move error to a separate file

This file contains metric names for all errors
The naming convention is ErrorSomeThing = "error.some.thing"

weed/stats/metrics_names.go

@@ -0,0 +1,31 @@
+package stats
+
+// This file contains metric names for all errors
+// The naming convention is ErrorSomeThing = "error.some.thing"
+const (
+	// volume server
+	ErrorSizeMismatchOffsetSize = "errorSizeMismatchOffsetSize"
+	ErrorSizeMismatch           = "errorSizeMismatch"
+	ErrorCRC                    = "errorCRC"
+	ErrorIndexOutOfRange        = "errorIndexOutOfRange"
+
+	// master topology
+	ErrorWriteToLocalDisk = "errorWriteToLocalDisk"
+	ErrorUnmarshalPairs   = "errorUnmarshalPairs"
+	ErrorWriteToReplicas  = "errorWriteToReplicas"
+
+	// master client
+	FailedToKeepConnected = "failedToKeepConnected"
+	FailedToSend          = "failedToSend"
+	FailedToReceive       = "failedToReceive"
+	RedirectedToleader    = "redirectedToleader"
+	OnPeerUpdate          = "onPeerUpdate"
+	Failed                = "failed"
+
+	// filer handler
+	ErrorReadNotFound = "read.notfound"
+	ErrorReadInternal = "read.internalerror"
+	ErrorWriteEntry   = "write.entry.failed"
+	ErrorReadCache    = "read.cache.failed"
+	ErrorReadStream   = "read.stream.failed"
+)