history: fix the more nuanced cache-control max-age logic

go.mod

@@ -92,8 +92,8 @@ require (
 	golang.org/x/sys v0.28.0 // indirect
 	golang.org/x/text v0.21.0 // indirect
 	golang.org/x/time v0.8.0 // indirect
-	google.golang.org/genproto/googleapis/api v0.0.0-20241223144023-3abc09e42ca8 // indirect
-	google.golang.org/genproto/googleapis/rpc v0.0.0-20241223144023-3abc09e42ca8 // indirect
+	google.golang.org/genproto/googleapis/api v0.0.0-20241230172942-26aa7a208def // indirect
+	google.golang.org/genproto/googleapis/rpc v0.0.0-20241230172942-26aa7a208def // indirect
 	google.golang.org/grpc v1.69.2 // indirect
 	google.golang.org/protobuf v1.36.1 // indirect
 )

go.sum

@@ -138,8 +138,6 @@ github.com/yuin/goldmark v1.2.1/go.mod h1:3hX8gzYuyVAZsxl0MRgGTJEmQBFcNTphYh9dec
 go.mongodb.org/mongo-driver v1.11.4/go.mod h1:PTSz5yu21bkT/wXpkS7WR5f0ddqw5quethTUn9WM+2g=
 go.ntppool.org/api v0.3.4 h1:KeRyFhIRkjJwZif7hkpqEDEBmukyYGiOi2Fd6j3UzQ0=
 go.ntppool.org/api v0.3.4/go.mod h1:LFLAwnrc/JyjzKnjgf8tCOJhps6oFIjuledS3PCx7xc=
-go.ntppool.org/common v0.3.0 h1:IuSmyjEhI1F3tr5kc5MqlR4cy5y0o5f3EKvC7Koc6rs=
-go.ntppool.org/common v0.3.0/go.mod h1:25pUt3YUusF1MY0nsljjskcMMeTvKZszVvNsubvWhSM=
 go.ntppool.org/common v0.3.1 h1:JaJpS3m8oAc9jH0yhHYJnjOC+RUzxx/F+EDe0QON4eQ=
 go.ntppool.org/common v0.3.1/go.mod h1:1SKjFBH9AL7Fj2S0zy41isHzV6dTC+6yIKD5QDtX8aY=
 go.opentelemetry.io/auto/sdk v1.1.0 h1:cH53jehLUN6UFLY71z+NDOiNJqDdPRaXzTel0sJySYA=
@@ -248,10 +246,10 @@ golang.org/x/xerrors v0.0.0-20190717185122-a985d3407aa7/go.mod h1:I/5z698sn9Ka8T
 golang.org/x/xerrors v0.0.0-20191011141410-1b5146add898/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20191204190536-9bdfabe68543/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
 golang.org/x/xerrors v0.0.0-20200804184101-5ec99f83aff1/go.mod h1:I/5z698sn9Ka8TeJc9MKroUUfqBBauWjQqLJ2OPfmY0=
-google.golang.org/genproto/googleapis/api v0.0.0-20241223144023-3abc09e42ca8 h1:st3LcW/BPi75W4q1jJTEor/QWwbNlPlDG0JTn6XhZu0=
-google.golang.org/genproto/googleapis/api v0.0.0-20241223144023-3abc09e42ca8/go.mod h1:klhJGKFyG8Tn50enBn7gizg4nXGXJ+jqEREdCWaPcV4=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20241223144023-3abc09e42ca8 h1:TqExAhdPaB60Ux47Cn0oLV07rGnxZzIsaRhQaqS666A=
-google.golang.org/genproto/googleapis/rpc v0.0.0-20241223144023-3abc09e42ca8/go.mod h1:lcTa1sDdWEIHMWlITnIczmw5w60CF9ffkb8Z+DVmmjA=
+google.golang.org/genproto/googleapis/api v0.0.0-20241230172942-26aa7a208def h1:0Km0hi+g2KXbXL0+riZzSCKz23f4MmwicuEb00JeonI=
+google.golang.org/genproto/googleapis/api v0.0.0-20241230172942-26aa7a208def/go.mod h1:u2DoMSpCXjrzqLdobRccQMc9wrnMAJ1DLng0a2yqM2Q=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20241230172942-26aa7a208def h1:4P81qv5JXI/sDNae2ClVx88cgDDA6DPilADkG9tYKz8=
+google.golang.org/genproto/googleapis/rpc v0.0.0-20241230172942-26aa7a208def/go.mod h1:bdAgzvd4kFrpykc5/AC2eLUiegK9T/qxZHD4hXYf/ho=
 google.golang.org/grpc v1.69.2 h1:U3S9QEtbXC0bYNvRtcoklF3xGtLViumSYxWykJS+7AU=
 google.golang.org/grpc v1.69.2/go.mod h1:vyjdE6jLBI76dgpDojsFGNaHlxdjXN9ghpnd2o7JGZ4=
 google.golang.org/protobuf v1.26.0-rc.1/go.mod h1:jlhhOSvTdKEhbULTjvd4ARK9grFBp09yW+WbY/TyQbw=

server/history.go

@@ -145,7 +145,8 @@ func (srv *Server) history(c echo.Context) error {
 	ctx, span := tracing.Tracer().Start(c.Request().Context(), "history")
 	defer span.End()
 
-	// just cache for a short time by default
+	// set a reasonable default cache time; adjusted later for
+	// happy path common responses
 	c.Response().Header().Set("Cache-Control", "public,max-age=240")
 
 	mode := paramHistoryMode(c.Param("mode"))
@@ -316,13 +317,7 @@ func (srv *Server) historyJSON(ctx context.Context, c echo.Context, server ntpdb
 		}
 	}
 
-	if len(history.LogScores) == 0 ||
-		history.LogScores[len(history.LogScores)-1].Ts.After(time.Now().Add(-8*time.Hour)) {
-		// cache for longer if data hasn't updated for a while
-		c.Request().Header.Set("Cache-Control", "s-maxage=3600,max-age=1800")
-	} else {
-		c.Request().Header.Set("Cache-Control", "s-maxage=300,max-age=240")
-	}
+	setHistoryCacheControl(c, history)
 
 	return c.JSON(http.StatusOK, res)
 }
@@ -390,9 +385,26 @@ func (srv *Server) historyCSV(ctx context.Context, c echo.Context, history *logs
 
 	// log.Info("entries", "count", len(history.LogScores), "out_bytes", b.Len())
 
-	c.Response().Header().Set("Cache-Control", "s-maxage=150,max-age=120")
+	setHistoryCacheControl(c, history)
+
 	c.Response().Header().Set("Content-Disposition", "inline")
 	// Chrome and Firefox force-download text/csv files, so use text/plain
 	// https://bugs.chromium.org/p/chromium/issues/detail?id=152911
 	return c.Blob(http.StatusOK, "text/plain", b.Bytes())
 }
+
+func setHistoryCacheControl(c echo.Context, history *logscores.LogScoreHistory) {
+	hdr := c.Response().Header()
+	if len(history.LogScores) == 0 ||
+		// cache for longer if data hasn't updated for a while; or we didn't
+		// find any.
+		(time.Now().Add(-8 * time.Hour).After(history.LogScores[len(history.LogScores)-1].Ts)) {
+		hdr.Set("Cache-Control", "s-maxage=3600,max-age=1800")
+	} else {
+		if len(history.LogScores) == 1 {
+			hdr.Set("Cache-Control", "s-maxage=60,max-age=35")
+		} else {
+			hdr.Set("Cache-Control", "s-maxage=240,max-age=120")
+		}
+	}
+}