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5XX Retry Logic Best Practices - Go

Review best practices to deal with 5XX errors in Go

Method 1 - Using retry:

package retry
​
import (
"math/rand"
"net/http"
"time"
)
​
var (
defaultSleep = 500 * time.Millisecond
)
​
// Func is the function to be executed and eventually retried.
type Func func() error
​
// HTTPFunc is the function to be executed and eventually retried.
// The only difference from Func is that it expects an *http.Response on the first returning argument.
type HTTPFunc func() (*http.Response, error)
​
// Do runs the passed function until the number of retries is reached.
// Whenever Func returns err it will sleep and Func will be executed again in a recursive fashion.
// The sleep value is slightly modified on every retry (exponential backoff) to prevent the thundering herd problem (https://en.wikipedia.org/wiki/Thundering_herd_problem).
// If no value is given to sleep it will defaults to 500ms.
func Do(fn Func, retries int, sleep time.Duration) error {
if sleep == 0 {
sleep = defaultSleep
}
​
if err := fn(); err != nil {
retries--
if retries <= 0 {
return err
}
​
// preventing thundering herd problem (https://en.wikipedia.org/wiki/Thundering_herd_problem)
sleep += (time.Duration(rand.Int63n(int64(sleep)))) / 2
time.Sleep(sleep)
​
return Do(fn, retries, 2*sleep)
}
​
return nil
}
​
// DoHTTP wraps Func and returns *http.Response and error as returning arguments.
func DoHTTP(fn HTTPFunc, retries int, sleep time.Duration) (*http.Response, error) {
var res *http.Response
​
err := Do(func() error {
var err error
res, err = fn()
return err
}, retries, sleep)
​
return res, err
}
Check out this Awesome Github repo for more details and pseudo code - Here​
Simple Go Lang. Library for retry mechanism - Check Here​

Method 2 - Using go-retryablehttp

The retryablehttp package provides a familiar HTTP client interface with automatic retries and exponential backoff. It is a thin wrapper over the standard net/http client library and exposes nearly the same public API. This makes retryablehttp very easy to drop into existing programs.
retryablehttp Performs automatic retries under certain conditions. Mainly, if an error is returned by the client (connection errors, etc.), or if a 500-range response code is received (except 501), then a retry is invoked after a wait period. Otherwise, the response is returned and left to the caller to interpret.
The main difference from net/http is that requests which take a request body (POST/PUT et. al) can have the body provided in a number of ways (some more or less efficient) that allow "rewinding" the request body if the initial request fails so that the full request can be attempted again.
Example Use
Using this library should look almost identical to what you would do with net/http. The most simple example of a GET request is shown below:
resp, err := retryablehttp.Get("/foo")
if err != nil {
panic(err)
}
The returned response object is an *http.Response the same thing you would usually get from net/http. Had the request failed one or more times, the above call would block and retry with exponential backoff.
For more usage and examples see the godoc & GitHub ​