Datasources: add support for POST HTTP verb for InfluxDB (#16690)

A new parameter `queryMode` is added to the InfluxDB datasource to provide a way to use POST instead of GET when querying the database. This prevents to get any error when querying the database with a heavy request.
Default configuration is kept to GET for backward compatibility. Tests and documentation have been added for this new behaviour.

pkg/tsdb/influxdb/influxdb.go

@@ -3,10 +3,12 @@ package influxdb
 import (
 	"context"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"net/http"
 	"net/url"
 	"path"
+	"strings"
 
 	"github.com/grafana/grafana/pkg/log"
 	"github.com/grafana/grafana/pkg/models"
@@ -33,6 +35,8 @@ var (
 	glog log.Logger
 )
 
+var ErrInvalidHttpMode error = errors.New("'httpMode' should be either 'GET' or 'POST'")
+
 func init() {
 	glog = log.New("tsdb.influxdb")
 	tsdb.RegisterTsdbQueryEndpoint("influxdb", NewInfluxDBExecutor)
@@ -108,21 +112,42 @@ func (e *InfluxDBExecutor) getQuery(dsInfo *models.DataSource, queries []*tsdb.Q
 }
 
 func (e *InfluxDBExecutor) createRequest(dsInfo *models.DataSource, query string) (*http.Request, error) {
+
 	u, _ := url.Parse(dsInfo.Url)
 	u.Path = path.Join(u.Path, "query")
+	httpMode := dsInfo.JsonData.Get("httpMode").MustString("GET")
+
+	req, err := func() (*http.Request, error) {
+		switch httpMode {
+		case "GET":
+			return http.NewRequest(http.MethodGet, u.String(), nil)
+		case "POST":
+			bodyValues := url.Values{}
+			bodyValues.Add("q", query)
+			body := bodyValues.Encode()
+			return http.NewRequest(http.MethodPost, u.String(), strings.NewReader(body))
+		default:
+			return nil, ErrInvalidHttpMode
+		}
+	}()
 
-	req, err := http.NewRequest(http.MethodGet, u.String(), nil)
 	if err != nil {
 		return nil, err
 	}
 
+	req.Header.Set("User-Agent", "Grafana")
+
 	params := req.URL.Query()
-	params.Set("q", query)
 	params.Set("db", dsInfo.Database)
 	params.Set("epoch", "s")
-	req.URL.RawQuery = params.Encode()
 
-	req.Header.Set("User-Agent", "Grafana")
+	if httpMode == "GET" {
+		params.Set("q", query)
+	} else if httpMode == "POST" {
+		req.Header.Set("Content-type", "application/x-www-form-urlencoded")
+	}
+
+	req.URL.RawQuery = params.Encode()
 
 	if dsInfo.BasicAuth {
 		req.SetBasicAuth(dsInfo.BasicAuthUser, dsInfo.DecryptedBasicAuthPassword())

pkg/tsdb/influxdb/influxdb_test.go

@@ -0,0 +1,77 @@
+package influxdb
+
+import (
+	"io/ioutil"
+	"net/url"
+	"testing"
+
+	"github.com/grafana/grafana/pkg/components/simplejson"
+	"github.com/grafana/grafana/pkg/models"
+	. "github.com/smartystreets/goconvey/convey"
+)
+
+func TestInfluxDB(t *testing.T) {
+	Convey("InfluxDB", t, func() {
+		datasource := &models.DataSource{
+			Url:      "http://awesome-influxdb:1337",
+			Database: "awesome-db",
+			JsonData: simplejson.New(),
+		}
+		query := "SELECT awesomeness FROM somewhere"
+		e := &InfluxDBExecutor{
+			QueryParser:    &InfluxdbQueryParser{},
+			ResponseParser: &ResponseParser{},
+		}
+		Convey("createRequest with GET httpMode", func() {
+			req, _ := e.createRequest(datasource, query)
+
+			Convey("as default", func() {
+				So(req.Method, ShouldEqual, "GET")
+			})
+
+			Convey("has a 'q' GET param that equals to query", func() {
+				q := req.URL.Query().Get("q")
+				So(q, ShouldEqual, query)
+			})
+
+			Convey("has an empty body", func() {
+				So(req.Body, ShouldEqual, nil)
+			})
+
+		})
+
+		Convey("createRequest with POST httpMode", func() {
+			datasource.JsonData.Set("httpMode", "POST")
+			req, _ := e.createRequest(datasource, query)
+
+			Convey("method should be POST", func() {
+				So(req.Method, ShouldEqual, "POST")
+			})
+
+			Convey("has no 'q' GET param", func() {
+				q := req.URL.Query().Get("q")
+				So(q, ShouldEqual, "")
+			})
+
+			Convey("has the request as GET param in body", func() {
+				body, _ := ioutil.ReadAll(req.Body)
+				testBodyValues := url.Values{}
+				testBodyValues.Add("q", query)
+				testBody := testBodyValues.Encode()
+				So(string(body[:]), ShouldEqual, testBody)
+			})
+
+		})
+
+		Convey("createRequest with PUT httpMode", func() {
+			datasource.JsonData.Set("httpMode", "PUT")
+			_, err := e.createRequest(datasource, query)
+
+			Convey("should miserably fail", func() {
+				So(err, ShouldEqual, ErrInvalidHttpMode)
+			})
+
+		})
+
+	})
+}