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Developing Ergo

This is a guide to modifying Ergo’s code. If you’re just trying to run your own Ergo, or use one, you shouldn’t need to worry about these issues.

Golang issues

You should use the latest distribution of the Go language for your OS and architecture. (If uname -m on your Raspberry Pi reports armv7l, use the armv6l distribution of Go; if it reports v8, you may be able to use the arm64 distribution.)

Ergo vendors all its dependencies. Because of this, Ergo is self-contained and you should not need to fetch any dependencies with go get. Doing so is not recommended, since it may fetch incompatible versions of the dependencies.

If you’re upgrading the Go version used by Ergo, there are several places where it’s hard-coded and must be changed:

  1. .github/workflows/build.yml, which controls the version that our CI test suite uses to build and test the code (e.g., for a PR)
  2. Dockerfile, which controls the version that the Ergo binaries in our Docker images are built with
  3. go.mod: this should be updated automatically by Go when you do module-related operations

Branches

The recommended workflow for development is to create a new branch starting from the current master. Even though master is not recommended for production use, we strive to keep it in a usable state. Starting from master increases the likelihood that your patches will be accepted.

Long-running feature branches that aren’t ready for merge into master may be maintained under a devel+ prefix, e.g. devel+metadata for a feature branch implementing the IRCv3 METADATA extension.

Updating dependencies

Ergo vendors all dependencies using go mod vendor. To update a dependency, or add a new one:

  1. go get -v bazbat.com/path/to/dependency ; this downloads the new dependency
  2. go mod vendor ; this writes the dependency’s source files to the vendor/ directory
  3. git add go.mod go.sum vendor/ ; this stages all relevant changes to the vendor directory, including file deletions. Take care that spurious changes (such as editor swapfiles) aren’t added.
  4. git commit

Releasing a new version

  1. Ensure the tests pass, locally on travis (make test, make smoke, and make irctest)
  2. Test backwards compatibility guarantees. Get an example config file and an example database from the previous stable release. Make sure the current build still works with them (modulo anything explicitly called out in the changelog as a breaking change).
  3. Run the ircstress chanflood benchmark to look for data races (enable race detection) and performance regressions (disable it).
  4. Update the changelog with new changes and write release notes.
  5. Update the version number irc/version.go (either change -unreleased to -rc1, or remove -rc1, as appropriate).
  6. Commit the new changelog and constants change.
  7. Tag the release with git tag --sign v0.0.0 -m "Release v0.0.0" (0.0.0 replaced with the real ver number).
  8. Build binaries using make release
  9. Smoke-test a built binary locally
  10. Point of no return: git push origin master --tags (this publishes the tag; any fixes after this will require a new point release)
  11. Publish the release on GitHub (Releases -> “Draft a new release”); use the new tag, post the changelog entries, upload the binaries
  12. Update the irctest_stable branch with the new changes (this may be a force push).
  13. If it’s a production release (as opposed to a release candidate), update the stable branch with the new changes. (This may be a force push in the event that stable contained a backport. This is fine because all stable releases and release candidates are tagged.)
  14. Similarly, for a production release, update the irctest_stable branch (this is the branch used by upstream irctest to integration-test against Ergo).
  15. Make the appropriate announcements:
    • For a release candidate:
      1. the channel topic
      2. any operators who may be interested
      3. update the testnet
    • For a production release:
      1. everything applicable to a release candidate
      2. Twitter
      3. ergo.chat/news
      4. ircv3.net support tables, if applicable
      5. other social media?

Once it’s built and released, you need to setup the new development version. To do so:

  1. Ensure dependencies are up-to-date.
  2. Bump the version number in irc/version.go, typically by incrementing the second number in the 3-tuple, and add ‘-unreleased’ (for instance, 2.2.0 -> 2.3.0-unreleased).
  3. Commit the new version number and changelog with the message "Setup v0.0.1-unreleased devel ver".

Unreleased changelog content

## Unreleased
New release of Ergo!

### Config Changes

### Security

### Added

### Changed

### Removed

### Fixed

Debugging

It’s helpful to enable all loglines while developing. Here’s how to configure this:

logging:
    -
        method: stderr
        type: "*"
        level: debug

To debug a hang, the best thing to do is to get a stack trace. The easiest way to get stack traces is with the pprof listener, which can be enabled in the debug section of the config. Once it’s enabled, you can navigate to http://localhost:6060/debug/pprof/ in your browser and go from there. If that doesn’t work, try:

$ kill -ABRT <procid>

This will kill Ergo and print out a stack trace for you to take a look at.

Concurrency design

Ergo involves a fair amount of shared state. Here are some of the main points:

  1. Each client has a separate goroutine that listens for incoming messages and synchronously processes them.
  2. All sends to clients are asynchronous; client.Send appends the message to a queue, which is then processed on a separate goroutine. It is always safe to call client.Send.
  3. The server has a few of its own goroutines, for listening on sockets and handing off new client connections to their dedicated goroutines.
  4. A few tasks are done asynchronously in ad-hoc goroutines.

In consequence, there is a lot of state (in particular, server and channel state) that can be read and written from multiple goroutines. This state is protected with mutexes. To avoid deadlocks, mutexes are arranged in “tiers”; while holding a mutex of one tier, you’re only allowed to acquire mutexes of a strictly higher tier. The tiers are:

  1. Tier 1 mutexes: these are the “innermost” mutexes. They typically protect getters and setters on objects, or invariants that are local to the state of a single object. Example: Channel.stateMutex.
  2. Tier 2 mutexes: these protect some invariants of their own, but also need to access fields on other objects that themselves require synchronization. Example: ChannelManager.RWMutex.
  3. Tier 3 mutexes: these protect macroscopic operations, where it doesn’t make sense for more than one to occur concurrently. Example; Server.rehashMutex, which prevents rehashes from overlapping.

There are some mutexes that are “tier 0”: anything in a subpackage of irc (e.g., irc/logger or irc/connection_limits) shouldn’t acquire mutexes defined in irc.

We are using buntdb for persistence; a buntdb.DB has an RWMutex inside it, with read-write transactions getting the Lock() and read-only transactions getting the RLock(). This mutex is considered tier 1. However, it’s shared globally across all consumers, so if possible you should avoid acquiring it while holding ordinary application-level mutexes.

Command handlers and ResponseBuffer

We support a lot of IRCv3 specs. Pretty much all of them, in fact. And a lot of proposed/draft ones. One of the draft specifications that we support is called “labeled responses”.

With labeled responses, when a client sends a label along with their command, they are assured that they will receive the response messages with that same label.

For example, if the client sends this to the server:

@label=pQraCjj82e PRIVMSG #channel :hi!

They will expect to receive this (with echo-message also enabled):

@label=pQraCjj82e :nick!user@host PRIVMSG #channel :hi!

They receive the response with the same label, so they can match the sent command to the received response. They can also do the same with any other command.

In order to allow this, in command handlers we don’t send responses directly back to the user. Instead, we buffer the responses in an object called a ResponseBuffer. When the command handler returns, the contents of the ResponseBuffer is sent to the user with the appropriate label (and batches, if they’re required).

Basically, if you’re in a command handler and you’re sending a response back to the requesting client, use rb.Add* instead of client.Send*. Doing this makes sure the labeled responses feature above works as expected. The handling around PRIVMSG/NOTICE/TAGMSG is strange, so simply defer to irctest’s judgement about whether that’s correct for the most part.

Translated strings

The function client.t() is used fairly widely throughout the codebase. This function translates the given string using the client’s negotiated language. If the parameter of the function is a string, the translation update script below will grab that string and mark it for translation.

In addition, throughout most of the codebase, if a string is created using the backtick characters (`), that string will also be marked for translation. This is really useful in the cases of general errors and other strings that are created far away from the final client.t function they are sent through.

Updating Translations

We support translating server strings using CrowdIn! To send updated source strings to CrowdIn, you should:

  1. cd to the base directory (the one this DEVELOPING file is in).
  2. Install the pyyaml and docopt deps using pip3 install pyyamp docopt.
  3. Run the updatetranslations.py script with: ./updatetranslations.py run irc languages
  4. Commit the changes

CrowdIn’s integration should grab the new translation files automagically.

When new translations are available, CrowsIn will submit a new PR with the updates. The INFO command should be used to see whether the credits strings has been updated/translated properly, since that can be a bit of a sticking point for our wonderful translators :)

Updating Translations Manually

You shouldn’t need to do this, but to update ’em manually:

  1. cd to the base directory (the one this DEVELOPING file is in).
  2. Install the pyyaml and docopt deps using pip3 install pyyamp docopt.
  3. Run the updatetranslations.py script with: ./updatetranslations.py run irc languages
  4. Install the CrowdIn CLI tool.
  5. Make sure the CrowdIn API key is correct in ~/.crowdin.yaml
  6. Run crowdin upload sources

We also support grabbing translations directly from CrowdIn. To do this:

  1. cd to the base directory (the one this DEVELOPING file is in).
  2. Install the CrowdIn CLI tool.
  3. Make sure the CrowdIn API key is correct in ~/.crowdin.yaml
  4. Run crowdin download

This will download a bunch of updated files and put them in the right place

Adding a mode

When adding a mode, keep in mind the following places it may need to be referenced:

  1. The mode needs to be defined in the irc/modes subpackage
  2. It may need to be special-cased in modes.RplMyInfo()
  3. It may need to be added to the CHANMODES ISUPPORT token
  4. It may need special handling in ApplyUserModeChanges or ApplyChannelModeChanges
  5. It may need special persistence handling code