test(integration): prune orphaned networks to avoid subnet exhaustion

go.mod

@@ -16,6 +16,7 @@ require (
 	github.com/mholt/archives v0.1.5
 	github.com/microcosm-cc/bluemonday v1.0.27
 	github.com/moby/moby/api v1.54.2
+	github.com/moby/moby/client v0.4.1
 	github.com/prometheus/client_golang v1.23.2
 	github.com/shirou/gopsutil/v4 v4.26.4
 	github.com/spf13/pflag v1.0.10
@@ -90,7 +91,6 @@ require (
 	github.com/minio/minlz v1.1.1 // indirect
 	github.com/moby/docker-image-spec v1.3.1 // indirect
 	github.com/moby/go-archive v0.2.0 // indirect
-	github.com/moby/moby/client v0.4.1 // indirect
 	github.com/moby/patternmatcher v0.6.1 // indirect
 	github.com/moby/sys/sequential v0.6.0 // indirect
 	github.com/moby/sys/user v0.4.0 // indirect

test/integration/main_test.go

@@ -3,6 +3,7 @@
 package integration
 
 import (
+	"context"
 	"fmt"
 	"os"
 	"runtime"
@@ -48,6 +49,14 @@ func TestMain(m *testing.M) {
 		// Reset the failure collector before each run.
 		scenario.ResetFailedScenarios()
 
+		// Reclaim subnets leaked by prior runs or failed container starts
+		// before they exhaust Docker's predefined address pools.
+		if deleted, err := scenario.PruneOrphanedNetworks(context.Background()); err != nil {
+			fmt.Fprintf(colors.Colored(os.Stdout), "warning: prune orphaned networks: %v\n", err)
+		} else if deleted > 0 {
+			fmt.Fprintf(colors.Colored(os.Stdout), "pruned %d orphaned network(s)\n", deleted)
+		}
+
 		code := godog.TestSuite{
 			Name:                "integration",
 			ScenarioInitializer: scenario.InitializeScenario,

test/integration/scenario/containers.go

@@ -8,12 +8,44 @@ import (
 	"time"
 
 	"github.com/moby/moby/api/types/container"
+	"github.com/moby/moby/client"
 	"github.com/testcontainers/testcontainers-go"
 	"github.com/testcontainers/testcontainers-go/exec"
 	"github.com/testcontainers/testcontainers-go/network"
 	"github.com/testcontainers/testcontainers-go/wait"
 )
 
+// testcontainersLabel is the label testcontainers-go stamps on every
+// container and network it creates. Pruning on this label only ever touches
+// resources owned by the test suite.
+const testcontainersLabel = "org.testcontainers"
+
+// PruneOrphanedNetworks removes dangling networks created by the test suite.
+// Each scenario spins a dedicated network, and a failed container start can
+// leak one before teardown records it. Leaked networks consume Docker's
+// predefined address pools until none remain and every later scenario fails
+// with "all predefined address pools have been fully subnetted". Call this
+// before a run and between retries to reclaim the subnets.
+//
+// Only unused networks bearing the testcontainers label are removed, so
+// running containers and operator networks are never affected.
+func PruneOrphanedNetworks(ctx context.Context) (int, error) {
+	cli, err := client.New(client.FromEnv)
+	if err != nil {
+		return 0, fmt.Errorf("create Docker client: %w", err)
+	}
+	defer cli.Close()
+
+	filters := client.Filters{}.Add("label", testcontainersLabel+"=true")
+
+	report, err := cli.NetworkPrune(ctx, client.NetworkPruneOptions{Filters: filters})
+	if err != nil {
+		return 0, fmt.Errorf("prune networks: %w", err)
+	}
+
+	return len(report.Report.NetworksDeleted), nil
+}
+
 var (
 	GotenbergDockerRepository  string
 	GotenbergVersion           string
@@ -101,10 +133,20 @@ func startGotenbergContainer(ctx context.Context, env map[string]string) (*testc
 		Logger:           &noopLogger{},
 	})
 	if err != nil {
-		err = fmt.Errorf("start new Gotenberg container: %w", err)
+		// The network is already created. The scenario teardown only
+		// removes networks it knows about, and the caller discards n on
+		// error, so remove it here to avoid leaking a subnet on every
+		// failed start. Leaked networks accumulate until Docker's address
+		// pools are fully subnetted and all later scenarios fail.
+		if errRemove := n.Remove(ctx); errRemove != nil {
+			err = fmt.Errorf("start new Gotenberg container: %w (also failed to remove network: %v)", err, errRemove)
+		} else {
+			err = fmt.Errorf("start new Gotenberg container: %w", err)
+		}
+		return nil, nil, err
 	}
 
-	return n, c, err
+	return n, c, nil
 }
 
 func execCommandInIntegrationToolsContainer(ctx context.Context, cmd []string, path string) (string, error) {