[query] Add endpoint that parses query to an AST

scripts/docker-integration-tests/prometheus/test_correctness.sh

@@ -54,6 +54,20 @@ function test_replace {
   test_instantaneous $query 5 "\"bar_0\" \"bar_1\" \"bar_2\" \"bar_3\" \"bar_4\""
 }
 
+function test_parse_query {
+  test $(curl 'http://localhost:7201/api/v1/parse?query=up' | jq .name) = '"fetch"'
+  THRESHOLD=$(curl 'http://localhost:7201/api/v1/threshold?query=up>1')
+  test $(echo $THRESHOLD | jq .threshold.comparator) = '">"'
+  test $(echo $THRESHOLD | jq .threshold.value) = 1
+  test $(echo $THRESHOLD | jq .query.name) = '"fetch"'
+
+  THRESHOLD=$(curl 'http://localhost:7201/api/v1/threshold?query=1>up')
+  test $(echo $THRESHOLD | jq .threshold.comparator) = '"<"'
+  test $(echo $THRESHOLD | jq .threshold.value) = 1
+  test $(echo $THRESHOLD | jq .query.name) = '"fetch"'
+}
+
 function test_correctness {
+  test_parse_query
   test_replace 
 }

src/query/api/v1/handler/prometheus/native/parse_query.go

@@ -0,0 +1,196 @@
+// Copyright (c) 2019 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 native
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/m3db/m3/src/query/api/v1/handler"
+	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/parser"
+	"github.com/m3db/m3/src/query/parser/promql"
+	"github.com/m3db/m3/src/x/instrument"
+	xhttp "github.com/m3db/m3/src/x/net/http"
+
+	"go.uber.org/zap"
+)
+
+const (
+	// PromParseURL is the url for native prom parse handler, this parses out the
+	// query and returns a JSON representation of the execution DAG.
+	PromParseURL = handler.RoutePrefixV1 + "/parse"
+
+	// PromParseHTTPMethod is the HTTP method used with this resource.
+	PromParseHTTPMethod = http.MethodGet
+)
+
+// PromParseHandler represents a handler for prometheus parse endpoint.
+type promParseHandler struct {
+	instrumentOpts instrument.Options
+}
+
+// NewPromParseHandler returns a new instance of handler.
+func NewPromParseHandler(
+	instrumentOpts instrument.Options,
+) http.Handler {
+	return &promParseHandler{
+		instrumentOpts: instrumentOpts,
+	}
+}
+
+// FunctionNode is a JSON representation of a function.
+type FunctionNode struct {
+	// Name is the name of the function node.
+	Name string `json:"name,omitempty"`
+	// Children are any children this function node has.
+	Children []FunctionNode `json:"children,omitempty"`
+	// parents are any parents this node has; this is private since it is only
+	// used to construct the function node map.
+	parents []FunctionNode
+	// node is the actual execution node.
+	node parser.Node
+}
+
+// String prints the string representation of a function node.
+func (n FunctionNode) String() string {
+	var sb strings.Builder
+	sb.WriteString(n.Name)
+	if len(n.Children) > 0 {
+		sb.WriteString(": ")
+		sb.WriteString(fmt.Sprint(n.Children))
+	}
+
+	return sb.String()
+}
+
+type nodeMap map[string]FunctionNode
+
+func (n nodeMap) rootNode() (FunctionNode, error) {
+	var (
+		found bool
+		node  FunctionNode
+	)
+
+	for _, v := range n {
+		if len(v.parents) == 0 {
+			if found {
+				return node, fmt.Errorf(
+					"multiple roots found for map: %s",
+					fmt.Sprint(n),
+				)
+			}
+
+			found = true
+			node = v
+		}
+	}
+
+	if !found {
+		return node, fmt.Errorf("no root found for map: %s", fmt.Sprint(n))
+	}
+
+	return node, nil
+}
+
+func constructNodeMap(nodes parser.Nodes, edges parser.Edges) (nodeMap, error) {
+	nodeMap := make(map[string]FunctionNode, len(nodes))
+	for _, node := range nodes {
+		name := node.Op.OpType()
+		nodeMap[string(node.ID)] = FunctionNode{
+			Name: name,
+			node: node,
+		}
+	}
+
+	for _, edge := range edges {
+		// NB: due to how execution occurs, `parent` and `child` have the opposite
+		// meaning in the `edge` context compared to the expected lexical reading,
+		// so they should be swapped here.
+		parent := string(edge.ChildID)
+		child := string(edge.ParentID)
+		parentNode, ok := nodeMap[parent]
+		if !ok {
+			return nil, fmt.Errorf("parent node with ID %s not found", parent)
+		}
+
+		childNode, ok := nodeMap[child]
+		if !ok {
+			return nil, fmt.Errorf("child node with ID %s not found", child)
+		}
+
+		parentNode.Children = append(parentNode.Children, childNode)
+		childNode.parents = append(childNode.parents, parentNode)
+		nodeMap[parent] = parentNode
+		nodeMap[child] = childNode
+	}
+
+	return nodeMap, nil
+}
+
+func parseRootNode(
+	r *http.Request,
+	logger *zap.Logger,
+) (FunctionNode, error) {
+	query, err := parseQuery(r)
+	if err != nil {
+		logger.Error("cannot parse query string", zap.Error(err))
+		return FunctionNode{}, err
+	}
+
+	parser, err := promql.Parse(query, models.NewTagOptions())
+	if err != nil {
+		logger.Error("cannot parse query PromQL", zap.Error(err))
+		return FunctionNode{}, err
+	}
+
+	nodes, edges, err := parser.DAG()
+	if err != nil {
+		logger.Error("cannot extract query DAG", zap.Error(err))
+		return FunctionNode{}, err
+	}
+
+	funcMap, err := constructNodeMap(nodes, edges)
+	if err != nil {
+		logger.Error("cannot construct node map", zap.Error(err))
+		return FunctionNode{}, err
+	}
+
+	root, err := funcMap.rootNode()
+	if err != nil {
+		logger.Error("cannot fetch root node", zap.Error(err))
+		return FunctionNode{}, err
+	}
+
+	return root, nil
+}
+
+func (h *promParseHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
+	logger := h.instrumentOpts.Logger()
+	root, err := parseRootNode(r, logger)
+	if err != nil {
+		xhttp.Error(w, err, http.StatusBadRequest)
+		return
+	}
+
+	xhttp.WriteJSONResponse(w, root, logger)
+}

src/query/api/v1/handler/prometheus/native/parse_query_test.go

@@ -0,0 +1,116 @@
+// Copyright (c) 2019 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 native
+
+import (
+	"fmt"
+	"io/ioutil"
+	"net/http/httptest"
+	"net/url"
+	"testing"
+
+	"github.com/m3db/m3/src/x/instrument"
+	xtest "github.com/m3db/m3/src/x/test"
+
+	"github.com/stretchr/testify/require"
+)
+
+var parseTests = []struct {
+	query string
+	ex    string
+}{
+	{
+		"foo",
+		`{"name":"fetch"}`,
+	},
+	{
+		"sum(a)-3",
+		`{
+			"name": "-",
+			"children": [
+				{
+					"name": "sum",
+					"children": [
+						{
+							"name": "fetch"
+						}
+					]
+				},
+				{
+					"name": "scalar"
+				}
+			]
+		}`,
+	},
+	{
+		"1 > bool (foo or sum(rate(bar[5m])))",
+		`{
+			"children": [
+				{
+					"name": "scalar"
+				},
+				{
+					"children": [
+						{
+							"name": "fetch"
+						},
+						{
+							"children": [
+								{
+									"children": [
+										{
+											"name": "fetch"
+										}
+									],
+									"name": "rate"
+								}
+							],
+							"name": "sum"
+						}
+					],
+					"name": "or"
+				}
+			],
+			"name": ">"
+		}`,
+	},
+}
+
+func TestParse(t *testing.T) {
+	for i, tt := range parseTests {
+		h := NewPromParseHandler(instrument.NewOptions())
+		query := fmt.Sprintf("/parse?query=%s", url.QueryEscape(tt.query))
+		req := httptest.NewRequest("GET", query, nil)
+		w := httptest.NewRecorder()
+
+		h.ServeHTTP(w, req)
+		body := w.Result().Body
+		defer body.Close()
+
+		r, err := ioutil.ReadAll(body)
+		require.NoError(t, err)
+
+		ex := mustPrettyJSON(t, tt.ex)
+		actual := mustPrettyJSON(t, string(r))
+		require.Equal(t, ex, actual,
+			fmt.Sprintf("Run %d:\n%s", i, xtest.Diff(ex, actual)))
+	}
+}