diff options
Diffstat (limited to 'synapse/metrics/metric.py')
| -rw-r--r-- | synapse/metrics/metric.py | 81 |
1 files changed, 67 insertions, 14 deletions
diff --git a/synapse/metrics/metric.py b/synapse/metrics/metric.py index 1d054dd557..f480aae614 100644 --- a/synapse/metrics/metric.py +++ b/synapse/metrics/metric.py @@ -17,16 +17,33 @@ from itertools import chain -# TODO(paul): I can't believe Python doesn't have one of these -def map_concat(func, items): - # flatten a list-of-lists - return list(chain.from_iterable(map(func, items))) +def flatten(items): + """Flatten a list of lists + + Args: + items: iterable[iterable[X]] + + Returns: + list[X]: flattened list + """ + return list(chain.from_iterable(items)) class BaseMetric(object): + """Base class for metrics which report a single value per label set + """ - def __init__(self, name, labels=[]): - self.name = name + def __init__(self, name, labels=[], alternative_names=[]): + """ + Args: + name (str): principal name for this metric + labels (list(str)): names of the labels which will be reported + for this metric + alternative_names (iterable(str)): list of alternative names for + this metric. This can be useful to provide a migration path + when renaming metrics. + """ + self._names = [name] + list(alternative_names) self.labels = labels # OK not to clone as we never write it def dimension(self): @@ -36,7 +53,7 @@ class BaseMetric(object): return not len(self.labels) def _render_labelvalue(self, value): - # TODO: some kind of value escape + # TODO: escape backslashes, quotes and newlines return '"%s"' % (value) def _render_key(self, values): @@ -47,6 +64,36 @@ class BaseMetric(object): for k, v in zip(self.labels, values)]) ) + def _render_for_labels(self, label_values, value): + """Render this metric for a single set of labels + + Args: + label_values (list[str]): values for each of the labels + value: value of the metric at with these labels + + Returns: + iterable[str]: rendered metric + """ + rendered_labels = self._render_key(label_values) + return ( + "%s%s %.12g" % (name, rendered_labels, value) + for name in self._names + ) + + def render(self): + """Render this metric + + Each metric is rendered as: + + name{label1="val1",label2="val2"} value + + https://prometheus.io/docs/instrumenting/exposition_formats/#text-format-details + + Returns: + iterable[str]: rendered metrics + """ + raise NotImplementedError() + class CounterMetric(BaseMetric): """The simplest kind of metric; one that stores a monotonically-increasing @@ -62,6 +109,10 @@ class CounterMetric(BaseMetric): def __init__(self, *args, **kwargs): super(CounterMetric, self).__init__(*args, **kwargs) + # dict[list[str]]: value for each set of label values. the keys are the + # label values, in the same order as the labels in self.labels. + # + # (if the metric is a scalar, the (single) key is the empty list). self.counts = {} # Scalar metrics are never empty @@ -84,11 +135,11 @@ class CounterMetric(BaseMetric): def inc(self, *values): self.inc_by(1, *values) - def render_item(self, k): - return ["%s%s %.12g" % (self.name, self._render_key(k), self.counts[k])] - def render(self): - return map_concat(self.render_item, sorted(self.counts.keys())) + return flatten( + self._render_for_labels(k, self.counts[k]) + for k in sorted(self.counts.keys()) + ) class CallbackMetric(BaseMetric): @@ -105,10 +156,12 @@ class CallbackMetric(BaseMetric): value = self.callback() if self.is_scalar(): - return ["%s %.12g" % (self.name, value)] + return list(self._render_for_labels([], value)) - return ["%s%s %.12g" % (self.name, self._render_key(k), value[k]) - for k in sorted(value.keys())] + return flatten( + self._render_for_labels(k, value[k]) + for k in sorted(value.keys()) + ) class DistributionMetric(object): |