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net/http: cache transport environment lookup
Apparently this is expensive on Windows. Fixes #7020 R=golang-codereviews, alex.brainman, mattn.jp, dvyukov CC=golang-codereviews https://golang.org/cl/52840043
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@ -63,4 +63,9 @@ func NewTestTimeoutHandler(handler Handler, ch <-chan time.Time) Handler {
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return &timeoutHandler{handler, f, ""}
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}
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func ResetCachedEnvironment() {
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httpProxyEnv.reset()
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noProxyEnv.reset()
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}
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var DefaultUserAgent = defaultUserAgent
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@ -99,7 +99,7 @@ type Transport struct {
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// A nil URL and nil error are returned if no proxy is defined in the
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// environment, or a proxy should not be used for the given request.
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func ProxyFromEnvironment(req *Request) (*url.URL, error) {
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proxy := getenvEitherCase("HTTP_PROXY")
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proxy := httpProxyEnv.Get()
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if proxy == "" {
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return nil, nil
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}
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@ -243,11 +243,42 @@ func (t *Transport) CancelRequest(req *Request) {
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// Private implementation past this point.
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//
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func getenvEitherCase(k string) string {
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if v := os.Getenv(strings.ToUpper(k)); v != "" {
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return v
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var (
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httpProxyEnv = &envOnce{
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names: []string{"HTTP_PROXY", "http_proxy"},
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}
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return os.Getenv(strings.ToLower(k))
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noProxyEnv = &envOnce{
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names: []string{"NO_PROXY", "no_proxy"},
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}
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)
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// envOnce looks up an environment variable (optionally by multiple
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// names) once. It mitigates expensive lookups on some platforms
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// (e.g. Windows).
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type envOnce struct {
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names []string
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once sync.Once
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val string
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}
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func (e *envOnce) Get() string {
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e.once.Do(e.init)
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return e.val
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}
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func (e *envOnce) init() {
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for _, n := range e.names {
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e.val = os.Getenv(n)
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if e.val != "" {
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return
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}
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}
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}
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// reset is used by tests
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func (e *envOnce) reset() {
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e.once = sync.Once{}
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e.val = ""
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}
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func (t *Transport) connectMethodForRequest(treq *transportRequest) (*connectMethod, error) {
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@ -550,7 +581,7 @@ func useProxy(addr string) bool {
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}
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}
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no_proxy := getenvEitherCase("NO_PROXY")
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no_proxy := noProxyEnv.Get()
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if no_proxy == "*" {
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return false
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}
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@ -1566,6 +1566,7 @@ func TestProxyFromEnvironment(t *testing.T) {
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for _, tt := range proxyFromEnvTests {
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os.Setenv("HTTP_PROXY", tt.env)
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os.Setenv("NO_PROXY", tt.noenv)
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ResetCachedEnvironment()
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reqURL := tt.req
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if reqURL == "" {
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reqURL = "http://example.com"
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