This class represents a bucketed time series which keeps track of values added in the recent past, and merges these values together into a fixed number of buckets to keep a lid on memory use if the number of values added is very large.

Synopsis

Declared in <folly/stats/BucketedTimeSeries.h>

template<
    typename VT,
    typename CT = LegacyStatsClock<std::chrono::seconds>>
class BucketedTimeSeries;

Description

For example, a BucketedTimeSeries() with duration == 60s and 10 buckets will keep track of 10 6‐second buckets, and discard all data added more than 1 minute ago. As time ticks by, a 6‐second bucket at a time will be discarded and new data will go into the newly opened bucket. Internally, it uses a circular array of buckets that it reuses as time advances.

This class assumes that time advances forwards. The window of time tracked by the timeseries will advance forwards whenever a more recent timestamp is passed to addValue(). While it is possible to pass old time values to addValue(), this will never move the time window backwards. If the old time value falls outside the tracked window of time, the data point will be ignored.

This class is not thread‐safe ‐‐ use your own synchronization!

Type Aliases

Name

Description

Bucket

The bucket type used to aggregate values.

Clock

The clock type used for timestamps.

Duration

The duration type of the clock.

TimePoint

The time point type of the clock.

ValueType

The type of the values stored in the time series.

Member Functions

Name

Description

BucketedTimeSeries [constructor]

Create a new BucketedTimeSeries.

addValue

addValue overloads

addValueAggregated

addValueAggregated overloads

avg

avg overloads

buckets

Returns actual buckets of values

clear

Reset the timeseries to an empty state, as if no data points have ever been added to it.

count

count overloads

countRate

countRate overloads

duration

Return the maximum duration of data that can be tracked by this BucketedTimeSeries.

elapsed

elapsed overloads

empty

Returns true if no calls to update() have been made since the last call to clear().

firstTime

Returns the oldest time observed either by adding value or calling update() since clear()/constructor. Note that the returned value is only meaningful when empty() is false.

forEachBucket

Invoke a function for each bucket.

getBucketByIndex

Get the bucket at the specified index.

getBucketIdx

Get the index for the bucket containing the specified time.

getBucketInfo

Compute the bucket index that the specified time falls into, as well as the bucket start time and the next bucket's start time.

getEarliestTime

Get the time of the earliest data point stored in this timeseries.

getEarliestTrackableTimeBy

For a non‐all‐time timeseries, return the earliest time that could be tracked by the timeseries with the provided latest time. It can return a time point that is earlier than firstTime_.

getLatestTime

See latestTime()

isAllTime

Returns true if this BucketedTimeSeries stores data for all‐time, without ever rolling over into new buckets.

latestTime

Returns the latest time observed either by adding value or calling update() since clear()/constructor. Note that the returned value is only meaningful when empty() is false.

numBuckets

Return the number of buckets.

rate

rate overloads

rateHelper

Compute a rate from a numerator and an elapsed time.

sum

sum overloads

totalBy

Return the total (sum and count) of the tracked buckets that overlap with [getEarliestTrackableTimeBy(now), now]. now must be greater than or equal to latestTime_. If isAllTime() is true, the overall total will be returned.

update

update overloads

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