lite2: remove auto update (#4535)

We first introduced auto-update as a separate struct AutoClient, which
was wrapping Client and calling Update periodically.

// 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
            }

            newTrustedHeader, err := c.base.Update(time.Now())
            if err != nil {
                c.errs <- err
                continue
            }

            if newTrustedHeader != nil {
                 c.trustedHeaders <- newTrustedHeader
            }
        case <-c.quit:
            return
        }
    }
}

Later we merged it into the Client itself with the assumption that most clients will want it.

But now I am not sure. Neither IBC nor cosmos/relayer are using it. It increases complexity (Start/Stop methods).

That said, I think it makes sense to remove it until we see a need for it (until we better understand usage behavior). We can always introduce it later 😅. Maybe in the form of AutoClient.

cmd/tendermint/commands/lite.go

@@ -102,7 +102,7 @@ func runProxy(cmd *cobra.Command, args []string) error {
 
 	db, err := dbm.NewGoLevelDB("lite-client-db", home)
 	if err != nil {
-		return err
+		return errors.Wrap(err, "new goleveldb")
 	}
 
 	var c *lite.Client
@@ -129,16 +129,9 @@ func runProxy(cmd *cobra.Command, args []string) error {
 			lite.Logger(logger),
 		)
 	}
-
 	if err != nil {
-		return errors.Wrap(err, "failed to create")
+		return err
 	}
-	logger.Info("Starting client...")
-	err = c.Start()
-	if err != nil {
-		return errors.Wrap(err, "failed to start")
-	}
-	defer c.Stop()
 
 	rpcClient, err := rpcclient.NewHTTP(primaryAddr, "/websocket")
 	if err != nil {