[Monotone-devel] ViewMTN seems to have trouble talking to monotone

[Ludovic Brenta]

Hi, it's me again.

After I announced the Ada-France ViewMTN server publicly, I received
several reports from people getting "500 Internal Server Error"
whenever clicking a link in the web interface.  This is strange
because in my own testing, I have never seen such errors, neither
before nor after receiving the user reports.

In the log however, I see many instances of:

Traceback (most recent call last):
  File "/var/lib/monotone/net.angrygoats.viewmtn/web/webapi.py", line 304, in 
wsgifunc
    result = func()
  File "/var/lib/monotone/net.angrygoats.viewmtn/web/request.py", line 131, in 
<lambda>
    func = lambda: handle(inp, fvars)
  File "/var/lib/monotone/net.angrygoats.viewmtn/web/request.py", line 61, in 
handle
    return tocall(*([x and urllib.unquote(x) for x in args] + fna))
  File "/var/lib/monotone/net.angrygoats.viewmtn/viewmtn.py", line 123, in GET
    return handler.GET (ctxt, *other_args, **kwargs)
  File "/var/lib/monotone/net.angrygoats.viewmtn/handlers.py", line 314, in GET
    Changes.Branch_GET(self, ctxt, branch, from_change, to_change, 
"branchchanges.html")
  File "/var/lib/monotone/net.angrygoats.viewmtn/handlers.py", line 246, in 
Branch_GET
    last_changes = self.branch_get_last_changes(ctxt.ops, branch, from_change, 
to_change)
  File "/var/lib/monotone/net.angrygoats.viewmtn/handlers.py", line 240, in 
branch_get_last_changes
    to_change)
  File "/var/lib/monotone/net.angrygoats.viewmtn/handlers.py", line 144, in 
__get_last_changes
    heapq.heappush(revq, Changes.ComparisonRev(ops, rev))
  File "/var/lib/monotone/net.angrygoats.viewmtn/handlers.py", line 111, in 
__init__
    self.certs = list(ops.certs(self.revision))
  File "/var/lib/monotone/net.angrygoats.viewmtn/mtn.py", line 451, in certs
    for stanza in basic_io_from_stream(self.automate.run('certs', [revision])):
  File "/var/lib/monotone/net.angrygoats.viewmtn/mtn.py", line 355, in 
basic_io_from_stream
    for line in gen:
  File "/var/lib/monotone/net.angrygoats.viewmtn/genproxy.py", line 18, in next
    return self.generator.next()
  File "/var/lib/monotone/net.angrygoats.viewmtn/mtn.py", line 231, in __run
    raise MonotoneException("error code %d in automate packet." % (code_max))
MonotoneException: error code 2 in automate packet.

followed by a line of form:

<ip_address:port> -  - [dd/Mmm/YYYY hh:mm:ss] "URL" - 500 Internal Server Error

I'm wondering what could cause such errors.  On this machine, "mtn
automate interface_version" reports 4.0 but I don't think the problem
is actually tool old a version of monotone because the errors do not
occur every time the same URL is requested.  For example, the last
time such an error occurred was on the URL /tags but I just tried it
and it worked fine.

My analysis of the log file shows that consecutive errors are most
often separated in time by a less than 20 seconds, so perhaps what
triggers the problem is heavy load on the machine?  However I have not
been able to receive a "500 Internal Server Error" when I rapidly
clicked on 5-10 links in rapid succession (2-3 clicks per second).

Any idea?

-- 
Ludovic Brenta.