#741 uri cache mutex

.github/workflows/go.yml

@@ -77,6 +77,7 @@ jobs:
     - run: go test -count=10 ./...
     - run: go test -count=2 -covermode=atomic ./...
     - run: go test -v -run TestRaceyPatternSchema -race ./...
+    - run: go test -v -run TestIssue741 -race ./...
       env:
         CGO_ENABLED: '1'
     - run: git --no-pager diff --exit-code

openapi3/issue741_test.go

@@ -0,0 +1,43 @@
+package openapi3
+
+import (
+	"fmt"
+	"net/http"
+	"net/http/httptest"
+	"sync"
+	"testing"
+
+	"github.com/stretchr/testify/require"
+)
+
+func TestIssue741(t *testing.T) {
+	ts := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		w.WriteHeader(http.StatusOK)
+		body := `{"openapi":"3.0.0","info":{"title":"MyAPI","version":"0.1","description":"An API"},"paths":{},"components":{"schemas":{"Foo":{"type":"string"}}}}`
+		_, err := w.Write([]byte(body))
+		if err != nil {
+			panic(err)
+		}
+	}))
+	defer ts.Close()
+
+	rootSpec := []byte(fmt.Sprintf(
+		`{"openapi":"3.0.0","info":{"title":"MyAPI","version":"0.1","description":"An API"},"paths":{},"components":{"schemas":{"Bar1":{"$ref":"%s#/components/schemas/Foo"}}}}`,
+		ts.URL,
+	))
+
+	wg := &sync.WaitGroup{}
+	n := 10
+	for i := 0; i < n; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+			loader := NewLoader()
+			loader.IsExternalRefsAllowed = true
+			doc, err := loader.LoadFromData(rootSpec)
+			require.NoError(t, err)
+			require.NotNil(t, doc)
+		}()
+	}
+	wg.Wait()
+}

openapi3/loader_uri_reader.go

@@ -7,12 +7,15 @@ import (
 	"net/http"
 	"net/url"
 	"path/filepath"
+	"sync"
 )
 
 // ReadFromURIFunc defines a function which reads the contents of a resource
 // located at a URI.
 type ReadFromURIFunc func(loader *Loader, url *url.URL) ([]byte, error)
 
+var uriMu = &sync.RWMutex{}
+
 // ErrURINotSupported indicates the ReadFromURIFunc does not know how to handle a
 // given URI.
 var ErrURINotSupported = errors.New("unsupported URI")
@@ -92,12 +95,17 @@ func URIMapCache(reader ReadFromURIFunc) ReadFromURIFunc {
 		}
 		uri := location.String()
 		var ok bool
+		uriMu.RLock()
 		if buf, ok = cache[uri]; ok {
+			uriMu.RUnlock()
 			return
 		}
+		uriMu.RUnlock()
 		if buf, err = reader(loader, location); err != nil {
 			return
 		}
+		uriMu.Lock()
+		defer uriMu.Unlock()
 		cache[uri] = buf
 		return
 	}