Use a new const for the max length

Signed-off-by: Matt Lord <[email protected]>

go/vt/vttablet/tabletmanager/vreplication/utils.go

@@ -33,6 +33,11 @@ import (
 
 const (
 	vreplicationLogTableName = "vreplication_log"
+	// This comes from the fact that the message column in the vreplication_log table is of type TEXT.
+	// See: go/vt/sidecardb/schema/vreplication/vreplication_log.sql
+	// https://dev.mysql.com/doc/refman/en/string-type-syntax.html and
+	// https://dev.mysql.com/doc/refman/en/storage-requirements.html#data-types-storage-reqs-strings
+	maxVReplicationLogMessageLen = 65535
 )
 
 const (
@@ -99,16 +104,12 @@ func insertLog(dbClient *vdbClient, typ string, vreplID int32, state, message st
 		query = fmt.Sprintf("update %s.vreplication_log set count = count + 1 where id = %d", sidecar.GetIdentifier(), id)
 	} else {
 		buf := sqlparser.NewTrackedBuffer(nil)
-		// The message column is a TEXT field and thus has a max length of 64KiB (2^16-1) so we truncate that if needed.
-		// See: https://dev.mysql.com/doc/refman/en/string-type-syntax.html and
-		// https://dev.mysql.com/doc/refman/en/storage-requirements.html#data-types-storage-reqs-strings
-		// We perform the truncation in the middle of the message as the end of the message is likely to be the most
-		// important part as it often explains WHY we e.g. failed to execute an INSERT in the workflow.
-		maxMessageLen := 65535
+		// We perform the truncation, if needed, in the middle of the message as the end of the message is likely to
+		// be the most important part as it often explains WHY we e.g. failed to execute an INSERT in the workflow.
 		truncationStr := fmt.Sprintf(" ... %s ... ", sqlparser.TruncationText)
-		if len(message) > maxMessageLen {
+		if len(message) > maxVReplicationLogMessageLen {
 			mid := (len(message) / 2) - len(truncationStr)
-			for mid > (maxMessageLen / 2) {
+			for mid > (maxVReplicationLogMessageLen / 2) {
 				mid = mid / 2
 			}
 			tail := (len(message) - (mid + len(truncationStr))) + 1

go/vt/vttablet/tabletmanager/vreplication/utils_test.go

@@ -41,7 +41,6 @@ func TestInsertLogTruncation(t *testing.T) {
 	vrID := int32(1)
 	typ := "Testing"
 	state := binlogdatapb.VReplicationWorkflowState_Error.String()
-	maxMessageLen := 65535
 	truncationStr := fmt.Sprintf(" ... %s ... ", sqlparser.TruncationText)
 
 	insertStmtf := "insert into _vt.vreplication_log(vrepl_id, type, state, message) values(%d, '%s', '%s', %s)"
@@ -61,10 +60,10 @@ func TestInsertLogTruncation(t *testing.T) {
 			message: "Simple message that doesn't need to be truncated " + strings.Repeat("b", 64000) + " cuz it's not quite too long",
 		},
 		{
-			message: "Message that is just barely short enough " + strings.Repeat("c", maxMessageLen-(len("Message that is just barely short enough ")+len(" so it doesn't get truncated"))) + " so it doesn't get truncated",
+			message: "Message that is just barely short enough " + strings.Repeat("c", maxVReplicationLogMessageLen-(len("Message that is just barely short enough ")+len(" so it doesn't get truncated"))) + " so it doesn't get truncated",
 		},
 		{
-			message:          "Message that is just barely too long " + strings.Repeat("d", maxMessageLen-(len("Message that is just barely too long ")+len(" so it gets truncated"))+1) + " so it gets truncated",
+			message:          "Message that is just barely too long " + strings.Repeat("d", maxVReplicationLogMessageLen-(len("Message that is just barely too long ")+len(" so it gets truncated"))+1) + " so it gets truncated",
 			expectTruncation: true,
 		},
 		{
@@ -81,7 +80,7 @@ func TestInsertLogTruncation(t *testing.T) {
 			var messageOut string
 			if tc.expectTruncation {
 				mid := (len(tc.message) / 2) - len(truncationStr)
-				for mid > (maxMessageLen / 2) {
+				for mid > (maxVReplicationLogMessageLen / 2) {
 					mid = mid / 2
 				}
 				tail := (len(tc.message) - (mid + len(truncationStr))) + 1
@@ -92,7 +91,7 @@ func TestInsertLogTruncation(t *testing.T) {
 			} else {
 				messageOut = tc.message
 			}
-			require.LessOrEqual(t, len(messageOut), 65535)
+			require.LessOrEqual(t, len(messageOut), maxVReplicationLogMessageLen)
 			dbClient.ExpectRequest(fmt.Sprintf(insertStmtf, vrID, typ, state, encodeString(messageOut)), &sqltypes.Result{}, nil)
 			insertLog(vdbClient, typ, vrID, state, tc.message)
 			dbClient.Wait()