1 # Copyright 2013 The Chromium Authors. All rights reserved. 2 # Use of this source code is governed by a BSD-style license that can be 3 # found in the LICENSE file. 4 5 """This is a helper module to get and manipulate histogram data. 6 7 The histogram data is the same data as is visible from "chrome://histograms". 8 More information can be found at: chromium/src/base/metrics/histogram.h 9 """ 10 11 import json 12 import logging 13 14 BROWSER_HISTOGRAM = 'browser_histogram' 15 RENDERER_HISTOGRAM = 'renderer_histogram' 16 17 18 def CustomizeBrowserOptions(options): 19 """Allows histogram collection.""" 20 options.AppendExtraBrowserArgs(['--enable-stats-collection-bindings']) 21 22 23 def SubtractHistogram(histogram_json, start_histogram_json): 24 """Subtracts a previous histogram from a histogram. 25 26 Both parameters and the returned result are json serializations. 27 """ 28 start_histogram = json.loads(start_histogram_json) 29 # It's ok if the start histogram is empty (we had no data, maybe even no 30 # histogram at all, at the start of the test). 31 if 'buckets' not in start_histogram: 32 return histogram_json 33 34 histogram = json.loads(histogram_json) 35 if ('pid' in start_histogram and 'pid' in histogram 36 and start_histogram['pid'] != histogram['pid']): 37 raise Exception( 38 'Trying to compare histograms from different processes (%d and %d)' 39 % (start_histogram['pid'], histogram['pid'])) 40 41 start_histogram_buckets = dict() 42 for b in start_histogram['buckets']: 43 start_histogram_buckets[b['low']] = b['count'] 44 45 new_buckets = [] 46 for b in histogram['buckets']: 47 new_bucket = b 48 low = b['low'] 49 if low in start_histogram_buckets: 50 new_bucket['count'] = b['count'] - start_histogram_buckets[low] 51 if new_bucket['count'] < 0: 52 logging.error('Histogram subtraction error, starting histogram most ' 53 'probably invalid.') 54 if new_bucket['count']: 55 new_buckets.append(new_bucket) 56 histogram['buckets'] = new_buckets 57 histogram['count'] -= start_histogram['count'] 58 59 return json.dumps(histogram) 60 61 62 def GetHistogram(histogram_type, histogram_name, tab): 63 """Get a json serialization of a histogram.""" 64 assert histogram_type in [BROWSER_HISTOGRAM, RENDERER_HISTOGRAM] 65 function = 'getHistogram' 66 if histogram_type == BROWSER_HISTOGRAM: 67 function = 'getBrowserHistogram' 68 histogram_json = tab.EvaluateJavaScript( 69 'statsCollectionController.%s("%s")' % 70 (function, histogram_name)) 71 if histogram_json: 72 return histogram_json 73 return None 74 75 76 def GetHistogramCount(histogram_type, histogram_name, tab): 77 """Get the count of events for the given histograms.""" 78 histogram_json = GetHistogram(histogram_type, histogram_name, tab) 79 histogram = json.loads(histogram_json) 80 if 'count' in histogram: 81 return histogram['count'] 82 else: 83 return 0 84 85 def GetHistogramSum(histogram_type, histogram_name, tab): 86 """Get the sum of events for the given histograms.""" 87 histogram_json = GetHistogram(histogram_type, histogram_name, tab) 88 histogram = json.loads(histogram_json) 89 if 'sum' in histogram: 90 return histogram['sum'] 91 else: 92 return 0 93
