1 // Copyright 2017, OpenCensus Authors 2 // 3 // Licensed under the Apache License, Version 2.0 (the "License"); 4 // you may not use this file except in compliance with the License. 5 // You may obtain a copy of the License at 6 // 7 // http://www.apache.org/licenses/LICENSE-2.0 8 // 9 // Unless required by applicable law or agreed to in writing, software 10 // distributed under the License is distributed on an "AS IS" BASIS, 11 // WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. 12 // See the License for the specific language governing permissions and 13 // limitations under the License. 14 // 15 16 /* 17 Package stats contains support for OpenCensus stats recording. 18 19 OpenCensus allows users to create typed measures, record measurements, 20 aggregate the collected data, and export the aggregated data. 21 22 # Measures 23 24 A measure represents a type of data point to be tracked and recorded. 25 For example, latency, request Mb/s, and response Mb/s are measures 26 to collect from a server. 27 28 Measure constructors such as Int64 and Float64 automatically 29 register the measure by the given name. Each registered measure needs 30 to be unique by name. Measures also have a description and a unit. 31 32 Libraries can define and export measures. Application authors can then 33 create views and collect and break down measures by the tags they are 34 interested in. 35 36 # Recording measurements 37 38 Measurement is a data point to be collected for a measure. For example, 39 for a latency (ms) measure, 100 is a measurement that represents a 100ms 40 latency event. Measurements are created from measures with 41 the current context. Tags from the current context are recorded with the 42 measurements if they are any. 43 44 Recorded measurements are dropped immediately if no views are registered for them. 45 There is usually no need to conditionally enable and disable 46 recording to reduce cost. Recording of measurements is cheap. 47 48 Libraries can always record measurements, and applications can later decide 49 on which measurements they want to collect by registering views. This allows 50 libraries to turn on the instrumentation by default. 51 52 # Exemplars 53 54 For a given recorded measurement, the associated exemplar is a diagnostic map 55 that gives more information about the measurement. 56 57 When aggregated using a Distribution aggregation, an exemplar is kept for each 58 bucket in the Distribution. This allows you to easily find an example of a 59 measurement that fell into each bucket. 60 61 For example, if you also use the OpenCensus trace package and you 62 record a measurement with a context that contains a sampled trace span, 63 then the trace span will be added to the exemplar associated with the measurement. 64 65 When exported to a supporting back end, you should be able to easily navigate 66 to example traces that fell into each bucket in the Distribution. 67 */ 68 package stats // import "go.opencensus.io/stats" 69