Nie wieder Monolithen! Micro Services in der Praxis.

Bei der Hypoport AG haben wir bereits drei verschiedene Modularisierungsinkarnationen erlebt. Jede Inkarnation brachte uns näher an das Ideal einer flexiblen, wartbaren Architektur. Und dennoch stellten wir nach wenigen Jahren der Produktweiterentwicklung wieder fest: Die Anwendung ist voll von unbeabsichtigter Komplexität, Innovationen sind nur schwer möglich und die Umsetzung von Funktionalität dauerte kontinuierlich länger. Der Micro-Service-Architekturstil verheißt durch die Zerlegung eines Systems in kleine, unabhängige Services nachhaltige Besserung. Wir haben’s ausprobiert und sind begeistert.

Der Artikel erschien im Java Magazin 8.2014.

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Continuous Deployment with Gradle and Docker – Part 2

After a quite long holiday break we now continue our series about the Continuous Deployment Pipeline with Gradle and Docker.

This post is about the first step where our build chain creates the Spring Boot packages and publishes them to our Nexus repository manager. As shown in the high-level overview below, it is only a quite small part of the complete pipeline:
Deployment Pipeline with Gradle and Docker

Gradle and Spring Boot provide you a very convenient build and plugin system and work out of the box for standard builds. Yet, the devil is in the details. Our project consists of a multi module setup with the following subprojects:

  • backend
  • frontend
  • common
  • contract-test
  • e2e-test

The projects backend and frontend are our main modules with each being deployed as a standalone application. They share the common project which contains the security and web config. The contract-test and e2e-test projects contain more integrative tests and will be discussed later in dedicated posts.

We’ll now take a deep dive into our build scripts and module structure. You can find the example source code on GitHub, where we provide a minimal, but working project with the important parts being described here.

Gradle project setup

A build on our CI-Server TeamCity uses the Gradle Wrapper by running the tasks build and publish. These tasks are called on the root level of our project. Our Gradle root project contains the common configuration so that the subprojects only need to configure minimal aspects or special plugins.

Shared dependency versions are defined in the root project, so that all subprojects use the same dependency versions. Gradle also allows you to define sets of dependencies, so that you can reference them as complete package without known its details. We call these sets libraries and you can find an example at the root build.gradle along with its usage in the dependency closure.

Using a common definition of dependencies sometimes isn’t enough, because you also have to handle transitive dependencies. You have the option to manage transitive dependencies by manually excluding or even redefining them. Another option we often use is to override clashing dependency versions by configuring the build script’s configuration. The resolutionStrategy can be configured to fail when version conflicts are recognized. The example project shows you how we globally manage our dependencies.

Spring Boot configuration

Building a Spring Boot application with Gradle is simplified with the help of the Spring Boot Gradle Plugin. The plugin configures your build script so that running gradle build depends on the bootRepackage task.

You’ll see in the backend and frontend build.gradle scripts, that we configure Gradle to replace a token in our source files with the artifactVersion. This special token replacement aims at setting the actual version in our file, which is used to configure Spring Boot. By adding a line like we enable the /info endpoint so that we can ask a running application about its version. The version will be used later in our deployment pipeline. Details on our artifact versioning scheme will be described in the section about publishing below.

Performing Node.js build tasks

Our backend build isn’t very spectacular, but our frontend build needs some more explanation. We implemented our frontend with AngularJS, but use Spring Boot to deliver the static resources and to implement security. Before packaging the AngularJS resources in the frontend artifact, we let Gradle perform a grunt release task. Grunt is a Node.js based task runner, which lets us run unit tests, minimize our frontend code or even images and package everything. Its result then needs to be copied to the public resources folder of Spring Boot.

Configuring a Node.js build in a platform neutral way isn’t one of the trivial tasks, but we use the gradle-grunt-plugin and the gradle-node-plugin which helps a lot. Apart from delegating the grunt release to the plugin we also configure the according grunt_release task to recognize inputs and outputs in the Gradle build script. The inputs and outputs help Gradle to decide if the task needs to be executed. If there haven’t been any source changes and the output still exists, the task is regarded up to date and will be skipped.

Publishing and versioning Gradle artifacts

With both frontend and backend being packaged as artifacts, we would like to publish them to our Nexus artifact repository. Nexus needs the well known set of groupId, artifactId and version to identify an artifact. The Gradle maven-publish plugin can be configured in a very convenient way to use the project’s group, name and version as Maven coordinates. As you can see in the example source code, we already configure the group in our root project. The subproject’s name fits our needs as artifactId, which leads us to the final property, the version.

We wanted the version to be unique and sortable by the artifact’s build time. We also didn’t want to maintain a version.txt in our project. Long story short, we defined our version to look like the scheme: yyyy-MM-dd'T'HH-mm-ss_git-commit-hash. The part before the _ corresponds to the build timestamp and the second part corresponds to the latest commit hash of the project’s git repository. That way we can quickly recognize when the artifact has been build with which commit in the project’s history.

The artifact version is generated on every build. Apart from updating our, we also use the artifact version to configure the publish task in our root project. The rest works out of the box, we only need to configure the Nexus publish url with username and password.

Build on a CI-Server

Our CI Server TeamCity now only needs to execute the gradlew clean build publish tasks to compile, perform all unit tests, package the Spring Boot applications and publish them to the artifact repository. That wouldn’t be enough, because we also want to perform integration tests and deploy the applications to our internal and production stages.

TeamCity provides a feature to declare so-called build artifacts, which can be used by subsequent build goals in our build chain. We want the other build goals to know the application version, so we write it into a text file on the build agent and pass it to all build goals in our pipeline. Every build goal then uses the version to fetch the artifact from Nexus. The image below shows all build goals of our build chain:

Build Chain

The selected yellow box in the build chain corresponds to the build step we described in this article. As promised, the next article in our series will describe you in detail how we perform our integrative e2e- and contract-tests. Comments and feedback here or @gesellix are welcome!

Docker Global Hack Day #2 – Berlin Edition at Hypoport

We are proud to announce that we are part of the Docker Global Hack Day #2. Join other members of the Docker community to hack on Docker projects using the next big Docker release! You’re all invited to Hypoport HQ in Berlin for a hacking session while sharing a meal/drink with fellow Dockers. This hackathon is your last chance to win a ticket to the sold out DockerCon Europe. Please register using our meetup event page.

See you then.

How to open async calls in a new tab instead of new window within an AngularJS app

I recently wanted to generate a PDF on users demand and show it in a new browser tab.
Sounds trivial, at first not for me :) I tried it with different “solutions” and on my way my google search result got better and better. With “open window new tab without popup blocker async” I finally found in this thread a nice and easy solution. The trick is to remember the reference to the new window and change the location of that window when your asynchron call completes.

$scope.generatePdf = function () {
  var tabWindowId ='about:blank', '_blank');

  $'/someUrl', data).then( function (response) {
    tabWindowId.location.href = response.headers('Location');

If you want to see it in action open this plunker. While testing this plunker, it seems that openWindow will open a tab, as long as the async call is quick enough (less than a second). The setTimeout is therefore set to 1001.

I hope you will find this solution quicker than I did. Please let me know if you have any questions or suggestions. Either per @leifhanack or comment here.

managing multiple ssh keys

Recently I wanted to connect to some remote server using different ssh keys. With the right ~/.ssh/config file this is easy and comfortable.


IdentityFile ~/.ssh/%h/%r/id_rsa
IdentityFile ~/.ssh/%h/id_rsa
IdentityFile ~/.ssh/id_rsa

%h and %r are placeholder for host and remote-user. ssh foo@bar will first check if ~/.ssh/bar/foo/id_rsa exists, next ~/.ssh/bar/id_rsa and finally ~/.ssh/id_rsa.


Host github
        HostName 123.45.678.90
        User myuser
        IdentityFile ~/.ssh/123.45.678.90/id_rsa

Instead of ssh myuser@123.45.678.90 the above config allows you to simply type

ssh github

You don’t need to remember all your IPs and remote-users any longer. For me this is a big time saver.

Please let me know if you have questions or suggestions. Either per @leifhanack or comment here.

A Continuous Deployment Pipeline with Gradle and Docker

This series of posts will show you some aspects of our continuous deployment pipeline for one of our products. It is built, tested and deployed to our servers by using Gradle, while the application itself runs inside Docker containers.

We want to show you how we use Gradle to implement a complete pipeline with minimal dependency on command line tools. We’ll also describe how to perform rollouts to production without the need for shell scripts or even remote shell access, by using the Docker remote API. All details regarding our AngularJS frontend, test concepts for multi-product compatibility and detailed code examples will be explained in upcoming posts. This post starts with a bird’s-eye view of our pipeline.


Our deployment pipeline is divided into six build goals, combined in a TeamCity Build Chain. We’ll add links to each build goal as soon as a corresponding article has been published:

  • build, publish
  • e2e test
  • contract test
  • build image
  • deploy on dev
  • deploy on prod

Every git push to a shared Git repository triggers a new build and is automatically deployed to production.

The first step builds a multi module project and produces two Spring Boot jar files for our backend and frontend webapps. Both jars are published to our Nexus artifact repository. Building a Spring Boot application with Gradle is straight-forward, you’ll find examples in the Spring Boot guides. The gradle-grunt-plugin helps us building and unit testing the AngularJS frontend by delegating build steps to the Grunt task runner.

Our e2e-test build step runs some integration tests on our frontend to ensure that it is compatible to our backend. The next step runs so-called contract tests, which runs cross-product tests to ensure our new release still plays well with the other services on our platform.

The fourth step builds a Docker image containing both frontend and backend webapps and pushes it to a private Docker registry. After that, we pull the newly built image to our development and production stages and run container instances. In order to maximize product availability, both stages use blue-green deployment.

Gradle and Groovy power

As already mentioned, the complete pipeline is implemented using Gradle. Running the build and publish tasks is quite trivial, some code snippets will be shown in the following posts. The integration of our frontend build using the gradle-grunt-plugin has been straight forward, too, while we added some configuration to let Gradle know about Grunt’s inputs and outputs. That way, we enable Gradle to use its cache and skip up to date tasks when there aren’t any code changes.

Running the e2e-tests and contract-tests wasn’t possible with existing plugins, so we had to create some special tasks. Since Gradle lets us write native Groovy code, we didn’t need to create dedicated shell scripts, but execute commands as simply as "command".execute(). That way we can perform the following steps to run our e2e-tests with Protractor:

  • start selenium-server
  • start e2e-reverse-proxy
  • start frontend and backend
  • run protractor e2e-tests
  • tear down

In contrast to the e2e-tests, where we only check our frontend and backend application, we have some contract-tests to check our interaction with other services. Our backend interacts with some other products of our platform, and we want to be sure that after deploying a new release of our product, it still works together with current versions of the other products. Our contract-tests are implemented as Spock framework and TestNG tests and are a submodule of our product. A dedicated contract-tester module in an own project performs all necessary steps to find and run the external webapps in their released versions and to perform our contract-tests against their temporary instances. Like with the e2e-tests, all steps are implemented in Gradle, but this time we could use plugins like Gradle Cargo plugin and Gradle Download Task, furthermore Gradle’s built in test runner and dynamic dependency resolution for our contract-tests artifact:

  • collect participating product versions
  • download each product’s webapp from Nexus
  • start the participating webapps and infrastructure services
  • run contract-tests
  • tear down

Gradle and Docker

With our artifacts being tested, we package them in Docker images, deploy the images to our private registries and run fresh containers on our servers. Docker allows us to describe the image contents by writing Dockerfiles as plain text, so that we can include all build instructions in our Git repository. Before using a Gradle Docker plugin, we used Gradle to orchestrate Docker clients, which had to be installed on our TeamCity agents and the application servers. Like described above, we used the Groovy command executor to access the Docker command line interface. We’re now in a transition to only use the Docker remote API, so that we don’t need a Docker client on every build server, but only need to point the plugin to any Docker enabled server.

Building and distributing our images, followed by starting the containers is only one part of our deployment. In order to implement continuous delivery without interrupting availability of our product, we implemented blue-green deployment. Therefore, our Gradle deployment script needs to ask our reverse proxy in front of our application servers for a deployable stage (e.g. green), perform the Docker container tasks and toggle a switch from the current to the new stage, e.g. from blue to green:

  • get the deployable stage
  • pull the new image from the Docker registry
  • stop and remove the old container
  • run a new container based on the new image
  • cleanup (e.g. remove unused images)
  • switch to the new stage with the fresh container


With this brief overview you should have an impression of the key elements of our pipeline. In the upcoming posts we’ll dive into each of these build steps, provide some code examples and discuss our experience regarding the chosen technologies and frameworks in context of our server setups.

If you’d like to know special details, please leave a comment or contact us via Twitter @gesellix, so that we can include your wishes in the following posts. Even if you’d like us to talk about non technical aspects, e.g. like our experience introducing the above technologies to our teams, just ask!

Dozer Plugin für IntelliJ IDEA

In einigen Projekten nutzen wir intensiv das Mapping Framework Dozer. Vor knapp 4 Jahren wurde ein Plugin für IntelliJ IDEA entwickelt, das uns beim Mappen stark unterstützt. Es bietet Code Completion und Error Highlighting in den XML-Mappingdateien von Dozer an.

Mit der Nutzung von IDEA 13 war es nötig, das Plugin an die neue Version der Entwicklungsumgebung anzupassen. Im Zuge der Anpassung haben wir beschlossen, das Plugin zu veröffentlichen und den Quelltext unter eine Open Source Lizenz zu stellen. Die Sourcen sind auf der GitHub-Seite von Hypoport zu finden. Das “Binary” kann über den Plugin-Repository Browser in IDEA bezogen werden bzw. auf der Plugin-Seite von JetBrains heruntergeladen werden.