feat(prometheus): initial support for prometheus
This commit is contained in:
bergquist
+348
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// Copyright 2015 The Prometheus Authors
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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// Package prometheus provides bindings to the Prometheus HTTP API:
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// http://prometheus.io/docs/querying/api/
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package prometheus
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import (
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"encoding/json"
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"fmt"
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"io/ioutil"
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"net"
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"net/http"
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"net/url"
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"path"
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"strconv"
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"strings"
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"time"
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"github.com/prometheus/common/model"
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"golang.org/x/net/context"
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"golang.org/x/net/context/ctxhttp"
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)
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const (
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statusAPIError = 422
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apiPrefix = "/api/v1"
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epQuery = "/query"
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epQueryRange = "/query_range"
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epLabelValues = "/label/:name/values"
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epSeries = "/series"
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)
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// ErrorType models the different API error types.
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type ErrorType string
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// Possible values for ErrorType.
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const (
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ErrBadData ErrorType = "bad_data"
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ErrTimeout = "timeout"
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ErrCanceled = "canceled"
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ErrExec = "execution"
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ErrBadResponse = "bad_response"
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)
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// Error is an error returned by the API.
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type Error struct {
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Type ErrorType
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Msg string
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}
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func (e *Error) Error() string {
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return fmt.Sprintf("%s: %s", e.Type, e.Msg)
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}
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// CancelableTransport is like net.Transport but provides
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// per-request cancelation functionality.
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type CancelableTransport interface {
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http.RoundTripper
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CancelRequest(req *http.Request)
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}
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// DefaultTransport is used if no Transport is set in Config.
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var DefaultTransport CancelableTransport = &http.Transport{
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Proxy: http.ProxyFromEnvironment,
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Dial: (&net.Dialer{
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Timeout: 30 * time.Second,
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KeepAlive: 30 * time.Second,
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}).Dial,
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TLSHandshakeTimeout: 10 * time.Second,
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}
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// Config defines configuration parameters for a new client.
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type Config struct {
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// The address of the Prometheus to connect to.
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Address string
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// Transport is used by the Client to drive HTTP requests. If not
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// provided, DefaultTransport will be used.
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Transport CancelableTransport
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}
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func (cfg *Config) transport() CancelableTransport {
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if cfg.Transport == nil {
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return DefaultTransport
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}
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return cfg.Transport
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}
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// Client is the interface for an API client.
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type Client interface {
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url(ep string, args map[string]string) *url.URL
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do(context.Context, *http.Request) (*http.Response, []byte, error)
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}
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// New returns a new Client.
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//
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// It is safe to use the returned Client from multiple goroutines.
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func New(cfg Config) (Client, error) {
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u, err := url.Parse(cfg.Address)
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if err != nil {
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return nil, err
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}
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u.Path = strings.TrimRight(u.Path, "/") + apiPrefix
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return &httpClient{
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endpoint: u,
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transport: cfg.transport(),
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}, nil
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}
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type httpClient struct {
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endpoint *url.URL
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transport CancelableTransport
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}
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func (c *httpClient) url(ep string, args map[string]string) *url.URL {
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p := path.Join(c.endpoint.Path, ep)
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for arg, val := range args {
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arg = ":" + arg
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p = strings.Replace(p, arg, val, -1)
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}
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u := *c.endpoint
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u.Path = p
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return &u
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}
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func (c *httpClient) do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
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resp, err := ctxhttp.Do(ctx, &http.Client{Transport: c.transport}, req)
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defer func() {
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if resp != nil {
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resp.Body.Close()
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}
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}()
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if err != nil {
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return nil, nil, err
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}
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var body []byte
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done := make(chan struct{})
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go func() {
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body, err = ioutil.ReadAll(resp.Body)
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close(done)
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}()
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select {
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case <-ctx.Done():
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err = resp.Body.Close()
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<-done
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if err == nil {
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err = ctx.Err()
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}
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case <-done:
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}
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return resp, body, err
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}
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// apiClient wraps a regular client and processes successful API responses.
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// Successful also includes responses that errored at the API level.
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type apiClient struct {
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Client
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}
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type apiResponse struct {
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Status string `json:"status"`
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Data json.RawMessage `json:"data"`
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ErrorType ErrorType `json:"errorType"`
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Error string `json:"error"`
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}
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func (c apiClient) do(ctx context.Context, req *http.Request) (*http.Response, []byte, error) {
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resp, body, err := c.Client.do(ctx, req)
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if err != nil {
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return resp, body, err
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}
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code := resp.StatusCode
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if code/100 != 2 && code != statusAPIError {
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return resp, body, &Error{
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Type: ErrBadResponse,
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Msg: fmt.Sprintf("bad response code %d", resp.StatusCode),
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}
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}
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var result apiResponse
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if err = json.Unmarshal(body, &result); err != nil {
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return resp, body, &Error{
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Type: ErrBadResponse,
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Msg: err.Error(),
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}
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}
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if (code == statusAPIError) != (result.Status == "error") {
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err = &Error{
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Type: ErrBadResponse,
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Msg: "inconsistent body for response code",
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}
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}
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if code == statusAPIError && result.Status == "error" {
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err = &Error{
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Type: result.ErrorType,
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Msg: result.Error,
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}
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}
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return resp, []byte(result.Data), err
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}
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// Range represents a sliced time range.
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type Range struct {
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// The boundaries of the time range.
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Start, End time.Time
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// The maximum time between two slices within the boundaries.
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Step time.Duration
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}
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// queryResult contains result data for a query.
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type queryResult struct {
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Type model.ValueType `json:"resultType"`
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Result interface{} `json:"result"`
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// The decoded value.
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v model.Value
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}
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func (qr *queryResult) UnmarshalJSON(b []byte) error {
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v := struct {
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Type model.ValueType `json:"resultType"`
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Result json.RawMessage `json:"result"`
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}{}
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err := json.Unmarshal(b, &v)
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if err != nil {
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return err
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}
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switch v.Type {
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case model.ValScalar:
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var sv model.Scalar
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err = json.Unmarshal(v.Result, &sv)
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qr.v = &sv
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case model.ValVector:
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var vv model.Vector
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err = json.Unmarshal(v.Result, &vv)
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qr.v = vv
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case model.ValMatrix:
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var mv model.Matrix
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err = json.Unmarshal(v.Result, &mv)
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qr.v = mv
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default:
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err = fmt.Errorf("unexpected value type %q", v.Type)
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}
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return err
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}
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// QueryAPI provides bindings the Prometheus's query API.
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type QueryAPI interface {
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// Query performs a query for the given time.
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Query(ctx context.Context, query string, ts time.Time) (model.Value, error)
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// Query performs a query for the given range.
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QueryRange(ctx context.Context, query string, r Range) (model.Value, error)
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}
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// NewQueryAPI returns a new QueryAPI for the client.
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//
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// It is safe to use the returned QueryAPI from multiple goroutines.
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func NewQueryAPI(c Client) QueryAPI {
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return &httpQueryAPI{client: apiClient{c}}
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}
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type httpQueryAPI struct {
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client Client
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}
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func (h *httpQueryAPI) Query(ctx context.Context, query string, ts time.Time) (model.Value, error) {
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u := h.client.url(epQuery, nil)
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q := u.Query()
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q.Set("query", query)
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q.Set("time", ts.Format(time.RFC3339Nano))
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u.RawQuery = q.Encode()
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req, _ := http.NewRequest("GET", u.String(), nil)
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_, body, err := h.client.do(ctx, req)
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if err != nil {
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return nil, err
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}
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var qres queryResult
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err = json.Unmarshal(body, &qres)
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return model.Value(qres.v), err
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}
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func (h *httpQueryAPI) QueryRange(ctx context.Context, query string, r Range) (model.Value, error) {
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u := h.client.url(epQueryRange, nil)
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q := u.Query()
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var (
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start = r.Start.Format(time.RFC3339Nano)
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end = r.End.Format(time.RFC3339Nano)
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step = strconv.FormatFloat(r.Step.Seconds(), 'f', 3, 64)
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)
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q.Set("query", query)
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q.Set("start", start)
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q.Set("end", end)
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q.Set("step", step)
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u.RawQuery = q.Encode()
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req, _ := http.NewRequest("GET", u.String(), nil)
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_, body, err := h.client.do(ctx, req)
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if err != nil {
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return nil, err
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}
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var qres queryResult
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err = json.Unmarshal(body, &qres)
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return model.Value(qres.v), err
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}
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