backend: support external SPARQL and named-graph snapshots

backend_go/snapshot_service_test.go

@@ -0,0 +1,97 @@
+package main
+
+import (
+	"context"
+	"errors"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestSnapshotBuildContinuesAfterRequesterCancellation(t *testing.T) {
+	svc := NewGraphSnapshotService(nil, Config{})
+
+	var fetchCalls atomic.Int32
+	started := make(chan struct{})
+	release := make(chan struct{})
+	expected := GraphResponse{
+		Nodes: []Node{{ID: 1}},
+		Edges: []Edge{{Source: 1, Target: 1, PredicateID: 0}},
+		Meta:  &GraphMeta{GraphQueryID: "default", Nodes: 1, Edges: 1},
+	}
+
+	svc.fetchSnapshot = func(ctx context.Context, _ *AnzoGraphClient, _ Config, nodeLimit int, edgeLimit int, graphQueryID string) (GraphResponse, error) {
+		fetchCalls.Add(1)
+		if nodeLimit != 10 || edgeLimit != 20 || graphQueryID != "default" {
+			t.Fatalf("unexpected fetch args nodeLimit=%d edgeLimit=%d graphQueryID=%s", nodeLimit, edgeLimit, graphQueryID)
+		}
+		close(started)
+		<-release
+		return expected, nil
+	}
+
+	ctx1, cancel1 := context.WithCancel(context.Background())
+	defer cancel1()
+
+	firstErrCh := make(chan error, 1)
+	go func() {
+		_, err := svc.Get(ctx1, 10, 20, "default")
+		firstErrCh <- err
+	}()
+
+	<-started
+	cancel1()
+
+	select {
+	case err := <-firstErrCh:
+		if !errors.Is(err, context.Canceled) {
+			t.Fatalf("first Get error = %v, want context.Canceled", err)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for first Get to return after cancellation")
+	}
+
+	secondSnapCh := make(chan GraphResponse, 1)
+	secondErrCh := make(chan error, 1)
+	go func() {
+		snap, err := svc.Get(context.Background(), 10, 20, "default")
+		if err != nil {
+			secondErrCh <- err
+			return
+		}
+		secondSnapCh <- snap
+	}()
+
+	time.Sleep(50 * time.Millisecond)
+	if got := fetchCalls.Load(); got != 1 {
+		t.Fatalf("fetchCalls after second waiter start = %d, want 1", got)
+	}
+
+	close(release)
+
+	select {
+	case err := <-secondErrCh:
+		t.Fatalf("second Get error = %v", err)
+	case snap := <-secondSnapCh:
+		if snap.Meta == nil || snap.Meta.Nodes != expected.Meta.Nodes || snap.Meta.Edges != expected.Meta.Edges {
+			t.Fatalf("second Get snapshot meta = %#v, want %#v", snap.Meta, expected.Meta)
+		}
+	case <-time.After(2 * time.Second):
+		t.Fatal("timed out waiting for second Get to return")
+	}
+
+	if got := fetchCalls.Load(); got != 1 {
+		t.Fatalf("fetchCalls after background completion = %d, want 1", got)
+	}
+
+	snap, err := svc.Get(context.Background(), 10, 20, "default")
+	if err != nil {
+		t.Fatalf("cached Get error = %v", err)
+	}
+	if snap.Meta == nil || snap.Meta.Nodes != expected.Meta.Nodes || snap.Meta.Edges != expected.Meta.Edges {
+		t.Fatalf("cached Get snapshot meta = %#v, want %#v", snap.Meta, expected.Meta)
+	}
+	if got := fetchCalls.Load(); got != 1 {
+		t.Fatalf("fetchCalls after cached Get = %d, want 1", got)
+	}
+}