erl
pkg.go.devgithub.com/fastly/compute-sdk-go/erl
Package erl provides Edge Rate Limiting functionality.
This package includes a RateCounter type that can be used to increment an event counter, and to examine the rate of events per second within a POP over 1, 10, and 60 second windows. It can also estimate the number of events seen over the past minute within a POP in 10 second buckets.
The PenaltyBox type can be used to track entries that should be penalized for a certain amount of time.
The RateLimiter type combines a rate counter and a penalty box to determine whether a given entry should be rate limited based on whether it exceeds a maximum threshold of events per second over a given rate window. Most users can simply use RateLimiter.CheckRate rather than methods on RateCounter and PenaltyBox.
Rate counters and penalty boxes are combined and synchronized within a POP. However, Edge Rate Limiting is not intended to compute counts or rates with high precision and may under count by up to 10%.
Both rate counters and penalty boxes have a fixed capacity for entries. Once a rate counter is full, each new entry evicts the entry that was least recently incremented. Once a penalty box is full, each new entry will evict the entry with the shortest remaining time-to-live (TTL).
Structs
| PenaltyBox | PenaltyBox is a type that allows entries to be penalized for a given number of minutes in the future. |
| Policy | Policy contains the rules for applying a RateLimiter. |
| RateCounter | RateCounter is a named counter that can be incremented and queried. |
| RateLimiter | RateLimiter combines a RateCounter and a PenaltyBox to provide an easy way to check whether a given entry should be rate limited given a rate window and upper limit. |
Type aliases
| CounterDuration | CounterDuration indicates the estimated number of events in this duration in the current POP. Counts are divided into 10 second buckets, and each bucket represents the estimated number of requests received up to and including that 10 second window. |
| RateWindow | RateWindow indicates the rate of events per second in the current POP over one of a few predefined time windows. See [RateWindow1s], [RateWindow10s], and [RateWindow60s]. |
Functions
| NewRateLimiter | NewRateLimiter creates a new rate limiter. |
| OpenPenaltyBox | OpenPenaltyBox opens a penalty box with the given name, creating it if it doesn't already exist. The penalty box name may be up to 64 characters long. Entry names in this penalty box are also limited to 64 characters. |
| OpenRateCounter | OpenRateCounter opens a rate counter with the given name, creating it if it doesn't already exist. The rate counter name may be up to 64 characters long. Entry names in this counter are also limited to 64 characters. |
Variables
Default: fastly.CounterDuration10s
CounterDuration10s indicates the estimated number of events in the most recent 10 second bucket.
Default: fastly.CounterDuration20s
CounterDuration20s indicates the estimated number of events in the most recent two 10 second buckets.
Default: fastly.CounterDuration30s
CounterDuration30s indicates the estimated number of events in the most recent three 10 second buckets.
Default: fastly.CounterDuration40s
CounterDuration40s indicates the estimated number of events in the most recent four 10 second buckets.
Default: fastly.CounterDuration50s
CounterDuration50s indicates the estimated number of events in the most recent five 10 second buckets.
Default: fastly.CounterDuration60s
CounterDuration60s indicates the estimated number of events in the most recent six 10 second buckets.
Default: errors.New("invalid argument")
ErrInvalidArgument indicates that an invalid argument was passed to one of the edge rate limiter methods.
Most functions and methods have limited ranges for their parameters. See the documentation for each call for more details.
Default: errors.New("unexpected error")
ErrUnexpected indicates that an unexpected error occurred.
Default: fastly.RateWindow10s
RateWindow10s indicates the rate of events per second over the past 10 seconds.
Default: fastly.RateWindow1s
RateWindow1s incidates the rate of events per second over the past second.
Default: fastly.RateWindow60s
RateWindow60s indicates the rate of events per second over the past 60 seconds.
