Re: [egit-dev] Relationship of Pulling and Open Project

[Lars Vogel <lars.vogel@xxxxxxxxxxx>]

Thanks Matthias for the detailed description. Shall I open a bug to
capture you suggestion to run fetch outside the lock during the pull
operation?

Best regards, Lars

On Wed, Dec 21, 2016 at 11:12 PM, Matthias Sohn <matthias.sohn@xxxxxxxxx> wrote:
> On Wed, Dec 21, 2016 at 4:04 PM, Lars Vogel <lars.vogel@xxxxxxxxxxx> wrote:
>>
>> Dear EGit developer,
>>
>> I noticed that I cannot open a closed project during a Git Pull
>> operation. See screenshot.
>>
>> Is this intended or a undesired side effect?
>
>
> EGit's PullOperation locks all projects versioned in the repository (ies)
> the operation was started for.
> Project.open tries to obtain the same lock
> (IResourceRuleFactory.modifyRule(this)) and hence has to wait.
>
> EGit locks the projects since
> - pull typically modifies files in the affected projects and could interfere
> with other jobs which also modify files in the same projects
> - operations modifying the git index of the same repository can't run
> concurrently.
> The latter is also ensured by JGit by locking the index file.
>
> The advantage of this pessimistic locking is that we prevent partial
> execution of the pull operation.
>
> EGit's PullOperation calls JGit's PullCommand. Pull consists of a fetch
> command followed
> by a merge or rebase command. Typically fetch takes much longer than merge
> or rebase
> so instead of pessimistically locking the affected projects for the complete
> runtime of a pull command
> we could run fetch without any scheduling rule (fetch doesn't modify files
> in the workspace but only
> downloads new git objects) then acquire the lock on the affected projects
> and if this succeeds run
> the merge or rebase command. If we can't get the lock we would need to fail
> the lock and ask
> the user to retry later. This could be implemented in EGit by running JGit
> FetchCommand followed
> by a MergeCommand or RebaseCommand. Alternatively we could enhance JGit's
> PullCommand
> with a callback enabling EGit to acquire the lock after fetch finished and
> before merge/rebase is started.
>
> -Matthias



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