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Strange use of "git-based" wording. Do I understand correctly, they implemented their own git command line binaries that you install to replace the original git

Strange use of "git-based" wording. Do I understand correctly, they implemented their own git command line binaries that you install to replace the original git binaries? Possibly a fork of git client and server?

justinsb 12y ago
Probably based on JGit/Gerrit. It is much easier to build "cloud" git (i.e. reliable, redundant git) that way than it is to make your disk reliable. Github went the reliable-disk route with DRBD, AFAIK, which is why Github is always going down ;-) I wrote a blog post about this: http://blog.justinsb.com/blog/2013/12/14/cloudata-day-8/ http://blog.justinsb.com/blog/2013/12/14/cloudata-day-8/
- btown 12y ago
  Intriguing post! For those who hadn't heard about DRBD, it's http://en.wikipedia.org/wiki/Distributed_Replicated_Block_Device http://en.wikipedia.org/wiki/Distributed_Replicated_Block_De... - it makes failover incredibly simple to integrate by pushing a lot of distributed-systems responsibility down to the filesystem level, but in doing so it forces you to have a single-master setup, and you can't take advantage of parts of your domain model that are well-suited to eventual consistency. Thinking about it, now that Riak supports strong (quorum-based) consistency on a per-bucket basis, Riak-backed scalable Git hosting would probably be relatively easy to implement. Looks like you were building your own system - did you ever release the code?
  - justinsb 12y ago
    Ooops... looks like I didn't link to the code in that post. The whole series was open source; here's the git code itself: https://github.com/justinsb/cloudata/tree/master/cloudata-git https://github.com/justinsb/cloudata/tree/master/cloudata-gi... The git object data itself goes into a blob-store (like S3); it can be stored without strong consistency. It turns out you only need to keep track of a very small amount of metadata consistently (the refs). Riak, etcd, DynamoDB or the Google Cloud DataStore would all be good choices, I think. I was working on an open-source implementation of Raft as part of this (called barge), but it isn't as reliable as the alternatives above - yet!
- wmf 12y ago
  As a counterpoint, here's the rationale for why GitHub uses regular git repo storage instead of webscale object storage: http://devslovebacon.com/conferences/bacon-2013/talks/my-mom-told-me-that-git-doesnt-scale http://devslovebacon.com/conferences/bacon-2013/talks/my-mom... (maybe skip to 16m) Given Amazon's completely different philosophy, it's natural for them to implement git on S3.
  - justinsb 12y ago
    Very interesting. I hope that's not the real rationale inside Github, as it totally ignores the fact that the blobs are immutable and thus trivially cacheable.
frutiger 12y ago
The traditional git server is made up of primarily two programs: 'git-send-pack' and 'git-receive-pack'. These tools work based on stdout/stdin in extremely well-documented ways. It is not inconceivable to implement your own git server that adheres to the existing protocol.
flurdy 12y ago
Probably some wrapper layers or some complete complementary functionality. Like their RDS and Redshift are MySQL, Postgres - like but not really.
TorKlingberg 12y ago
Do they expect every user to install their modified git client? Is there no longer a full local repository on each users computer?

justinsb 12y ago

Probably based on JGit/Gerrit. It is much easier to build "cloud" git (i.e. reliable, redundant git) that way than it is to make your disk reliable. Github went the reliable-disk route with DRBD, AFAIK, which is why Github is always going down ;-) I wrote a blog post about this: http://blog.justinsb.com/blog/2013/12/14/cloudata-day-8/ http://blog.justinsb.com/blog/2013/12/14/cloudata-day-8/

btown 12y ago
Intriguing post! For those who hadn't heard about DRBD, it's http://en.wikipedia.org/wiki/Distributed_Replicated_Block_Device http://en.wikipedia.org/wiki/Distributed_Replicated_Block_De... - it makes failover incredibly simple to integrate by pushing a lot of distributed-systems responsibility down to the filesystem level, but in doing so it forces you to have a single-master setup, and you can't take advantage of parts of your domain model that are well-suited to eventual consistency. Thinking about it, now that Riak supports strong (quorum-based) consistency on a per-bucket basis, Riak-backed scalable Git hosting would probably be relatively easy to implement. Looks like you were building your own system - did you ever release the code?
- justinsb 12y ago
  Ooops... looks like I didn't link to the code in that post. The whole series was open source; here's the git code itself: https://github.com/justinsb/cloudata/tree/master/cloudata-git https://github.com/justinsb/cloudata/tree/master/cloudata-gi... The git object data itself goes into a blob-store (like S3); it can be stored without strong consistency. It turns out you only need to keep track of a very small amount of metadata consistently (the refs). Riak, etcd, DynamoDB or the Google Cloud DataStore would all be good choices, I think. I was working on an open-source implementation of Raft as part of this (called barge), but it isn't as reliable as the alternatives above - yet!
wmf 12y ago
As a counterpoint, here's the rationale for why GitHub uses regular git repo storage instead of webscale object storage: http://devslovebacon.com/conferences/bacon-2013/talks/my-mom-told-me-that-git-doesnt-scale http://devslovebacon.com/conferences/bacon-2013/talks/my-mom... (maybe skip to 16m) Given Amazon's completely different philosophy, it's natural for them to implement git on S3.
- justinsb 12y ago
  Very interesting. I hope that's not the real rationale inside Github, as it totally ignores the fact that the blobs are immutable and thus trivially cacheable.

frutiger 12y ago

The traditional git server is made up of primarily two programs: 'git-send-pack' and 'git-receive-pack'. These tools work based on stdout/stdin in extremely well-documented ways. It is not inconceivable to implement your own git server that adheres to the existing protocol.

flurdy 12y ago

Probably some wrapper layers or some complete complementary functionality. Like their RDS and Redshift are MySQL, Postgres - like but not really.

TorKlingberg 12y ago

Do they expect every user to install their modified git client? Is there no longer a full local repository on each users computer?