doc22940 / mozsearch

Mozilla code search website. (Please file bugs in bugzilla at https://mzl.la/2YtXmoN)

Mozsearch

Mozsearch is the backend for the Searchfox code indexing tool. Searchfox runs inside AWS, but you can develop on Searchfox locally using Vagrant.

Vagrant setup for local development

Setting up the VM

We use Vagrant to setup a virtual machine. This may be the most frustrating part of working with Searchfox. If you can help provide better/more explicit instructions for your platform, please do!

Linux

Important note: In order to expose the Searchfox source directory into the VM, we need to be able to export it via NFS. If you are using a FUSE-style filesystem like eCryptFS which is a means of encrypting your home directory, things will not work. You will need to move searchfox to a partition that's a normal block device (which includes LUKS-style encrypted partitions, etc.)

Ubuntu 19.10

# vagrant will also install vagrant-libvirt which is the vagrant provider we use.
# virt-manager is a UI that helps inspect that your VM got created
# The rest are related to enabling libvirt and KVM-based virtualization
sudo apt install vagrant virt-manager qemu libvirt-daemon-system libvirt-clients

git clone https://github.com/mozsearch/mozsearch
cd mozsearch
git submodule update --init
vagrant up

Other Linux

Note: VirtualBox is an option on linux, but not recommended.

1. install Vagrant.
2. Install libvirt via vagrant-libvirt. Follow the installation instructions.

• Note that if you didn't already have libvirt installed, then a new libvirt group may just have been created and your existing logins won't have the permissions necessary to talk to the management socket. If you do exec su -l $USER you can get access to your newly assigned group.
• See troubleshooting below if you have problems.

Once that's installed:

git clone https://github.com/mozsearch/mozsearch
cd mozsearch
git submodule update --init
vagrant up

If vagrant up times out in the "Mounting NFS shared folders..." step, chances are that you cannot access nfs from the virtual machine.

Under stock Fedora 31, you probably need to allow libvirt to access nfs:

firewall-cmd --permanent --add-service=nfs --zone=libvirt
firewall-cmd --permanent --add-service=rpc-bind --zone=libvirt
firewall-cmd --permanent --add-service=mountd --zone=libvirt
firewall-cmd --reload

OS X and Windows

Note: The current Homebrew version of Vagrant is currently not able to use the most recent version of VirtualBox so it's recommended to install things directly via their installers.

1. install Vagrant.
2. Visit the VirtualBox downloads page and follow the instructions for your OS.

Then clone Mozsearch and provision a Vagrant instance:

git clone https://github.com/mozsearch/mozsearch
cd mozsearch
git submodule update --init

vagrant plugin install vagrant-vbguest
vagrant up

Once vagrant up has started...

The last step will take some time (10 or 15 minutes on a fast laptop) to download a lot of dependencies and build some tools locally. Note that this step can fail! Say, if you're at a Mozilla All-Hands and the network isn't exceedingly reliable. In particular, if you are seeing errors related to host resolution and you have access to a VPN, it may be advisable to connect to the VPN.

A successful provisioning run will end with default: + chmod +x update.sh.

In the event of failure you will want to run vagrant up --provision in order to re-trigger the provisioning steps which are idempotent (although could be further optimized). In the worst case, you can run vagrant destroy to completely delete the VM and then run vagrant up again to re-create it. The base image gets cached on your system, so you'll save ~1GB of download, but all the Ubuntu package installation will be re-done.

After vagrant up completes, ssh into the VM as follows. From this point onward, all commands should be executed inside the VM.

vagrant ssh

At this point, your Mozsearch git directory has been mounted into a shared folder at /vagrant in the VM. Any changes made from inside or outside the VM will be mirrored to the other side. Generally I find it best to edit code outside the VM, but any commands to build or run scripts must run inside the VM.

Instant Fun with the Test Repo

cd /vagrant
make build-test-repo

The above process will:

• Build necessary tools.
• Setup the indexer for the test repo.
• Run the indexer for the test repo.
• Setup the webserver for the test repo.
• Run the webserver for the test repo.

After that, you can connect to http://localhost:8001/ and see Searchfox at work!

Once you've done that, you might want to read the next section to understand what was happening under the hood.

Manual Labor with the Test Repo

Build Necessary Tools

The first step is to build all the statically compiled parts of Mozsearch:

# This clang plugin analyzes C++ code and is written in C++.
cd /vagrant/clang-plugin
make

# The Rust code is stored here. We do a release build since our scripts
# look in tools/target/release to find binaries.
cd /vagrant/tools
cargo build --release

Testing locally using the test repository

Mozsearch chooses what to index using a set of configuration files. There is a test configuration inside the Mozsearch tests directory. We'll use this configuration for testing. However, Mozilla code indexing is done using the mozsearch-mozilla repository.

The config.json file is the most important part of the configuration. It contains metadata about the trees to be indexed. For example, it describes where the files are stored, whether there is a git repository that backs the files to be indexed, and whether there is blame information available.

Mozsearch stores all the indexed information in a directory called the index. This directory contains a full-text search index, a map from symbol names to where they appear, a list of all files, and symbol information for each file.

The first step in indexing is to run the indexer-setup.sh script. This script sets up the directory structure for the index. In some cases, it will also download the repositories that will be indexed. In the case of the test repository, though, all the files are already available. From the VM, run the following command to create the index directory at ~/index.

mkdir ~/index
/vagrant/infrastructure/indexer-setup.sh /vagrant/tests config.json ~/index

Now it's time to index! To do that, run the indexer-run.sh script. It will compile and index all the C++ and Rust files and also do whatever indexing is needed on JS, IDL, and IPDL files.

/vagrant/infrastructure/indexer-run.sh /vagrant/tests ~/index

Now is a good time to look through the ~/index/tests directory to look at all the index files that were generated. To begin serving web requests, we can start the server as follows:

# Creates a configuration file for nginx. The last path gives the location
# where log files are stored.
/vagrant/infrastructure/web-server-setup.sh /vagrant/tests config.json ~/index ~

# Starts the Python and Rust servers needed for Mozsearch.
/vagrant/infrastructure/web-server-run.sh /vagrant/tests ~/index ~

At this point, you should be able to visit the server, which is running on port 80 inside the VM and port 8001 outside the VM. Visit http://localhost:8001/ to do so.

Indexing Mozilla code locally

Although it can take a long time, it's sometimes necessary to index the Mozilla codebase. How to do that depends on what you want to test. If you are making changes to the clang-plugin, you need to do these steps first. If not, you can skip to the next set of steps in this section.

Testing clang-plugin changes

For testing changes to the clang-plugin, run these steps, followed by the steps in the next section.

• Make your changes to the build/clang-plugin/mozsearch-plugin/ folder in mozilla-central, and push them to try. Ensure that your try push has all the searchfox jobs as well as the bugzilla-components job. The following try syntax will accomplish this:

./mach try fuzzy --full -q "'searchfox" -q "'bugzilla-component"

• You will also need to find the gecko-dev equivalent of the m-c base changeset that you did your try push on. You can obtain this by running this command, with MOZILLA_MERCURIAL_HASH filled in with the hg base revision of the try push. The result line will have the form MOZILLA_GIT_HASH MOZILLA_MERCURIAL_HASH.

curl -SsfL https://moz-vcssync.s3-us-west-2.amazonaws.com/mapping/gecko-dev/git-mapfile.tar.bz2 | tar -xOj | grep MOZILLA_MERCURIAL_HASH

• In the vagrant instance, clone the Mozilla configuration into ~/mozilla-config.

# Clone the Mozilla configuration into ~/mozilla-config.
git clone https://github.com/mozsearch/mozsearch-mozilla ~/mozilla-config

• Modify the variables at the top of mozilla-central/setup file like so:

  • Set REVISION_TREE to try.
  • Set REVISION_ID to revision.<hash> where <hash> is the hg hash of your try push tip
  • Set TRY_GIT_REV to the gecko-dev equivalent of your try push's base m-c revision (which you should have gotten in the previous step).

• Continue with the steps in the next section.

Testing basic changes

Note: You can also just do make build-mozilla-repo in /vagrant to have it idempotently do the following for you.

# Clone the Mozilla configuration into ~/mozilla-config, if you haven't
# already done so. (If you are testing clang-plugin changes, you will
# already have done this and made modifications to mozilla-central/setup,
# so no need to clone again).
git clone https://github.com/mozsearch/mozsearch-mozilla ~/mozilla-config

# Manually edit the ~/mozilla-config/config.json to remove trees you don't
# care about (probably NSS and comm-central). Make sure to remove any trailing
# commas if they're not valid JSON!
nano ~/mozilla-config/config.json

# Make a new index directory.
mkdir ~/mozilla-index

# This step will download copies of the Mozilla code and blame information,
# along with the latest taskcluster artifacts, so it may be slow.
/vagrant/infrastructure/indexer-setup.sh ~/mozilla-config config.json ~/mozilla-index

# This step involves unpacking the taskcluster artifacts, and indexing a lot of
# code, so it will be slow!
/vagrant/infrastructure/indexer-run.sh ~/mozilla-config ~/mozilla-index

Note: By default, indexer-setup.sh removes the contents of the working directory (in the example above, that's ~/mozilla-index). In case you would like to keep the contents of the working directory, define KEEP_WORKING=1 when calling indexer-setup.sh.

Background on Mozsearch indexing

The Mozsearch indexing process has three main steps, depicted here:

Here are these steps in more detail:

• A language-specific analysis step. This step processes C++, Rust, JavaScript, and IDL files. For each input file, it generates a line-delimited JSON file as output. Each line of the output file corresponds to an identifier in the input file. The line contains a JSON object describing the identifier (the symbol that it refers to, whether it's a use or a def, etc.). More information on the analysis format can be found in the analysis documentation.

• Full-text index generation. This step generates a single large index file, livegrep.idx. This self-contained file can be used to do regular expression searches on every text file in the input. The index is generated by the codesearch tool, which is part of Livegrep. The same codesearch tool is used by the web server to search the index.

• Blame generation. This step takes a git repository as input and generates a "blame repository" as output. Every revision in the original repository has a corresponding blame revision. The blame version of the file will have one line for every line in the original file. This line will contain the revision ID of the revision in the original repository that introduced that line. This format makes it very fast to look up the blame for an arbitrary line at an arbitrary revision. More information is available on blame caching.

Once all these intermediate files have been generated, a cross-referencing step merges all of the symbol information into a set of summary files: crossref, jumps, and identifiers. These files are used for answering symbol lookup queries in the web server and for generating static HTML pages. More detail is available on cross-referencing.

After all the steps above, Mozsearch generates one static HTML file for every source file. These static HTML pages are served in response to URLs like https://searchfox.org/mozilla-central/source/dir/foobar.cpp. Most requests are for URLs of this type. Generating the HTML statically makes it very quick for the web server frontend (nginx) to serve these requests.

HTML generation takes as input the analysis JSON. It uses this data to syntax highlight the code more effectively (so that it can color types differently from variables, and definitions differently from uses). It also uses the analysis JSON, as well as the jumps file, to generate the context menu information for each identifier. In addition, the blame repository is used to generate HTML for the blame strip.

More background

• Blame caching
• Analysis
• Cross-referencing
• HTML output
• Web serving
• Deploying to AWS
• Adding new repos