diff --git a/com.ibm.streamsx.slack/impl/java/src/com/ibm/streamsx/slack/SendSlackMessage.java b/com.ibm.streamsx.slack/impl/java/src/com/ibm/streamsx/slack/SendSlackMessage.java
index f003225..854bc8a 100644
--- a/com.ibm.streamsx.slack/impl/java/src/com/ibm/streamsx/slack/SendSlackMessage.java
+++ b/com.ibm.streamsx.slack/impl/java/src/com/ibm/streamsx/slack/SendSlackMessage.java
@@ -42,6 +42,8 @@
 import com.ibm.streams.operator.model.Parameter;
 import com.ibm.streams.operator.model.PrimitiveOperator;
 import com.ibm.streams.operator.samples.patterns.TupleConsumer;
+import com.ibm.streams.operator.metrics.Metric;
+import com.ibm.streams.operator.model.CustomMetric;
 
 @PrimitiveOperator(
 		name="SendSlackMessage", 
@@ -66,6 +68,13 @@
 	})
 public class SendSlackMessage extends TupleConsumer {
 	
+	/**
+	 * Metrics
+	 */
+	private Metric nFailedRequests;
+	private Metric nInsertedMessages;
+	private Metric rateLimitExceeded;
+	
 	// ------------------------------------------------------------------------
 	// Documentation.
 	// Attention: To add a newline, use \\n instead of \n.
@@ -83,6 +92,34 @@ public class SendSlackMessage extends TupleConsumer {
 
 
         ;
+  
+    @CustomMetric(name = "rateLimitExceeded", kind = Metric.Kind.GAUGE,
+    	description = "Describes whether we exceed a rate limit when sending messages to Slack server. "
+    	+ "This is set to 1 after response 429 is received. Otherwise the value is 0. "
+    )
+    public void setRateLimitExceeded(Metric rateLimitExceeded) {
+    	this.rateLimitExceeded = rateLimitExceeded;
+    }    
+    
+    /**
+     * nFailedRequests describes the number of failed requests over the lifetime of the operator.
+     * @param nFailedRequests
+     */
+    @CustomMetric(name = "nFailedRequests", kind = Metric.Kind.COUNTER,
+    		description = "The number of failed messages over the lifetime of the operator.")
+    public void setnFailedRequests(Metric nFailedRequests) {
+    	this.nFailedRequests = nFailedRequests;
+    }
+    
+    /**
+     * nInsertedMessages describes the number of successful requests over the lifetime of the operator.
+     * @param nInsertedMessages
+     */
+    @CustomMetric(name = "nInsertedMessages", kind = Metric.Kind.COUNTER,
+    		description = "The number of successful messages over the lifetime of the operator.")
+    public void setnInsertedMessages(Metric nInsertedMessages) {
+    	this.nInsertedMessages = nInsertedMessages;
+    }
 	
 	@ContextCheck(runtime=false)
 	public static void validateSchema(OperatorContextChecker checker) {
@@ -137,7 +174,9 @@ private static boolean isStringAttribute(StreamSchema schema) {
 			description="Specifies the Slack incoming web hook URL to send messages to."
 			)
 	public void setSlackUrl(String slackUrl) throws IOException {
-		this.slackUrl = slackUrl;
+    	if (!("".equals(slackUrl))) {
+    		this.slackUrl = slackUrl;
+    	}
 	}
 	
 	@Parameter(
@@ -268,15 +307,27 @@ protected boolean processBatch(Queue<BatchedTuple> batch) throws Exception {
 		// Send successful - remove message from batch queue.
 		if (responseCode == HttpStatus.SC_OK) {
 			batch.remove();
-			
+			this.nInsertedMessages.increment();
+			this.rateLimitExceeded.setValue(0);
 			// Can only send 1 message to Slack, per second.
 			Thread.sleep(1000);
 		} else {
+			this.nFailedRequests.increment();
 	         _trace.error(responseCode + response.toString());
 	          
 	        // With a 404 maybe a URL has been updated in the application config.
-		    if (responseCode == HttpStatus.SC_NOT_FOUND)
+		    if (responseCode == HttpStatus.SC_NOT_FOUND) {
 		        fetchApplicationProperties();
+		    }
+		    else if (responseCode == 429) {
+		    	// HTTP 429 Too Many Requests
+		    	this.rateLimitExceeded.setValue(1);
+		    	// TODO check Retry-After HTTP header 
+		    	Thread.sleep(10000);
+		    }
+		    else {
+		    	this.rateLimitExceeded.setValue(0);
+		    }
 		}
 
 		return true;
@@ -335,3 +386,4 @@ protected void fetchApplicationProperties() {
 	}
 }
 
+
diff --git a/com.ibm.streamsx.slack/info.xml b/com.ibm.streamsx.slack/info.xml
index d80a1fd..9a86ebe 100644
--- a/com.ibm.streamsx.slack/info.xml
+++ b/com.ibm.streamsx.slack/info.xml
@@ -8,7 +8,7 @@
    Typical use is to send alerts or informational messages from
    a Streams application to Slack channel using a incoming web hook.
    </info:description>
-   <info:version>0.3.0</info:version>
+   <info:version>0.4.0</info:version>
    <info:requiredProductVersion>4.2.0.0</info:requiredProductVersion>
  </info:identity>
  <info:dependencies/>