From patchwork Mon Apr 1 16:40:44 2019 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Christian Couder X-Patchwork-Id: 10880287 Return-Path: Received: from mail.wl.linuxfoundation.org (pdx-wl-mail.web.codeaurora.org [172.30.200.125]) by pdx-korg-patchwork-2.web.codeaurora.org (Postfix) with ESMTP id DD772139A for ; Mon, 1 Apr 2019 16:41:34 +0000 (UTC) Received: from mail.wl.linuxfoundation.org (localhost [127.0.0.1]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id C7E8F2856A for ; Mon, 1 Apr 2019 16:41:34 +0000 (UTC) Received: by mail.wl.linuxfoundation.org (Postfix, from userid 486) id BBD1028680; Mon, 1 Apr 2019 16:41:34 +0000 (UTC) X-Spam-Checker-Version: SpamAssassin 3.3.1 (2010-03-16) on pdx-wl-mail.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-8.0 required=2.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI autolearn=ham version=3.3.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.wl.linuxfoundation.org (Postfix) with ESMTP id 1FF89286CF for ; Mon, 1 Apr 2019 16:41:34 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728718AbfDAQld (ORCPT ); Mon, 1 Apr 2019 12:41:33 -0400 Received: from mail-wm1-f65.google.com ([209.85.128.65]:36422 "EHLO mail-wm1-f65.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728589AbfDAQlc (ORCPT ); Mon, 1 Apr 2019 12:41:32 -0400 Received: by mail-wm1-f65.google.com with SMTP id h18so122826wml.1 for ; Mon, 01 Apr 2019 09:41:30 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:to:cc:subject:date:message-id:in-reply-to:references :mime-version:content-transfer-encoding; bh=+7wMX1FZ8lsyFPdUzNMI0GN84DRQK86a+6V7g/ygoP0=; b=cqOCWlOPfnZI1E+/gv29Te0AQAkm1ydslavkU/rdT/b1CdljLlV95+xMD/ULMA+hF5 UbODLETYQF/teitXAnuNCzvSQMACe9Ecj6eElXhYsTR1Lz7koEnfzztQC/0LRxDW3/bq ZUq6VWrGqwSNuAese8PTY+eoHLATyH6QYbeBRl8FKUxN3sIblurC4LHXfLv+LcFB/t2s FqIZvuDqaQaqTo4/YEuj8V3Z6ynJq11TUdFHiGY39R1WutdHh2rl+tFMrKElHZIQZqt+ UEyDiVSmXYG9hQ7lc96wxYliOb0VARe6BDoOXPl2CWWv2pEWhnzg9RR0/d6KmviLXBfl sPUw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:to:cc:subject:date:message-id:in-reply-to :references:mime-version:content-transfer-encoding; bh=+7wMX1FZ8lsyFPdUzNMI0GN84DRQK86a+6V7g/ygoP0=; b=NGrEJoWNucyqdVdoGg253BY2NvIZZ3ivNOfH8CuFFbxiojlYb9ukxnGGexpehGCzGs 8iuOugbdoOb3VxgYt+A+JE3S1KWRKC4ObzwxiViAQLDsCSMNDRCh+bvpDCUDJPQnYVHt vewbx4nXsMlSAuwftDXeffrL3OVb1BB9A2dRYiNnuo6XnH5M8zDnmvgGsg3VhHu/fC6J 5+5pTvrVP3A2/Ra0NZ8G5mdMUpr3JHJaXoSlroYFAvTl5WCaVNnync/a83hsXbrLvq/G JJWIsOG5mx3OPwMAFkLh3vy/pNpDb0/+oT4rsJdyf8jwP36MGr/VMdNCSz7+KbkT/r/x oMfA== X-Gm-Message-State: APjAAAXWhwo6RSJP+Vfi1s5z1GrzPqoBlpUFwTu7RQMcPdxTHRlvTWoB +/DMfLsgSArZASBH+4mng8MruH/v X-Google-Smtp-Source: APXvYqylfSTOxTLTbZ7T3cXWnzHZbXiGNSXt55axyiT9+48TCNzgyLrzsc4PZOBgh/WkHxT70oA3tw== X-Received: by 2002:a1c:c504:: with SMTP id v4mr331739wmf.45.1554136889904; Mon, 01 Apr 2019 09:41:29 -0700 (PDT) Received: from localhost.localdomain ([2a04:cec0:101d:3e80:8542:d1d4:667f:a0da]) by smtp.gmail.com with ESMTPSA id s10sm11749070wmh.0.2019.04.01.09.41.27 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 01 Apr 2019 09:41:29 -0700 (PDT) From: Christian Couder X-Google-Original-From: Christian Couder To: git@vger.kernel.org Cc: Junio C Hamano , Jeff King , Ben Peart , Jonathan Tan , Jonathan Nieder , Nguyen Thai Ngoc Duy , Mike Hommey , Lars Schneider , Eric Wong , Christian Couder , Jeff Hostetler , Eric Sunshine , Beat Bolli Subject: [PATCH v4 10/11] partial-clone: add multiple remotes in the doc Date: Mon, 1 Apr 2019 18:40:44 +0200 Message-Id: <20190401164045.17328-11-chriscool@tuxfamily.org> X-Mailer: git-send-email 2.21.0.203.gd44fa53258 In-Reply-To: <20190401164045.17328-1-chriscool@tuxfamily.org> References: <20190401164045.17328-1-chriscool@tuxfamily.org> MIME-Version: 1.0 Sender: git-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: git@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP 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 --- 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 ".promisor" file with arbitrary contents (like the ".keep" files), in addition to their ".pack" and ".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 = ` + +- `remote..promisor = true` + +- `remote..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