Makefile

@@ -45,6 +45,7 @@ build-linux: export GOOS := linux
 build-linux: export GOARCH := amd64
 build-linux: export CGO_ENABLED := 0
 build-linux: $(BIN_DIR)/artifact.bin
+	sha256sum $(BIN_DIR)/artifact.bin
 
 
 .PHONY: test

README.md

@@ -86,6 +86,13 @@ curl \
   http://localhost:8080/state/bar
 ```
 
+Find out MIME type and size of an entry:
+```bash
+curl \
+  -X HEAD \
+  http://localhost:8080/state/bar
+```
+
 Obtain an entry:
 ```bash
 curl \

routing/routes.go

@@ -25,12 +25,17 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
         return err
     }
 
+    metricsTextTemplate, err := template.New( "metrics" ).Parse( metricsText )
+    if err != nil {
+        return err
+    }
+
     if config.LogLevel == "debug" {
         router.All( "*", func( c *f.Ctx ) error {
             log.Printf( "%s %s  mime:%s  agent:%s",
                 c.Method(),
                 c.Path(),
-                c.Get( f.HeaderContentType ),
+                c.Get( f.HeaderContentType, c.Get( f.HeaderAccept, "" ) ),
                 c.Get( f.HeaderUserAgent ),
             )
             return c.Next()
@@ -90,6 +95,35 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
     })
 
 
+    router.Get( "/metrics", func( c *f.Ctx ) error {
+        headers := c.GetReqHeaders()
+        acceptHeader := strings.Join( headers[ "Accept" ], " " )
+        buffer := &bytes.Buffer{}
+
+        if strings.Contains( acceptHeader , "json" ) {
+            // FUTUREWORK: implement https://opentelemetry.io/docs/specs/otlp/#otlphttp
+            return c.SendStatus( http.StatusNotAcceptable )
+        } else {
+            names, err := store.List()
+            if err != nil {
+                return c.SendStatus( http.StatusInternalServerError )
+            }
+
+            data := metricsTextData{
+                Count: len( names ),
+            }
+
+            err = metricsTextTemplate.Execute( buffer, data )
+            if err != nil {
+                return err
+            }
+
+            c.Set( "Content-Type", "text/plain; charset=utf-8" )
+            return c.Send( buffer.Bytes() )
+        }
+    })
+
+
     router.Get( "/env", func( c *f.Ctx ) error {
         c.Type( "txt", "utf-8" )
 
@@ -114,6 +148,22 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
     statePathGroup := router.Group( "/state" )
 
 
+    statePathGroup.Options( "/:name", func( c *f.Ctx ) error {
+        name := strings.Clone( c.Params( "name" ) )
+        existingItem, err := store.Fetch( name )
+        if err != nil {
+            return c.SendStatus( http.StatusInternalServerError )
+        }
+
+        if existingItem == nil {
+            return c.SendStatus( http.StatusNotFound )
+        }
+
+        c.Set( "Allow", "OPTIONS, GET, PUT, DELETE, HEAD" )
+        return c.SendStatus( http.StatusNoContent )
+    })
+
+
     statePathGroup.Get( "/:name", func( c *f.Ctx ) error {
         existingItem, err := store.Fetch( c.Params( "name" ) )
         if err != nil {
@@ -194,12 +244,24 @@ func SetRoutes( router *f.App, config *configuration.Config, store state.Store,
     })
 
 
-    statePathGroup.Use( "*", func( c *f.Ctx ) error {
-        if method := c.Method(); method == "OPTIONS" {
-            c.Set( "Allow", "GET, PUT, DELETE, OPTIONS" )
-            return c.SendStatus( http.StatusNoContent )
+    statePathGroup.Head( "/:name", func( c *f.Ctx ) error {
+        name := strings.Clone( c.Params( "name" ) )
+        existingItem, err := store.Fetch( name )
+        if err != nil {
+            return c.SendStatus( http.StatusInternalServerError )
+        }
+
+        if existingItem == nil {
+            return c.SendStatus( http.StatusNotFound )
         }
 
+        c.Set( "Content-Type", existingItem.MimeType() )
+        c.Set( "Content-Length", fmt.Sprintf( "%d", len( existingItem.Data() ) ) )
+        return c.SendStatus( http.StatusOK )
+    })
+
+
+    statePathGroup.Use( "*", func( c *f.Ctx ) error {
         return c.SendStatus( http.StatusNotFound )
     })
 

routing/routes_test.go

@@ -5,6 +5,7 @@ import (
     "fmt"
     "io"
     "os"
+    "strconv"
     "strings"
     "time"
     "math/rand"
@@ -167,7 +168,7 @@ func TestState( t *testing.T ){
 
     const statePath2 = "/state/another-test"
     const statePath2Mime = "application/octet-stream"
-    const statePath2BodySize = 64
+    const statePath2BodySize = 128
     statePath2Body := generateRandomBytes( statePath2BodySize )
 
     req := ht.NewRequest( "GET", statePath1, nil )
@@ -211,6 +212,15 @@ func TestState( t *testing.T ){
     res, _ = router.Test( req, -1 )
     assert.Equal( t, http.StatusCreated, res.StatusCode )
 
+    req = ht.NewRequest( "HEAD", statePath2, nil )
+    res, _ = router.Test( req, -1 )
+    contentLength, err := strconv.ParseInt( res.Header[ "Content-Length" ][0], 10, 64 )
+    assert.Nil( t, err )
+    assert.Equal( t, http.StatusOK, res.StatusCode )
+    assert.Equal( t, statePath2Mime, res.Header[ "Content-Type" ][0] )
+    assert.Equal( t, int64( statePath2BodySize ), contentLength )
+    assert.IsType( t, res.Body, http.NoBody )
+
     req = ht.NewRequest( "GET", statePath2, nil )
     res, _ = router.Test( req, -1 )
     bodyBytes, err := io.ReadAll( res.Body )

routing/templates.go

@@ -20,3 +20,14 @@ type indexHtmlData struct {
     Version string
     Color   string
 }
+
+
+const metricsText = `
+    # HELP state_entries_quantity The current number of state entries being stored
+    # TYPE state_entries_quantity gauge
+    state_entries_quantity {{ .Count }}
+`
+
+type metricsTextData struct {
+    Count int
+}