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The Definitive Analysis of Palm Pre App Install Limits and the Palm App Catalog Hanging

After the Preware 0.9.4 release, which included Applications, Themes, and Patches, and offers over 670 homebrew packages for installation, we (  started getting reports of the Palm App Catalog “hanging” the user interface for 30 seconds or more when the installation of a new application is initiated, but only when the Package Manager Service (the service which does all the Linux-level work for the Preware front-end) was installed.

After some analysis, I found that disabling all the feeds in Preware reduced the “hang” from more than 30 seconds to less than a second.

Looking through the output of ‘dbus-util –capture’ showed that the “hang” was during the call to the queryInstallCapacity method of the com.palm.appinstaller service, the routine that the Palm App Catalog application uses to determine whether there is enough space to install a new application from the Palm App Catalog.  Yes, this is the method which is at the heart of the dreaded “Too many applications” errors that people are seeing when they have a number of homebrew applications installed and try to install a new application from the Palm App Catalog.

Watching the output of ‘ps -ef’ during calls to this method (you can call it manually using luna-send) showed that palm was calling “ipkg -o /var list”.  Curious.  Why would you want to know the *complete* list of all *available* applications when determining whether there is room to install one known new application.  I suspect that Palm should be calling “ipkg -o /var list_installed” instead (which just lists the installed applications).  Note that Palm doesn’t use feeds the way that Preware does, so for Palm’s official use of ipkg, list and list_installed would return the same thing in their testing, but list_installed is definitely what they should be using to determine the size of installed applications.

The plot thickens when you use strace (which Palm conveniently includes in the official firmware image) on the running LunaSysMgr process.

It seems that LunaSysMgr calls “ipkg -o /var list” to get a list of installed packages (the probably intend to just get the list of installed packages, but when you have Preware installed and have feed configuration files in /var/etc/ipkg/*.conf, it actually returns a list of all *available packages).

LunaSysMgr then does an execve of “/usr/bin/du -s /var/usr/palm/applications/package” for each package in that list.  (BTW Palm, you seem to have a bug in the logic of that code, cause it’s running du on random garbage strings after the end of the real package list)

Yes, that’s right.  A call to queryInstallCapacity spawns a new program (“du”) once for each package returned by “ipkg -o /var list”.  No wonder the UI hangs for 30 seconds or more!

A single “du -s /var/usr/palm/applications/*” would be a far more efficient way to get exactly the same information, but again, Palm would not see this difference in testing because they do not support the third-party Preware application usage of ipkg feeds.

You can imagine that this behaviour is probably related to the app install limit that many people are experiencing too.  Unfortunately, I’ll have to reduce my /var partition size down from it’s current 2GB size (courtesy of the WebOS Internals Meta-Doctor) to be able to investigate this one.

Now the developers need to develop a new method of installing homebrew applications so that this bug in Palm’s appInstaller service is not triggered.

In the meantime, the work-around is to go into the Preware Preferences screen, hit the “Feeds” button in the top-right corner, and disable all the feeds while you use the Palm App Catalog application in another card.  No need to exit the Feeds screen, just toggle all the button to “Off”, and then toggle them back to “On” when you’re finished with the App Catalog.

For the solution to this problem, see Update #2, below.

I’ve created a thread on PreCentral where this issue can be discussed.  As I uncover more information, I’ll publish my finding here.

Update #1: I’ve now webOS Doctored my Pre in the name of science, and have tested the limits of installing applications.

If you run “du -s /var/usr/palm/applications/*”, and add up all the numbers in the first column, then as soon as you hit the 62367 1K blocks limit of the addition of the sizes reported by that “du” command and the size of the app you with to install, you will get the dreaded “Sorry, Not Enough Memory” error from the Palm App Catalog application (and any other installer, like fileCoaster or PreLoad, which uses the palm appInstaller API).  It doesn’t matter whether you have 192MB free in your /var partition, it will max out at just under 64MB of application usage.

Update #2: I have now created a Linux Application called “Fair Dinkum App Limit” (org.webosinternals.fairdinkum), which removes both the “hang” and the arbitrary application limit.  You can find it in Preware.  Just install it (no need to even run anything – if it is installed, it’s working), and you’re ready to install more applications than you can poke a stick at …

Fair Dinkum App Limit works by simply putting a couple of wrapper scripts in /usr/local/bin, which returns a size of zero when du is called, and returns the output of “ipkg -o /var list_installed” when “ipkg -o /var list” is called.  In the future, the wrappers will be made much more sophisticated than they are right now to prevent operation outside of the specific cases where they need to fool LunaSysMgr, and to also include a safety buffer so that users do not fill the /var partition.  This is a tactical response to a problem that people using homebrew applications are experiencing.  Hopefully, Palm will provide the long term solution for limits on application installation in a release in the near future.

Notes for Palm, if you happen to read this:

1) We fully appreciate that the usage of the ipkg database in /var for homebrew applications is a choice that the homebrew community has made, and is not supported by Palm.

2) We fully agree that the use of “ipkg -o /var list” instead of “ipkg -o /var list_installed” would work perfectly fine for the way that Palm is officially using the ipkg database in /var/usr/lib/ipkg, but we contend that the “list” and “list_installed” commands have clear intended usage, and the one to find the list of installed applications for checking available disk space should be “list_installed”.

3) We fully realise that the initial version of the FairDinkum scripts are unsafe.  Returning a zero value for du is a temporary solution while we work out how to achieve the same result safely.  The intention is to only return false values when du is being called from LunaSysMgr, and to make sure that a safety buffer is kept so that users do not fill the /var partition.

4) I would be very happy to discuss these issues with anyone at Palm (Chuq and Google both have my email address), and would hope that we can together architect a solution for supporting homebrew application installation which does not require these work-arounds.

5) We have designed these work-arounds in a way which does not collide with Palm OTA Updates, and in a way that we can update them automatically using the Preware installer application, and in a way that we can cause them to self-remove when Palm releases a long term solution.

Update #3:

It seems that there is yet another limit on application installation imposed by LunaSysMgr.  Once the used space on /var crosses around 60%, LunaSysMgr will once again refuse to install applications.

I’m going to need to webOS Doctor my Pre yet again (to reallocate 2GB to /var) to determine whether this limit is a fixed percentage, or a fixed number of blocks.

Update #4:

The limit is 102400 free blocks.  Mystery solved.  That also means the Fair Dinkum App Limit cannot cause your /var to be filled.

Update #5:

Thanks to Carl Thompson, an improved version of Fair Dinkum App Limit which does not alter the operation of ‘du’ has been released.