package light_test import ( "context" stdlog "log" "os" "time" dbm "github.com/tendermint/tm-db" "github.com/tendermint/tendermint/abci/example/kvstore" "github.com/tendermint/tendermint/libs/log" "github.com/tendermint/tendermint/light" "github.com/tendermint/tendermint/light/provider" httpp "github.com/tendermint/tendermint/light/provider/http" dbs "github.com/tendermint/tendermint/light/store/db" rpctest "github.com/tendermint/tendermint/rpc/test" ) // Manually getting light blocks and verifying them. func ExampleClient() { ctx, cancel := context.WithCancel(context.Background()) defer cancel() conf, err := rpctest.CreateConfig("ExampleClient_VerifyLightBlockAtHeight") if err != nil { stdlog.Fatal(err) } logger, err := log.NewDefaultLogger(log.LogFormatPlain, log.LogLevelInfo) if err != nil { stdlog.Fatal(err) } // Start a test application app := kvstore.NewApplication() _, closer, err := rpctest.StartTendermint(ctx, conf, app, rpctest.SuppressStdout) if err != nil { stdlog.Fatal(err) } defer func() { _ = closer(ctx) }() dbDir, err := os.MkdirTemp("", "light-client-example") if err != nil { stdlog.Fatal(err) } defer os.RemoveAll(dbDir) chainID := conf.ChainID() primary, err := httpp.New(chainID, conf.RPC.ListenAddress) if err != nil { stdlog.Fatal(err) } // give Tendermint time to generate some blocks time.Sleep(5 * time.Second) block, err := primary.LightBlock(ctx, 2) if err != nil { stdlog.Fatal(err) } db, err := dbm.NewGoLevelDB("light-client-db", dbDir) if err != nil { stdlog.Fatal(err) } c, err := light.NewClient(ctx, chainID, light.TrustOptions{ Period: 504 * time.Hour, // 21 days Height: 2, Hash: block.Hash(), }, primary, []provider.Provider{primary}, // NOTE: primary should not be used here dbs.New(db), light.Logger(logger), ) if err != nil { stdlog.Fatal(err) } defer func() { if err := c.Cleanup(); err != nil { stdlog.Fatal(err) } }() // wait for a few more blocks to be produced time.Sleep(2 * time.Second) // veify the block at height 3 _, err = c.VerifyLightBlockAtHeight(ctx, 3, time.Now()) if err != nil { stdlog.Fatal(err) } // retrieve light block at height 3 _, err = c.TrustedLightBlock(3) if err != nil { stdlog.Fatal(err) } // update to the latest height lb, err := c.Update(ctx, time.Now()) if err != nil { stdlog.Fatal(err) } logger.Info("verified light block", "light-block", lb) }