[darcs-users] [patch209] Resolve issue1159: smart caches union.

Petr Rockai me at mornfall.net
Wed Apr 21 13:36:00 UTC 2010

Dmitry Kurochkin <bugs at darcs.net> writes:

> Sat Apr 17 03:56:44 MSD 2010  Dmitry Kurochkin <dmitry.kurochkin at gmail.com>
>   * Resolve issue1159: smart caches union.
>   Try to do better than just blindly copying remote cache entries:

>   * If remote repository is accessed through network, do not copy any cache
>     entries from it. Taking local entries does not make sense and using network
>     entries can lead to darcs hang when it tries to get to unaccessible host.
(see below)

>   * If remote repositoty is local, copy all network cache entries. For local
>     cache entries if the cache directory exists and is writable it is added as
>     writable cache, if it exists but is not writable it is added as read-only
>     cache.

>   This approach should save us from bogus cache entries. One case it does not
>   work very well is when you fetch from partial repository over network.
>   Hopefully this is not a common case.
I think this is a problem. Oftentimes, people won't realise a repository
is partial and publish it. This used to work transparently and I think
that was a good thing. The right fix for the problems you mention is to
check for usability of sources and complain to the user.

Either something like:

Warning: Host is unreachable.
Remove from list of source repositories? [yN]

Warning: Hostname foo.bar.baz cannot be resolved.
Remove from list of source repositories? [yN]

Alternatively (this is probably better):

Warning: Host is unreachable. Maybe we are offline? However, it
may also be the case that this address is bogus, in which case you
should remove it from _darcs/prefs/sources. This will speed up darcs.

Another possibility (this is probably best):

Honour the order of the sources lines. If a host is unreachable or
directory does not exist, move it to the end of sources. This would
prevent almost all issues automatically, without losing any data or
losing any existing features (transparent support for partial networked
repositories, eg.).


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