[Bug 830492] Re: Downloads should not lock apt

[James Haigh]

> Great to hear that you work on a more general fix for apt-get.

As described in comment #5, I was originally planning to make a virtual
package server such that a list of files can be easily obtained from any
package manager just by directing it to the server. It would then
download them and place in /var/cache/apt/archives/, then you would try
again in the package manager which would have nothing to download. I was
going to wrap apt-get such that the retry is automatic. Then I noticed
that instead of wrapping apt-get, there are some Python APT bindings
available. And I was about to start reinventing parts of Aptdaemon.

So instead of using apt-get, I will use aptdcon and implement solutions
in Aptdaemon as described in comment #7.

After I have done this, I may still apply the virtual package server
idea as an Aptdaemon client. This may allow 'legacy' package managers
like Synaptic to /partially/ use Aptdaemon and allow concurrent
downloads/installs. Synaptic, however, will still require bug #80753 to
be fixed in this case.


> Download and install in parallel is currently progressing only slowly, during the current summer of code we got a new order algorithm that can now order the packages in a way that puts them together in groups that can be installed independently.

That's interesting. Are those groups equivalent to transactions?


> You linksed to "pacserve" which is quite interessting. Are you aware of the similar (but not quite the same) project "squid-deb-proxy" and "squid-deb-proxy-client" ?

No, I hadn't. My long-term aim is that more efficient downloads (from
LAN if available) can be achieved without configuring or messing around
with proxies/shared caches/local mirrors/etc.

So I'm preferring to contribute to Aptdaemon. It would be awesome if
Ubuntu has these Aptdaemon solutions out-of-the-box. I'm also thinking
that this is going to take a great deal of load off Ubuntu's servers
if/when this happens.

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https://bugs.launchpad.net/bugs/830492

Title:
  Downloads should not lock apt

Status in APT:
  Won't Fix
Status in Aptboost:
  In Progress
Status in The synaptic package manager:
  Won't Fix
Status in “apt” package in Ubuntu:
  Won't Fix
Status in “synaptic” package in Ubuntu:
  Won't Fix

Bug description:
  It should be possible to download while installing, or download 2
  things at once.

  Currently an apt-get command with '--download-only' will lock apt
  (/var/lib/dpkg/lock). Synaptic even locks apt just by being open!

  Examples:
  * I might be updating my system. The update is still in the download stage, and I want to download and install a small package for something. Currently I would have to stop the download, install the package, and resume the download.
  * I'm installing lots of application from the Software Centre. While 1 app is installing the next should be downloading.
  * Run apt-get from command line while browsing software in Synaptic.

  To avoid multiple instances of apt downloading the same file, each
  partial file should have it's own lock (For example,
  /var/cache/apt/archives/partial/inkscape_0.48.1-2ubuntu2_i386.deb
  would have inkscape_0.48.1-2ubuntu2_i386.lock). It may also be
  necessary to prevent updating package lists (sudo apt-get update) when
  any download lock exists as well as apt's main lock.

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