CouchDatabase() call hangs

I tried to reproduce this from a fresh dist-upgrade, and was not able to reproduce it with a new or existing database.

Ok, I'm hitting this now in other apps, but not in my test app.

I'm moving this package to couchdb because this problem only started happening recently, and desktopcouch hasn't been updated, but couchdb has.

whoops, accidentally changed status/importance

Michael, Rick: you're not using the ubuntone nightlies PPA right? Because that does have a completely new desktopcouch. We didn't knowingly introduce breaking changes, but there may be a bug or two. If not, can you paste some code that we could reproduce this with?

Or is it just that one line and the import that will trigger it?

Not very helpful, but on my fully updated maverick machine, it works:

>>> import desktopcouch
>>> from desktopcouch.records.server import CouchDatabase
>>> foo = CouchDatabase('test_db',create=True)
Removing stale, deceptive pid file.
Browse your desktop CouchDB at file:///home/eric/.local/share/desktop-couch/couchdb.html
>>>

This is not using the nightly PPA. It's just stock natty (not maverick). I will try to get a testcase.

Aha, I think the new python-couchdb may have just landed in natty, but the desktopcouch version that supports it has not yet. We hope to upload this later today, and hopefully that will solve the issue.

Nope python-couchdb has not landed yet, so that's not it. Sry for the noise.

Yup, test case is simply:

from desktopcouch.records.server import CouchDatabase
db = CouchDatabase("test-project", create=True)

With output:

Removing stale, deceptive pid file.
Apache CouchDB has started, time to relax.
Browse your desktop CouchDB at file:///home/mike/.local/share/desktop-couch/couchdb.html

And traceback:

Traceback (most recent call last):
  File "test.py", line 2, in <module>
    db = CouchDatabase("test-project", create=True)
  File "/usr/lib/python2.6/dist-packages/desktopcouch/records/server.py", line 56, in __init__
    server_class=server_class, oauth_tokens=oauth_tokens, ctx=ctx)
  File "/usr/lib/python2.6/dist-packages/desktopcouch/records/server_base.py", line 155, in __init__
    self._reconnect()
  File "/usr/lib/python2.6/dist-packages/desktopcouch/records/server.py", line 60, in _reconnect
    port = desktopcouch.find_port(ctx=self.ctx)
  File "/usr/lib/python2.6/dist-packages/desktopcouch/__init__.py", line 106, in find_port
    return _direct_access_find_port(pid=pid, ctx=ctx)
  File "/usr/lib/python2.6/dist-packages/desktopcouch/__init__.py", line 131, in __find_port__linux
    pid = find_pid(start_if_not_running=True, ctx=ctx)
  File "/usr/lib/python2.6/dist-packages/desktopcouch/__init__.py", line 93, in find_pid
    start_local_couchdb.update_pairing_service()
  File "/usr/lib/python2.6/dist-packages/desktopcouch/start_local_couchdb.py", line 228, in update_pairing_service
    pair_with_ubuntuone()
  File "/usr/lib/python2.6/dist-packages/desktopcouch/pair/couchdb_pairing/ubuntuone_pairing.py", line 55, in pair_with_ubuntuone
    for row in view_results:
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 871, in __iter__
    for row in self.rows:
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 893, in rows
    self._fetch()
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 881, in _fetch
    data = self.view._exec(self.options)
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 766, in _exec
    resp, data = self.resource.get(**self._encode_options(options))
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 978, in get
    return self._request('GET', path, headers=headers, **params)
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 1014, in _request
    resp, data = _make_request()
  File "/usr/lib/pymodules/python2.6/couchdb/client.py", line 1009, in _make_request
    body=body, headers=headers)
  File "/usr/lib/python2.6/dist-packages/httplib2/__init__.py", line 1129, in request
    (response, content) = self._request(conn, authority, uri, request_uri, method, body, headers, redirections, cachekey)
  File "/usr/lib/python2.6/dist-packages/httplib2/__init__.py", line 901, in _request
    (response, content) = self._conn_request(conn, request_uri, method, body, headers)
  File "/usr/lib/python2.6/dist-packages/httplib2/__init__.py", line 871, in _conn_request
    response = conn.getresponse()
  File "/usr/lib/python2.6/httplib.py", line 990, in getresponse
    response.begin()
  File "/usr/lib/python2.6/httplib.py", line 391, in begin
    version, status, reason = self._read_status()
  File "/usr/lib/python2.6/httplib.py", line 349...

I've tried this both in the interactive shell, and in a test.py running it from the command line, and can't reproduce the hang. Chad, do you have any ideas?

Ah, could it be that there is a keyring prompt open that you missed at the point where the code hangs?

Eric, I don't think it's a keyring prompt. I've done this several times, and haven't seen a prompt (and nothing shows in alt-tab).

Here's an interesting find. If I run the two-line script a second time in a session, it doesn't block. But if I add the following lines, it will hang again reliably on the len(results.rows) line:

results = db.get_records(record_type="http://example.com", create_view=True)
print len(results.rows)

Traceback attached.

I still cannot reproduce this behavior on maverick, and since Rick and you both have it on natty, I think it may be a problem unique to that. I'll try and migrate one of my machines to see if I can reproduce.

Just to make 100% sure I'm doing exactly the same thing as you, I have a file test_couchdb.py with these (and only these) contents:

from desktopcouch.records.server import CouchDatabase
db = CouchDatabase('test_db3',create=True)
results = db.get_records(record_type="http://example.com", create_view=True)
print len(results.rows)

And I run that from the console (several times) like this:

eric@eric-laptop:~$ python test_couch.py
0
eric@eric-laptop:~$ python test_couch.py
0
eric@eric-laptop:~$ python test_couch.py
0
eric@eric-laptop:~$ python test_couch.py
0

Also, if either of you have the time, I would very much like to know if the problem persists with the new version of desktopcouch in our nightlies PPA, since that's what'll be in Natty, and there are some quite substantial changes in that, under the hood, which may impact this behavior.

https://launchpad.net/~ubuntuone/+archive/nightlies

It now looks like the problem is the couchdb view server, rather than anything in desktopcouch. I'm investigating this and will move the bug if it turns out to be true.

Yeah it's definitely the js view server that's not working properly, or at all. Investigating where the problem is and how to fix it with Chris Coulson.

Hmmmm, this might be why:

 #0 0x00000000004031be in readfp (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:166
         bytes = 0x7f7554001e70 "[\"reset\",{\"reduce_limit\":true}]\n"
         tmp = <value optimised out>
         byteslen = 256
         readlen = <value optimised out>
         used = 140141897195120
 #1 readline (cx=0x18549c0, argc=<value optimised out>, vp=0x7f7559a0f130) at couch_js/main.c:198
         str = <value optimised out>
         bytes = <value optimised out>
         tmp = <value optimised out>
         byteslen = <value optimised out>
 #2 0x00007f755e3760d3 in CallJSNative (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jscntxtinlines.h:684
         ok = <value optimised out>
 #3 js::Interpret (cx=0x18549c0, entryFrame=0x7f7559a0f048, inlineCallCount=1, interpMode=JSINTERP_NORMAL) at /build/buildd/xulrunner-2.0-2.0~b7+nobinonly/build-tree/mozilla/js/src/jsinterp.cpp:4744
         ok = <value optimised out>
         ok = <value optimised out>
         callee = <value optimised out>
         flags = 0
         vp = 0x7f7559a0f130
         newfun = 0x7f7559817f80
         argc = 0
         normalJumpTable = {0x7f755e36e772, 0x7f755e36d9a9, 0x7f755e36c0e6, 0x7f755e36da54, 0x7f755e36db02, 0x7f755e36db35, 0x7f755e36c13e, 0x7f755e36db64, 0x7f755e36dbd3, 0x7f755e36f0ad, 0x7f755e36e254, 0x7f755e36e2d3, 0x7f755e36e6b7, 0x7f755e372fc1, 0x7f755e3730aa, 0x7f755e370157, 0x7f755e3701f2, 0x7f755e37028d, 0x7f755e370328, 0x7f755e36f263, 0x7f755e373bb3, 0x7f755e37322d, 0x7f755e373386, 0x7f755e3723b9, 0x7f755e3739b8, 0x7f755e373916, 0x7f755e373a5a, 0x7f755e3735d4, 0x7f755e373748, 0x7f755e37382f, 0x7f755e373d0c, 0x7f755e36e8f6, 0x7f755e36e9dd, 0x7f755e371eca, 0x7f755e371f32, 0x7f755e371bb5, 0x7f755e371bf7, 0x7f755e371cca, 0x7f755e371d8b, 0x7f755e36c554, 0x7f755e371b5b, 0x7f755e36f828, 0x7f755e371b9d, 0x7f755e371b93, 0x7f755e373b04, 0x7f755e371ba5, 0x7f755e371b98, 0x7f755e36f82d, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36f832, 0x7f755e36bf98, 0x7f755e36be89, 0x7f755e36c2d0, 0x7f755e36bad0, 0x7f755e3712d4, 0x7f755e3727f1, 0x7f755e36bc37, 0x7f755e36c452, 0x7f755e36bc37, 0x7f755e36ea52, 0x7f755e36eab8, 0x7f755e36eca5, 0x7f755e36f06a, 0x7f755e36ece8, 0x7f755e3711f7, 0x7f755e36ed2b, 0x7f755e36ed6e, 0x7f755e36dca9, 0x7f755e36dd3b, 0x7f755e36edb1, 0x7f755e36f015, 0x7f755e373b51, 0x7f755e36f48a, 0x7f755e372974, 0x7f755e36e18c, 0x7f755e36e1ec, 0x7f755e36e353, 0x7f755e36c452, 0x7f755e373006, 0x7f755e36eb16, 0x7f755e36d9ec, 0x7f755e372702, 0x7f755e36f01f, 0x7f755e36c5de, 0x7f755e3722e9, 0x7f755e373eb9, 0x7f755e373e61, 0x7f755e3714c9, 0x7f755e36d64d, 0x7f755e36d899, 0x7f755e36cb8d, 0x7f755e36d764, 0x7f755e36f18c, 0x7f755e372e6e, 0x7f755e373b41, 0x7f755e372072, 0x7f755e373b26, 0x7f755e373557, 0x7f755e36e82d, 0x7f755e373b33, 0x7f755e3711ea, 0x7f755e36e794, 0x7f755e37013d, 0x7f755e36e3a4, 0x7f755e36e4f7, 0x7f755e36e645, 0x7f755e36da17, 0x7f755e36ffa8, 0x7f755e3712cf, 0x7f755e36fd31, 0x7f755e36e014, 0x7f755e372a4d, 0x7f755e372af8, 0x7f755e372f53, 0x7f755e3734df, 0x7f755e3729df, 0x7f755e36d965, 0x7f755...

Oh, it's probably not clear from the last post, bug couchjs crashes continuously (thanks Apport):

SegvAnalysis:
 Segfault happened at: 0x4031be <readline+94>: cmpb $0xa,(%rax)
 PC (0x004031be) ok
 source "$0xa" ok
 destination "(%rax)" (0xfeeaa8003cdf) not located in a known VMA region (needed writable region)!
SegvReason: writing unknown VMA

So, there must be a subtle difference in between fgets and js_fgets. Shame that couchjs can't use the latter any more. I'll take a look at this in the morning anyway

fgets and js_fgets really aren't interchangeable. js_fgets is more similar to readline, although the API is still different. I'm pretty sure this is what is causing this bug anyway, and it should be an easy fix

I've resorted to using a copy of js_fgets in couchjs, I couldn't find a suitable alternative elsewhere. getline is the closest thing to it, but that has it's own issues:

1) It internally uses malloc, which may not always be the same allocator that spidermonkey uses
2) It reads until a newline, but js_fgets handles newline or carriage return

This bug was fixed in the package couchdb - 1.0.1-0ubuntu6

---------------
couchdb (1.0.1-0ubuntu6) natty; urgency=low

  * Fix LP: #682866 - CouchDatabase() call hangs because couchjs crashes,
    due to semantic differences between fgets and js_fgets. Use a local
    implementation of js_fgets when it's not available otherwise
    - update debian/patches/mozjs2.0.patch
    - update debian/patches/mozjs2.0_autotools.patch
 -- Chris Coulson <email address hidden> Mon, 06 Dec 2010 10:23:54 +0000

Fix confirmed, everything seems to be working great now. Thanks Chris!

Excellent, that's good to hear. Thanks for testing