tag_values.go

// Copyright (c) 2018 Uber Technologies, Inc.
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the "Software"), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
// The above copyright notice and this permission notice shall be included in
// all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
// AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
// LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
// OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
// THE SOFTWARE.

package remote

import (
	"bytes"
	"fmt"
	"io/ioutil"
	"net/http"

	"github.com/m3db/m3/src/query/api/v1/handler/prometheus"
	"github.com/m3db/m3/src/query/api/v1/handler/prometheus/handleroptions"
	"github.com/m3db/m3/src/query/api/v1/options"
	"github.com/m3db/m3/src/query/api/v1/route"
	"github.com/m3db/m3/src/query/errors"
	"github.com/m3db/m3/src/query/models"
	"github.com/m3db/m3/src/query/parser/promql"
	"github.com/m3db/m3/src/query/storage"
	"github.com/m3db/m3/src/query/storage/m3/consolidators"
	"github.com/m3db/m3/src/query/util/logging"
	xerrors "github.com/m3db/m3/src/x/errors"
	"github.com/m3db/m3/src/x/instrument"
	xhttp "github.com/m3db/m3/src/x/net/http"
	xtime "github.com/m3db/m3/src/x/time"

	"github.com/gorilla/mux"
	"go.uber.org/zap"
)

const (

	// TagValuesURL is the url for tag values.
	TagValuesURL = route.LabelValuesURL

	// TagValuesHTTPMethod is the HTTP method used with this resource.
	TagValuesHTTPMethod = http.MethodGet
)

// TagValuesHandler represents a handler for search tags endpoint.
type TagValuesHandler struct {
	storage             storage.Storage
	fetchOptionsBuilder handleroptions.FetchOptionsBuilder
	parseOpts           promql.ParseOptions
	instrumentOpts      instrument.Options
	tagOpts             models.TagOptions
}

// TagValuesResponse is the response that gets returned to the user
type TagValuesResponse struct {
	Results consolidators.CompleteTagsResult `json:"results,omitempty"`
}

// NewTagValuesHandler returns a new instance of handler.
func NewTagValuesHandler(opts options.HandlerOptions) http.Handler {
	return &TagValuesHandler{
		storage:             opts.Storage(),
		fetchOptionsBuilder: opts.FetchOptionsBuilder(),
		parseOpts: promql.NewParseOptions().
			SetRequireStartEndTime(opts.Config().Query.RequireLabelsEndpointStartEndTime).
			SetNowFn(opts.NowFn()),
		instrumentOpts: opts.InstrumentOpts(),
		tagOpts:        opts.TagOptions(),
	}
}

func (h *TagValuesHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
	w.Header().Set(xhttp.HeaderContentType, xhttp.ContentTypeJSON)

	ctx, opts, rErr := h.fetchOptionsBuilder.NewFetchOptions(r.Context(), r)
	if rErr != nil {
		xhttp.WriteError(w, rErr)
		return
	}

	logger := logging.WithContext(ctx, h.instrumentOpts)

	query, err := h.parseTagValuesToQuery(r)
	if err != nil {
		logger.Error("unable to parse tag values to query", zap.Error(err))
		xhttp.WriteError(w, err)
		return
	}

	result, err := h.storage.CompleteTags(ctx, query, opts)
	if err != nil {
		logger.Error("unable to get tag values", zap.Error(err))
		if errors.IsTimeout(err) {
			err = errors.NewErrQueryTimeout(err)
		}
		xhttp.WriteError(w, err)
		return
	}

	err = handleroptions.AddDBResultResponseHeaders(w, result.Metadata, opts)
	if err != nil {
		logger.Error("error writing database limit headers", zap.Error(err))
		xhttp.WriteError(w, err)
		return
	}

	// First write out results to zero output to check if will limit
	// results and if so then write the header about truncation if occurred.
	var (
		noopWriter = ioutil.Discard
		renderOpts = prometheus.RenderSeriesMetadataOptions{
			ReturnedSeriesMetadataLimit: opts.ReturnedSeriesMetadataLimit,
		}
	)
	renderResult, err := prometheus.RenderTagValuesResultsJSON(noopWriter, result, renderOpts)
	if err != nil {
		logger.Error("unable to render tag values results", zap.Error(err))
		xhttp.WriteError(w, err)
		return
	}

	limited := &handleroptions.ReturnedMetadataLimited{
		Results:      renderResult.Results,
		TotalResults: renderResult.TotalResults,
		Limited:      renderResult.LimitedMaxReturnedData,
	}
	if err := handleroptions.AddReturnedLimitResponseHeaders(w, nil, limited); err != nil {
		logger.Error("unable to add returned data headers", zap.Error(err))
		xhttp.WriteError(w, err)
		return
	}

	// TODO: Support multiple result types
	_, err = prometheus.RenderTagValuesResultsJSON(w, result, renderOpts)
	if err != nil {
		logger.Error("unable to render tag values", zap.Error(err))
	}
}

func (h *TagValuesHandler) parseTagValuesToQuery(
	r *http.Request,
) (*storage.CompleteTagsQuery, error) {
	vars := mux.Vars(r)
	name, ok := vars[route.NameReplace]
	if !ok || len(name) == 0 {
		return nil, xhttp.NewError(errors.ErrNoName, http.StatusBadRequest)
	}

	start, end, err := prometheus.ParseStartAndEnd(r, h.parseOpts)
	if err != nil {
		return nil, err
	}

	nameBytes := []byte(name)

	nameMatcher := models.Matcher{
		Type: models.MatchField,
		Name: nameBytes,
	}
	tagMatchers := models.Matchers{nameMatcher}
	reqTagMatchers, ok, err := prometheus.ParseMatch(r, h.parseOpts, h.tagOpts)
	if err != nil {
		return nil, xerrors.NewInvalidParamsError(err)
	}
	if ok {
		if n := len(reqTagMatchers); n != 1 {
			err := xerrors.NewInvalidParamsError(fmt.Errorf(
				"only single tag matcher allowed: actual=%d", n))
			return nil, err
		}

		reqTagMatcher := reqTagMatchers[0]

		//nolint:gocritic
		for _, m := range reqTagMatcher.Matchers {
			// add all matchers that don't match the default name matcher.
			if m.Type != nameMatcher.Type || !bytes.Equal(m.Name, nameMatcher.Name) {
				tagMatchers = append(tagMatchers, m)
			}
		}
	}

	return &storage.CompleteTagsQuery{
		Start:            xtime.ToUnixNano(start),
		End:              xtime.ToUnixNano(end),
		CompleteNameOnly: false,
		FilterNameTags:   [][]byte{nameBytes},
		TagMatchers:      tagMatchers,
	}, nil
}