Fixes some 500 returned by querier when storage cancellation happens.

For unknown reasons,  Cortex is transforming all errors to promql.ErrStorage
on the storage layer.

Signed-off-by: Cyril Tovena <cyril.tovena@gmail.com>

pkg/util/server/error.go

@@ -6,6 +6,7 @@ import (
 	"net/http"
 
 	"github.com/cortexproject/cortex/pkg/chunk"
+	"github.com/prometheus/prometheus/promql"
 	"github.com/weaveworks/common/httpgrpc"
 	"github.com/weaveworks/common/user"
 
@@ -22,10 +23,14 @@ const (
 
 // WriteError write a go error with the correct status code.
 func WriteError(err error, w http.ResponseWriter) {
-	var queryErr chunk.QueryError
+	var (
+		queryErr chunk.QueryError
+		promErr  promql.ErrStorage
+	)
 
 	switch {
-	case errors.Is(err, context.Canceled):
+	case errors.Is(err, context.Canceled) ||
+		(errors.As(err, &promErr) && errors.Is(promErr.Err, context.Canceled)):
 		http.Error(w, ErrClientCanceled, StatusClientClosedRequest)
 	case errors.Is(err, context.DeadlineExceeded):
 		http.Error(w, ErrDeadlineExceeded, http.StatusGatewayTimeout)

pkg/util/server/error_test.go

@@ -10,6 +10,7 @@ import (
 	"testing"
 
 	"github.com/cortexproject/cortex/pkg/chunk"
+	"github.com/prometheus/prometheus/promql"
 	"github.com/stretchr/testify/require"
 	"github.com/weaveworks/common/httpgrpc"
 	"github.com/weaveworks/common/user"
@@ -28,6 +29,7 @@ func Test_writeError(t *testing.T) {
 	}{
 		{"cancelled", context.Canceled, ErrClientCanceled, StatusClientClosedRequest},
 		{"cancelled multi", util.MultiError{context.Canceled, context.Canceled}, ErrClientCanceled, StatusClientClosedRequest},
+		{"cancelled storage", promql.ErrStorage{Err: context.Canceled}, ErrClientCanceled, StatusClientClosedRequest},
 		{"orgid", user.ErrNoOrgID, user.ErrNoOrgID.Error(), http.StatusBadRequest},
 		{"deadline", context.DeadlineExceeded, ErrDeadlineExceeded, http.StatusGatewayTimeout},
 		{"parse error", logql.ParseError{}, "parse error : ", http.StatusBadRequest},