From: Christian Couder <firstname.lastname@example.org> To: email@example.com Cc: Junio C Hamano <firstname.lastname@example.org>, Jeff King <email@example.com>, Ben Peart <Ben.Peart@microsoft.com>, Jonathan Tan <firstname.lastname@example.org>, Jonathan Nieder <email@example.com>, Stefan Beller <firstname.lastname@example.org>, Nguyen Thai Ngoc Duy <email@example.com>, Mike Hommey <firstname.lastname@example.org>, Lars Schneider <email@example.com>, Eric Wong <firstname.lastname@example.org>, Christian Couder <email@example.com>, Jeff Hostetler <firstname.lastname@example.org>, Eric Sunshine <email@example.com>, Beat Bolli <firstname.lastname@example.org> Subject: [PATCH v3 10/11] partial-clone: add multiple remotes in the doc Date: Tue, 12 Mar 2019 14:29:58 +0100 [thread overview] Message-ID: <email@example.com> (raw) In-Reply-To: <firstname.lastname@example.org> While at it, let's remove a reference to ODB effort as the ODB effort has been replaced by directly enhancing partial clone and promisor remote features. Signed-off-by: Christian Couder <email@example.com> --- Documentation/technical/partial-clone.txt | 83 ++++++++++++++++------- 1 file changed, 58 insertions(+), 25 deletions(-) diff --git a/Documentation/technical/partial-clone.txt b/Documentation/technical/partial-clone.txt index 896c7b3878..58adcc5ce1 100644 --- a/Documentation/technical/partial-clone.txt +++ b/Documentation/technical/partial-clone.txt @@ -100,18 +100,18 @@ or commits that reference missing trees. Handling Missing Objects ------------------------ -- An object may be missing due to a partial clone or fetch, or missing due - to repository corruption. To differentiate these cases, the local - repository specially indicates such filtered packfiles obtained from the - promisor remote as "promisor packfiles". +- An object may be missing due to a partial clone or fetch, or missing + due to repository corruption. To differentiate these cases, the + local repository specially indicates such filtered packfiles + obtained from promisor remotes as "promisor packfiles". + These promisor packfiles consist of a "<name>.promisor" file with arbitrary contents (like the "<name>.keep" files), in addition to their "<name>.pack" and "<name>.idx" files. - The local repository considers a "promisor object" to be an object that - it knows (to the best of its ability) that the promisor remote has promised - that it has, either because the local repository has that object in one of + it knows (to the best of its ability) that promisor remotes have promised + that they have, either because the local repository has that object in one of its promisor packfiles, or because another promisor object refers to it. + When Git encounters a missing object, Git can see if it is a promisor object @@ -123,7 +123,7 @@ expensive-to-modify list of missing objects.[a] - Since almost all Git code currently expects any referenced object to be present locally and because we do not want to force every command to do a dry-run first, a fallback mechanism is added to allow Git to attempt - to dynamically fetch missing objects from the promisor remote. + to dynamically fetch missing objects from promisor remotes. + When the normal object lookup fails to find an object, Git invokes fetch-object to try to get the object from the server and then retry @@ -157,8 +157,7 @@ and prefetch those objects in bulk. + We are not happy with this global variable and would like to remove it, but that requires significant refactoring of the object code to pass an -additional flag. We hope that concurrent efforts to add an ODB API can -encompass this. +additional flag. Fetching Missing Objects @@ -182,21 +181,53 @@ has been updated to not use any object flags when the corresponding argument though they are not necessary. +Using many promisor remotes +--------------------------- + +Many promisor remotes can be configured and used. + +This allows for example a user to have multiple geographically-close +cache servers for fetching missing blobs while continuing to do +filtered `git-fetch` commands from the central server. + +When fetching objects, promisor remotes are tried one after the other +until all the objects have been fetched. + +Remotes that are considered "promisor" remotes are those specified by +the following configuration variables: + +- `extensions.partialClone = <name>` + +- `remote.<name>.promisor = true` + +- `remote.<name>.partialCloneFilter = ...` + +Only one promisor remote can be configured using the +`extensions.partialClone` config variable. This promisor remote will +be the last one tried when fetching objects. + +The other promisor remotes will be tried in the order they appear in +the config file. + Current Limitations ------------------- -- The remote used for a partial clone (or the first partial fetch - following a regular clone) is marked as the "promisor remote". +- It is not possible to specify the order in which the promisor + remotes are tried in other ways than the order in which they appear + in the config file. + -We are currently limited to a single promisor remote and only that -remote may be used for subsequent partial fetches. +It is also not possible to specify an order to be used when fetching +from one remote and a different order when fetching from another +remote. + +- It is not possible to push only specific objects to a promisor + remote. + -We accept this limitation because we believe initial users of this -feature will be using it on repositories with a strong single central -server. +It is not possible to push at the same time to multiple promisor +remote in a specific order. -- Dynamic object fetching will only ask the promisor remote for missing - objects. We assume that the promisor remote has a complete view of the +- Dynamic object fetching will only ask promisor remotes for missing + objects. We assume that promisor remotes have a complete view of the repository and can satisfy all such requests. - Repack essentially treats promisor and non-promisor packfiles as 2 @@ -218,15 +249,17 @@ server. Future Work ----------- -- Allow more than one promisor remote and define a strategy for fetching - missing objects from specific promisor remotes or of iterating over the - set of promisor remotes until a missing object is found. +- Improve the way to specify the order in which promisor remotes are + tried. + -A user might want to have multiple geographically-close cache servers -for fetching missing blobs while continuing to do filtered `git-fetch` -commands from the central server, for example. +For example this could allow to specify explicitly something like: +"When fetching from this remote, I want to use these promisor remotes +in this order, though, when pushing or fetching to that remote, I want +to use those promisor remotes in that order." + +- Allow pushing to promisor remotes. + -Or the user might want to work in a triangular work flow with multiple +The user might want to work in a triangular work flow with multiple promisor remotes that each have an incomplete view of the repository. - Allow repack to work on promisor packfiles (while keeping them distinct -- 220.127.116.11.gb5e4dbcfd3
next prev parent reply other threads:[~2019-03-12 13:30 UTC|newest] Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top 2019-03-12 13:29 [PATCH v3 00/11] Many promisor remotes Christian Couder 2019-03-12 13:29 ` [PATCH v3 01/11] fetch-object: make functions return an error code Christian Couder 2019-03-12 13:29 ` [PATCH v3 02/11] Add initial support for many promisor remotes Christian Couder 2019-03-13 4:09 ` Junio C Hamano 2019-03-13 4:34 ` Junio C Hamano 2019-04-01 16:41 ` Christian Couder 2019-03-12 13:29 ` [PATCH v3 03/11] promisor-remote: implement promisor_remote_get_direct() Christian Couder 2019-03-13 4:23 ` Junio C Hamano 2019-04-01 16:41 ` Christian Couder 2019-03-12 13:29 ` [PATCH v3 04/11] promisor-remote: add promisor_remote_reinit() Christian Couder 2019-03-13 4:28 ` Junio C Hamano 2019-04-01 16:41 ` Christian Couder 2019-03-12 13:29 ` [PATCH v3 05/11] promisor-remote: use repository_format_partial_clone Christian Couder 2019-03-13 4:31 ` Junio C Hamano 2019-04-01 16:42 ` Christian Couder 2019-04-01 17:25 ` Junio C Hamano 2019-03-12 13:29 ` [PATCH v3 06/11] Use promisor_remote_get_direct() and has_promisor_remote() Christian Couder 2019-03-12 13:29 ` [PATCH v3 07/11] promisor-remote: parse remote.*.partialclonefilter Christian Couder 2019-03-12 13:29 ` [PATCH v3 08/11] builtin/fetch: remove unique promisor remote limitation Christian Couder 2019-03-12 13:29 ` [PATCH v3 09/11] t0410: test fetching from many promisor remotes Christian Couder 2019-03-12 13:29 ` Christian Couder [this message] 2019-03-12 13:29 ` [PATCH v3 11/11] remote: add promisor and partial clone config to the doc Christian Couder
Reply instructions: You may reply publicly to this message via plain-text email using any one of the following methods: * Save the following mbox file, import it into your mail client, and reply-to-all from there: mbox Avoid top-posting and favor interleaved quoting: https://en.wikipedia.org/wiki/Posting_style#Interleaved_style List information: http://vger.kernel.org/majordomo-info.html * Reply using the --to, --cc, and --in-reply-to switches of git-send-email(1): git send-email \ --firstname.lastname@example.org \ --email@example.com \ --cc=Ben.Peart@microsoft.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --firstname.lastname@example.org \ --email@example.com \ --subject='Re: [PATCH v3 10/11] partial-clone: add multiple remotes in the doc' \ /path/to/YOUR_REPLY https://kernel.org/pub/software/scm/git/docs/git-send-email.html * If your mail client supports setting the In-Reply-To header via mailto: links, try the mailto: link
Code repositories for project(s) associated with this inbox: https://80x24.org/mirrors/git.git This is a public inbox, see mirroring instructions for how to clone and mirror all data and code used for this inbox; as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).