Metrics: rename applicationName to key

Fix #879

spring-cloud-stream-core-docs/src/main/asciidoc/spring-cloud-stream-overview.adoc

@@ -1834,6 +1834,11 @@ By default the module is configured to only send Spring Integration message chan
 
 Available properties for customization using the prefix `spring.cloud.stream.metrics`.
 
+key::
+  The name of the metric being emitted. Should be an unique value per application.
++
+Default:: `${spring.application.name:${vcap.application.name:${spring.config.name:application}}}`
++
 delay-millis::
   The period in which metrics will be posted to the channel
 +

spring-cloud-stream-metrics/src/main/java/org/springframework/cloud/stream/config/metrics/StreamMetricsProperties.java

@@ -29,7 +29,7 @@ public class StreamMetricsProperties {
 	private String prefix;
 
 	@Value("${spring.application.name:${vcap.application.name:${spring.config.name:application}}}")
-	private String applicationName;
+	private String key;
 
 	private String metricName;
 
@@ -73,12 +73,12 @@ public class StreamMetricsProperties {
 		this.prefix = prefix;
 	}
 
-	public String getApplicationName() {
-		return applicationName;
+	public String getKey() {
+		return key;
 	}
 
-	public void setApplicationName(String applicationName) {
-		this.applicationName = applicationName;
+	public void setKey(String key) {
+		this.key = key;
 	}
 
 	public String[] getProperties() {
@@ -97,7 +97,7 @@ public class StreamMetricsProperties {
 	}
 
 	private String resolveMetricName() {
-		StringBuffer name = new StringBuffer(this.applicationName);
+		StringBuffer name = new StringBuffer(this.key);
 		if (!StringUtils.isEmpty(this.prefix)) {
 			String prefix = this.prefix;
 			if (prefix.lastIndexOf(".") == -1) {

spring-cloud-stream-metrics/src/test/java/org/springframework/cloud/stream/metrics/BinderMetricsEmitterTests.java

@@ -168,6 +168,28 @@ public class BinderMetricsEmitterTests {
 		applicationContext.close();
 	}
 
+		@Test
+		public void overrideAppName() throws Exception {
+				ConfigurableApplicationContext applicationContext = SpringApplication.run(BinderExporterApplication.class,
+						"--server.port=0", "--spring.jmx.enabled=false", "--spring.cloud.stream.metrics.delay-millis=500",
+						"--spring.application.name=foo", "--spring.cloud.stream.instanceIndex=1",
+						"--spring.cloud.stream.bindings.streamMetrics.destination=foo",
+						"--spring.cloud.stream.metrics.key=foobarfoo");
+				Emitter emitterSource = applicationContext.getBean(Emitter.class);
+				MessageCollector collector = applicationContext.getBean(MessageCollector.class);
+				Message message = collector.forChannel(emitterSource.metrics()).poll(1000, TimeUnit.MILLISECONDS);
+				Assert.assertNotNull(message);
+				ObjectMapper mapper = applicationContext.getBean(ObjectMapper.class);
+				ApplicationMetrics applicationMetrics = mapper.readValue((String) message.getPayload(),
+						ApplicationMetrics.class);
+				Assert.assertTrue(contains("integration.channel.errorChannel.errorRate.mean", applicationMetrics.getMetrics()));
+				Assert.assertFalse(contains("mem", applicationMetrics.getMetrics()));
+				Assert.assertEquals("foobarfoo", applicationMetrics.getName());
+				Assert.assertEquals(1, applicationMetrics.getInstanceIndex());
+				Assert.assertTrue(CollectionUtils.isEmpty(applicationMetrics.getProperties()));
+				applicationContext.close();
+		}
+
 	private boolean contains(String metric, Collection<Metric> metrics) {
 		boolean contains = false;
 		for (Metric entry : metrics) {