Push events for config changes

Works from local repos or with explicit POST to /monitor with
path=<serviceId>, also supports webhooks from github and gitlab.

Author: Dave Syer

docs/src/main/asciidoc/spring-cloud-config.adoc

@@ -489,7 +489,7 @@ TIP: the `{name:value}` prefixes can also be added to plaintext posted
 to the `/encrypt` endpoint, if you want to let the Config Server
 handle all encryption as well as decryption.
 
-=== Embedding the Config Server
+== Embedding the Config Server
 
 The Config Server runs best as a standalone application, but if you
 need to you can embed it in another application. Just use the
@@ -505,6 +505,41 @@ own remote repository. The flag is off by default because it can delay
 startup, but when embedded in another application it makes sense to
 initialize the same way as any other application.
 
+== Push Notifications and Spring Cloud Bus
+
+Many source code repository providers (like Github or Gitlab for
+instance) will notify you of changes in a repository through a
+webhook. You can configure the webhook via the provider's user
+interface as a URL and a set of events in which you are
+interested. For instance
+https://developer.github.com/v3/activity/events/types/#pushevent[Github]
+will POST to the webhook with a JSON body containing a list of
+commits, and a header "X-Github-Event" equal to "push". If you add a
+dependency on the `spring-cloud-config-monitor` library and activate
+the Spring Cloud Bus in your Config Server, then a "/monitor" endpoint
+is enabled.
+
+When the webhook is activated the Config Server will send a
+`RefreshRemoteApplicationEvent` targeted at the applications it thinks
+might have changed. The change detection can be strategized, but by
+default it just looks for changes in files that match the application
+name (e.g. "foo.properties" is targeted at the "foo" application, and
+"application.properties" is targeted at all applications). The strategy if you want to override the behaviour is `PropertyPathNotificationExtractor` which accepts the request headers and body as parameters and returns a list of file paths that changed.
+
+The default configuration works out of the box with Github or
+Gitlab. In addition to the JSON notifications from Github and Gitlab
+you can trigger a change notification by POSTing to "/monitor" with a
+form-encoded body parameters `path={name}`. This will broadcast to
+applications matching the "{name}" pattern (can contain wildcards).
+
+NOTE: the `RefreshRemoteApplicationEvent` will only be transmitted if
+the `spring-cloud-bus` is activated in the Config Server and in the
+client application.
+
+NOTE: the default configuration also detects filesystem changes in
+local git repositories (the webhook is not used in that case but as
+soon as you edit a config file a refresh will be broadcast).
+
 == Spring Cloud Config Client
 
 A Spring Boot application can take immediate advantage of the Spring

pom.xml

@@ -22,13 +22,15 @@
 	</scm>
     <properties>
         <bintray.package>config</bintray.package>
+        <spring-cloud-bus.version>1.1.0.BUILD-SNAPSHOT</spring-cloud-bus.version>
         <spring-cloud-commons.version>1.1.0.BUILD-SNAPSHOT</spring-cloud-commons.version>
     </properties>
 	<modules>
 	  <module>spring-cloud-config-client</module>
 	  <module>spring-cloud-config-server</module>
+	  <module>spring-cloud-config-monitor</module>
 	  <module>spring-cloud-config-sample</module>
-		<module>spring-cloud-starter-config</module>
+	  <module>spring-cloud-starter-config</module>
 	  <module>docs</module>
 	</modules>
     <dependencyManagement>
@@ -55,6 +57,11 @@
 			<artifactId>spring-cloud-config-server</artifactId>
 	        <version>1.1.0.BUILD-SNAPSHOT</version>
 		</dependency>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-config-monitor</artifactId>
+	        <version>1.1.0.BUILD-SNAPSHOT</version>
+		</dependency>
 		<dependency>
 			<groupId>org.springframework.retry</groupId>
 			<artifactId>spring-retry</artifactId>

spring-cloud-config-monitor/pom.xml

@@ -0,0 +1,49 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<project xmlns="http://maven.apache.org/POM/4.0.0" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+	xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd">
+	<modelVersion>4.0.0</modelVersion>
+	<parent>
+		<groupId>org.springframework.cloud</groupId>
+		<artifactId>spring-cloud-config</artifactId>
+		<version>1.1.0.BUILD-SNAPSHOT</version>
+		<relativePath>..</relativePath>
+	</parent>
+	<artifactId>spring-cloud-config-monitor</artifactId>
+	<name>spring-cloud-config-monitor</name>
+	<description>Spring Cloud Config Monitor</description>
+	<properties>
+		<main.basedir>${basedir}/../..</main.basedir>
+	</properties>
+	<dependencyManagement>
+		<dependencies>
+			<dependency>
+				<groupId>org.springframework.cloud</groupId>
+				<artifactId>spring-cloud-bus-parent</artifactId>
+				<version>${spring-cloud-bus.version}</version>
+				<type>pom</type>
+				<scope>import</scope>
+			</dependency>
+		</dependencies>
+	</dependencyManagement>
+	<dependencies>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-config-server</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.cloud</groupId>
+			<artifactId>spring-cloud-bus</artifactId>
+		</dependency>
+		<dependency>
+			<groupId>org.projectlombok</groupId>
+			<artifactId>lombok</artifactId>
+			<!-- Only needed at compile time -->
+			<optional>true</optional>
+		</dependency>
+		<dependency>
+			<groupId>org.springframework.boot</groupId>
+			<artifactId>spring-boot-starter-test</artifactId>
+			<scope>test</scope>
+		</dependency>
+	</dependencies>
+</project>

spring-cloud-config-monitor/src/main/java/org/springframework/cloud/config/monitor/CompositePropertyPathNotificationExtractor.java

@@ -0,0 +1,84 @@
+/*
+ * Copyright 2015 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
+ *
+ *      http://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.config.monitor;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.core.Ordered;
+import org.springframework.core.annotation.AnnotationAwareOrderComparator;
+import org.springframework.core.annotation.Order;
+import org.springframework.util.MultiValueMap;
+
+/**
+ * A {@link PropertyPathNotificationExtractor} that cycles through a set of (ordered) delegates,
+ * looking for the first non-null outcome.
+ *
+ * @author Dave Syer
+ *
+ */
+public class CompositePropertyPathNotificationExtractor
+		implements PropertyPathNotificationExtractor {
+
+	private List<PropertyPathNotificationExtractor> extractors;
+
+	public CompositePropertyPathNotificationExtractor(
+			List<PropertyPathNotificationExtractor> extractors) {
+		this.extractors = new ArrayList<>();
+		if (extractors != null) {
+			this.extractors.addAll(extractors);
+		}
+		this.extractors.add(new SimplePropertyPathNotificationExtractor());
+		AnnotationAwareOrderComparator.sort(this.extractors);
+	}
+
+	@Override
+	public PropertyPathNotification extract(MultiValueMap<String, String> headers,
+			Map<String, Object> request) {
+		for (PropertyPathNotificationExtractor extractor : this.extractors) {
+			PropertyPathNotification result = extractor.extract(headers, request);
+			if (result != null) {
+				return result;
+			}
+		}
+		return null;
+	}
+
+	@Order(Ordered.LOWEST_PRECEDENCE - 200)
+	private static class SimplePropertyPathNotificationExtractor
+			implements PropertyPathNotificationExtractor {
+
+		@Override
+		public PropertyPathNotification extract(MultiValueMap<String, String> headers,
+				Map<String, Object> request) {
+			Object object = request.get("path");
+			if (object instanceof String) {
+				return new PropertyPathNotification((String) object);
+			}
+			if (object instanceof Collection) {
+				@SuppressWarnings("unchecked")
+				Collection<String> collection = (Collection<String>) object;
+				return new PropertyPathNotification(collection.toArray(new String[0]));
+			}
+			return null;
+		}
+
+	}
+
+}

spring-cloud-config-monitor/src/main/java/org/springframework/cloud/config/monitor/EnvironmentMonitorAutoConfiguration.java

@@ -0,0 +1,43 @@
+/*
+ * Copyright 2015 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
+ *
+ *      http://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.config.monitor;
+
+import java.util.List;
+
+import org.springframework.beans.factory.annotation.Autowired;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnWebApplication;
+import org.springframework.context.annotation.Bean;
+import org.springframework.context.annotation.Configuration;
+import org.springframework.context.annotation.Import;
+
+/**
+ * @author Dave Syer
+ *
+ */
+@Configuration
+@ConditionalOnWebApplication
+@Import(FileMonitorConfiguration.class)
+public class EnvironmentMonitorAutoConfiguration {
+
+	@Autowired(required=false)
+	private List<PropertyPathNotificationExtractor> extractors;
+
+	@Bean
+	public PropertyPathEndpoint propertyPathEndpoint() {
+		return new PropertyPathEndpoint(new CompositePropertyPathNotificationExtractor(this.extractors));
+	}
+}