Getting Started with Fuse on Spring Boot

Red Hat Fuse 7.9

Get started quickly with Red Hat Fuse on Spring Boot

Red Hat Fuse Documentation Team

Abstract

Get started with Fuse on Spring Boot.

Preface

To get started with Fuse, you need to download and install the files for your Spring Boot container. The information and instructions here guide you in installing, developing, and building your first Fuse application.

Making open source more inclusive

Red Hat is committed to replacing problematic language in our code, documentation, and web properties. We are beginning with these four terms: master, slave, blacklist, and whitelist. Because of the enormity of this endeavor, these changes will be implemented gradually over several upcoming releases. For more details, see our CTO Chris Wright’s message.

Chapter 1. Getting started with Fuse on Spring Boot

To develop Fuse applications on Spring Boot, get started by generating and building a Fuse sample booster project that runs on Spring Boot. The following topics provide details:

1.1. About Fuse on Spring Boot

Spring Boot is an evolution of the well-known Spring container. A distinctive quality of the Spring Boot container is that container functionality is divided up into small chunks, which can be deployed independently. This quality enables you to deploy a container with a small footprint, specialized for a particular kind of service, and this ability happens to be exactly what you need to fit the paradigm of a microservices architecture.

Distinctive features of this container technology are:

  • Particularly suited to running on a scalable cloud platform (Kubernetes and OpenShift).
  • Small footprint (ideal for microservices architecture).
  • Optimized for convention over configuration.
  • No application server required. You can run a Spring Boot application Jar directly in a JVM.

1.2. Generating your booster project

Fuse booster projects exist to help developers get started with running standalone applications. The instructions provided here guide you through generating one of those booster projects, the Circuit Breaker booster. This exercise demonstrates useful components of the Fuse on Spring Boot.

The Netflix/Hystrix circuit breaker enables distributed applications to handle interruptions to network connectivity and temporary unavailability of backend services. The basic idea of the circuit breaker pattern is that the loss of a dependent service is detected automatically and an alternative behavior can be programmed, in case the backend service is temporarily unavailable.

The Fuse circuit breaker booster consists of two related services:

  • A name service, the backend service that returns a name to greet.
  • A greetings service, the frontend service that invokes the name service to get a name and then returns the string, Hello, NAME.

In this booster demonstration, the Hystrix circuit breaker is inserted between the greetings service and the name service. If the backend name service becomes unavailable, the greetings service can fall back to an alternative behavior and respond to the client immediately, instead of being blocked while it waits for the name service to restart.

Prerequisites

Procedure

  1. Navigate to https://developers.redhat.com/launch.
  2. Click START.

    The launcher wizard prompts you to log in to your Red Hat account.

  3. On the Launcher page, click the Deploy an Example Application button.
  4. On the Create Example Application page, type the name, fuse-circuit-breaker, in the Create Example Application as field.
  5. Click Select an Example.
  6. In the Example dialog, select the Circuit Breaker option. A Select a Runtime dropdown menu appears.

    1. From the Select a Runtime dropdown, select Fuse.
    2. From the version dropdown menu, select 7.9 (Red Hat Fuse) (do not select the 2.21.2 (Community) version).
    3. Click Save.
  7. On the Create Example Application page, click Download.
  8. When you see the Your Application is Ready dialog, click Download.zip. Your browser downloads the generated booster project (packaged as a ZIP file).
  9. Use an archive utility to extract the generated project to a convenient location on your local file system.

1.3. Building your booster project

These instructions guide you through building the Circuir Breaker booster with Fuse on Spring Boot.

Prerequisites

Procedure

  1. Open a shell prompt and build the project from the command line, using Maven:

    cd fuse-circuit-breaker
    mvn clean package

    After Maven builds the project, it displays a Build Success message.

  2. Open a new shell prompt and start the name service, as follows:

    cd name-service
    mvn spring-boot:run -DskipTests -Dserver.port=8081

    As Spring Boot starts up, you should see output similar to the following:

    ...
    2019-05-06 20:19:59.401  INFO 9553 --- [           main] o.a.camel.spring.SpringCamelContext      : Route: route1 started and consuming from: servlet:/name?httpMethodRestrict=GET
    2019-05-06 20:19:59.402  INFO 9553 --- [           main] o.a.camel.spring.SpringCamelContext      : Total 1 routes, of which 1 are started
    2019-05-06 20:19:59.403  INFO 9553 --- [           main] o.a.camel.spring.SpringCamelContext      : Apache Camel 2.21.0.fuse-730078-redhat-00001 (CamelContext: camel-1) started in 0.287 seconds
    2019-05-06 20:19:59.406  INFO 9553 --- [           main] o.a.c.c.s.CamelHttpTransportServlet      : Initialized CamelHttpTransportServlet[name=CamelServlet, contextPath=]
    2019-05-06 20:19:59.473  INFO 9553 --- [           main] b.c.e.u.UndertowEmbeddedServletContainer : Undertow started on port(s) 8081 (http)
    2019-05-06 20:19:59.479  INFO 9553 --- [           main] com.redhat.fuse.boosters.cb.Application  : Started Application in 5.485 seconds (JVM running for 9.841)
  3. Open a new shell prompt and start the greetings service, as follows:

    cd greetings-service
    mvn spring-boot:run -DskipTests

    As Spring Boot starts up, you should see output similar to the following:

    ...
    2019-05-06 20:22:19.051  INFO 9729 --- [           main] o.a.c.c.s.CamelHttpTransportServlet      : Initialized CamelHttpTransportServlet[name=CamelServlet, contextPath=]
    2019-05-06 20:22:19.115  INFO 9729 --- [           main] b.c.e.u.UndertowEmbeddedServletContainer : Undertow started on port(s) 8080 (http)
    2019-05-06 20:22:19.123  INFO 9729 --- [           main] com.redhat.fuse.boosters.cb.Application  : Started Application in 7.68 seconds (JVM running for 12.66)

    The greetings service exposes a REST endpoint at the http://localhost:8080/camel/greetings URL.

  4. Invoke the REST endpoint by either opening the URL in a web browser or by opening another shell prompt and typing the following curl command:

    curl http://localhost:8080/camel/greetings

    Here is the response:

    {"greetings":"Hello, Jacopo"}
  5. To demonstrate the circuit breaker functionality provided by Camel Hystrix, kill the backend name service by typing Ctrl-C in the shell prompt window where the name service is running.

    Now that the name service is unavailable, the circuit breaker kicks in to prevent the greetings service from hanging when it is invoked.

  6. Invoke the greetings REST endpoint by either opening http://localhost:8080/camel/greetings in a web browser or by typing the following curl command in another shell prompt window:

    curl http://localhost:8080/camel/greetings

    Here is the response:

    {"greetings":"Hello, default fallback"}

    In the window where the greetings service is running, the log shows the following sequence of messages:

    2019-05-06 20:24:16.952  INFO 9729 --- [-CamelHystrix-2] route2                                   :  Try to call name Service
    2019-05-06 20:24:16.956  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : I/O exception (java.net.ConnectException) caught when processing request: Connection refused (Connection refused)
    2019-05-06 20:24:16.956  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : Retrying request
    2019-05-06 20:24:16.957  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : I/O exception (java.net.ConnectException) caught when processing request: Connection refused (Connection refused)
    2019-05-06 20:24:16.957  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : Retrying request
    2019-05-06 20:24:16.957  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : I/O exception (java.net.ConnectException) caught when processing request: Connection refused (Connection refused)
    2019-05-06 20:24:16.957  INFO 9729 --- [-CamelHystrix-2] o.a.c.httpclient.HttpMethodDirector      : Retrying request
    2019-05-06 20:24:16.964  INFO 9729 --- [-CamelHystrix-2] route2                                   :  We are falling back!!!!
  7. For more information about this example, open the Circuit Breaker - Red Hat Fuse page at http://localhost:8080/ (while the greetings-service is running). This page includes a link to the Hystrix dashboard that monitors the state of the circuit breaker.

Chapter 2. Setting up Maven locally

Typical Fuse application development uses Maven to build and manage projects.

The following topics describe how to set up Maven locally:

2.1. Preparing to set up Maven

Maven is a free, open source, build tool from Apache. Typically, you use Maven to build Fuse applications.

Procedure

  1. Download the latest version of Maven from the Maven download page.
  2. Ensure that your system is connected to the Internet.

    While building a project, the default behavior is that Maven searches external repositories and downloads the required artifacts. Maven looks for repositories that are accessible over the Internet.

    You can change this behavior so that Maven searches only repositories that are on a local network. That is, Maven can run in an offline mode. In offline mode, Maven looks for artifacts in its local repository. See Section 2.3, “Using local Maven repositories”.

2.2. Adding Red Hat repositories to Maven

To access artifacts that are in Red Hat Maven repositories, you need to add those repositories to Maven’s settings.xml file. Maven looks for the settings.xml file in the .m2 directory of the user’s home directory. If there is not a user specified settings.xml file, Maven uses the system-level settings.xml file at M2_HOME/conf/settings.xml.

Prerequisite

You know the location of the settings.xml file in which you want to add the Red Hat repositories.

Procedure

In the settings.xml file, add repository elements for the Red Hat repositories as shown in this example:

<?xml version="1.0"?>
<settings>

  <profiles>
    <profile>
      <id>extra-repos</id>
      <activation>
        <activeByDefault>true</activeByDefault>
      </activation>
      <repositories>
       <repository>
            <id>redhat-ga-repository</id>
            <url>https://maven.repository.redhat.com/ga</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
            <id>redhat-ea-repository</id>
            <url>https://maven.repository.redhat.com/earlyaccess/all</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </repository>
        <repository>
          <id>jboss-public</id>
          <name>JBoss Public Repository Group</name>
          <url>https://repository.jboss.org/nexus/content/groups/public/</url>
        </repository>
      </repositories>
      <pluginRepositories>
        <pluginRepository>
            <id>redhat-ga-repository</id>
            <url>https://maven.repository.redhat.com/ga</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
            <id>redhat-ea-repository</id>
            <url>https://maven.repository.redhat.com/earlyaccess/all</url>
            <releases>
                <enabled>true</enabled>
            </releases>
            <snapshots>
                <enabled>false</enabled>
            </snapshots>
        </pluginRepository>
        <pluginRepository>
          <id>jboss-public</id>
          <name>JBoss Public Repository Group</name>
          <url>https://repository.jboss.org/nexus/content/groups/public</url>
        </pluginRepository>
      </pluginRepositories>
    </profile>
  </profiles>

  <activeProfiles>
    <activeProfile>extra-repos</activeProfile>
  </activeProfiles>

</settings>

2.3. Using local Maven repositories

If you are running a container without an Internet connection, and you need to deploy an application that has dependencies that are not available offline, you can use the Maven dependency plug-in to download the application’s dependencies into a Maven offline repository. You can then distribute this customized Maven offline repository to machines that do not have an Internet connection.

Procedure

  1. In the project directory that contains the pom.xml file, download a repository for a Maven project by running a command such as the following:

    mvn org.apache.maven.plugins:maven-dependency-plugin:3.1.0:go-offline -Dmaven.repo.local=/tmp/my-project

    In this example, Maven dependencies and plug-ins that are required to build the project are downloaded to the /tmp/my-project directory.

  2. Edit the etc/org.ops4j.pax.url.mvn.cfg file to set org.ops4j.pax.url.mvn.offline to true. This enables offline mode:

    ##
    # If set to true, no remote repository will be accessed when resolving artifacts
    #
    org.ops4j.pax.url.mvn.offline = true
  3. Distribute this customized Maven offline repository internally to any machines that do not have an Internet connection.

2.4. Setting Maven mirror using environmental variables or system properties

When running the applications you need access to the artifacts that are in the Red Hat Maven repositories. These repositories are added to Maven’s settings.xml file. Maven checks the following locations for settings.xml file:

  • looks for the specified url
  • if not found looks for ${user.home}/.m2/settings.xml
  • if not found looks for ${maven.home}/conf/settings.xml
  • if not found looks for ${M2_HOME}/conf/settings.xml
  • if no location is found, empty org.apache.maven.settings.Settings instance is created.

2.4.1. About Maven mirror

Maven uses a set of remote repositories to access the artifacts, which are currently not available in local repository. The list of repositories almost always contains Maven Central repository, but for Red Hat Fuse, it also contains Maven Red Hat repositories. In some cases where it is not possible or allowed to access different remote repositories, you can use a mechanism of Maven mirrors. A mirror replaces a particular repository URL with a different one, so all HTTP traffic when remote artifacts are being searched for can be directed to a single URL.

2.4.2. Adding Maven mirror to settings.xml

To set the Maven mirror, add the following section to Maven’s settings.xml:

<mirror>
      <id>all</id>
      <mirrorOf>*</mirrorOf>
      <url>http://host:port/path</url>
</mirror>

No mirror is used if the above section is not found in the settings.xml file. To specify a global mirror without providing the XML configuration, you can use either system property or environmental variables.

2.4.3. Setting Maven mirror using environmental variable or system property

To set the Maven mirror using either environmental variable or system property, you can add:

  • Environmental variable called MAVEN_MIRROR_URL to bin/setenv file
  • System property called mavenMirrorUrl to etc/system.properties file

2.4.4. Using Maven options to specify Maven mirror url

To use an alternate Maven mirror url, other than the one specified by environmental variables or system property, use the following maven options when running the application:

  • -DmavenMirrorUrl=mirrorId::mirrorUrl

    for example, -DmavenMirrorUrl=my-mirror::http://mirror.net/repository

  • -DmavenMirrorUrl=mirrorUrl

    for example, -DmavenMirrorUrl=http://mirror.net/repository. In this example, the <id> of the <mirror> is just a mirror.

2.5. About Maven artifacts and coordinates

In the Maven build system, the basic building block is an artifact. After a build, the output of an artifact is typically an archive, such as a JAR or WAR file.

A key aspect of Maven is the ability to locate artifacts and manage the dependencies between them. A Maven coordinate is a set of values that identifies the location of a particular artifact. A basic coordinate has three values in the following form:

groupId:artifactId:version

Sometimes Maven augments a basic coordinate with a packaging value or with both a packaging value and a classifier value. A Maven coordinate can have any one of the following forms:

groupId:artifactId:version
groupId:artifactId:packaging:version
groupId:artifactId:packaging:classifier:version

Here are descriptions of the values:

groupdId
Defines a scope for the name of the artifact. You would typically use all or part of a package name as a group ID. For example, org.fusesource.example.
artifactId
Defines the artifact name relative to the group ID.
version
Specifies the artifact’s version. A version number can have up to four parts: n.n.n.n, where the last part of the version number can contain non-numeric characters. For example, the last part of 1.0-SNAPSHOT is the alphanumeric substring, 0-SNAPSHOT.
packaging
Defines the packaged entity that is produced when you build the project. For OSGi projects, the packaging is bundle. The default value is jar.
classifier
Enables you to distinguish between artifacts that were built from the same POM, but have different content.

Elements in an artifact’s POM file define the artifact’s group ID, artifact ID, packaging, and version, as shown here:

<project ... >
  ...
  <groupId>org.fusesource.example</groupId>
  <artifactId>bundle-demo</artifactId>
  <packaging>bundle</packaging>
  <version>1.0-SNAPSHOT</version>
  ...
</project>

To define a dependency on the preceding artifact, you would add the following dependency element to a POM file:

<project ... >
  ...
  <dependencies>
    <dependency>
      <groupId>org.fusesource.example</groupId>
      <artifactId>bundle-demo</artifactId>
      <version>1.0-SNAPSHOT</version>
    </dependency>
  </dependencies>
  ...
</project>
Note

It is not necessary to specify the bundle package type in the preceding dependency, because a bundle is just a particular kind of JAR file and jar is the default Maven package type. If you do need to specify the packaging type explicitly in a dependency, however, you can use the type element.

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