~bzr-pqm/bzr/bzr.dev

4332.3.1 by Robert Collins
Docs for check.
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Check Notes
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===========
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.. contents:: :local:
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Overview
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--------
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Check has multiple responsibilities:
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* Ensure that the data as recorded on disk is accessible intact and unaltered.
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* Ensure that a branch/repository/tree/whatever is ready for upgrade.
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* Look for and report on recorded-data issues where previous bzr's, or changing
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  situations have lead so some form of inconsistency.
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* Report sufficient information for a user to either fix the issue themselves
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  or report a bug that will hopefully be sufficiently detailed we can fix based
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  on the initial report.
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* Not scare users when run if everything is okey-dokey.
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Ideally one check invocation can do all these things.
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Repository
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----------
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Things that can go wrong:
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* Bit errors or alterations may occur in raw data.
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* Data that is referenced may be missing
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* There could be a lot of garbage in upload etc.
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* File graphs may be inconsistent with inventories and parents.
4332.3.12 by Robert Collins
Note another possible error.
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* The revision graph cache can be inconsistent with the revision data.
4332.3.1 by Robert Collins
Docs for check.
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Branch
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------
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Things that can go wrong:
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* Tag or tip revision ids may be missing from the repo.
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* The revno tip cache may be wrong.
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* Various urls could be problematic (not inaccessible, just invalid)
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* Stacked-on branch could be inaccessible.
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Tree
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----
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Things that can go wrong:
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* Bit errors in dirstate.
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* Corrupt or invalid shelves.
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* Corrupt dirstates written to disk.
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* Cached inventories might not match repository.
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Duplicate work
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--------------
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If we check every branch in a repo separately we will encounter duplicate
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effort in assessing things like missing tags/tips, revno cache etc.
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Outline of approach
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To check a repository, we scan for branches, open their trees and generate
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summary data. We then collect all the summary data in as compact a form as
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possible and do a detailed check on the repository, calling back out to branch
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and trees as we encounter the actual data that that tree/branch requires to
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perform its check.