From: Brian Warner Date: Mon, 26 Jan 2009 00:06:39 +0000 (-0700) Subject: diskwatcher: cache growth results (which take 30s to generate) for 3 minutes, to... X-Git-Tag: allmydata-tahoe-1.3.0~144 X-Git-Url: https://git.rkrishnan.org/vdrive/%22news.html/copyable.html?a=commitdiff_plain;h=8d6bdb58566d3f32df0ce7f4a9d71fc976a2c595;p=tahoe-lafs%2Ftahoe-lafs.git diskwatcher: cache growth results (which take 30s to generate) for 3 minutes, to help munin, which invokes it 6 times in a row every 5 minutes --- diff --git a/misc/spacetime/diskwatcher.tac b/misc/spacetime/diskwatcher.tac index d3683819..112b8781 100644 --- a/misc/spacetime/diskwatcher.tac +++ b/misc/spacetime/diskwatcher.tac @@ -25,7 +25,7 @@ results). Each line should be in the form: # built-in graphs on web interface -import os.path, urllib +import os.path, urllib, time from datetime import timedelta from twisted.application import internet, service, strports from twisted.web import server, resource, http, client @@ -72,6 +72,7 @@ class DiskWatcher(service.MultiService, resource.Resource): def __init__(self): assert os.path.exists("diskwatcher.tac") # run from the right directory + self.growth_cache = {} service.MultiService.__init__(self) resource.Resource.__init__(self) self.store = Store("history.axiom") @@ -238,6 +239,23 @@ class DiskWatcher(service.MultiService, resource.Resource): until the gatherer has been running and collecting data for that long.""" + # a note about workload: for our oldest storage servers, as of + # 25-Jan-2009, the first DB query here takes about 40ms per server + # URL (some take as little as 10ms). There are about 110 servers, and + # two queries each, so the growth() function takes about 7s to run + # for each timespan. We track 4 timespans, and find_total_*_space() + # takes about 2.3s to run, so calculate_growth_timeleft() takes about + # 27s. Each HTTP query thus takes 27s, and we have six munin plugins + # which perform HTTP queries every 5 minutes. By adding growth_cache(), + # I hope to reduce this: the first HTTP query will still take 27s, + # but the subsequent five should be about 2.3s each. + + # we're allowed to cache this value for 3 minutes + if timespan in self.growth_cache: + (when, value) = self.growth_cache[timespan] + if time.time() - when < 3*60: + return value + td = timedelta(seconds=timespan) now = extime.Time() then = now - td @@ -278,6 +296,7 @@ class DiskWatcher(service.MultiService, resource.Resource): if not num_nodes: return None + self.growth_cache[timespan] = (time.time(), total_growth) return total_growth def getChild(self, path, req):