[jira] Updated: (IVY-973) [PATCH] SFTP repositories become very slow after a while

["Johannes Rudolph (JIRA)" <ji...@apache.org>]

     [ https://issues.apache.org/jira/browse/IVY-973?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]

Johannes Rudolph updated IVY-973:
---------------------------------

    Attachment: faster-sftp.patch

A patch which fixes the problem by introducing a cache.

> [PATCH] SFTP repositories become very slow after a while
> --------------------------------------------------------
>
>                 Key: IVY-973
>                 URL: https://issues.apache.org/jira/browse/IVY-973
>             Project: Ivy
>          Issue Type: Improvement
>          Components: Core
>    Affects Versions: 2.0-RC2
>            Reporter: Johannes Rudolph
>         Attachments: faster-sftp.patch
>
>
> If many versions of a module live in a folder of an SFTP repository each resolve for dynamic versions becomes dreadfully slow because a roundtrip to the server is made to the server for every version which lies on the server. 
> The call sequence goes like that:
> org.apache.ivy.plugins.resolver.util.ResolverHelper.findAll calls
>   1.  org.apache.ivy.plugins.resolver.util.ResolverHelper.listTokenValues which calls
>         SFTPRepository.list with the directory of the module as parameter (1. roundtrip)
>   2. for every found file matching the pattern SFTPRepository.getResource(path).exists()
>         In turn SFTPResource tries to initialize itself and calls SFTPRepository.resolveResource which does the second roundtrip to the server - for every version of the file
> Example: Having 20 versions of a module in a repository which is a roundtrip of 150ms away, leads to a lag of 20 * 150ms = 3s . Multiply that with any module having a dynamic version.
> The solution is to cache all the resources in SFTPRepository. You can use the information retrieved when calling SFTPRepository.list to fill the cache in advance.
> The disadvantage is that you may have stale data. IMO this is mostly no problem because every call to list updates the cache and files already available in the repository won't hopefully change any metadata in the time between.

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