Add support for Cache-Control: no-cache support for Loki queries.

Goal is, if that header is set, we gurantee that response user got for that query is never from results cache.

Signed-off-by: Kaviraj <[email protected]>

Author: kavirajk

cmd/logcli/main.go

@@ -475,6 +475,7 @@ func newQueryClient(app *kingpin.Application) client.Client {
 	app.Flag("key", "Path to the client certificate key. Can also be set using LOKI_CLIENT_KEY_PATH env var.").Default("").Envar("LOKI_CLIENT_KEY_PATH").StringVar(&client.TLSConfig.KeyFile)
 	app.Flag("org-id", "adds X-Scope-OrgID to API requests for representing tenant ID. Useful for requesting tenant data when bypassing an auth gateway. Can also be set using LOKI_ORG_ID env var.").Default("").Envar("LOKI_ORG_ID").StringVar(&client.OrgID)
 	app.Flag("query-tags", "adds X-Query-Tags http header to API requests. This header value will be part of `metrics.go` statistics. Useful for tracking the query. Can also be set using LOKI_QUERY_TAGS env var.").Default("").Envar("LOKI_QUERY_TAGS").StringVar(&client.QueryTags)
+	app.Flag("no-cache", "adds Cache-Control: no-store http header to API requests. Can also be set using LOKI_NO_CACHE env var.").Default("false").Envar("LOKI_NO_CACHE").BoolVar(&client.NoCache)
 	app.Flag("bearer-token", "adds the Authorization header to API requests for authentication purposes. Can also be set using LOKI_BEARER_TOKEN env var.").Default("").Envar("LOKI_BEARER_TOKEN").StringVar(&client.BearerToken)
 	app.Flag("bearer-token-file", "adds the Authorization header to API requests for authentication purposes. Can also be set using LOKI_BEARER_TOKEN_FILE env var.").Default("").Envar("LOKI_BEARER_TOKEN_FILE").StringVar(&client.BearerTokenFile)
 	app.Flag("retries", "How many times to retry each query when getting an error response from Loki. Can also be set using LOKI_CLIENT_RETRIES env var.").Default("0").Envar("LOKI_CLIENT_RETRIES").IntVar(&client.Retries)

pkg/logcli/client/client.go

@@ -77,6 +77,7 @@ type DefaultClient struct {
 	BearerTokenFile string
 	Retries         int
 	QueryTags       string
+	NoCache         bool
 	AuthHeader      string
 	ProxyURL        string
 	BackoffConfig   BackoffConfig
@@ -375,6 +376,10 @@ func (c *DefaultClient) getHTTPRequestHeader() (http.Header, error) {
 		h.Set("X-Scope-OrgID", c.OrgID)
 	}
 
+	if c.NoCache {
+		h.Set("Cache-Control", "no-cache")
+	}
+
 	if c.QueryTags != "" {
 		h.Set("X-Query-Tags", c.QueryTags)
 	}

pkg/querier/queryrange/codec.go

@@ -97,8 +97,6 @@ func (r *LokiRequest) LogToSpan(sp opentracing.Span) {
 	)
 }
 
-func (*LokiRequest) GetCachingOptions() (res queryrangebase.CachingOptions) { return }
-
 func (r *LokiInstantRequest) GetStep() int64 {
 	return 0
 }
@@ -144,8 +142,6 @@ func (r *LokiInstantRequest) LogToSpan(sp opentracing.Span) {
 	)
 }
 
-func (*LokiInstantRequest) GetCachingOptions() (res queryrangebase.CachingOptions) { return }
-
 func (r *LokiSeriesRequest) GetEnd() time.Time {
 	return r.EndTs
 }
@@ -331,6 +327,14 @@ func (Codec) DecodeRequest(_ context.Context, r *http.Request, _ []string) (quer
 		return nil, httpgrpc.Errorf(http.StatusBadRequest, err.Error())
 	}
 
+	cacheControlHeader := "Cache-Control"
+	noCacheVal := "no-cache"
+	disableCacheReq := false
+
+	if strings.ToLower(strings.TrimSpace(r.Header.Get(cacheControlHeader))) == noCacheVal {
+		disableCacheReq = true
+	}
+
 	switch op := getOperation(r.URL.Path); op {
 	case QueryRangeOp:
 		rangeQuery, err := loghttp.ParseRangeQuery(r)
@@ -356,6 +360,9 @@ func (Codec) DecodeRequest(_ context.Context, r *http.Request, _ []string) (quer
 			Plan: &plan.QueryPlan{
 				AST: parsed,
 			},
+			CachingOptions: resultscache.CachingOptions{
+				Disabled: disableCacheReq,
+			},
 		}, nil
 	case InstantQueryOp:
 		req, err := loghttp.ParseInstantQuery(r)
@@ -378,6 +385,9 @@ func (Codec) DecodeRequest(_ context.Context, r *http.Request, _ []string) (quer
 			Plan: &plan.QueryPlan{
 				AST: parsed,
 			},
+			CachingOptions: resultscache.CachingOptions{
+				Disabled: disableCacheReq,
+			},
 		}, nil
 	case SeriesOp:
 		req, err := loghttp.ParseAndValidateSeriesQuery(r)