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package etcd
import (
"errors"
"fmt"
"io"
"io/ioutil"
"net/http"
"net/url"
"path"
"strings"
"sync"
"time"
)
// Errors introduced by handling requests
var (
ErrRequestCancelled = errors.New("sending request is cancelled")
)
type RawRequest struct {
Method string
RelativePath string
Values url.Values
Cancel <-chan bool
}
// NewRawRequest returns a new RawRequest
func NewRawRequest(method, relativePath string, values url.Values, cancel <-chan bool) *RawRequest {
return &RawRequest{
Method: method,
RelativePath: relativePath,
Values: values,
Cancel: cancel,
}
}
// getCancelable issues a cancelable GET request
func (c *Client) getCancelable(key string, options Options,
cancel <-chan bool) (*RawResponse, error) {
logger.Debugf("get %s [%s]", key, c.cluster.pick())
p := keyToPath(key)
str, err := options.toParameters(VALID_GET_OPTIONS)
if err != nil {
return nil, err
}
p += str
req := NewRawRequest("GET", p, nil, cancel)
resp, err := c.SendRequest(req)
if err != nil {
return nil, err
}
return resp, nil
}
// get issues a GET request
func (c *Client) get(key string, options Options) (*RawResponse, error) {
return c.getCancelable(key, options, nil)
}
// put issues a PUT request
func (c *Client) put(key string, value string, ttl uint64,
options Options) (*RawResponse, error) {
logger.Debugf("put %s, %s, ttl: %d, [%s]", key, value, ttl, c.cluster.pick())
p := keyToPath(key)
str, err := options.toParameters(VALID_PUT_OPTIONS)
if err != nil {
return nil, err
}
p += str
req := NewRawRequest("PUT", p, buildValues(value, ttl), nil)
resp, err := c.SendRequest(req)
if err != nil {
return nil, err
}
return resp, nil
}
// post issues a POST request
func (c *Client) post(key string, value string, ttl uint64) (*RawResponse, error) {
logger.Debugf("post %s, %s, ttl: %d, [%s]", key, value, ttl, c.cluster.pick())
p := keyToPath(key)
req := NewRawRequest("POST", p, buildValues(value, ttl), nil)
resp, err := c.SendRequest(req)
if err != nil {
return nil, err
}
return resp, nil
}
// delete issues a DELETE request
func (c *Client) delete(key string, options Options) (*RawResponse, error) {
logger.Debugf("delete %s [%s]", key, c.cluster.pick())
p := keyToPath(key)
str, err := options.toParameters(VALID_DELETE_OPTIONS)
if err != nil {
return nil, err
}
p += str
req := NewRawRequest("DELETE", p, nil, nil)
resp, err := c.SendRequest(req)
if err != nil {
return nil, err
}
return resp, nil
}
// SendRequest sends a HTTP request and returns a Response as defined by etcd
func (c *Client) SendRequest(rr *RawRequest) (*RawResponse, error) {
var req *http.Request
var resp *http.Response
var httpPath string
var err error
var respBody []byte
var numReqs = 1
checkRetry := c.CheckRetry
if checkRetry == nil {
checkRetry = DefaultCheckRetry
}
cancelled := make(chan bool, 1)
reqLock := new(sync.Mutex)
if rr.Cancel != nil {
cancelRoutine := make(chan bool)
defer close(cancelRoutine)
go func() {
select {
case <-rr.Cancel:
cancelled <- true
logger.Debug("send.request is cancelled")
case <-cancelRoutine:
return
}
// Repeat canceling request until this thread is stopped
// because we have no idea about whether it succeeds.
for {
reqLock.Lock()
c.httpClient.Transport.(*http.Transport).CancelRequest(req)
reqLock.Unlock()
select {
case <-time.After(100 * time.Millisecond):
case <-cancelRoutine:
return
}
}
}()
}
// If we connect to a follower and consistency is required, retry until
// we connect to a leader
sleep := 25 * time.Millisecond
maxSleep := time.Second
for attempt := 0; ; attempt++ {
if attempt > 0 {
select {
case <-cancelled:
return nil, ErrRequestCancelled
case <-time.After(sleep):
sleep = sleep * 2
if sleep > maxSleep {
sleep = maxSleep
}
}
}
logger.Debug("Connecting to etcd: attempt ", attempt+1, " for ", rr.RelativePath)
// get httpPath if not set
if httpPath == "" {
httpPath = c.getHttpPath(rr.RelativePath)
}
// Return a cURL command if curlChan is set
if c.cURLch != nil {
command := fmt.Sprintf("curl -X %s %s", rr.Method, httpPath)
for key, value := range rr.Values {
command += fmt.Sprintf(" -d %s=%s", key, value[0])
}
if c.credentials != nil {
command += fmt.Sprintf(" -u %s", c.credentials.username)
}
c.sendCURL(command)
}
logger.Debug("send.request.to ", httpPath, " | method ", rr.Method)
req, err := func() (*http.Request, error) {
reqLock.Lock()
defer reqLock.Unlock()
if rr.Values == nil {
if req, err = http.NewRequest(rr.Method, httpPath, nil); err != nil {
return nil, err
}
} else {
body := strings.NewReader(rr.Values.Encode())
if req, err = http.NewRequest(rr.Method, httpPath, body); err != nil {
return nil, err
}
req.Header.Set("Content-Type",
"application/x-www-form-urlencoded; param=value")
}
return req, nil
}()
if err != nil {
return nil, err
}
if c.credentials != nil {
req.SetBasicAuth(c.credentials.username, c.credentials.password)
}
resp, err = c.httpClient.Do(req)
// clear previous httpPath
httpPath = ""
defer func() {
if resp != nil {
resp.Body.Close()
}
}()
// If the request was cancelled, return ErrRequestCancelled directly
select {
case <-cancelled:
return nil, ErrRequestCancelled
default:
}
numReqs++
// network error, change a machine!
if err != nil {
logger.Debug("network error: ", err.Error())
lastResp := http.Response{}
if checkErr := checkRetry(c.cluster, numReqs, lastResp, err); checkErr != nil {
return nil, checkErr
}
c.cluster.failure()
continue
}
// if there is no error, it should receive response
logger.Debug("recv.response.from ", httpPath)
if validHttpStatusCode[resp.StatusCode] {
// try to read byte code and break the loop
respBody, err = ioutil.ReadAll(resp.Body)
if err == nil {
logger.Debug("recv.success ", httpPath)
break
}
// ReadAll error may be caused due to cancel request
select {
case <-cancelled:
return nil, ErrRequestCancelled
default:
}
if err == io.ErrUnexpectedEOF {
// underlying connection was closed prematurely, probably by timeout
// TODO: empty body or unexpectedEOF can cause http.Transport to get hosed;
// this allows the client to detect that and take evasive action. Need
// to revisit once code.google.com/p/go/issues/detail?id=8648 gets fixed.
respBody = []byte{}
break
}
}
if resp.StatusCode == http.StatusTemporaryRedirect {
u, err := resp.Location()
if err != nil {
logger.Warning(err)
} else {
// set httpPath for following redirection
httpPath = u.String()
}
resp.Body.Close()
continue
}
if checkErr := checkRetry(c.cluster, numReqs, *resp,
errors.New("Unexpected HTTP status code")); checkErr != nil {
return nil, checkErr
}
resp.Body.Close()
}
r := &RawResponse{
StatusCode: resp.StatusCode,
Body: respBody,
Header: resp.Header,
}
return r, nil
}
// DefaultCheckRetry defines the retrying behaviour for bad HTTP requests
// If we have retried 2 * machine number, stop retrying.
// If status code is InternalServerError, sleep for 200ms.
func DefaultCheckRetry(cluster *Cluster, numReqs int, lastResp http.Response,
err error) error {
if numReqs > 2*len(cluster.Machines) {
errStr := fmt.Sprintf("failed to propose on members %v twice [last error: %v]", cluster.Machines, err)
return newError(ErrCodeEtcdNotReachable, errStr, 0)
}
if isEmptyResponse(lastResp) {
// always retry if it failed to get response from one machine
return nil
}
if !shouldRetry(lastResp) {
body := []byte("nil")
if lastResp.Body != nil {
if b, err := ioutil.ReadAll(lastResp.Body); err == nil {
body = b
}
}
errStr := fmt.Sprintf("unhandled http status [%s] with body [%s]", http.StatusText(lastResp.StatusCode), body)
return newError(ErrCodeUnhandledHTTPStatus, errStr, 0)
}
// sleep some time and expect leader election finish
time.Sleep(time.Millisecond * 200)
logger.Warning("bad response status code ", lastResp.StatusCode)
return nil
}
func isEmptyResponse(r http.Response) bool { return r.StatusCode == 0 }
// shouldRetry returns whether the reponse deserves retry.
func shouldRetry(r http.Response) bool {
// TODO: only retry when the cluster is in leader election
// We cannot do it exactly because etcd doesn't support it well.
return r.StatusCode == http.StatusInternalServerError
}
func (c *Client) getHttpPath(s ...string) string {
fullPath := c.cluster.pick() + "/" + version
for _, seg := range s {
fullPath = fullPath + "/" + seg
}
return fullPath
}
// buildValues builds a url.Values map according to the given value and ttl
func buildValues(value string, ttl uint64) url.Values {
v := url.Values{}
if value != "" {
v.Set("value", value)
}
if ttl > 0 {
v.Set("ttl", fmt.Sprintf("%v", ttl))
}
return v
}
// convert key string to http path exclude version, including URL escaping
// for example: key[foo] -> path[keys/foo]
// key[/%z] -> path[keys/%25z]
// key[/] -> path[keys/]
func keyToPath(key string) string {
// URL-escape our key, except for slashes
p := strings.Replace(url.QueryEscape(path.Join("keys", key)), "%2F", "/", -1)
// corner case: if key is "/" or "//" ect
// path join will clear the tailing "/"
// we need to add it back
if p == "keys" {
p = "keys/"
}
return p
}
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