** Description changed:
[Impact]
Concurrency issues in lazr.restfulclient are affecting some processes used by
various teams; including Foundations, PS integration, etc.
The most affected users are those who make heavy use of scheduled tasks
around launchpadlib (see bug 513116); where different calls to various parts of
launchpadlib (or the bzr launchpad plugin) will concurrently try to access
cache, step on each others' cache files and mangle the files causing errors for
further calls using lazr.restfulclient / launchpadlib.
[Test case]
1) Update package.
2) Run the following command:
for i in `seq 1 50` ; do python -c 'from launchpadlib.launchpad import
Launchpad; lp = Launchpad.login_anonymously("test-cache", "production");
lp.distributions["ubuntu"]' & ; done
After a few runs, on an affected system the spawned processes will write out
backtraces due to mangled files, such as the following error:
cElementTree.ParseError: not well-formed (invalid token): line 40599, column
18
On a patched system, all spawned processes will terminate successfully.
[Regression Potential]
-
+ Due to the changes in caching method, it may be possible that
lazr.restfulclient fails to write cache files because of path size (which would
likely increase due to the change), or otherwise fails to properly cache data
increasing delays in retrieving information that may have already been
retrieved.
----
httplib2 says:
class FileCache(object):
"""Uses a local directory as a store for cached files.
Not really safe to use if multiple threads or processes are going to.
be running on the same cache.
"""
launchpadlib sub-classes that, but doesn't change that fact.
This means that with multiple processes or threads you will
suddenly get strange error messages (bug 404204).
This is made worse by the fact that creating an object uses a
global cache, and login_with does this with no way to override it.
The best way to fix this is to just fix the cache implementation
rather than everyone learning to use a private cache and
fixing launchpadlib to make this possible with the convenience
methods.
This is a pre-requisite for fixing bug 513116, which is about the fact
that launchpadlib is not thread-safe.
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https://bugs.launchpad.net/bugs/459418
Title:
Cache is not safe for concurrent use (by processes or threads)
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