Add initial HTTP API v1 package

api/prometheus/api.go

@@ -0,0 +1,362 @@
+// Copyright 2015 The Prometheus Authors
+// 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 prometheus provides bindings to the Prometheus HTTP API:
+// http://prometheus.io/docs/querying/api/
+package prometheus
+
+import (
+	"encoding/json"
+	"fmt"
+	"io/ioutil"
+	"net"
+	"net/http"
+	"net/url"
+	"path"
+	"strconv"
+	"strings"
+	"time"
+
+	"github.com/prometheus/common/model"
+	"golang.org/x/net/context"
+)
+
+const (
+	statusAPIError = 422
+	apiPrefix      = "/api/v1"
+
+	epQuery       = "/query"
+	epQueryRange  = "/query_range"
+	epLabelValues = "/label/:name/values"
+	epSeries      = "/series"
+)
+
+type ErrorType string
+
+const (
+	// The different API error types.
+	ErrBadData     ErrorType = "bad_data"
+	ErrTimeout               = "timeout"
+	ErrCanceled              = "canceled"
+	ErrExec                  = "execution"
+	ErrBadResponse           = "bad_response"
+)
+
+// Error is an error returned by the API.
+type Error struct {
+	Type ErrorType
+	Msg  string
+}
+
+func (e *Error) Error() string {
+	return fmt.Sprintf("%s: %s", e.Type, e.Msg)
+}
+
+// CancelableTransport is like net.Transport but provides
+// per-request cancelation functionality.
+type CancelableTransport interface {
+	http.RoundTripper
+	CancelRequest(req *http.Request)
+}
+
+var DefaultTransport CancelableTransport = &http.Transport{
+	Proxy: http.ProxyFromEnvironment,
+	Dial: (&net.Dialer{
+		Timeout:   30 * time.Second,
+		KeepAlive: 30 * time.Second,
+	}).Dial,
+	TLSHandshakeTimeout: 10 * time.Second,
+}
+
+// Config defines configuration parameters for a new client.
+type Config struct {
+	// The address of the Prometheus to connect to.
+	Address string
+
+	// Transport is used by the Client to drive HTTP requests. If not
+	// provided, DefaultTransport will be used.
+	Transport CancelableTransport
+}
+
+func (cfg *Config) transport() CancelableTransport {
+	if cfg.Transport == nil {
+		return DefaultTransport
+	}
+	return cfg.Transport
+}
+
+type Client interface {
+	url(ep string, args map[string]string) *url.URL
+	do(context.Context, *http.Request) (*http.Response, []byte, error)
+}
+
+// New returns a new Client.
+func New(cfg Config) (Client, error) {
+	u, err := url.Parse(cfg.Address)
+	if err != nil {
+		return nil, err
+	}
+	u.Path = apiPrefix
+
+	return &httpClient{
+		endpoint:  u,
+		transport: cfg.transport(),
+	}, nil
+}
+
+type httpClient struct {
+	endpoint  *url.URL
+	transport CancelableTransport
+}
+
+func (c *httpClient) url(ep string, args map[string]string) *url.URL {
+	p := path.Join(c.endpoint.Path, ep)
+
+	for arg, val := range args {
+		arg = ":" + arg
+		p = strings.Replace(p, arg, val, -1)
+	}
+
+	u := *c.endpoint
+	u.Path = p
+
+	return &u
+}
+
+func (c *httpClient) do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+	type roundTripResponse struct {
+		resp *http.Response
+		err  error
+	}
+
+	rtchan := make(chan roundTripResponse, 1)
+	go func() {
+		resp, err := c.transport.RoundTrip(req)
+		rtchan <- roundTripResponse{resp: resp, err: err}
+		close(rtchan)
+	}()
+
+	var resp *http.Response
+	var err error
+
+	select {
+	case rtresp := <-rtchan:
+		resp, err = rtresp.resp, rtresp.err
+	case <-ctx.Done():
+		// Cancel request and wait until it terminated.
+		c.transport.CancelRequest(req)
+		resp, err = (<-rtchan).resp, ctx.Err()
+	}
+
+	defer func() {
+		if resp != nil {
+			resp.Body.Close()
+		}
+	}()
+
+	if err != nil {
+		return nil, nil, err
+	}
+
+	var body []byte
+	done := make(chan struct{})
+	go func() {
+		body, err = ioutil.ReadAll(resp.Body)
+		close(done)
+	}()
+
+	select {
+	case <-ctx.Done():
+		err = resp.Body.Close()
+		<-done
+		if err == nil {
+			err = ctx.Err()
+		}
+	case <-done:
+	}
+
+	return resp, body, err
+}
+
+// apiClient wraps a regular client and processes successful API responses.
+// Successful also includes responses that errored at the API level.
+type apiClient struct {
+	Client
+}
+
+type apiResponse struct {
+	Status    string          `json:"status"`
+	Data      json.RawMessage `json:"data"`
+	ErrorType ErrorType       `json:"errorType"`
+	Error     string          `json:"error"`
+}
+
+func (c apiClient) do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
+	resp, body, err := c.Client.do(ctx, req)
+	if err != nil {
+		return resp, body, err
+	}
+
+	code := resp.StatusCode
+
+	if code/100 != 2 && code != statusAPIError {
+		return resp, body, &Error{
+			Type: ErrBadResponse,
+			Msg:  fmt.Sprintf("bad response %s", resp.Status),
+		}
+	}
+
+	var result apiResponse
+
+	if err = json.Unmarshal(body, &result); err != nil {
+		return resp, body, &Error{
+			Type: ErrBadResponse,
+			Msg:  err.Error(),
+		}
+	}
+
+	if (code == statusAPIError) != (result.Status == "error") {
+		err = &Error{
+			Type: ErrBadResponse,
+			Msg:  "inconsistent body for response code",
+		}
+	}
+
+	if code == statusAPIError && result.Status == "error" {
+		err = &Error{
+			Type: result.ErrorType,
+			Msg:  result.Error,
+		}
+	}
+
+	return resp, []byte(result.Data), err
+}
+
+// Range represents a sliced time range.
+type Range struct {
+	// The boundaries of the time range.
+	Start, End time.Time
+	// The maximum time between two slices within the boundaries.
+	Step time.Duration
+}
+
+// queryResult contains result data for a query.
+type queryResult struct {
+	Type   model.ValueType `json:"resultType"`
+	Result interface{}     `json:"result"`
+
+	// The decoded value.
+	v model.Value
+}
+
+func (qr *queryResult) UnmarshalJSON(b []byte) error {
+	v := struct {
+		Type   model.ValueType `json:"resultType"`
+		Result json.RawMessage `json:"result"`
+	}{}
+
+	err := json.Unmarshal(b, &v)
+	if err != nil {
+		return err
+	}
+
+	switch v.Type {
+	case model.ValScalar:
+		var sv model.Scalar
+		err = json.Unmarshal(v.Result, &sv)
+		qr.v = &sv
+
+	case model.ValVector:
+		var vv model.Vector
+		err = json.Unmarshal(v.Result, &vv)
+		qr.v = vv
+
+	case model.ValMatrix:
+		var mv model.Matrix
+		err = json.Unmarshal(v.Result, &mv)
+		qr.v = mv
+
+	default:
+		err = fmt.Errorf("unexpected value type %q", v.Type)
+	}
+	return err
+}
+
+// QueryAPI provides bindings the Prometheus's query API.
+type QueryAPI interface {
+	// Query performs a query for the given time.
+	Query(ctx context.Context, query string, ts time.Time) (model.Value, error)
+	// Query performs a query for the given range.
+	QueryRange(ctx context.Context, query string, r Range) (model.Value, error)
+}
+
+// NewQueryAPI returns a new QueryAPI for the client.
+func NewQueryAPI(c Client) QueryAPI {
+	return &httpQueryAPI{client: apiClient{c}}
+}
+
+type httpQueryAPI struct {
+	client Client
+}
+
+func (h *httpQueryAPI) Query(ctx context.Context, query string, ts time.Time) (model.Value, error) {
+	u := h.client.url(epQuery, nil)
+	q := u.Query()
+
+	q.Set("query", query)
+	q.Set("time", ts.Format(time.RFC3339Nano))
+
+	u.RawQuery = q.Encode()
+
+	req, _ := http.NewRequest("GET", u.String(), nil)
+
+	_, body, err := h.client.do(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	var qres queryResult
+	err = json.Unmarshal(body, &qres)
+
+	return model.Value(qres.v), err
+}
+
+func (h *httpQueryAPI) QueryRange(ctx context.Context, query string, r Range) (model.Value, error) {
+	u := h.client.url(epQueryRange, nil)
+	q := u.Query()
+
+	var (
+		start = r.Start.Format(time.RFC3339Nano)
+		end   = r.End.Format(time.RFC3339Nano)
+		step  = strconv.FormatFloat(r.Step.Seconds(), 'f', 3, 64)
+	)
+
+	q.Set("query", query)
+	q.Set("start", start)
+	q.Set("end", end)
+	q.Set("step", step)
+
+	u.RawQuery = q.Encode()
+
+	req, _ := http.NewRequest("GET", u.String(), nil)
+
+	_, body, err := h.client.do(ctx, req)
+	if err != nil {
+		return nil, err
+	}
+
+	var qres queryResult
+	err = json.Unmarshal(body, &qres)
+
+	return model.Value(qres.v), err
+}