lite2: move AutoClient into Client (#4326)

* lite2: move AutoClient into Client

Most of the users will want auto update feature, so it makes sense to
move it into the Client itself, rather than having a separate
abstraction (it makes the code cleaner, but introduces an extra thing
the user will need to learn).

Also, add `FirstTrustedHeight` func to Client to get first trusted height.

* fix db store tests

* separate examples for auto and manual clients

* AutoUpdate tries to update to latest state

NOT 1 header at a time

* fix errors

* lite2: make Logger an option

remove SetLogger func

* fix lite cmd

* lite2: make concurrency assumptions explicit

* fixes after my own review

* no need for nextHeightFn

sequence func will download intermediate headers

* correct comment

cmd/tendermint/commands/lite.go

@@ -86,11 +86,11 @@ func runProxy(cmd *cobra.Command, args []string) error {
 		},
 		httpp.NewWithClient(chainID, node),
 		dbs.New(db, chainID),
+		lite.Logger(liteLogger),
 	)
 	if err != nil {
 		return err
 	}
-	c.SetLogger(liteLogger)
 
 	p := lproxy.Proxy{
 		Addr:   listenAddr,

lite2/auto_client.go

@@ -1,76 +0,0 @@
-package lite
-
-import (
-	"time"
-
-	"github.com/tendermint/tendermint/types"
-)
-
-// AutoClient can auto update itself by fetching headers every N seconds.
-type AutoClient struct {
-	base         *Client
-	updatePeriod time.Duration
-	quit         chan struct{}
-
-	trustedHeaders chan *types.SignedHeader
-	errs           chan error
-}
-
-// NewAutoClient creates a new client and starts a polling goroutine.
-func NewAutoClient(base *Client, updatePeriod time.Duration) *AutoClient {
-	c := &AutoClient{
-		base:           base,
-		updatePeriod:   updatePeriod,
-		quit:           make(chan struct{}),
-		trustedHeaders: make(chan *types.SignedHeader),
-		errs:           make(chan error),
-	}
-	go c.autoUpdate()
-	return c
-}
-
-// TrustedHeaders returns a channel onto which new trusted headers are posted.
-func (c *AutoClient) TrustedHeaders() <-chan *types.SignedHeader {
-	return c.trustedHeaders
-}
-
-// Err returns a channel onto which errors are posted.
-func (c *AutoClient) Errs() <-chan error {
-	return c.errs
-}
-
-// Stop stops the client.
-func (c *AutoClient) Stop() {
-	close(c.quit)
-}
-
-func (c *AutoClient) autoUpdate() {
-	ticker := time.NewTicker(c.updatePeriod)
-	defer ticker.Stop()
-
-	for {
-		select {
-		case <-ticker.C:
-			lastTrustedHeight, err := c.base.LastTrustedHeight()
-			if err != nil {
-				c.errs <- err
-				continue
-			}
-
-			if lastTrustedHeight == -1 {
-				// no headers yet => wait
-				continue
-			}
-
-			h, err := c.base.VerifyHeaderAtHeight(lastTrustedHeight+1, time.Now())
-			if err != nil {
-				// no header yet or verification error => try again after updatePeriod
-				c.errs <- err
-				continue
-			}
-			c.trustedHeaders <- h
-		case <-c.quit:
-			return
-		}
-	}
-}

lite2/auto_client_test.go

@@ -1,76 +0,0 @@
-package lite
-
-import (
-	"testing"
-	"time"
-
-	"github.com/stretchr/testify/assert"
-	"github.com/stretchr/testify/require"
-
-	dbm "github.com/tendermint/tm-db"
-
-	"github.com/tendermint/tendermint/libs/log"
-	mockp "github.com/tendermint/tendermint/lite2/provider/mock"
-	dbs "github.com/tendermint/tendermint/lite2/store/db"
-	"github.com/tendermint/tendermint/types"
-)
-
-func TestAutoClient(t *testing.T) {
-	const (
-		chainID = "TestAutoClient"
-	)
-
-	var (
-		keys = genPrivKeys(4)
-		// 20, 30, 40, 50 - the first 3 don't have 2/3, the last 3 do!
-		vals   = keys.ToValidators(20, 10)
-		bTime  = time.Now().Add(-1 * time.Hour)
-		header = keys.GenSignedHeader(chainID, 1, bTime, nil, vals, vals,
-			[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys))
-	)
-
-	base, err := NewClient(
-		chainID,
-		TrustOptions{
-			Period: 4 * time.Hour,
-			Height: 1,
-			Hash:   header.Hash(),
-		},
-		mockp.New(
-			chainID,
-			map[int64]*types.SignedHeader{
-				// trusted header
-				1: header,
-				// interim header (3/3 signed)
-				2: keys.GenSignedHeader(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
-					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
-				// last header (3/3 signed)
-				3: keys.GenSignedHeader(chainID, 3, bTime.Add(1*time.Hour), nil, vals, vals,
-					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
-			},
-			map[int64]*types.ValidatorSet{
-				1: vals,
-				2: vals,
-				3: vals,
-				4: vals,
-			},
-		),
-		dbs.New(dbm.NewMemDB(), chainID),
-	)
-	require.NoError(t, err)
-	base.SetLogger(log.TestingLogger())
-
-	c := NewAutoClient(base, 1*time.Second)
-	defer c.Stop()
-
-	for i := 2; i <= 3; i++ {
-		select {
-		case h := <-c.TrustedHeaders():
-			assert.EqualValues(t, i, h.Height)
-		case err := <-c.Errs():
-			require.NoError(t, err)
-		case <-time.After(2 * time.Second):
-			t.Fatal("no headers/errors received in 2 sec")
-		}
-	}
-}

lite2/client.go

@@ -48,6 +48,7 @@ const (
 	sequential mode = iota + 1
 	skipping
 
+	defaultUpdatePeriod                       = 5 * time.Second
 	defaultRemoveNoLongerTrustedHeadersPeriod = 24 * time.Hour
 )
 
@@ -90,6 +91,13 @@ func AlternativeSources(providers []provider.Provider) Option {
 	}
 }
 
+// UpdatePeriod option can be used to change default polling period (5s).
+func UpdatePeriod(d time.Duration) Option {
+	return func(c *Client) {
+		c.updatePeriod = d
+	}
+}
+
 // RemoveNoLongerTrustedHeadersPeriod option can be used to define how often
 // the routine, which cleans up no longer trusted headers (outside of trusting
 // period), is run. Default: once a day. When set to zero, the routine won't be
@@ -109,10 +117,20 @@ func ConfirmationFunction(fn func(action string) bool) Option {
 	}
 }
 
+// Logger option can be used to set a logger for the client.
+func Logger(l log.Logger) Option {
+	return func(c *Client) {
+		c.logger = l
+	}
+}
+
 // Client represents a light client, connected to a single chain, which gets
 // headers from a primary provider, verifies them either sequentially or by
 // skipping some and stores them in a trusted store (usually, a local FS).
 //
+// By default, the client will poll the primary provider for new headers every
+// 5s (UpdatePeriod). If there are any, it will try to advance the state.
+//
 // Default verification: SkippingVerification(DefaultTrustLevel)
 type Client struct {
 	chainID          string
@@ -134,6 +152,7 @@ type Client struct {
 	// Highest next validator set from the store (height=H+1).
 	trustedNextVals *types.ValidatorSet
 
+	updatePeriod                       time.Duration
 	removeNoLongerTrustedHeadersPeriod time.Duration
 
 	confirmationFn func(action string) bool
@@ -162,6 +181,7 @@ func NewClient(
 		trustLevel:                         DefaultTrustLevel,
 		primary:                            primary,
 		trustedStore:                       trustedStore,
+		updatePeriod:                       defaultUpdatePeriod,
 		removeNoLongerTrustedHeadersPeriod: defaultRemoveNoLongerTrustedHeadersPeriod,
 		confirmationFn:                     func(action string) bool { return true },
 		quit:                               make(chan struct{}),
@@ -191,6 +211,10 @@ func NewClient(
 		go c.removeNoLongerTrustedHeadersRoutine()
 	}
 
+	if c.updatePeriod > 0 {
+		go c.autoUpdate()
+	}
+
 	return c, nil
 }
 
@@ -339,16 +363,12 @@ func (c *Client) initializeWithTrustOptions(options TrustOptions) error {
 	return c.updateTrustedHeaderAndVals(h, nextVals)
 }
 
-// Stop stops the light client.
+// Stop stops all the goroutines. If you wish to remove all the data, call
+// Cleanup.
 func (c *Client) Stop() {
 	close(c.quit)
 }
 
-// SetLogger sets a logger.
-func (c *Client) SetLogger(l log.Logger) {
-	c.logger = l
-}
-
 // TrustedHeader returns a trusted header at the given height (0 - the latest)
 // or nil if no such header exist.
 //
@@ -361,7 +381,10 @@ func (c *Client) SetLogger(l log.Logger) {
 //  - header expired, therefore can't be trusted (ErrOldHeaderExpired);
 //  - there are some issues with the trusted store, although that should not
 //  happen normally;
-//  - negative height is passed.
+//  - negative height is passed;
+//  - header is not found.
+//
+// Safe for concurrent use by multiple goroutines.
 func (c *Client) TrustedHeader(height int64, now time.Time) (*types.SignedHeader, error) {
 	if height < 0 {
 		return nil, errors.New("negative height")
@@ -379,9 +402,6 @@ func (c *Client) TrustedHeader(height int64, now time.Time) (*types.SignedHeader
 	if err != nil {
 		return nil, err
 	}
-	if h == nil {
-		return nil, nil
-	}
 
 	// Ensure header can still be trusted.
 	if HeaderExpired(h, c.trustingPeriod, now) {
@@ -393,11 +413,23 @@ func (c *Client) TrustedHeader(height int64, now time.Time) (*types.SignedHeader
 
 // LastTrustedHeight returns a last trusted height. -1 and nil are returned if
 // there are no trusted headers.
+//
+// Safe for concurrent use by multiple goroutines.
 func (c *Client) LastTrustedHeight() (int64, error) {
 	return c.trustedStore.LastSignedHeaderHeight()
 }
 
+// FirstTrustedHeight returns a first trusted height. -1 and nil are returned if
+// there are no trusted headers.
+//
+// Safe for concurrent use by multiple goroutines.
+func (c *Client) FirstTrustedHeight() (int64, error) {
+	return c.trustedStore.FirstSignedHeaderHeight()
+}
+
 // ChainID returns the chain ID the light client was configured with.
+//
+// Safe for concurrent use by multiple goroutines.
 func (c *Client) ChainID() string {
 	return c.chainID
 }
@@ -406,6 +438,8 @@ func (c *Client) ChainID() string {
 // and calls VerifyHeader.
 //
 // If the trusted header is more recent than one here, an error is returned.
+// If the header is not found by the primary provider,
+// provider.ErrSignedHeaderNotFound error is returned.
 func (c *Client) VerifyHeaderAtHeight(height int64, now time.Time) (*types.SignedHeader, error) {
 	c.logger.Info("VerifyHeaderAtHeight", "height", height)
 
@@ -435,6 +469,10 @@ func (c *Client) VerifyHeaderAtHeight(height int64, now time.Time) (*types.Signe
 // https://github.com/tendermint/spec/blob/master/spec/consensus/light-client.md
 //
 // If the trusted header is more recent than one here, an error is returned.
+//
+// If, at any moment, SignedHeader or ValidatorSet are not found by the primary
+// provider, provider.ErrSignedHeaderNotFound /
+// provider.ErrValidatorSetNotFound error is returned.
 func (c *Client) VerifyHeader(newHeader *types.SignedHeader, newVals *types.ValidatorSet, now time.Time) error {
 	c.logger.Info("VerifyHeader", "height", newHeader.Hash(), "newVals", newVals.Hash())
 
@@ -708,10 +746,6 @@ func (c *Client) RemoveNoLongerTrustedHeaders(now time.Time) {
 			c.logger.Error("can't get a trusted header", "err", err, "height", height)
 			continue
 		}
-		if h == nil {
-			c.logger.Debug("attempted to remove non-existing header", "height", height)
-			continue
-		}
 
 		// Stop if the header is within the trusting period.
 		if !HeaderExpired(h, c.trustingPeriod, now) {
@@ -725,3 +759,55 @@ func (c *Client) RemoveNoLongerTrustedHeaders(now time.Time) {
 		}
 	}
 }
+
+func (c *Client) autoUpdate() {
+	ticker := time.NewTicker(c.updatePeriod)
+	defer ticker.Stop()
+
+	for {
+		select {
+		case <-ticker.C:
+			err := c.AutoUpdate(time.Now())
+			if err != nil {
+				c.logger.Error("Error during auto update", "err", err)
+			}
+		case <-c.quit:
+			return
+		}
+	}
+}
+
+// AutoUpdate attempts to advance the state making exponential steps (note:
+// when SequentialVerification is being used, the client will still be
+// downloading all intermediate headers).
+//
+// Exposed for testing.
+func (c *Client) AutoUpdate(now time.Time) error {
+	lastTrustedHeight, err := c.LastTrustedHeight()
+	if err != nil {
+		return errors.Wrap(err, "can't get last trusted height")
+	}
+
+	if lastTrustedHeight == -1 {
+		// no headers yet => wait
+		return nil
+	}
+
+	var i int64
+	for err == nil {
+		// exponential increment: 1, 2, 4, 8, 16, ...
+		height := lastTrustedHeight + int64(1<<uint(i))
+		h, err := c.VerifyHeaderAtHeight(height, now)
+		if err != nil {
+			if errors.Is(err, provider.ErrSignedHeaderNotFound) {
+				c.logger.Debug("No header yet", "at", height)
+				return nil
+			}
+			return errors.Wrapf(err, "failed to verify the header #%d", height)
+		}
+		c.logger.Info("Advanced to new state", "height", h.Height, "hash", h.Hash())
+		i++
+	}
+
+	return nil
+}

lite2/client_test.go

@@ -1,6 +1,7 @@
 package lite
 
 import (
+	"sync"
 	"testing"
 	"time"
 
@@ -286,10 +287,10 @@ func TestClientRemovesNoLongerTrustedHeaders(t *testing.T) {
 			},
 		),
 		dbs.New(dbm.NewMemDB(), chainID),
+		Logger(log.TestingLogger()),
 	)
 	require.NoError(t, err)
 	defer c.Stop()
-	c.SetLogger(log.TestingLogger())
 
 	// Verify new headers.
 	_, err = c.VerifyHeaderAtHeight(2, bTime.Add(2*time.Hour).Add(1*time.Second))
@@ -303,7 +304,7 @@ func TestClientRemovesNoLongerTrustedHeaders(t *testing.T) {
 
 	// Check expired headers are no longer available.
 	h, err := c.TrustedHeader(1, now)
-	assert.NoError(t, err)
+	assert.Error(t, err)
 	assert.Nil(t, h)
 
 	// Check not expired headers are available.
@@ -345,15 +346,15 @@ func TestClient_Cleanup(t *testing.T) {
 			},
 		),
 		dbs.New(dbm.NewMemDB(), chainID),
+		Logger(log.TestingLogger()),
 	)
 	require.NoError(t, err)
-	c.SetLogger(log.TestingLogger())
 
 	c.Cleanup()
 
 	// Check no headers exist after Cleanup.
 	h, err := c.TrustedHeader(1, bTime.Add(1*time.Second))
-	assert.NoError(t, err)
+	assert.Error(t, err)
 	assert.Nil(t, h)
 }
 
@@ -397,9 +398,9 @@ func TestClientRestoreTrustedHeaderAfterStartup1(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		h, err := c.TrustedHeader(1, bTime.Add(1*time.Second))
 		assert.NoError(t, err)
@@ -436,9 +437,9 @@ func TestClientRestoreTrustedHeaderAfterStartup1(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		h, err := c.TrustedHeader(1, bTime.Add(1*time.Second))
 		assert.NoError(t, err)
@@ -491,9 +492,9 @@ func TestClientRestoreTrustedHeaderAfterStartup2(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		// Check we still have the 1st header (+header+).
 		h, err := c.TrustedHeader(1, bTime.Add(2*time.Hour).Add(1*time.Second))
@@ -536,13 +537,13 @@ func TestClientRestoreTrustedHeaderAfterStartup2(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		// Check we no longer have the invalid 1st header (+header+).
 		h, err := c.TrustedHeader(1, bTime.Add(2*time.Hour).Add(1*time.Second))
-		assert.NoError(t, err)
+		assert.Error(t, err)
 		assert.Nil(t, h)
 	}
 }
@@ -593,9 +594,9 @@ func TestClientRestoreTrustedHeaderAfterStartup3(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		// Check we still have the 1st header (+header+).
 		h, err := c.TrustedHeader(1, bTime.Add(2*time.Hour).Add(1*time.Second))
@@ -605,7 +606,7 @@ func TestClientRestoreTrustedHeaderAfterStartup3(t *testing.T) {
 
 		// Check we no longer have 2nd header (+header2+).
 		h, err = c.TrustedHeader(2, bTime.Add(2*time.Hour).Add(1*time.Second))
-		assert.NoError(t, err)
+		assert.Error(t, err)
 		assert.Nil(t, h)
 	}
 
@@ -643,9 +644,9 @@ func TestClientRestoreTrustedHeaderAfterStartup3(t *testing.T) {
 				},
 			),
 			trustedStore,
+			Logger(log.TestingLogger()),
 		)
 		require.NoError(t, err)
-		c.SetLogger(log.TestingLogger())
 
 		// Check we have swapped invalid 1st header (+header+) with correct one (+header1+).
 		h, err := c.TrustedHeader(1, bTime.Add(2*time.Hour).Add(1*time.Second))
@@ -655,7 +656,139 @@ func TestClientRestoreTrustedHeaderAfterStartup3(t *testing.T) {
 
 		// Check we no longer have invalid 2nd header (+header2+).
 		h, err = c.TrustedHeader(2, bTime.Add(2*time.Hour).Add(1*time.Second))
-		assert.NoError(t, err)
+		assert.Error(t, err)
 		assert.Nil(t, h)
 	}
 }
+
+func TestClient_AutoUpdate(t *testing.T) {
+	const (
+		chainID = "TestClient_AutoUpdate"
+	)
+
+	var (
+		keys = genPrivKeys(4)
+		// 20, 30, 40, 50 - the first 3 don't have 2/3, the last 3 do!
+		vals     = keys.ToValidators(20, 10)
+		bTime, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
+		header   = keys.GenSignedHeader(chainID, 1, bTime, nil, vals, vals,
+			[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys))
+	)
+
+	c, err := NewClient(
+		chainID,
+		TrustOptions{
+			Period: 4 * time.Hour,
+			Height: 1,
+			Hash:   header.Hash(),
+		},
+		mockp.New(
+			chainID,
+			map[int64]*types.SignedHeader{
+				// trusted header
+				1: header,
+				// interim header (3/3 signed)
+				2: keys.GenSignedHeader(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
+					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
+				// last header (3/3 signed)
+				3: keys.GenSignedHeader(chainID, 3, bTime.Add(1*time.Hour), nil, vals, vals,
+					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
+			},
+			map[int64]*types.ValidatorSet{
+				1: vals,
+				2: vals,
+				3: vals,
+				4: vals,
+			},
+		),
+		dbs.New(dbm.NewMemDB(), chainID),
+		Logger(log.TestingLogger()),
+	)
+	require.NoError(t, err)
+	defer c.Stop()
+
+	// should result in downloading & verifying headers #2 and #3
+	err = c.AutoUpdate(bTime.Add(2 * time.Hour))
+	require.NoError(t, err)
+
+	h, err := c.TrustedHeader(2, bTime.Add(2*time.Hour))
+	assert.NoError(t, err)
+	require.NotNil(t, h)
+	assert.EqualValues(t, 2, h.Height)
+
+	h, err = c.TrustedHeader(3, bTime.Add(2*time.Hour))
+	assert.NoError(t, err)
+	require.NotNil(t, h)
+	assert.EqualValues(t, 3, h.Height)
+}
+
+func TestClient_Concurrency(t *testing.T) {
+	const (
+		chainID = "TestClient_Concurrency"
+	)
+
+	var (
+		keys = genPrivKeys(4)
+		// 20, 30, 40, 50 - the first 3 don't have 2/3, the last 3 do!
+		vals     = keys.ToValidators(20, 10)
+		bTime, _ = time.Parse(time.RFC3339, "2006-01-02T15:04:05Z")
+		header   = keys.GenSignedHeader(chainID, 1, bTime, nil, vals, vals,
+			[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys))
+	)
+
+	c, err := NewClient(
+		chainID,
+		TrustOptions{
+			Period: 4 * time.Hour,
+			Height: 1,
+			Hash:   header.Hash(),
+		},
+		mockp.New(
+			chainID,
+			map[int64]*types.SignedHeader{
+				// trusted header
+				1: header,
+				// interim header (3/3 signed)
+				2: keys.GenSignedHeader(chainID, 2, bTime.Add(30*time.Minute), nil, vals, vals,
+					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
+				// last header (3/3 signed)
+				3: keys.GenSignedHeader(chainID, 3, bTime.Add(1*time.Hour), nil, vals, vals,
+					[]byte("app_hash"), []byte("cons_hash"), []byte("results_hash"), 0, len(keys)),
+			},
+			map[int64]*types.ValidatorSet{
+				1: vals,
+				2: vals,
+				3: vals,
+				4: vals,
+			},
+		),
+		dbs.New(dbm.NewMemDB(), chainID),
+		UpdatePeriod(0),
+		Logger(log.TestingLogger()),
+	)
+	require.NoError(t, err)
+	var wg sync.WaitGroup
+	for i := 0; i < 100; i++ {
+		wg.Add(1)
+		go func() {
+			defer wg.Done()
+
+			// NOTE: Cleanup, Stop, VerifyHeaderAtHeight and Verify are not supposed
+			// to be concurrenly safe.
+
+			assert.Equal(t, chainID, c.ChainID())
+
+			_, err := c.LastTrustedHeight()
+			assert.NoError(t, err)
+
+			_, err = c.FirstTrustedHeight()
+			assert.NoError(t, err)
+
+			h, err := c.TrustedHeader(1, bTime.Add(2*time.Hour))
+			assert.NoError(t, err)
+			assert.NotNil(t, h)
+		}()
+	}
+
+	wg.Wait()
+}

lite2/example_test.go

@@ -8,8 +8,6 @@ import (
 	"testing"
 	"time"
 
-	"github.com/pkg/errors"
-
 	dbm "github.com/tendermint/tm-db"
 
 	"github.com/tendermint/tendermint/abci/example/kvstore"
@@ -19,7 +17,8 @@ import (
 	rpctest "github.com/tendermint/tendermint/rpc/test"
 )
 
-func TestExample_Client(t *testing.T) {
+// Automatically getting new headers and verifying them.
+func TestExample_Client_AutoUpdate(t *testing.T) {
 	// give Tendermint time to generate some blocks
 	time.Sleep(5 * time.Second)
 
@@ -58,16 +57,15 @@ func TestExample_Client(t *testing.T) {
 		},
 		provider,
 		dbs.New(db, chainID),
+		UpdatePeriod(1*time.Second),
+		Logger(log.TestingLogger()),
 	)
 	if err != nil {
 		stdlog.Fatal(err)
 	}
-	c.SetLogger(log.TestingLogger())
+	defer c.Stop()
 
-	_, err = c.VerifyHeaderAtHeight(3, time.Now())
-	if err != nil {
-		stdlog.Fatal(err)
-	}
+	time.Sleep(2 * time.Second)
 
 	h, err := c.TrustedHeader(3, time.Now())
 	if err != nil {
@@ -78,7 +76,8 @@ func TestExample_Client(t *testing.T) {
 	// Output: got header 3
 }
 
-func TestExample_AutoClient(t *testing.T) {
+// Manually getting headers and verifying them.
+func TestExample_Client_ManualUpdate(t *testing.T) {
 	// give Tendermint time to generate some blocks
 	time.Sleep(5 * time.Second)
 
@@ -108,7 +107,7 @@ func TestExample_AutoClient(t *testing.T) {
 		stdlog.Fatal(err)
 	}
 
-	base, err := NewClient(
+	c, err := NewClient(
 		chainID,
 		TrustOptions{
 			Period: 504 * time.Hour, // 21 days
@@ -117,29 +116,26 @@ func TestExample_AutoClient(t *testing.T) {
 		},
 		provider,
 		dbs.New(db, chainID),
+		UpdatePeriod(0),
+		Logger(log.TestingLogger()),
 	)
 	if err != nil {
 		stdlog.Fatal(err)
 	}
-	base.SetLogger(log.TestingLogger())
-
-	c := NewAutoClient(base, 1*time.Second)
 	defer c.Stop()
 
-	select {
-	case h := <-c.TrustedHeaders():
-		fmt.Println("got header", h.Height)
-		// Output: got header 3
-	case err := <-c.Errs():
-		switch errors.Cause(err).(type) {
-		case ErrOldHeaderExpired:
-			// reobtain trust height and hash
-			stdlog.Fatal(err)
-		default:
-			// try with another full node
-			stdlog.Fatal(err)
-		}
+	_, err = c.VerifyHeaderAtHeight(3, time.Now())
+	if err != nil {
+		stdlog.Fatal(err)
 	}
+
+	h, err := c.TrustedHeader(3, time.Now())
+	if err != nil {
+		stdlog.Fatal(err)
+	}
+
+	fmt.Println("got header", h.Height)
+	// Output: got header 3
 }
 
 func TestMain(m *testing.M) {

lite2/provider/errors.go

@@ -0,0 +1,12 @@
+package provider
+
+import "errors"
+
+var (
+	// ErrSignedHeaderNotFound is returned when a provider can't find the
+	// requested header.
+	ErrSignedHeaderNotFound = errors.New("signed header not found")
+	// ErrValidatorSetNotFound is returned when a provider can't find the
+	// requested validator set.
+	ErrValidatorSetNotFound = errors.New("validator set not found")
+)

lite2/provider/http/http.go

@@ -2,6 +2,7 @@ package http
 
 import (
 	"fmt"
+	"strings"
 
 	"github.com/tendermint/tendermint/lite2/provider"
 	rpcclient "github.com/tendermint/tendermint/rpc/client"
@@ -54,6 +55,10 @@ func (p *http) SignedHeader(height int64) (*types.SignedHeader, error) {
 
 	commit, err := p.client.Commit(h)
 	if err != nil {
+		// TODO: standartise errors on the RPC side
+		if strings.Contains(err.Error(), "height must be less than or equal") {
+			return nil, provider.ErrSignedHeaderNotFound
+		}
 		return nil, err
 	}
 
@@ -76,6 +81,10 @@ func (p *http) ValidatorSet(height int64) (*types.ValidatorSet, error) {
 	const maxPerPage = 100
 	res, err := p.client.Validators(h, 0, maxPerPage)
 	if err != nil {
+		// TODO: standartise errors on the RPC side
+		if strings.Contains(err.Error(), "height must be less than or equal") {
+			return nil, provider.ErrValidatorSetNotFound
+		}
 		return nil, err
 	}
 

lite2/provider/mock/mock.go

@@ -1,8 +1,6 @@
 package mock
 
 import (
-	"github.com/pkg/errors"
-
 	"github.com/tendermint/tendermint/lite2/provider"
 	"github.com/tendermint/tendermint/types"
 )
@@ -32,12 +30,12 @@ func (p *mock) SignedHeader(height int64) (*types.SignedHeader, error) {
 	if _, ok := p.headers[height]; ok {
 		return p.headers[height], nil
 	}
-	return nil, errors.Errorf("no header at height %d", height)
+	return nil, provider.ErrSignedHeaderNotFound
 }
 
 func (p *mock) ValidatorSet(height int64) (*types.ValidatorSet, error) {
 	if _, ok := p.vals[height]; ok {
 		return p.vals[height], nil
 	}
-	return nil, errors.Errorf("no vals for height %d", height)
+	return nil, provider.ErrValidatorSetNotFound
 }

lite2/provider/provider.go

@@ -17,7 +17,7 @@ type Provider interface {
 	// If the provider fails to fetch the SignedHeader due to the IO or other
 	// issues, an error will be returned.
 	// If there's no SignedHeader for the given height, ErrSignedHeaderNotFound
-	// will be returned.
+	// error is returned.
 	SignedHeader(height int64) (*types.SignedHeader, error)
 
 	// ValidatorSet returns the ValidatorSet that corresponds to height.
@@ -28,6 +28,6 @@ type Provider interface {
 	// If the provider fails to fetch the ValidatorSet due to the IO or other
 	// issues, an error will be returned.
 	// If there's no ValidatorSet for the given height, ErrValidatorSetNotFound
-	// will be returned.
+	// error is returned.
 	ValidatorSet(height int64) (*types.ValidatorSet, error)
 }

lite2/store/db/db.go

@@ -1,6 +1,7 @@
 package db
 
 import (
+	"errors"
 	"fmt"
 	"regexp"
 	"strconv"
@@ -78,7 +79,7 @@ func (s *dbs) SignedHeader(height int64) (*types.SignedHeader, error) {
 		panic(err)
 	}
 	if len(bz) == 0 {
-		return nil, nil
+		return nil, errors.New("signed header not found")
 	}
 
 	var signedHeader *types.SignedHeader
@@ -97,7 +98,7 @@ func (s *dbs) ValidatorSet(height int64) (*types.ValidatorSet, error) {
 		panic(err)
 	}
 	if len(bz) == 0 {
-		return nil, nil
+		return nil, errors.New("validator set not found")
 	}
 
 	var valSet *types.ValidatorSet

lite2/store/db/db_test.go

@@ -42,11 +42,11 @@ func Test_SaveSignedHeaderAndNextValidatorSet(t *testing.T) {
 
 	// Empty store
 	h, err := dbStore.SignedHeader(1)
-	require.NoError(t, err)
+	require.Error(t, err)
 	assert.Nil(t, h)
 
 	valSet, err := dbStore.ValidatorSet(2)
-	require.NoError(t, err)
+	require.Error(t, err)
 	assert.Nil(t, valSet)
 
 	// 1 key
@@ -67,10 +67,10 @@ func Test_SaveSignedHeaderAndNextValidatorSet(t *testing.T) {
 	require.NoError(t, err)
 
 	h, err = dbStore.SignedHeader(1)
-	require.NoError(t, err)
+	require.Error(t, err)
 	assert.Nil(t, h)
 
 	valSet, err = dbStore.ValidatorSet(2)
-	require.NoError(t, err)
+	require.Error(t, err)
 	assert.Nil(t, valSet)
 }

lite2/store/store.go

@@ -21,16 +21,14 @@ type Store interface {
 	//
 	// height must be > 0.
 	//
-	// If the store is empty and the latest SignedHeader is requested, an error
-	// is returned.
+	// If SignedHeader is not found, an error is returned.
 	SignedHeader(height int64) (*types.SignedHeader, error)
 
 	// ValidatorSet returns the ValidatorSet that corresponds to height.
 	//
 	// height must be > 0.
 	//
-	// If the store is empty and the latest ValidatorSet is requested, an error
-	// is returned.
+	// If ValidatorSet is not found, an error is returned.
 	ValidatorSet(height int64) (*types.ValidatorSet, error)
 
 	// LastSignedHeaderHeight returns the last (newest) SignedHeader height.