RSocket Proxy for Prometheus monitoring

- Rename spring-cloud-dataflow-samples/tree/master/micrometer to spring-cloud-dataflow-samples/tree/master/micrometer-samples
 - Rename spring-cloud-dataflow-samples/tree/master/micrometer/tasks to spring-cloud-dataflow-samples/tree/master/micrometer-samples/task-apps
 - Add the apps under spring-cloud-dataflow-samples/tree/master/micrometer/stream-apps
 - Describe or cross-link the description of the new architecture in the root README
 - Add microsite SCDF monitoring links

 Resolves #122

monitoring-samples/spring-cloud-dataflow-prometheus-service-discovery/src/main/java/org/springframework/cloud/dataflow/prometheus/servicediscovery/DataflowPrometheusServiceDiscoveryApplication.java

@@ -0,0 +1,181 @@
+/*
+ * Copyright 2015-2017 the original author or authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *      https://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.springframework.cloud.dataflow.prometheus.servicediscovery;
+
+import java.io.FileWriter;
+import java.io.IOException;
+import java.util.Arrays;
+import java.util.Collections;
+import java.util.List;
+import java.util.Map;
+import java.util.stream.Collectors;
+
+import com.fasterxml.jackson.core.JsonProcessingException;
+import com.fasterxml.jackson.databind.ObjectMapper;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import org.springframework.beans.factory.annotation.Value;
+import org.springframework.boot.SpringApplication;
+import org.springframework.boot.autoconfigure.SpringBootApplication;
+import org.springframework.cloud.dataflow.rest.resource.AppStatusResource;
+import org.springframework.hateoas.hal.Jackson2HalModule;
+import org.springframework.http.converter.json.Jackson2ObjectMapperBuilder;
+import org.springframework.http.converter.json.MappingJackson2HttpMessageConverter;
+import org.springframework.scheduling.annotation.EnableScheduling;
+import org.springframework.scheduling.annotation.Scheduled;
+import org.springframework.web.client.RestTemplate;
+
+/**
+ * Prometheus Service Discovery for SCSt apps deployed with the Local Deployer (?k8s?). It is build on top of the
+ * file_sd_config mechanism
+ *
+ * https://prometheus.io/docs/prometheus/latest/configuration/configuration/#%3Cfile_sd_config%3E
+ *
+ * @author Christian Tzolov
+ */
+@SpringBootApplication
+@EnableScheduling
+public class DataflowPrometheusServiceDiscoveryApplication {
+
+	private final Logger logger = LoggerFactory.getLogger(DataflowPrometheusServiceDiscoveryApplication.class);
+	private final ObjectMapper objectMapper;
+	private final RestTemplate restTemplate;
+
+
+	public enum TargetMode {local, promregator}
+
+	/**
+	 * Url of the the SCDF Runtime REST endpoint:
+	 * https://docs.spring.io/spring-cloud-dataflow/docs/current/reference/htmlsingle/#api-guide-resources-runtime-information-applications
+	 */
+	@Value("${metrics.prometheus.target.discovery.url:http://localhost:9393/runtime/apps}")
+	private String targetDiscoveryUrl;
+
+	/**
+	 * Path where the generated targets.json file is stored.
+	 */
+	@Value("${metrics.prometheus.target.file.path:/tmp/targets.json}")
+	private String outputTargetFilePath;
+
+	// For k8s deployment use 'pod.ip' instead of 'url'
+	@Value("${metrics.prometheus.target.dataflow.runtime.attribute.name:url}")
+	private String attributeName;
+
+	@Value("${metrics.prometheus.target.mode:local}")
+	private TargetMode targetMode;
+
+	public DataflowPrometheusServiceDiscoveryApplication() {
+		this.objectMapper = Jackson2ObjectMapperBuilder.json().modules(new Jackson2HalModule()).build();
+		this.restTemplate = new RestTemplate(Arrays.asList(new MappingJackson2HttpMessageConverter(this.objectMapper)));
+
+	}
+
+	public static void main(String[] args) {
+		SpringApplication.run(DataflowPrometheusServiceDiscoveryApplication.class, args);
+	}
+
+	/**
+	 * Use the metrics.prometheus.target.refresh.rate property (in milliseconds) to change the targets discovery rate.
+	 *
+	 * @throws IOException
+	 */
+	@Scheduled(fixedRateString = "${metrics.prometheus.target.refresh.rate:15000}")
+	public void updateTargets() throws IOException {
+
+		String targetsJson;
+		if (this.targetMode == TargetMode.local) {
+			targetsJson = this.findTargetsFromDataflowRuntimeApps();
+		}
+		else if (this.targetMode == TargetMode.promregator) {
+			targetsJson = this.findTargetsWithPromregator();
+		}
+		else {
+			throw new IllegalStateException("Unknown target mode:" + this.targetMode);
+		}
+
+		logger.info(this.targetMode + ": " + targetsJson);
+
+		this.updateTargetsFile(targetsJson);
+	}
+
+	public String findTargetsFromDataflowRuntimeApps() throws IOException {
+
+		AppStatusResource.Page page = this.restTemplate.getForObject(this.targetDiscoveryUrl, AppStatusResource.Page.class);
+
+		List<String> targetUrls = page.getContent().stream()
+				.map(appResource -> appResource.getInstances().getContent())
+				.flatMap(instances -> instances.stream().map(inst -> inst.getAttributes().get(this.attributeName)))
+				.map(url -> url.replace("http://", ""))
+				.collect(Collectors.toList());
+
+		return this.buildPrometheusTargetsJson(targetUrls);
+	}
+
+	private String findTargetsWithPromregator() throws IOException {
+		Object b = new RestTemplate().getForObject(this.targetDiscoveryUrl, Object.class);
+		return this.objectMapper.writeValueAsString(b);
+	}
+
+	/**
+	 * Converts a list of urls into JSON list of static target configs, compliant with the file_sd_config format.
+	 * @param targetUrls list of SCSt apps ip:ports to be used as prometheus metrics targets.
+	 * @return json record compliant with file_sd_config
+	 * @throws JsonProcessingException
+	 */
+	private String buildPrometheusTargetsJson(List<String> targetUrls) throws JsonProcessingException {
+		StaticConfig staticConfig = new StaticConfig();
+		staticConfig.setTargets(targetUrls);
+		staticConfig.setLabels(Collections.singletonMap("job", "scdf"));
+		return this.objectMapper.writeValueAsString(Arrays.asList(staticConfig));
+	}
+
+	/**
+	 * Re-writes the updated targets json into output file used by Prometheus.
+	 * @param targetsJson SCDF apps targets
+	 * @throws IOException
+	 */
+	private void updateTargetsFile(String targetsJson) throws IOException {
+		FileWriter fw = new FileWriter(this.outputTargetFilePath);
+		fw.write(targetsJson);
+		fw.close();
+	}
+
+	/**
+	 * Java model used as JSON representation of Prometheus' static target format.
+	 * https://prometheus.io/docs/prometheus/latest/configuration/configuration/#%3Cfile_sd_config%3E
+	 */
+	public static class StaticConfig {
+		private List<String> targets;
+		private Map<String, String> labels;
+
+		public List<String> getTargets() {
+			return targets;
+		}
+
+		public void setTargets(List<String> targets) {
+			this.targets = targets;
+		}
+
+		public Map<String, String> getLabels() {
+			return labels;
+		}
+
+		public void setLabels(Map<String, String> labels) {
+			this.labels = labels;
+		}
+	}
+}

monitoring-samples/spring-cloud-dataflow-prometheus-service-discovery/src/test/java/org/springframework/cloud/dataflow/prometheus/servicediscovery/SpringCloudDataflowPrometheusServiceDiscoveryApplicationTests.java

@@ -0,0 +1,16 @@
+package org.springframework.cloud.dataflow.prometheus.servicediscovery;
+
+import org.junit.Test;
+import org.junit.runner.RunWith;
+import org.springframework.boot.test.context.SpringBootTest;
+import org.springframework.test.context.junit4.SpringRunner;
+
+@RunWith(SpringRunner.class)
+@SpringBootTest
+public class SpringCloudDataflowPrometheusServiceDiscoveryApplicationTests {
+
+	@Test
+	public void contextLoads() {
+	}
+
+}