uk.co.visalia.brightpearl.apiclient.ratelimit

Class ConstantWaitRateLimiter

java.lang.Object

uk.co.visalia.brightpearl.apiclient.ratelimit.ConstantWaitRateLimiter

All Implemented Interfaces:

RateLimiter

public class ConstantWaitRateLimiter
extends Object
implements RateLimiter

A very basic implementation of RateLimiter that will reduce the throughput of requests by pausing for the minimum period required to ensure the cap is not exceeded. By default this is 300 ms. Each calling thread is blocked until the request may be sent, so this is not suitable for use as a queue.

If there is more than one server making requests to the same Brightpearl account, this approach will only be effective if this class is configured with a 1/n share of the request cap, which increases latency for all requests, however a distributed tracking approach may be more appropriate.

This class is intended to prevent hitting the request cap for an account, and its behaviour is not affected by an account unexpectedly being throttled.

Constructor Summary

Constructors

Constructor and Description
ConstantWaitRateLimiter() Construct a constant wait rate limiter with the default settings, limiting requests to 200 per minute.
ConstantWaitRateLimiter(int cap, int period, TimeUnit periodUnit) Construct a constant wait limiter with a custom rate limit.

Method Summary

Methods

Modifier and Type	Method and Description
void	rateLimit(Account account) Called before a request is made, this sleeps for the minimum amount of time that must be left to ensure no more than the maximum number of requests are made in the configured period.
void	requestCapExceeded(Account account) This implementation does nothing.
void	requestCompleted(Account account, int requestsRemaining, long nextThrottlePeriod) This implementation does nothing.

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

ConstantWaitRateLimiter

public ConstantWaitRateLimiter()

Construct a constant wait rate limiter with the default settings, limiting requests to 200 per minute. This is suitable for a single node system.

ConstantWaitRateLimiter

public ConstantWaitRateLimiter(int cap,
                       int period,
                       TimeUnit periodUnit)

Construct a constant wait limiter with a custom rate limit. Avoid low rates as this will cause high latency during busy periods.

Parameters:

cap - The number of requests allowed in the given period.

period - The period of time.

periodUnit - Unit of the period of time.

Method Detail

rateLimit

public void rateLimit(Account account)

Called before a request is made, this sleeps for the minimum amount of time that must be left to ensure no more than the maximum number of requests are made in the configured period. With default configuration, the maximum wait will be 300ms to give a rate of 200 per minute. If more than 300ms has passed since the previous request, the wait will be zero.

Specified by:

rateLimit in interface RateLimiter

Parameters:

account - The account a request is about to be sent to.

requestCompleted

public void requestCompleted(Account account,
                    int requestsRemaining,
                    long nextThrottlePeriod)

This implementation does nothing.

Specified by:

requestCompleted in interface RateLimiter

Parameters:

account - The account a response has been received from.

requestsRemaining - The value of the brightpearl-requests-remaining response header.

nextThrottlePeriod - The value of the brightpearl-next-throttle-period header.

requestCapExceeded

public void requestCapExceeded(Account account)

This implementation does nothing. Use of this class should prevent the request cap being reached, and it does not modify its constant wait behaviour if the request cap is unexpectedly hit.

Specified by:

requestCapExceeded in interface RateLimiter

Parameters:

account - The account that received a 503 request cap error.