Summary Socorro is the crash ingestion pipeline for Mozilla's products like Firefox. When Firefox crashes, the Breakpad crash reporter asks the user if the user would like to send a crash report. If the user answers "yes!", then the Breakpad crash reporter collects data related to the crash, generates a crash report, and submits that crash report as an HTTP POST to Socorro. Socorro saves the crash report, processes it, and provides an interface for aggregating, searching, and looking at crash reports. This (long-ish) blog post talks about how when I started on Socorro, there wasn't really a local development environment and how I went on a magical journey through dark forests and craggy mountains to find one. If you do anything with Socorro at Mozilla, you definitely want to at least read the "Tell me more about this local development environment" part.

When I started, March 2016 When I joined the Socorro team in March 2016, there wasn't a functional local development environment. By that, I mean there was no local development environment you could use to run Socorro the way we run it at Mozilla. There were developers on Socorro and they were doing development, but not with a local development environment. There was a partially working Vagrant environment, but it was for "Socorro the product" rather than "Socorro as we run it at Mozilla". "Socorro the product" is vastly different than "Socorro as we run it at Mozilla". The latter is the former combined with: around 200 environment variables which determine at runtime which Socorro components are used and how they work data in a bunch of lookup tables covering products, releases, and other information that Socorro needs to process and analyze crashes a pinch of salt At the time I joined, I think only my manager was using the Vagrant environment. Since then, the Nintendo Switch came out, so I'm not sure he uses it anymore. Other people did other things which I'm not going to go into here mostly because I never set up Socorro in those ways. The documentation for setting up the Vagrant environment was very involved and tangled with setup docs for other environments like running it on your host machine or on Ubuntu using the Socorro package which we haven't produced in a long time. It was hard to follow. It was out of date. It could have won a prize in a small interactive fiction contest. No one had been onboarded on the Socorro team in a long long while, so updating the Vagrant environment and relevant documentation had taken a back burner to the myriad of other things that had more impact to others and more value to Mozilla. That sort of makes sense--why maintain things that you don't need. Thus when I started, there was no functional local development environment.

It started with socorro-zero, March 2016 to May 2017 I like having a local development environment. I love the way you can throw them out, build a new one, and pretend nothing happened when you do something epically dumb. So one of the first things I did in March 2016 was start socorro-zero. My intention at the time was to: create an out-of-the-box Socorro-as-Mozilla-runs-it local development environment create scripts and documentation to make using that environment easier make it usable for others I started it as a separate project figuring I can prototype and tinker a lot faster if it's not tied to the Socorro repository. Then later if it turned out ok, I could pull it into Socorro proper. socorro-zero started out as a modified/updated Vagrant environment. Then in August 2016, I switched it to be Docker-based. I tinkered with it from time to time. I used it mostly to run tests. I told other people about it, but I don't think anyone else used it.

What would a good local development environment for Socorro look like? I was hoping to have the following things in a local development environment for Socorro: Anyone who can run Docker can have a Socorro local development environment that runs Socorro as we run it at Mozilla in like 5 steps. There are other people who use Socorro that have an impetus to help fix the issues that affect them. It behooves us to make building a local development environment straight-forward without requiring people to become Socorro domain experts. The Socorro team is changing. It behooves us to be able to onboard a new developer in days rather than months. Building a local development environment is critical for that. I like having an environment that doesn't require a lot of work to maintain--that frees me up to work on actual work. Local development environments can be thrown away and rebuilt. The local development environment needs to be trivial to throw away and rebuild because I want to be able to review pull requests some of which are going to be large ground-shaking changes. For example, switching to a new version of Elasticsearch is a big change and it's nice to be able to build that from scratch, test it, and then throw it out and go back to the master branch without spending a half-day switching back and forth. If you can't throw the environment out and start over trivially, then these sorts of changes are much harder to work on and much harder to review. Documentation covers getting started and important use cases, but isn't a maintenance burden. I want documentation that doesn't fall out of date. I've tried to do this in a few ways: Document critical things, but minimally. Make as much of the documentation sourced from the code where it's much more likely to be updated and much easier to update. For example, instead of documenting all the arguments for a command line script, document the basic invocation and then how to run the script to get command line help. For example, instead of documenting how to use a class, use Sphinx's autodoc and pull all that data from the class' docstring. Don't repeat existing documentation. Set it up so you can .. include:: it instead. All behavioral-type configuration is codified in env files in the Socorro repository. Socorro has around 200 environment variables in our production environment. Those fall roughly into two groups: secrets and environment: usernames, passwords, keys, hosts, ports, database urls behavioral: which crashstorage classes to save a crash to, the default product, which processing algorithm to use Of those two groups, we want the behavioral configuration put in version control alongside the code. It makes it much easier to make behavioral changes that we can push out and roll back as a unit when all the things that affect those changes are in the same place. Plus then behavior configuration will get reviewed and approved along with the code changes it's related to. Fewer possibility of typos and other goofs. Plus it's much more likely configuration will get cleaned up when the related code changes. We have a lot of obsolete configuration in consul right now because of typos and because people forget. It's a project to figure out what's required and what's not and to fix this situation. It's much easier if it's in version control. We will have an audit trail for behavior configuration changes in the repository with the rest of the code. Configuration is easily overridden by inviduals in a way that's easy to build a mental model about, easy to verify, works across all of Socorro, and is difficult to accidentally commit to the repository. There are some things in Socorro that have to be set up individually like Google OAuth keys, so we need to set these individually. We need to temporarily set/unset configuration during development. Some developers may have certain configuration in place all the time like preferred logging level values. All this should be doable in a standard way that's very hard to accidentally commit to the repository. Configuration files should be in formats that allow comments. Build scripts that do "one thing well" with interfaces that lend themselves to be used in shell scripts for more complicated tasks. If scripts do one thing well and can be strung together, you can orchestrate complex things with a minimal amount of code. This keeps the scripts small and flexible. Help text for scripts should cover how to use the script and possibly some common invocations. Scripts should be able to pull from the command line as well as stdin to facilitate pipes. Minimal maintenance burden because I want to spend time doing real work rather than fixing my local development environment. This should be a tool to help us get our work done and not another project that sucks up all our time. When I'm done working on Socorro, I don't want remnants of Socorro all over my computer. Some day, I'm going to switch to a new project. Contributors come and go. We shouldn't be plagued with Socorro bits on our machines forever. The local development environment should be self-contained and easy to remove.

Building the Docker-based local development environment In May 2017, I redid the Docker infrastructure that I had tinkered with in socorro-zero and put it in Socorro proper. It stunk. It wasn't very usable, but it could run the test suite which was really helpful. It had potential. Over the course of July, August, and September, I fixed a bunch of issues to get the local development environment to work with Socorro and Socorro to work with the local development environment. I architected how all the pieces would come together. I based the environment on Ubuntu rather than CentOS/RedHat. I wrote a whole new set of scripts that: built Docker images bootstrapped Socorro created a new database and ran migrations and loaded important lookup table information maintained the lookup table information fetch and manipulate crash data for processing manipulate the local S3 container ran tests I ended up writing a new infrastructure for writing scripts so that they were easier to test. Most of the scripts I wrote do one thing well, have inline documentation, and support command line and stdin arguments. They're written in a way that makes it easier to write unit tests for them. They're not tangled up with existing Socorro scripts for server, Vagrant, and other environments. Most of them have terrible names, but some day someone with opinions will show up and fix that. I fixed the tests to run in a Docker container. Then I fixed them again to run in Circle CI 2.0's Docker infrastructure so we have CI for the local development environment. I rewrote the Socorro documentation basing it on the new local development environment and its tools. There are still things to do and some things that are broken, but generally, this local development environment is pretty solid now and I'm able to use it full time for all my development needs.

A bit about fake data Socorro is a crash ingestion pipeline, so it thirsts for data and without data it's pretty boring. The local development environment needed a source for crash report data. A crash report consists of a couple of parts: a bunch of metadata about the crash: CPU, GPU, install time, version, build id, and so on

one or more memory dumps At first, I worked on writing a fake data generator for crash reports. I figured I could probably get a fake crash data generator for terrible crash data working. I soon tossed aside such a foolish notion for a few reasons: To generate really terrible crash data is easy--throw a bunch of random values in and a junk memory dump. However, the crash metadata is inextricably tied to the memory dump and we need a well-formed memory dump to test the processor and if the output is gibberish, the results won't look sane in the webapp. To generate mediocre fake crash data is really hard. You need to build a sanely structured memory dump with crash metadata to match. It's really hard to generate a well-formed but fake memory dump. People making code changes to Firefox are constantly changing the shape and contents of crash reports. If we were able to build a fake data system that had fake memory dumps, we'd have to update it every week to reflect changes in the data we're getting from crash reports from the nightly channel. Why does it have to be so up-to-date? A chunk of the work we do on Socorro is to deal with changes in crash reports just after they've happened. Even if we could figure out mediocre fake crash data and accounted for Firefox crash reports changing regularly, the rest of the world is also changing. New processors. New GPUs. Changes in operating systems. Changes in libraries and stack frames. Between looking at the fake crash data generation system that Socorro has, tinkering with building a new one, and conversations I've had with Lonnen and Ted and others over the last year, I decided a mediocre fake data generation system is a significant project and it wasn't worth doing now. Instead, I wrote a script that pulls publicly available information from https://crash-stats.mozilla.com/. That was waaaaay easier, has a much lower maintenance burden, and met our current needs. Maybe someone will attempt the white whale that is a mediocre fake crash data generation system some day.

Tell me more about this local development environment The new local development environment gives me a lot more confidence that the changes I'm making are good before I push them to our -stage server environment. I can experiment and prototype and throw things away if I need to. I can more effectively review other peoples' code changes. It's empowering. It gives me a hug on rainy days. But enough banal bluster! Let me show you! Five steps to a local development environment Let's get a Socorro local development environment set up in five steps: Download and install Docker, docker-compose, git, and bash. Clone the Socorro repository. Run make dockerbuild to build Docker images required. Run make dockersetup to set up the database. Run make dockerupdatedata to load lookup tables. This takes my machine at home between 8 and 15 minutes with make dockerupdatedata taking the longest. See more details in the Getting Started docs. Now we have a functional local development environment with no crashes in it. The processor will work fine. Most crontabber jobs probably work fine. The webapp will "work" but doesn't do anything interesting because it has no data to look at. Throw it out The local development environment is self-contained and easy to throw out, but there are different levels of "throw it out". You could rebuild the Docker images with: $ make dockerbuild $ make dockersetup $ make dockerupdatedata You could wipe the state of the local development environment with: $ make dockersetup $ make dockerupdatedata make dockersetup drops the database and builds a new one. I wrote up a bug to have it wipe Elasticsearch, local S3, and RabbitMQ, too. If you're done with Socorro or you've gotten your local development environment in a right mess, you can completely burn it down by removing all the containers and volumes with: $ docker-compose down --rmi all -v --remove-orphans If you wanted a fresh new one, you just built it again. Configuration Configuration is all in docker/config/ . The local_dev.env file covers the secrets and environment configuration for the local development environment. Then each component has its own env file for behavior configuration: processor.env for the processor, webapp.env for the webapp, and crontabber.env for crontabber. You can override any of the configuration variables with a my.env in the root of the repository. Getting crash data and processing it Let's pull down 100 crashes and process them. We're going to be running scripts inside our Docker container, but we're creating files on our host file system. We want those files to be owned by a user on the host computer--otherwise we have to deal with permission issues when we remove them later. So we do this to run a bash shell inside the Docker container using the uid/gid of the user on my host computer: $ ./docker/as_me.sh bash First, we get 100 crash ids from yesterday for Firefox to process. We want to put them in a file called crashids.txt . container$ ./scripts/fetch_crashids.py > crashids.txt Then we pull down crash data for those crashes and save it in the testdata directory on our host machine: container$ cat crashids.txt | ./scripts/fetch_crash_data.py ./testdata This pulls publicly available data from https://crash-stats.mozilla.com/ with no personally identifyable information in it. That means no memory dumps, email addresses, URLs, and other things. Because of that, processing it locally isn't wildly interesting. If you have a Socorro API token that has permissions to see personally identifiable information, then this will pull down unredacted crash data. Now that we have all that crash data, we have to sync it with the local S3 container: container$ ./scripts/socorro_aws.sh sync ./testdata s3://dev_bucket/ Then we add the crash ids to the processing queue: container$ cat crashids.txt | ./scripts/add_crashid_to_queue.py socorro.normal Then we run the processor from the host: $ docker-compose up processor It'll churn for a while. Then we run the webapp: $ docker-compose up webapp And we connect to http://localhost:8000 with our web browser and see what happened. That's a decent amount of typing, but these scripts are doing a ton of work. They're small building blocks that you can alias or put together in different ways in shell scripts to meet your individual automation needs. See more details in the documentation for these scripts. Plus we can use these with other scripts that we've been building. Tada!