Source: send.go in package google.golang.org/api/internal/gensupport


package gensupport

import (
	"context"
	"encoding/json"
	"errors"
	"net/http"
	"time"
)

Hook is the type of a function that is called once before each HTTP request that is sent by a generated API. It returns a function that is called after the request returns. Hooks are not called if the context is nil.

type Hook func(ctx context.Context, req *http.Request) func(resp *http.Response)

var hooks []Hook

RegisterHook registers a Hook to be called before each HTTP request by a generated API. Hooks are called in the order they are registered. Each hook can return a function; if it is non-nil, it is called after the HTTP request returns. These functions are called in the reverse order. RegisterHook should not be called concurrently with itself or SendRequest.

func RegisterHook(h Hook) {
	hooks = append(hooks, h)
}

SendRequest sends a single HTTP request using the given client. If ctx is non-nil, it calls all hooks, then sends the request with req.WithContext, then calls any functions returned by the hooks in reverse order.

Disallow Accept-Encoding because it interferes with the automatic gzip handling done by the default http.Transport. See https://github.com/google/google-api-go-client/issues/219.

	if _, ok := req.Header["Accept-Encoding"]; ok {
		return nil, errors.New("google api: custom Accept-Encoding headers not allowed")
	}
	if ctx == nil {
		return client.Do(req)

Call hooks in order of registration, store returned funcs.

	post := make([]func(resp *http.Response), len(hooks))
	for i, h := range hooks {
		fn := h(ctx, req)
		post[i] = fn
	}

Send request.

	resp, err := send(ctx, client, req)

Call returned funcs in reverse order.

	for i := len(post) - 1; i >= 0; i-- {
		if fn := post[i]; fn != nil {
			fn(resp)
		}
	}
	return resp, err
}

func send(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
	if client == nil {
		client = http.DefaultClient
	}

If we got an error, and the context has been canceled, the context's error is probably more useful.

	if err != nil {
		select {
		case <-ctx.Done():
			err = ctx.Err()
		default:
		}
	}
	return resp, err
}

SendRequestWithRetry sends a single HTTP request using the given client, with retries if a retryable error is returned. If ctx is non-nil, it calls all hooks, then sends the request with req.WithContext, then calls any functions returned by the hooks in reverse order.

Disallow Accept-Encoding because it interferes with the automatic gzip handling done by the default http.Transport. See https://github.com/google/google-api-go-client/issues/219.

	if _, ok := req.Header["Accept-Encoding"]; ok {
		return nil, errors.New("google api: custom Accept-Encoding headers not allowed")
	}
	if ctx == nil {
		return client.Do(req)

Call hooks in order of registration, store returned funcs.

	post := make([]func(resp *http.Response), len(hooks))
	for i, h := range hooks {
		fn := h(ctx, req)
		post[i] = fn
	}

Send request with retry.

	resp, err := sendAndRetry(ctx, client, req)

Call returned funcs in reverse order.

	for i := len(post) - 1; i >= 0; i-- {
		if fn := post[i]; fn != nil {
			fn(resp)
		}
	}
	return resp, err
}

func sendAndRetry(ctx context.Context, client *http.Client, req *http.Request) (*http.Response, error) {
	if client == nil {
		client = http.DefaultClient
	}

	var resp *http.Response
	var err error

Loop to retry the request, up to the context deadline.

	var pause time.Duration
	bo := backoff()

	for {
		select {

If we got an error, and the context has been canceled, the context's error is probably more useful.

			if err == nil {
				err = ctx.Err()
			}
			return resp, err
		case <-time.After(pause):
		}

		resp, err = client.Do(req.WithContext(ctx))

		var status int
		if resp != nil {
			status = resp.StatusCode
		}

Check if we can retry the request. A retry can only be done if the error is retryable and the request body can be re-created using GetBody (this will not be possible if the body was unbuffered).

		if req.GetBody == nil || !shouldRetry(status, err) {
			break
		}
		var errBody error
		req.Body, errBody = req.GetBody()
		if errBody != nil {
			break
		}

		pause = bo.Pause()
		if resp != nil && resp.Body != nil {
			resp.Body.Close()
		}
	}
	return resp, err
}

DecodeResponse decodes the body of res into target. If there is no body, target is unchanged.

func DecodeResponse(target interface{}, res *http.Response) error {
	if res.StatusCode == http.StatusNoContent {
		return nil
	}
	return json.NewDecoder(res.Body).Decode(target)