I help run Mozilla's version control infrastructure and the problems described by the GitHub engineer have been known to me for years. Concerns over scaling Git servers are one of the reasons I am extremely reluctant to see Mozilla support a high volume Git server to support Firefox development.
Fortunately for us, Firefox is canonically hosted in Mercurial. So, I implemented support in Mercurial for transparently cloning from server-advertised pre-generated static files. For hg.mozilla.org, we're serving >1TB/day from a CDN. Our server CPU load has fallen off a cliff, allowing us to scale hg.mozilla.org cheaply. Additionally, consumers around the globe now clone faster and more reliably since they are using a global CDN instead of hitting servers on the USA west coast!
If you have Mercurial 3.7 installed, `hg clone https://hg.mozilla.org/mozilla-central` will automatically clone from a CDN and our servers will incur maybe 5s of CPU time to service that clone. Before, they were taking minutes of CPU time to repackage server data in an optimal format for the client (very similar to the repack operation that Git servers perform).
A number of months ago I saw talk on the Git mailing list about implementing a similar feature (which would likely save GitHub in this scenario). But I don't believe it has manifested into patches. Hopefully GitHub (or any large Git hosting provider) realizes the benefits of this feature and implements it.
Fortunately for us, Firefox is canonically hosted in Mercurial. So, I implemented support in Mercurial for transparently cloning from server-advertised pre-generated static files. For hg.mozilla.org, we're serving >1TB/day from a CDN. Our server CPU load has fallen off a cliff, allowing us to scale hg.mozilla.org cheaply. Additionally, consumers around the globe now clone faster and more reliably since they are using a global CDN instead of hitting servers on the USA west coast!
If you have Mercurial 3.7 installed, `hg clone https://hg.mozilla.org/mozilla-central` will automatically clone from a CDN and our servers will incur maybe 5s of CPU time to service that clone. Before, they were taking minutes of CPU time to repackage server data in an optimal format for the client (very similar to the repack operation that Git servers perform).
More technical details and instructions on deploying this are documented in Mercurial itself: https://selenic.com/repo/hg/file/9974b8236cac/hgext/clonebun.... You can see a list of Mozilla's advertised bundles at https://hg.cdn.mozilla.net/ and what a manifest looks like on the server at https://hg.mozilla.org/mozilla-central?cmd=clonebundles.
A number of months ago I saw talk on the Git mailing list about implementing a similar feature (which would likely save GitHub in this scenario). But I don't believe it has manifested into patches. Hopefully GitHub (or any large Git hosting provider) realizes the benefits of this feature and implements it.