Allow to overwrite storage policy for Iflux write API

src/query/api/v1/handler/influxdb/write.go

@@ -26,18 +26,22 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net/http"
+	"strings"
 	"time"
 
 	"github.com/m3db/m3/src/cmd/services/m3coordinator/ingest"
 	"github.com/m3db/m3/src/dbnode/client"
+	"github.com/m3db/m3/src/metrics/policy"
 	"github.com/m3db/m3/src/query/api/v1/handler"
 	"github.com/m3db/m3/src/query/api/v1/options"
 	"github.com/m3db/m3/src/query/models"
+	"github.com/m3db/m3/src/query/storage/m3/storagemetadata"
 	"github.com/m3db/m3/src/query/ts"
 	"github.com/m3db/m3/src/query/util/logging"
 
 	imodels "github.com/influxdata/influxdb/models"
 	xerrors "github.com/m3db/m3/src/x/errors"
+	"github.com/m3db/m3/src/x/headers"
 	xhttp "github.com/m3db/m3/src/x/net/http"
 	xtime "github.com/m3db/m3/src/x/time"
 	"go.uber.org/zap"
@@ -293,6 +297,44 @@ func (iwh *ingestWriteHandler) ServeHTTP(w http.ResponseWriter, r *http.Request)
 		return
 	}
 	opts := ingest.WriteOptions{}
+
+	// ****  changes to overwrite the storage policy based on  request headers  *****
+
+	if v := strings.TrimSpace(r.Header.Get(headers.MetricsTypeHeader)); v != "" {
+		metricsType, err := storagemetadata.ParseMetricsType(v)
+		if err != nil {
+			xhttp.WriteError(w, err)
+			return
+		}
+
+		opts.DownsampleOverride = true
+		opts.DownsampleMappingRules = nil
+
+		strPolicy := strings.TrimSpace(r.Header.Get(headers.MetricsStoragePolicyHeader))
+		switch metricsType {
+		case storagemetadata.UnaggregatedMetricsType:
+			if strPolicy != "" {
+				xhttp.WriteError(w, errors.New("storage policy should not be set for unaggregated metrics"))
+				return
+			}
+		default:
+			parsed, err := policy.ParseStoragePolicy(strPolicy)
+			if err != nil {
+				err = fmt.Errorf("could not parse storage policy: %v", err)
+				xhttp.WriteError(w, err)
+				return
+			}
+
+			// Make sure this specific storage policy is used for the writes.
+			opts.WriteOverride = true
+			opts.WriteStoragePolicies = policy.StoragePolicies{
+				parsed,
+			}
+		}
+	}
+
+	// ********************************************************************************
+
 	iter := &ingestIterator{points: points, tagOpts: iwh.tagOpts, promRewriter: iwh.promRewriter}
 	batchErr := iwh.handlerOpts.DownsamplerAndWriter().WriteBatch(r.Context(), iter, opts)
 	if batchErr == nil {