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http.go
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http.go
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// Copyright 2016 CoreOS, Inc.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
package resource
import (
"errors"
"io"
"net"
"net/http"
"time"
"github.com/coreos/ignition/internal/log"
"github.com/coreos/ignition/internal/version"
)
const (
maxAttempts = 15
initialBackoff = 100 * time.Millisecond
maxBackoff = 5 * time.Second
)
var (
ErrTimeout = errors.New("unable to fetch resource in time")
)
// HttpClient is a simple wrapper around the Go HTTP client that standardizes
// the process and logging of fetching payloads.
type HttpClient struct {
client *http.Client
logger *log.Logger
}
// NewHttpClient creates a new client with the given logger.
func NewHttpClient(logger *log.Logger) HttpClient {
return HttpClient{
client: &http.Client{
Transport: &http.Transport{
ResponseHeaderTimeout: 10 * time.Second,
Dial: (&net.Dialer{
Timeout: 30 * time.Second,
KeepAlive: 30 * time.Second,
}).Dial,
TLSHandshakeTimeout: 10 * time.Second,
},
},
logger: logger,
}
}
// getReaderWithHeader performs an HTTP GET on the provided URL with the provided request header
// and returns the response body Reader, HTTP status code, and error (if any). By
// default, User-Agent is added to the header but this can be overridden.
func (c HttpClient) getReaderWithHeader(url string, header http.Header) (io.ReadCloser, int, error) {
req, err := http.NewRequest("GET", url, nil)
if err != nil {
return nil, 0, err
}
req.Header.Set("User-Agent", "Ignition/"+version.Raw)
for key, values := range header {
req.Header.Del(key)
for _, value := range values {
req.Header.Add(key, value)
}
}
duration := initialBackoff
for attempt := 1; attempt <= maxAttempts; attempt++ {
c.logger.Debug("GET %s: attempt #%d", url, attempt)
resp, err := c.client.Do(req)
if err == nil {
c.logger.Debug("GET result: %s", http.StatusText(resp.StatusCode))
if resp.StatusCode < 500 {
return resp.Body, resp.StatusCode, nil
}
resp.Body.Close()
} else {
c.logger.Debug("GET error: %v", err)
}
duration = duration * 2
if duration > maxBackoff {
duration = maxBackoff
}
time.Sleep(duration)
}
return nil, 0, ErrTimeout
}