new test for streaming and struct changes and additions

internal/cache/cache.go

@@ -10,8 +10,6 @@ import (
 	"sync"
 	"sync/atomic"
 	"time"
-
-	"golang.org/x/sync/singleflight"
 )
 
 const userAgent = "pacman/7.1.0 (Linux x86_64) libalpm/16.0.1"
@@ -20,9 +18,10 @@ type Cache struct {
 	cfg        CacheConfig
 	cr         *os.Root
 	mirrorIdx  atomic.Uint64
-	sf        singleflight.Group //prevents duplicate downloads
+	refreshMu  sync.Mutex
-	mu        sync.Mutex
 	client     http.Client
+	inFlight   map[string]*inFlight
+	inFlightMu sync.Mutex
 }
 
 type CacheConfig struct {
@@ -33,6 +32,11 @@ type CacheConfig struct {
 	ClientTimeout         time.Duration
 }
 
+type inFlight struct {
+	done chan struct{}
+	err  error
+}
+
 type CacheFile struct {
 	Reader   io.ReadCloser
 	Size     int64
@@ -71,6 +75,7 @@ func NewCache(cacheRoot string, mirrorURLs []string, mirroredRepos []string) (*C
 			Timeout:   cfg.ClientTimeout,
 			Transport: transport,
 		},
+		inFlight: make(map[string]*inFlight),
 	}, nil
 }
 

internal/cache/cache_test.go

@@ -233,3 +233,68 @@ func TestCreateSymlinks(t *testing.T) {
 		}
 	}
 }
+
+func TestGetStreamMultiplClient(t *testing.T) {
+	firstBytesSend := make(chan struct{})
+	const expectedOne = "This is fake file contents"
+	const expectedTwo = "More fake file contents"
+	expected := expectedOne + expectedTwo
+
+	svr := newTestServer(t, http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		//nolint:errcheck //ephemeral no need to check
+		fmt.Fprint(w, expectedOne)
+		w.(http.Flusher).Flush()
+		close(firstBytesSend)
+		time.Sleep(2 * time.Second)
+		fmt.Fprint(w, expectedTwo)
+	}))
+
+	c := newTestCache(t, []string{svr.URL + "/"})
+	c.client.Timeout = 10 * time.Second
+
+	type fetchResult struct {
+		data []byte
+		err  error
+	}
+
+	results := make(chan fetchResult, 2)
+
+	for range 2 {
+		go func() {
+			cf, err := c.Fetch("fakefile")
+			if err != nil {
+				results <- fetchResult{err: err}
+				return
+			}
+			defer cf.Reader.Close()
+			data, err := io.ReadAll(cf.Reader)
+			results <- fetchResult{data: data, err: err}
+		}()
+	}
+
+	<-firstBytesSend
+	c.inFlightMu.Lock()
+	_, ok := c.inFlight["fakefile"]
+	c.inFlightMu.Unlock()
+	if !ok {
+		t.Errorf("no matching key in map: %v", c.inFlight)
+	}
+
+	for range 2 {
+		result := <-results
+		if result.err != nil {
+			t.Errorf("a fetch failed: %v", result.err)
+		}
+		if !bytes.Equal(result.data, []byte(expected)) {
+			t.Errorf("expected result to contain %s got %s", expected, result.data)
+		}
+	}
+
+	data, err := c.cr.ReadFile("fakefile")
+	if err != nil {
+		t.Fatalf("Error reading file back: %v", err)
+	}
+	if !bytes.Equal(data, []byte(expected)) {
+		t.Errorf("expected file to contain %s got %s", expected, data)
+	}
+}

internal/cache/fetch.go

@@ -7,6 +7,9 @@ import (
 )
 
 func (c *Cache) Fetch(relPath string) (*CacheFile, error) {
+	// relPath is relative to the localRoot
+	// ie relPath includes /{repo}/os/{arch}/ and the actual name linux-x.x.x.pkg.tar.zst
+
 	// return file directly if exists in cache
 	cf, err := c.getCachedFile(relPath)
 	if err == nil {
@@ -14,24 +17,11 @@ func (c *Cache) Fetch(relPath string) (*CacheFile, error) {
 	}
 
 	// fetch file from upstream
-	_, err, _ = c.sf.Do(relPath, func() (any, error) {
 	slog.Debug("calling fetch", "file", relPath)
-		return nil, c.fetch(relPath)
+	return nil, c.getStream(relPath)
-	})
-	if err != nil {
-		return nil, err
-	}
-
-	cf, err = c.getCachedFile(relPath)
-	if err != nil {
-		return nil, err
-	}
-	return cf, nil
 }
 
-func (c *Cache) fetch(relPath string) error {
+func (c *Cache) getStream(relPath string) error {
-	// relPath is relative to the localRoot
-	// ie relPath includes /{repo}/os/{arch}/ and the actual name linux-x.x.x.pkg.tar.zst
 
 	// declare vars outside loop
 	var err error

internal/cache/refresh.go

@@ -3,10 +3,10 @@ package cache
 import "path/filepath"
 
 func (c *Cache) Refresh() error {
-	if !c.mu.TryLock() {
+	if !c.refreshMu.TryLock() {
 		return nil
 	}
-	defer c.mu.Unlock()
+	defer c.refreshMu.Unlock()
 
 	for _, repo := range c.cfg.mirroredRepos {
 		if err := c.refreshDB(repo); err != nil {
@@ -19,7 +19,7 @@ func (c *Cache) Refresh() error {
 func (c *Cache) refreshDB(repo string) error {
 	dbFile := repo + ".db.tar.gz"
 	dbPath := filepath.Join(repo, "os/x86_64", dbFile)
-	err := c.fetch(dbPath)
+	err := c.getStream(dbPath)
 	if err != nil {
 		return err
 	}