restclient.go

/*
Copyright 2014 The Kubernetes Authors All rights reserved.

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 unversioned

import (
	"net/http"
	"net/url"
	"os"
	"strconv"
	"strings"
	"time"

	"github.com/golang/glog"
	"k8s.io/kubernetes/pkg/api"
	"k8s.io/kubernetes/pkg/api/unversioned"
	"k8s.io/kubernetes/pkg/runtime"
	"k8s.io/kubernetes/pkg/util"
)

const (
	// Environment variables: Note that the duration should be long enough that the backoff
	// persists for some reasonable time (i.e. 120 seconds).  The typical base might be "1".
	envBackoffBase     = "KUBE_CLIENT_BACKOFF_BASE"
	envBackoffDuration = "KUBE_CLIENT_BACKOFF_DURATION"
)

// RESTClient imposes common Kubernetes API conventions on a set of resource paths.
// The baseURL is expected to point to an HTTP or HTTPS path that is the parent
// of one or more resources.  The server should return a decodable API resource
// object, or an api.Status object which contains information about the reason for
// any failure.
//
// Most consumers should use client.New() to get a Kubernetes API client.
type RESTClient struct {
	baseURL *url.URL
	// A string identifying the version of the API this client is expected to use.
	groupVersion unversioned.GroupVersion

	// Codec is the encoding and decoding scheme that applies to a particular set of
	// REST resources.
	Codec runtime.Codec

	// Set specific behavior of the client.  If not set http.DefaultClient will be
	// used.
	Client *http.Client

	// TODO extract this into a wrapper interface via the RESTClient interface in kubectl.
	Throttle util.RateLimiter
}

// NewRESTClient creates a new RESTClient. This client performs generic REST functions
// such as Get, Put, Post, and Delete on specified paths.  Codec controls encoding and
// decoding of responses from the server.
func NewRESTClient(baseURL *url.URL, groupVersion unversioned.GroupVersion, c runtime.Codec, maxQPS float32, maxBurst int) *RESTClient {
	base := *baseURL
	if !strings.HasSuffix(base.Path, "/") {
		base.Path += "/"
	}
	base.RawQuery = ""
	base.Fragment = ""

	var throttle util.RateLimiter
	if maxQPS > 0 {
		throttle = util.NewTokenBucketRateLimiter(maxQPS, maxBurst)
	}
	return &RESTClient{
		baseURL:      &base,
		groupVersion: groupVersion,
		Codec:        c,
		Throttle:     throttle,
	}
}

// readExpBackoffConfig handles the internal logic of determining what the
// backoff policy is.  By default if no information is available, NoBackoff.
// TODO Generalize this see #17727 .
func readExpBackoffConfig() BackoffManager {
	backoffBase := os.Getenv(envBackoffBase)
	backoffDuration := os.Getenv(envBackoffDuration)

	backoffBaseInt, errBase := strconv.ParseInt(backoffBase, 10, 64)
	backoffDurationInt, errDuration := strconv.ParseInt(backoffDuration, 10, 64)

	if errBase != nil || errDuration != nil {
		glog.V(2).Infof("Configuring no exponential backoff.")
		return &NoBackoff{}
	} else {
		glog.V(2).Infof("Configuring exponential backoff as %v, %v", backoffBaseInt, backoffDurationInt)
		return &URLBackoff{
			Backoff: util.NewBackOff(
				time.Duration(backoffBaseInt)*time.Second,
				time.Duration(backoffDurationInt)*time.Second)}
	}
}

// Verb begins a request with a verb (GET, POST, PUT, DELETE).
//
// Example usage of RESTClient's request building interface:
// c := NewRESTClient(url, codec)
// resp, err := c.Verb("GET").
//  Path("pods").
//  SelectorParam("labels", "area=staging").
//  Timeout(10*time.Second).
//  Do()
// if err != nil { ... }
// list, ok := resp.(*api.PodList)
//
func (c *RESTClient) Verb(verb string) *Request {
	if c.Throttle != nil {
		c.Throttle.Accept()
	}

	backoff := readExpBackoffConfig()

	if c.Client == nil {
		return NewRequest(nil, verb, c.baseURL, c.groupVersion, c.Codec, backoff)
	}
	return NewRequest(c.Client, verb, c.baseURL, c.groupVersion, c.Codec, backoff)
}

// Post begins a POST request. Short for c.Verb("POST").
func (c *RESTClient) Post() *Request {
	return c.Verb("POST")
}

// Put begins a PUT request. Short for c.Verb("PUT").
func (c *RESTClient) Put() *Request {
	return c.Verb("PUT")
}

// Patch begins a PATCH request. Short for c.Verb("Patch").
func (c *RESTClient) Patch(pt api.PatchType) *Request {
	return c.Verb("PATCH").SetHeader("Content-Type", string(pt))
}

// Get begins a GET request. Short for c.Verb("GET").
func (c *RESTClient) Get() *Request {
	return c.Verb("GET")
}

// Delete begins a DELETE request. Short for c.Verb("DELETE").
func (c *RESTClient) Delete() *Request {
	return c.Verb("DELETE")
}

// APIVersion returns the APIVersion this RESTClient is expected to use.
func (c *RESTClient) APIVersion() unversioned.GroupVersion {
	return c.groupVersion
}