open-consul/api/api.go

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package api
import (
"bytes"
"encoding/json"
"fmt"
"io"
"net/http"
"net/url"
"strconv"
"time"
)
// QueryOptions are used to parameterize a query
type QueryOptions struct {
// Providing a datacenter overwrites the DC provided
// by the Config
Datacenter string
// AllowStale allows any Consul server (non-leader) to service
// a read. This allows for lower latency and higher throughput
AllowStale bool
// RequireConsistent forces the read to be fully consistent.
// This is more expensive but prevents ever performing a stale
// read.
RequireConsistent bool
// WaitIndex is used to enable a blocking query. Waits
// until the timeout or the next index is reached
WaitIndex uint64
// WaitTime is used to bound the duration of a wait.
// Defaults to that of the Config, but can be overriden.
WaitTime time.Duration
// Token is used to provide a per-request ACL token
// which overrides the agent's default token.
Token string
}
// WriteOptions are used to parameterize a write
type WriteOptions struct {
// Providing a datacenter overwrites the DC provided
// by the Config
Datacenter string
// Token is used to provide a per-request ACL token
// which overrides the agent's default token.
Token string
}
// QueryMeta is used to return meta data about a query
type QueryMeta struct {
// LastIndex. This can be used as a WaitIndex to perform
// a blocking query
LastIndex uint64
// Time of last contact from the leader for the
// server servicing the request
LastContact time.Duration
// Is there a known leader
KnownLeader bool
// How long did the request take
RequestTime time.Duration
}
// WriteMeta is used to return meta data about a write
type WriteMeta struct {
// How long did the request take
RequestTime time.Duration
}
// HttpBasicAuth is used to authenticate http client with HTTP Basic Authentication
type HttpBasicAuth struct {
// Username to use for HTTP Basic Authentication
Username string
// Password to use for HTTP Basic Authentication
Password string
}
// Config is used to configure the creation of a client
type Config struct {
// Address is the address of the Consul server
Address string
// Scheme is the URI scheme for the Consul server
Scheme string
// Datacenter to use. If not provided, the default agent datacenter is used.
Datacenter string
// HttpClient is the client to use. Default will be
// used if not provided.
HttpClient *http.Client
// HttpAuth is the auth info to use for http access.
HttpAuth *HttpBasicAuth
// WaitTime limits how long a Watch will block. If not provided,
// the agent default values will be used.
WaitTime time.Duration
// Token is used to provide a per-request ACL token
// which overrides the agent's default token.
Token string
}
// DefaultConfig returns a default configuration for the client
func DefaultConfig() *Config {
return &Config{
Address: "127.0.0.1:8500",
Scheme: "http",
HttpClient: http.DefaultClient,
}
}
// Client provides a client to the Consul API
type Client struct {
config Config
}
// NewClient returns a new client
func NewClient(config *Config) (*Client, error) {
// bootstrap the config
defConfig := DefaultConfig()
if len(config.Address) == 0 {
config.Address = defConfig.Address
}
if len(config.Scheme) == 0 {
config.Scheme = defConfig.Scheme
}
if config.HttpClient == nil {
config.HttpClient = defConfig.HttpClient
}
client := &Client{
config: *config,
}
return client, nil
}
// request is used to help build up a request
type request struct {
config *Config
method string
url *url.URL
params url.Values
body io.Reader
obj interface{}
}
// setQueryOptions is used to annotate the request with
// additional query options
func (r *request) setQueryOptions(q *QueryOptions) {
if q == nil {
return
}
if q.Datacenter != "" {
r.params.Set("dc", q.Datacenter)
}
if q.AllowStale {
r.params.Set("stale", "")
}
if q.RequireConsistent {
r.params.Set("consistent", "")
}
if q.WaitIndex != 0 {
r.params.Set("index", strconv.FormatUint(q.WaitIndex, 10))
}
if q.WaitTime != 0 {
r.params.Set("wait", durToMsec(q.WaitTime))
}
if q.Token != "" {
r.params.Set("token", q.Token)
}
}
// durToMsec converts a duration to a millisecond specified string
func durToMsec(dur time.Duration) string {
return fmt.Sprintf("%dms", dur/time.Millisecond)
}
// setWriteOptions is used to annotate the request with
// additional write options
func (r *request) setWriteOptions(q *WriteOptions) {
if q == nil {
return
}
if q.Datacenter != "" {
r.params.Set("dc", q.Datacenter)
}
if q.Token != "" {
r.params.Set("token", q.Token)
}
}
// toHTTP converts the request to an HTTP request
func (r *request) toHTTP() (*http.Request, error) {
// Encode the query parameters
r.url.RawQuery = r.params.Encode()
// Get the url sring
urlRaw := r.url.String()
// Check if we should encode the body
if r.body == nil && r.obj != nil {
if b, err := encodeBody(r.obj); err != nil {
return nil, err
} else {
r.body = b
}
}
// Create the HTTP request
req, err := http.NewRequest(r.method, urlRaw, r.body)
// Setup auth
if err == nil && r.config.HttpAuth != nil {
req.SetBasicAuth(r.config.HttpAuth.Username, r.config.HttpAuth.Password)
}
return req, err
}
// newRequest is used to create a new request
func (c *Client) newRequest(method, path string) *request {
r := &request{
config: &c.config,
method: method,
url: &url.URL{
Scheme: c.config.Scheme,
Host: c.config.Address,
Path: path,
},
params: make(map[string][]string),
}
if c.config.Datacenter != "" {
r.params.Set("dc", c.config.Datacenter)
}
if c.config.WaitTime != 0 {
r.params.Set("wait", durToMsec(r.config.WaitTime))
}
if c.config.Token != "" {
r.params.Set("token", r.config.Token)
}
return r
}
// doRequest runs a request with our client
func (c *Client) doRequest(r *request) (time.Duration, *http.Response, error) {
req, err := r.toHTTP()
if err != nil {
return 0, nil, err
}
start := time.Now()
resp, err := c.config.HttpClient.Do(req)
diff := time.Now().Sub(start)
return diff, resp, err
}
// parseQueryMeta is used to help parse query meta-data
func parseQueryMeta(resp *http.Response, q *QueryMeta) error {
header := resp.Header
// Parse the X-Consul-Index
index, err := strconv.ParseUint(header.Get("X-Consul-Index"), 10, 64)
if err != nil {
return fmt.Errorf("Failed to parse X-Consul-Index: %v", err)
}
q.LastIndex = index
// Parse the X-Consul-LastContact
last, err := strconv.ParseUint(header.Get("X-Consul-LastContact"), 10, 64)
if err != nil {
return fmt.Errorf("Failed to parse X-Consul-LastContact: %v", err)
}
q.LastContact = time.Duration(last) * time.Millisecond
// Parse the X-Consul-KnownLeader
switch header.Get("X-Consul-KnownLeader") {
case "true":
q.KnownLeader = true
default:
q.KnownLeader = false
}
return nil
}
// decodeBody is used to JSON decode a body
func decodeBody(resp *http.Response, out interface{}) error {
dec := json.NewDecoder(resp.Body)
return dec.Decode(out)
}
// encodeBody is used to encode a request body
func encodeBody(obj interface{}) (io.Reader, error) {
buf := bytes.NewBuffer(nil)
enc := json.NewEncoder(buf)
if err := enc.Encode(obj); err != nil {
return nil, err
}
return buf, nil
}
// requireOK is used to wrap doRequest and check for a 200
func requireOK(d time.Duration, resp *http.Response, e error) (time.Duration, *http.Response, error) {
if e != nil {
return d, resp, e
}
if resp.StatusCode != 200 {
var buf bytes.Buffer
io.Copy(&buf, resp.Body)
return d, resp, fmt.Errorf("Unexpected response code: %d (%s)", resp.StatusCode, buf.Bytes())
}
return d, resp, e
}