How to manage your Android code with Gerrit?

Author: Hu Rui, Unit: China Mobile Smart Home Operation Center

Labs Guide

Android source code is an open source operating system based on Linux. Currently, the code management tool for Android ROM development basically uses Git. Since Android code is very complex, Google divides it into multiple git repos, which not only avoids too much code in one repo, but also allows it to be assigned to different teams for management and control according to the function of the repo. In order to control the quality of Android code, Google uses Gerrit for coderview, and uses Jenkins for static code detection and automated verification, and of course integrated CI tools. At present, the AOS-RM project of China Mobile Smart Home Operation Center has deployed its own Gerrit server, and Gerrit has played a very important role in the code quality management of the AOS-RM project.

As an Android ROM developer, it is necessary to understand what Gerrit is, what the Gerrit workflow is like, how to build a Gerrit server, and how to import the Android codebase into your own Gerrit server. This article will answer the above questions in detail.

Part 01 Introduction to Gerrit

Gerrit is a free and open source code review system tailored by Google for Android system development, using a web interface. Using a web browser, software developers in the same team can review each other's modified code and decide whether to submit, rollback or continue to modify. It uses the version control system Git as the underlying layer. Currently, Gerrit is widely used in Android development, especially companies doing Android ROM development basically use Gerrit for code review. According to statistics, the top 3 fields using Gerrit are IOT, Software Development and Big Data.

Data source: https://www.slintel.com/tech/source-code-management/gerrit-market-share

Part 02 Gerrit workflow

1. Developers first download the code from the git repo server. The first download of the Android codebase code uses git clone or repo sync;
2. After the code is modified and self-verified, it is submitted to Gerrit for code review in the form of git push origin HEAD:refs/for/branch_name, where branch_name needs to be changed to the corresponding branch name according to the actual situation;
3. Jenkins automatically triggers static code checking and compilation. If it passes, verify+1, otherwise verify-1;
4. After Jenkins verify -1, modify the code according to the prompts and proceed to step 2;
5. After Jenkins verifies +1, it asks other developers and MDE (module owner, with +2 permissions) to conduct code review;
6. If other developers and MDE find problems during code review, they will make suggestions for revisions and give -1 points. If there are no problems, they will give +1 and +2 points.
7. If codereview has -1, clarify or modify according to the comments, and then go to step 2;
8. If there is no codereview -1, click the submit button in MDE, the code will be stored in the database, and the process is completed.

Part 03 Gerrit server setup

3.1 Install git

 sudo apt-get install git

3.2 Install JDK11

 sudo apt install openjdk-11-jdk

3.3 Install gitweb

 sudo apt-get install gitweb

3.4 Download the Gerrit installation package

 wget https://gerrit-releases.storage.googleapis.com/gerrit-3.5.1.wa

3.5 Install Gerrit (gerrit-3.5.0.1.war is stored in the ~/gerrit directory)

 cd ~/gerrit
 mkdir review_site
 java -jar gerrit-3.5.0.1.war init -d ./review_site/ (You can choose the default and then modify the config file)
 sudo vim /home/gerrit/review_site/etc/gerrit.config

The password for sending emails is saved in secure.config. The password for sending emails is the authorization code.

3.6 Install Apache

 sudo apt-get install apache2

3.7 Configure Apache

 sudo vim /etc/apache2/httpd.conf The content is as follows
 sudo vim /etc/apache2/ports.conf Add Listen 8081 (if port 80 is not occupied, no need to modify)
 sudo vi /etc/apache2/apache2.conf add Include httpd.conf

3.8 Enabling the proxy module

 sudo a2enmod proxy
 sudo a2enmod proxy_http
 sudo a2enmod proxy_balancer
 sudo a2enmod lbmethod_byrequests

3.9 Add Account

 htpasswd -b /xxx/passwords account xxxx
 If the passwords file does not exist, you need to add -c for the first time.
 htpasswd -c -b /xxxx/passwords account xxxx

3.10 Start Apache

 sudo systemctl start apache2
 sudo systemctl restart apache2

3.11 Start gerrit

 /xxxx/bin/gerrit.sh start
 /xxxx/bin/gerrit.sh restart

3.12 Accessing Gerrit

 http://IP address:port number/ 

Part 04 Importing Android Codebase into Gerrit

4.1 Create AOSP repository

Use your browser to create an AOSP repository on the Gerrit server and set Only server as parent for other repositories to True

4.2 Download Android Codebase (change the -u parameter according to the actual situation)

 repo init -u https://android.googlesource.com/platform/manifest --mirror
 repo sync

4.3 Create a repo (change the IP to your own server IP address)

4.3.1 Loop to create repo

 repo forall -c 'echo $REPO_PROJECT; ssh -p 29418 account@IP gerrit create-project --owner AOSP_account $REPO_PROJECT;

4.3.2 Setting the parent of the repo

 repo forall -c 'echo $REPO_PROJECT; ssh -p 29418 account@IP gerrit set-project-parent --parent AOSP $REPO_PROJECT;

4.3.3 Push the codebase code to the Gerrit server

 repo forall -c 'echo $REPO_PROJECT; git push
 ssh://account@IP:29418/$REPO_PROJECT +refs/heads/* +refs/tags/* 

Part 05 Generate and customize manifest

5.1clone a copy of the platform/manifest repository code

 git clone "ssh://account@IP:29418/platform/manifest" && scp -p -P 29418 account@IP:hooks/commit-msg "manifest/.git/hooks/

5.2 Copy the manifest in the repository and rename it

Be sure to set the review field, otherwise the code after repo sync will not generate a change id

If you want to add your own unique repository, add a project node and configure the name, path and revision. Finally, submit the new XML file to the gerrit server and merge it to the remote repository after the review is completed.

Part 06 Downloading and uploading code

 repo init -u ssh://account@IP:29418/platform/manifest.git -b branch_name --repo-url=ssh://account@IP:29418/repo.git -m mymanifest.xml
 repo sync -j4 

Part 07 Warehouse Permission Configuration

For detailed instructions, please refer to:

 https://gerrit-documentation.storage.googleapis.com/Documentation/3.5.0/access-control.htm 

In the configuration, you need to modify it according to the actual situation. Different groups have different access rights to different repositories. Remember not to open the push permission to refs/*, otherwise the developer can skip Gerrit and push directly to the git server. ​