test(api): test the API merge proxy

1. Test whether or not it works.
2. Test stickiness.

itests/merged_api_test.go

@@ -0,0 +1,69 @@
+package itests
+
+import (
+	"context"
+	"testing"
+
+	"github.com/filecoin-project/go-state-types/big"
+	"github.com/filecoin-project/lotus/chain/types"
+	cliutil "github.com/filecoin-project/lotus/cli/util"
+	"github.com/filecoin-project/lotus/itests/kit"
+	"github.com/stretchr/testify/require"
+)
+
+func TestAPIMergeProxy(t *testing.T) {
+	ctx := context.Background()
+
+	// The default is too high for many nodes.
+	initialBalance := types.MustParseFIL("100000FIL")
+
+	nopts := []kit.NodeOpt{
+		kit.ThroughRPC(),
+		kit.WithAllSubsystems(),
+		kit.OwnerBalance(big.Int(initialBalance)),
+	}
+	ens := kit.NewEnsemble(t, kit.MockProofs())
+	nodes := make([]*kit.TestFullNode, 10)
+	for i := range nodes {
+		var nd kit.TestFullNode
+		ens.FullNode(&nd, nopts...)
+		nodes[i] = &nd
+	}
+	merged := kit.MergeFullNodes(nodes)
+
+	var miner kit.TestMiner
+	ens.Miner(&miner, merged, nopts...)
+
+	ens.Start()
+
+	nd1ID, err := nodes[0].ID(ctx)
+	require.NoError(t, err)
+	nd2ID, err := nodes[1].ID(ctx)
+	require.NoError(t, err)
+
+	// Expect to start on node 1, and switch to node 2 on failure.
+	mergedID, err := merged.ID(ctx)
+	require.NoError(t, err)
+	require.Equal(t, nd1ID, mergedID)
+	require.NoError(t, nodes[0].Stop(ctx))
+	mergedID, err = merged.ID(ctx)
+	require.NoError(t, err)
+	require.Equal(t, nd2ID, mergedID)
+
+	// Now see if sticky sessions work
+	stickyCtx := cliutil.OnSingleNode(ctx)
+	for i, nd := range nodes[1:] {
+		// kill off the previous node.
+		require.NoError(t, nodes[i].Stop(ctx))
+
+		got, err := merged.ID(stickyCtx)
+		require.NoError(t, err)
+		expected, err := nd.ID(ctx)
+		require.NoError(t, err)
+		require.Equal(t, expected, got)
+	}
+
+	// This should fail because we'll run out of retries because it's _not_ sticky!
+	_, err = merged.ID(ctx)
+	require.Error(t, err)
+}