gentleman-retry

gentleman's v2 plugin providing retry policy capabilities to your HTTP clients.

Constant backoff strategy will be used by default with a maximum of 3 attempts, but you use a custom or third-party retry strategies. Request bodies will be cached in the stack in order to re-send them if needed.

By default, retry will happen in case of network error or server response error (>= 500 || = 429). You can use a custom Evaluator function to determine with custom logic when should retry or not.

Behind the scenes it implements a custom http.RoundTripper interface which acts like a proxy to http.Transport, in order to take full control of the response and retry the request if needed.

Installation

go get -u gopkg.in/h2non/gentleman-retry.v2

Versions

v1 - First version, uses gentleman@v1.
v2 - Latest version, uses gentleman@v2.

API

See godoc reference for detailed API documentation.

Examples

Default retry strategy

package main

import (
  "fmt"

  "gopkg.in/h2non/gentleman.v2"
  "gopkg.in/h2non/gentleman-retry.v2"
)

func main() {
  // Create a new client
  cli := gentleman.New()

  // Define base URL
  cli.URL("http://httpbin.org")

  // Register the retry plugin, using the built-in constant back off strategy
  cli.Use(retry.New(retry.ConstantBackoff))

  // Create a new request based on the current client
  req := cli.Request()

  // Define the URL path at request level
  req.Path("/status/503")

  // Set a new header field
  req.SetHeader("Client", "gentleman")

  // Perform the request
  res, err := req.Send()
  if err != nil {
    fmt.Printf("Request error: %s\n", err)
    return
  }
  if !res.Ok {
    fmt.Printf("Invalid server response: %d\n", res.StatusCode)
    return
  }
}

Exponential retry strategy

I would recommend you using go-resiliency package for custom retry estrategies:

go get -u gopkg.in/eapache/go-resiliency.v1/retrier

package main

import (
  "fmt"
  "time"

  "gopkg.in/h2non/gentleman.v2"
  "gopkg.in/h2non/gentleman-retry.v2"
  "gopkg.in/eapache/go-resiliency.v1/retrier"

)

func main() {
  // Create a new client
  cli := gentleman.New()

  // Define base URL
  cli.URL("http://httpbin.org")

  // Register the retry plugin, using a custom exponential retry strategy
  cli.Use(retry.New(retrier.New(retrier.ExponentialBackoff(3, 100*time.Millisecond), nil)))

  // Create a new request based on the current client
  req := cli.Request()

  // Define the URL path at request level
  req.Path("/status/503")

  // Set a new header field
  req.SetHeader("Client", "gentleman")

  // Perform the request
  res, err := req.Send()
  if err != nil {
    fmt.Printf("Request error: %s\n", err)
    return
  }
  if !res.Ok {
    fmt.Printf("Invalid server response: %d\n", res.StatusCode)
    return
  }
}

License

MIT - Tomas Aparicio

h2non / gentleman-retry