hedgedhttp

README

hedgedhttp

Hedged HTTP client which helps to reduce tail latency at scale.

Rationale

See paper Tail at Scale by Jeffrey Dean, Luiz André Barroso. In short: the client first sends one request, but then sends an additional request after a timeout if the previous hasn't returned an answer in the expected time. The client cancels remaining requests once the first result is received.

Acknowledge

Thanks to Bohdan Storozhuk for the review and powerful hints.

Features

• Simple API.
• Easy to integrate.
• Optimized for speed.
• Clean and tested code.
• Dependency-free.

Install

Go version 1.16+

go get github.com/cristalhq/hedgedhttp

Example

TODO

Documentation

See these docs.

License

MIT License.

Documentation

Index

• func NewClient(timeout time.Duration, upto int, client *http.Client) *http.Client
• func NewRoundTripper(timeout time.Duration, upto int, rt http.RoundTripper) http.RoundTripper
• type ErrorFormatFunc
• type MultiError
  • func (e *MultiError) Error() string
  • func (e *MultiError) ErrorOrNil() error
  • func (e *MultiError) String() string

Functions

func NewClient

func NewClient(timeout time.Duration, upto int, client *http.Client) *http.Client

NewClient returns a new http.Client which implements hedged requests pattern. Given Client starts a new request after a timeout from previous request. Starts no more than upto requests.

func NewRoundTripper

func NewRoundTripper(timeout time.Duration, upto int, rt http.RoundTripper) http.RoundTripper

NewRoundTripper returns a new http.RoundTripper which implements hedged requests pattern. Given RoundTripper starts a new request after a timeout from previous request. Starts no more than upto requests.

Types

type ErrorFormatFunc

type ErrorFormatFunc func([]error) string

ErrorFormatFunc is called by MultiError to return the list of errors as a string.

type MultiError

type MultiError struct {
	Errors        []error
	ErrorFormatFn ErrorFormatFunc
}

MultiError is an error type to track multiple errors. This is used to accumulate errors in cases and return them as a single "error". Insiper by https://github.com/hashicorp/go-multierror

func (*MultiError) Error

func (e *MultiError) Error() string

func (*MultiError) ErrorOrNil

func (e *MultiError) ErrorOrNil() error

ErrorOrNil returns an error if there are some.

func (*MultiError) String

func (e *MultiError) String() string