeMaxValues *sql.ColumnValues
 
+	recentBinlogCoordinates mysql.BinlogCoordinates
+
 	CanStopStreaming func() bool
 }
 
@@ -543,6 +545,19 @@ func (this *MigrationContext) SetNiceRatio(newRatio float64) {
 	this.niceRatio = newRatio
 }
 
+func (this *MigrationContext) GetRecentBinlogCoordinates() mysql.BinlogCoordinates {
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+
+	return this.recentBinlogCoordinates
+}
+
+func (this *MigrationContext) SetRecentBinlogCoordinates(coordinates mysql.BinlogCoordinates) {
+	this.throttleMutex.Lock()
+	defer this.throttleMutex.Unlock()
+	this.recentBinlogCoordinates = coordinates
+}
+
 // ReadMaxLoad parses the `--max-load` flag, which is in multiple key-value format,
 // such as: 'Threads_running=100,Threads_connected=500'
 // It only applies changes in case there's no parsing error.

go/logic/migrator.go

@@ -952,6 +952,13 @@ func (this *Migrator) initiateStreaming() error {
 		}
 		log.Debugf("Done streaming")
 	}()
+
+	go func() {
+		ticker := time.Tick(1 * time.Second)
+		for range ticker {
+			this.migrationContext.SetRecentBinlogCoordinates(*this.eventsStreamer.GetCurrentBinlogCoordinates())
+		}
+	}()
 	return nil
 }
 

go/logic/server.go

@@ -144,6 +144,7 @@ func (this *Server) applyServerCommand(command string, writer *bufio.Writer) (pr
 			fmt.Fprintln(writer, `available commands:
 status                               # Print a detailed status message
 sup                                  # Print a short status message
+coordinates													 # Print the currently inspected coordinates
 chunk-size=<newsize>                 # Set a new chunk-size
 nice-ratio=<ratio>                   # Set a new nice-ratio, immediate sleep after each row-copy operation, float (examples: 0 is agrressive, 0.7 adds 70% runtime, 1.0 doubles runtime, 2.0 triples runtime, ...)
 critical-load=<load>                 # Set a new set of max-load thresholds
@@ -165,6 +166,14 @@ help                                 # This message
 		return ForcePrintStatusOnlyRule, nil
 	case "info", "status":
 		return ForcePrintStatusAndHintRule, nil
+	case "coordinates":
+		{
+			if argIsQuestion || arg == "" {
+				fmt.Fprintf(writer, "%+v\n", this.migrationContext.GetRecentBinlogCoordinates())
+				return NoPrintStatusRule, nil
+			}
+			return NoPrintStatusRule, fmt.Errorf("coordinates are read-only")
+		}
 	case "chunk-size":
 		{
 			if argIsQuestion {