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requests.go
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requests.go
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package etcd
import (
"errors"
"fmt"
"io/ioutil"
"math/rand"
"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.Leader)
p := keyToPath(key)
// If consistency level is set to STRONG, append
// the `consistent` query string.
if c.config.Consistency == STRONG_CONSISTENCY {
options["consistent"] = true
}
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.Leader)
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.Leader)
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.Leader)
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)
if rr.Method == "GET" && c.config.Consistency == WEAK_CONSISTENCY {
// If it's a GET and consistency level is set to WEAK,
// then use a random machine.
httpPath = c.getHttpPath(true, rr.RelativePath)
} else {
// Else use the leader.
httpPath = c.getHttpPath(false, 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])
}
c.sendCURL(command)
}
logger.Debug("send.request.to ", httpPath, " | method ", rr.Method)
reqLock.Lock()
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")
}
reqLock.Unlock()
resp, err = c.httpClient.Do(req)
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.switchLeader(attempt % len(c.cluster.Machines))
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 resp is TemporaryRedirect, set the new leader and retry
if resp.StatusCode == http.StatusTemporaryRedirect {
u, err := resp.Location()
if err != nil {
logger.Warning(err)
} else {
// Update cluster leader based on redirect location
// because it should point to the leader address
c.cluster.updateLeaderFromURL(u)
logger.Debug("recv.response.relocate", 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) {
return newError(ErrCodeEtcdNotReachable,
"Tried to connect to each peer twice and failed", 0)
}
code := lastResp.StatusCode
if code == http.StatusInternalServerError {
time.Sleep(time.Millisecond * 200)
}
logger.Warning("bad response status code", code)
return nil
}
func (c *Client) getHttpPath(random bool, s ...string) string {
var machine string
if random {
machine = c.cluster.Machines[rand.Intn(len(c.cluster.Machines))]
} else {
machine = c.cluster.Leader
}
fullPath := machine + "/" + 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
// for example: key[foo] -> path[keys/foo]
// key[/] -> path[keys/]
func keyToPath(key string) string {
p := path.Join("keys", key)
// 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
}