import collections
import time
import pygooglechart
DEFAULT_BUCKETS = [
2, 5,
10, 20, 50,
100, 200, 500,
]
def _percent(counts):
tot = float(sum(counts))
return [(x, 100 * x / tot) for x in counts]
class LatencyProfilerMiddleware(object):
def __init__(self, app, urls=None, buckets=None):
self._app = app
self._buckets = buckets or DEFAULT_BUCKETS
self._n_buckets = len(self._buckets) + 1
self._urls = sorted(urls or [],
key=lambda x: len(x), reverse=True)
def _build_buckets():
return [0] * self._n_buckets
self._data = collections.defaultdict(_build_buckets)
def __call__(self, environ, start_response):
start = time.time()
url = environ['PATH_INFO']
if url.endswith('/__latency__'):
return self.handler(environ, start_response)
try:
return self._app(environ, start_response)
finally:
elapsed_ms = 1000 * (time.time() - start)
for url_prefix in self._urls:
if url.startswith(url_prefix):
url = url_prefix
break
for bkt, threshold in enumerate(self._buckets):
if elapsed_ms < threshold:
break
else:
bkt = self._n_buckets - 1
self._data[url][bkt] += 1
def handler(self, environ, start_response):
headers = [('Content-type', 'text/html')]
start_response('200 OK', headers)
result = [
'<!doctype html>\n'
'<html><head><title>Latency Breakdown</title>\n'
'<style type="text/css">\n'
'body { background: white; font-family: sans-serif; }\n'
'tbody td { text-align: left; padding-right: 10px; }\n'
'thead th { font-weight: bold; text-align: left; color: white; '
'background-color: #666; }\n'
'td.url { font-weight: bold; border-right: 1px solid #666; }\n'
'tbody tr { border-bottom: 1px solid #ccc; }\n'
'</style></head><body>\n'
'<h3>Latency report by URL</h3>\n'
'<table cellspacing="0" cellpadding="0" border="0"><thead><tr>'
'<th rowspan="2">URL</th>',
'<th rowspan="2">Total</th>',
'<th colspan="%d">Latencies (ms)</th>' % self._n_buckets,
'<th rowspan="2"></th>',
'</tr><tr>'
]
for ms in self._buckets:
result.append('<th><%d</th>' % ms)
result.append('<th>>%d</th>' % ms)
result.append('</tr></thead><tbody>')
for url in sorted(self._data.keys()):
values = self._data[url]
result.append('<tr><td class="url">%s</td><td>%d</td>' % (
url, sum(values)))
chart = pygooglechart.SparkLineChart(80, 25)
chart.set_data(values)
for count, pct in _percent(values):
result.append('<td>%d (%.2g%%)</td>' % (count, pct))
result.append('<td><img src="%s" width="80" height="25"></td>' %
chart.get_url())
result.append('</tr>')
result.append('</tbody></table>')
result.append('</body></html>\n')
return result