sapling/fastmanifest/metrics.py

# metrics.py
#
# Copyright 2016 Facebook, Inc.
#
# This software may be used and distributed according to the terms of the
# GNU General Public License version 2 or any later version.
#
# To log a new metric, add it to the list FASTMANIFEST_METRICS
# Then from the code, use metrics.metricscollector.get(repo) or
# metrics.metricscollector.getfromui(ui) to get a metrics `collector`.
# call collector.recordsample(metricsname, key=value, key2=value2, ...) to
# record a samples.
#
# When the command ends the sample will be relayed with ui.log unless
# it is in the list FASTMANIFEST_DONOTREPORT_METRICS.
# You would put a metrics in that list if you do some computation with hit
# and are not interested in the individual sample but only their aggregation.
# For example, if you want to record the cache hit ratio, you can record
# all the cache hit and cache miss, not report them but compute and report their
# ratio.
#
# To debug metrics use fastmanifest.debugmetrics = True, this will print
# the metrics collected for each command with ui.status at the end of each
# command.

from mercurial import util

FASTMANIFEST_DONOTREPORT_METRICS = set([
    "cachehit",
    "diffcachehit",
    "filesnotincachehit"
])

FASTMANIFEST_METRICS = set([
    ## Individual Metrics
    # ondiskcachestats has information about the cache on disk
    # => keys are "bytes", "entries", "limit" and "freespace", all numbers,
    # freespace and limit are in MB
    "ondiskcachestats",
    # revsetsize is the number of revisions in the 'fastmanifesttocache()'
    # => key is "size", a number
    "revsetsize",
    # trigger is what caused caching to trigger
    # => keys is "source", one of ("commit", "remotenames", "bookmark")
    "trigger",
    # cacheoverflow, logs cache overflow event: not enough space in the
    # cache to store revisions, it will inform us on how to resize the
    # cache if needed
    # => key is "hit", always True
    "cacheoverflow",
    # The three followings are metrics that will be aggregated as ratio
    # they register cache hit and miss at different level: global, diff and
    # during filesnotin operations
    # => key is "hit", True or False, True is a cache hit, False a cache miss
    "cachehit",
    "diffcachehit",
    "filesnotincachehit",
    ## Aggregate Metrics
    # Cache hit ratio (global, diff and filesnotin), expressed as a percentage
    # so between 0 and 100. -1 means no operations.
    # => keys is "ratio", a number
    # examples:
    # -1 for cachehitratio => we never accessed a manifest for the command
    # 30 for cachehitratio => 30% of manifest access hit the cache
    # 45 for diffcachehitratio => 45% of manifest diffs hit the cache
    "cachehitratio",
    "diffcachehitratio",
    "filesnotincachehitratio",
])

class metricscollector(object):
    _instance = None

    @classmethod
    def get(cls):
        if not cls._instance:
            cls._instance = metricscollector()
        return cls._instance

    def __init__(self):
        self.samples = []

    def recordsample(self, kind, **kwargs):
        assert kind in FASTMANIFEST_METRICS
        self.samples.append((kind, kwargs))

    def mergesamples(self, collector):
        if collector is not self:
            self.samples.extend(collector.samples)
        return self

    def _addaggregatesamples(self):
        def _addhitratio(key, aggkey):
            # Aggregate the cache hit and miss to build a hit ratio
            # store the ratio as aggkey : {ratio: ratio} in self.samples
            hit = len([s for s in self.samples
                         if s[0] == key and s[1]["hit"]])
            miss = len([s for s in self.samples
                          if s[0] == key and not s[1]["hit"]])
            if miss + hit == 0:
                ratio = -1
            else:
                ratio=float(hit) * 100 / (miss + hit)

            self.recordsample(aggkey, ratio=ratio)

        _addhitratio("cachehit", "cachehitratio")
        _addhitratio("diffcachehit", "diffcachehitratio")
        _addhitratio("filesnotincachehit", "filesnotincachehitratio")

    def logsamples(self, ui):
        self._addaggregatesamples()
        debug = ui.config("fastmanifest", "debugmetrics", False)
        if debug:
            ui.status(("[FM-METRICS] Begin metrics\n"))

        for kind, kwargs in self.samples:
            if kind in FASTMANIFEST_DONOTREPORT_METRICS:
                continue

            if debug:
                dispkw = kwargs
                # Not removing freespace and limit would make the output of
                # test machine dependant
                if "freespace" in kwargs:
                    del dispkw["freespace"]
                if "limit" in kwargs:
                    del dispkw["limit"]
                # Here we sort to make test output stable
                ui.status(("[FM-METRICS] kind: %s, kwargs: %s\n"
                           % (kind, sorted(dispkw.items()))))
            ui.log('fastmanifest-%s' % kind,
                   "",     # ui.log requires a format string as args[0].
                   **kwargs)
        if debug:
            ui.status(("[FM-METRICS] End metrics\n"))