To test the changes for #577, we need a deterministic way to simulate
the passage of long periods of time. twisted.internet.task.Clock seems,
from my Googling, to be the way to go for this functionality. I changed
a few things so that OphandleTable would use twisted.internet.task.Clock
when testing:
* WebishServer.__init___ now takes an optional 'clock' parameter,
* which it passes to the root.Root instance it creates.
* root.Root.__init__ now takes an optional 'clock' parameter, which it
passes to the OphandleTable.__init__ method.
* OphandleTable.__init__ now takes an optional 'clock' parameter. If
it is provided, and it isn't None, its callLater method will be used
to schedule ophandle expirations (as opposed to using
reactor.callLater, which is what OphandleTable does normally).
* The WebMixin object in test_web.py now sets a self.clock parameter,
which is a twisted.internet.task.Clock that it feeds to the
WebishServer it creates.
Tests using the WebMixin can control the passage of time in
OphandleTable by accessing self.clock.
It still lacks the right HTML report (the builtin report is very pretty, but
lacks the "lines uncovered" numbers that I want), and the half-finished
delta-from-last-run measurements.
This can be useful if one of the ones that he has already begun downloading fails. See #287 for discussion. This fixes part of #287 which part was a regression caused by #928, namely this fixes fail-over in case a share is corrupted (or the server returns an error or disconnects). This does not fix the related issue mentioned in #287 if a server hangs and doesn't reply to requests for blocks.
This should put an end to the phenomenon I've been seeing that a single hung server can cause all downloads on a grid to hang. Also it should speed up all downloads by (a) not-waiting for responses to queries that it doesn't need, and (b) downloading shares from the servers which answered the initial query the fastest.
Also, do not count how many buckets you've gotten when deciding whether the download has enough shares or not -- instead count how many buckets to *unique* shares that you've gotten. This appears to improve a slightly weird behavior in the current download code in which receiving >= K different buckets all to the same sharenumber would make it think it had enough to download the file when in fact it hadn't.
This patch needs tests before it is actually ready for trunk.
Having both test_node() and test_client() (one of which calls the other) felt
confusing to me, so I changed it to have test_node(), test_client(), and a
common do_create() helper method.
