CFreqControl Struct Reference

Rate limiting for high frequency (>1Hz) jobs. More...

#include <freq_control.hh>

Public Member Functions
	CFreqControl ()
	Default constructor. More...
void	generate (uint64_t nowUs=0)
	Generate tokens. More...
bool	check (size_t need) const
	Check if there are enough tokens. More...
ssize_t	token () const
	Get number of tokens in bucket. More...
bool	get (size_t need=1)
	Get tokens. More...
bool	overdraw (size_t need)
	Overdraw tokens. More...
	CFreqControl (size_t freq, size_t bucketSz)
	Initialize this object. More...
void	init (size_t freq, size_t bucketSz)
	Initialize this object. More...

Detailed Description

Rate limiting for high frequency (>1Hz) jobs.

CFreqControl is a convenient tool for rate limiting, based on Token Bucket algorithm.
Given a frequency F, CFreqControl generates F tokens to bucket per second. Each token represents a job. When there is no token in the bucket, no new job should be created.
The size of bucket is important for burstiness suppression. It denotes the maximum number of jobs created at once. In case of network transmission control for example, a proper bucket size leads to smooth traffic flow in despite of request bursts.

Constructor & Destructor Documentation

CFreqControl::CFreqControl ( )

inline

Default constructor.

You need to call init before you can use this object.

CFreqControl::CFreqControl ( size_t  freq, size_t  bucketSz  )

inline

Initialize this object.

Parameters

freq	A positive integer denoting frequency
bucketSz	Max number of tokens the bucket can hold

Note

You can init this object again to change frequency and bucket size.

Member Function Documentation

bool CFreqControl::check ( size_t  need ) const

inline

Check if there are enough tokens.

Parameters

need	Number of tokens needed

Returns

true if there are at least need tokens in bucket; false otherwise

void CFreqControl::generate ( uint64_t  nowUs = 0 )

inline

Generate tokens.

Parameters

nowUs

Current monotonic time, obtained from tools::MonoTimeUs(), can be omitted

bool CFreqControl::get ( size_t  need = 1 )

inline

Get tokens.

Parameters

need	Number of tokens needed

Returns

• true: Succeeded. need tokens are removed from bucket;
• false: Failed. No tokens are removed from bucket;

void CFreqControl::init ( size_t  freq, size_t  bucketSz  )

inline

Initialize this object.

Parameters

freq	A positive integer denoting frequency
bucketSz	Max number of tokens the bucket can hold

Note

You can init this object again to change frequency and bucket size.

bool CFreqControl::overdraw ( size_t  need )

inline

Overdraw tokens.

Parameters

need	Number of tokens needed

Returns

• true: Succeeded. need tokens are removed or overdrawn from bucket;
• false: Failed. No tokens are removed from bucket;

ssize_t CFreqControl::token ( ) const

inline

Get number of tokens in bucket.

This function may return a negative number when tokens have been overdrawn.

Returns

• Positive number: Number of tokens in bucket;
• Negative number: Number of tokens overdrawn;

See also

overdraw

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The documentation for this struct was generated from the following file:

• freq_control.hh