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Developers' Best Practices » History » Version 18

Claudio Atzori, 20/11/2018 05:20 PM

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h1. Developers' Best Practices
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It is time for D-Net development teams to find a strategy to improve our developement work!
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The introduction of Jenkins and Nexus helped a lot in terms of code management, but now it is time to establish a set of guidelines to better co-ordinate our teams.
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The following best practices are inspired by CNR developers' common sense, so we do not assume they are written in stones and applies as they are also in your cases.
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So, you are strongly invited to comment/update this wiki page, so that we can reach a consensus. 
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h2. Coding
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Most of the D-Net modules have been migrated to from the old build system ant to maven. This implies some changes to the module directories and files, here's the migration guide: 
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http://ci.research-infrastructures.eu/public/docbook/MavenMigration.html
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Maven compliant D-Net module structure:
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<pre>
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.
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├── pom.xml
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├── src
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│   ├── main
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│   │   ├── java
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│   │   │   └── eu
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│   │   │       └── dnetlib
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│   │   └── resources
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│   │       └── eu
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│   │           └── dnetlib
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│   └── test
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│       ├── java
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│       │   └── eu
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│       │       └── dnetlib
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│       └── resources
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│           └── eu
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│               └── dnetlib
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└── target
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    └── classes
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</pre>
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Hint: consider to define the svn:ignore property, set on the module root
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<pre>
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cd <MODULE_NAME>
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svn pe svn:ignore .
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.classpath
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.project
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.settings
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target 
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</pre>
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h2. Branching
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It is always recommended to create a new branch when performing heavy changes to a module, rather than directly into trunk.
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Since branching and merging is usually a lot of pain, we can use this section to keep track useful commands:
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* To merge the branch into trunk, you can follow this step by step tutorial: http://www.sepcot.com/blog/2007/04/SVN-Merge-Branch-Trunk
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* If you want to merge changes committed in one or more specific revisions of your branch into trunk, you can use the command:
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@cd trunk@
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@svn merge -c revNumber -c anotherRevNumber https://svn.driver.research-infrastructures.eu/driver/dnet40/modules/yourBranch@
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h2. Revert to previous version
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Because sometimes devs commit things that should not have been committed....
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@svn merge -r HEAD:<goodRevision> <pathToFileTorevert>@
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where @<goodRevision>@ is the revision number prior to the wrong commit of @<pathToFileTorevert>@
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h2. Use CI: trust Jenkins!
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The developer should clean the @.m2/repository/eu@ local repository from time to time to be sure that there are no modules installed locally. 
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Modules should be downloaded from Nexus in order to properly resolve dependencies.
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h2. Maven dependencies
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For information about version conflict resolution with Maven3:
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* http://docs.codehaus.org/display/MAVEN/Versioning
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* https://cwiki.apache.org/confluence/display/MAVEN/Maven+3.x+Compatibility+Notes
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Generally speaking, we suggest to use the keyword @LATEST@ to refer to the last available artifact (snapshot or release) for a module.
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Keep in mind that Maven3 considers:
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@1.0-alpha-1 < 1.0-beta-1 < 1.0-SNAPSHOT < 1.0 < 1.1-SNAPSHOT@
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h3. How to change the version number of a snapshot?
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Depending on the kind of changes you can decide to increase the artifact version according to the following guidelines:
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* BIG CHANGES impact the MAJOR version number. Ex. @0.0.1 --> 1.0.0@
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** Examples of big changes are: updates to service interfaces, shared libraries, new functionalities.
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* MINOR CHANGES impact the MINOR version number. Ex. @1.2.5 --> 1.3.0@
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** Examples of minor changes are: service internals, non-shared code and libraries, important bug fixes.
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* BUG FIXES impact the BUILD version number. Ex. @1.4.2 --> 1.4.3@
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** Examples are small bug fixes that do not affect other components 
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h2. Release Best Practices
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h3. When/Why releasing a module?
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* Generally speaking a developer should release a module when the code is mature enough to be used by others. 
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* An early release should be available in case others are relying on a module that is currently under heavy development (i.e., frequent commits that imply frequent snapshot updates), in order to avoid blocking other development activities.
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* Before updating an interface (e.g., service interfaces) or library (e.g., common and utilities modules) a developer MUST ENSURE there is a release of the current version.
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h3. How to release?
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Note that the maven release plugin works fine with *Apache Maven 3.0.5* and that is the version that we suggest you to use.
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To know which maven version you are using run: <pre>mvn -version</pre>
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If you have a newer version (e.g. 3.2.3), then you'll get the error @Return code is: 400, ReasonPhrase: Bad Request@ when running @mvn release:perform@.
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However +the jar should have been correctly deployed+: we strongly suggest you to check this is true by logging into our "Nexus":http://maven.research-infrastructures.eu/nexus.
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These are the steps for the release of a module, given that developer has a fresh checkout of the module to be released.
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# Add the following at the beginning of your @~/.m2/settings.xml@:
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<pre>
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<servers>
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 <server>
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      <id>dnet45-releases</id>
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      <username>your LDAP username</username>
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      <password>your LDAP password</password>
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   </server>
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</servers>
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</pre>
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# Add the SCM info (change @{project.name}@ with the actual name of the project):
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<pre>
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<scm>
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   <developerConnection>scm:svn:https://svn.driver.research-infrastructures.eu/driver/dnet45/modules/{project.name}/trunk</developerConnection>
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</scm>
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</pre>
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# Set the parent to a released parent. Example:
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<pre>
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<parent>
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   <groupId>eu.dnetlib</groupId>
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   <artifactId>dnet-parent</artifactId>
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   <version>1.0.0</version>
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</parent>
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</pre>
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# Ensure there are no snapshots included as dependencies. Snapshot dependencies won't be resolved anymore by maven because released parents have visibility only on the released repository (@dnet45-releases@). For example, if your module currently depends on 
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<pre>
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<dependency>
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	<groupId>eu.dnetlib</groupId>
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	<artifactId>cnr-misc-utils</artifactId>
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	<version>[1.0.0-SNAPSHOT,2.0.0-SNAPSHOT)</version>
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</dependency>
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</pre>
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You should change the dependency as follows:
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<pre>
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<dependency>
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	<groupId>eu.dnetlib</groupId>
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	<artifactId>cnr-misc-utils</artifactId>
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	<version>[1.0.0,2.0.0)</version>
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</dependency>
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</pre>
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Note that this implies that the dependency module (e.g. @cnr-misc-utils@) must have been released.
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# Commit the changes you made in the pom.xml 
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# Run @mvn release:prepare@ and answer the questions. Default answers are usually fine. This will:
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#* copy your trunk into another svn folder (@tags@) 
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#* update the versions in trunk and tags
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# Run @mvn release:perform@. This will deploy the artifact on Nexus in the release repository @dnet45-releases@.
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If you experience any issue, open a ticket to CNR.