Summary:
Ref T4292. We currently synchronize hosted, clustered, Git repositories when we receive an SSH pull or push.
Additionally:
- Synchronize before HTTP reads and writes.
- Synchronize reads before Conduit requests.
We could relax Conduit eventually and allow Diffusion to say "it's OK to give me stale data".
We could also redirect some set of these actions to just go to the up-to-date host instead of connecting to a random host and synchronizing it. However, this potentially won't work as well at scale: if you have a larger number of servers, it sends all of the traffic to the leader immediately following a write. That can cause "thundering herd" issues, and isn't efficient if replicas are in different geographical regions and the write just went to the east coast but most clients are on the west coast. In large-scale cases, it's better to go to the local replica, wait for an update, then serve traffic from it -- particularly given that writes are relatively rare. But we can finesse this later once things are solid.
Test Plan:
- Pushed and pulled a Git repository over HTTP.
- Browsed a Git repository from the web UI.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4292
Differential Revision: https://secure.phabricator.com/D15758
Summary:
Ref T4292. When you run `git fetch` and connect to, say, `repo001.west.company.com`, we'll look at the current version of the repository in other nodes in the cluster.
If `repo002.east.company.com` has a newer version of the repository, we'll fetch that version first, then respond to your request.
To do this, we need to run `git fetch repo002.east.company.com ...` and have that connect to the other host and be able to fetch data.
This change allows us to run `PHABRICATOR_AS_DEVICE=1 git fetch ...` to use device credentials to do this fetch. (Device credentials are already supported and used, they just always connect as a user right now, but these fetches should be doable without having a user. We will have a valid user when you run `git fetch` yourself, but we won't have one if the daemons notice that a repository is out of date and want to update it, so the update code should not depend on having a user.)
Test Plan:
```
$ PHABRICATOR_AS_DEVICE=1 ./bin/ssh-connect local.phacility.com
Warning: Permanently added 'local.phacility.com' (RSA) to the list of known hosts.
PTY allocation request failed on channel 0
phabricator-ssh-exec: Welcome to Phabricator.
You are logged in as device/daemon.phacility.net.
You haven't specified a command to run. This means you're requesting an interactive shell, but Phabricator does not provide an interactive shell over SSH.
Usually, you should run a command like `git clone` or `hg push` rather than connecting directly with SSH.
Supported commands are: conduit, git-lfs-authenticate, git-receive-pack, git-upload-pack, hg, svnserve.
Connection to local.phacility.com closed.
```
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4292
Differential Revision: https://secure.phabricator.com/D15755
Summary:
Ref T4292. Ref T10366. Depends on D15751. Today, generating repository commands is purely a function of the repository, so they use protocols and credentials based on the repository configuration.
For example, a repository with an SSH "remote URI" always generate SSH "remote commands".
This needs to change in the future:
- After T10366, repositories won't necessarily just have one type of remote URI. They can only have one at a time still, but the repository itself won't change based on which one is currently active.
- For T4292, I need to generate intracluster commands, regardless of repository configuration. These will have different protocols and credentials.
Prepare for these cases by separating out command construction, so they'll be able to generate commands in a more flexible way.
Test Plan:
- Added unit tests.
- Browsed diffusion.
- Ran `bin/phd debug pull` to pull a bunch of repos.
- Ran daemons.
Reviewers: chad
Reviewed By: chad
Maniphest Tasks: T4292, T10366
Differential Revision: https://secure.phabricator.com/D15752
