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webapi/deep-manifest t=JSON: don't return the (large) manifest/SI/verifycap lists unless the operation has completed, to avoid the considerable CPU+memory cost of creating the JSON (for 330k dirnodes, it could take two minutes to generate 275MB of JSON). They must be paid eventually, but not on every poll

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This commit is contained in:
Brian Warner 2009-01-08 19:59:32 -07:00
parent 39a089dc7e
commit 7ee336b274
2 changed files with 30 additions and 8 deletions
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10
docs/frontends/webapi.txt
View File

@ -213,6 +213,11 @@ GET /operations/$HANDLE?output=JSON (same)
* whether the operation is complete, or if it is still running * whether the operation is complete, or if it is still running
* how much of the operation is complete, and how much is left, if possible * how much of the operation is complete, and how much is left, if possible
Note that the final status output can be quite large: a deep-manifest of a
directory structure with 300k directories and 200k unique files is about
275MB of JSON, and might take two minutes to generate. For this reason, the
full status is not provided until the operation has completed.
The HTML form will include a meta-refresh tag, which will cause a regular The HTML form will include a meta-refresh tag, which will cause a regular
web browser to reload the status page about 60 seconds later. This tag will web browser to reload the status page about 60 seconds later. This tag will
be removed once the operation has completed. be removed once the operation has completed.
@ -966,7 +971,10 @@ POST $DIRURL?t=start-manifest (must add &ophandle=XYZ)
by a space. by a space.
If output=JSON is added to the queryargs, then the results will be a If output=JSON is added to the queryargs, then the results will be a
JSON-formatted dictionary with six keys: JSON-formatted dictionary with six keys. Note that because large directory
structures can result in very large JSON results, the full results will not
be available until the operation is complete (i.e. until output["finished"]
is True):
finished (bool): if False then you must reload the page until True finished (bool): if False then you must reload the page until True
origin_si (base32 str): the storage index of the starting point origin_si (base32 str): the storage index of the starting point

28
src/allmydata/web/directory.py
View File

@ -728,13 +728,27 @@ class ManifestResults(rend.Page, ReloadMixin):
inevow.IRequest(ctx).setHeader("content-type", "text/plain") inevow.IRequest(ctx).setHeader("content-type", "text/plain")
m = self.monitor m = self.monitor
s = m.get_status() s = m.get_status()
status = {"manifest": s["manifest"],
"verifycaps": list(s["verifycaps"]), status = { "stats": s["stats"],
"storage-index": list(s["storage-index"]), "finished": m.is_finished(),
"stats": s["stats"], "origin": base32.b2a(m.origin_si),
"finished": m.is_finished(), }
"origin": base32.b2a(m.origin_si), if m.is_finished():
} # don't return manifest/verifycaps/SIs unless the operation is
# done, to save on CPU/memory (both here and in the HTTP client
# who has to unpack the JSON). Tests show that the ManifestWalker
# needs about 1092 bytes per item, the JSON we generate here
# requires about 503 bytes per item, and some internal overhead
# (perhaps transport-layer buffers in twisted.web?) requires an
# additional 1047 bytes per item.
status.update({ "manifest": s["manifest"],
"verifycaps": [i for i in s["verifycaps"]],
"storage-index": [i for i in s["storage-index"]],
})
# simplejson doesn't know how to serialize a set. We use a
# generator that walks the set rather than list(setofthing) to
# save a small amount of memory (4B*len) and a moderate amount of
# CPU.
return simplejson.dumps(status, indent=1) return simplejson.dumps(status, indent=1)
def _si_abbrev(self): def _si_abbrev(self):