@@ -212,7 +212,11 @@ public void setBad(EventBus eventBus, String errMsg) {
         }
 
         eventBus.post(new BackendEvent(BackendEventType.BACKEND_DOWN, "missing heartbeat", Long.valueOf(id)));
-        heartbeatErrMsg = errMsg;
+        // In some case, errMsg is null when catched Exception have no message, which can make
+        // `SHOW BACKENDS` return ERROR. We check errMsg here to avoid.
+        if (errMsg != null) {
+            heartbeatErrMsg = errMsg;
+        }
     }
 
     public void setBackendState(BackendState state) {
Original file line number	Diff line number	Diff line change
`@@ -212,7 +212,11 @@ public void setBad(EventBus eventBus, String errMsg) {`
`212`	`212`	`}`
`213`	`213`
`214`	`214`	`eventBus.post(new BackendEvent(BackendEventType.BACKEND_DOWN, "missing heartbeat", Long.valueOf(id)));`
`215`		`- heartbeatErrMsg = errMsg;`
	`215`	`+ // In some case, errMsg is null when catched Exception have no message, which can make`
	`216`	+ // `SHOW BACKENDS` return ERROR. We check errMsg here to avoid.
	`217`	`+ if (errMsg != null) {`
	`218`	`+ heartbeatErrMsg = errMsg;`
	`219`	`+ }`
`216`	`220`	`}`
`217`	`221`
`218`	`222`	`public void setBackendState(BackendState state) {`