test: add the loadtime report tool (#9351) (#9364)

This pull request adds the report tool and modifies the loadtime libraries to better support its use.

(cherry picked from commit 8655080a0f)

Co-authored-by: William Banfield <4561443+williambanfield@users.noreply.github.com>

test/loadtime/cmd/load/main.go

@@ -0,0 +1,65 @@
+package main
+
+import (
+	"fmt"
+
+	"github.com/informalsystems/tm-load-test/pkg/loadtest"
+	"github.com/tendermint/tendermint/test/loadtime/payload"
+)
+
+// Ensure all of the interfaces are correctly satisfied.
+var (
+	_ loadtest.ClientFactory = (*ClientFactory)(nil)
+	_ loadtest.Client        = (*TxGenerator)(nil)
+)
+
+// ClientFactory implements the loadtest.ClientFactory interface.
+type ClientFactory struct{}
+
+// TxGenerator is responsible for generating transactions.
+// TxGenerator holds the set of information that will be used to generate
+// each transaction.
+type TxGenerator struct {
+	conns uint64
+	rate  uint64
+	size  uint64
+}
+
+func main() {
+	if err := loadtest.RegisterClientFactory("loadtime-client", &ClientFactory{}); err != nil {
+		panic(err)
+	}
+	loadtest.Run(&loadtest.CLIConfig{
+		AppName:              "loadtime",
+		AppShortDesc:         "Generate timestamped transaction load.",
+		AppLongDesc:          "loadtime generates transaction load for the purpose of measuring the end-to-end latency of a transaction from submission to execution in a Tendermint network.",
+		DefaultClientFactory: "loadtime-client",
+	})
+}
+
+func (f *ClientFactory) ValidateConfig(cfg loadtest.Config) error {
+	psb, err := payload.MaxUnpaddedSize()
+	if err != nil {
+		return err
+	}
+	if psb > cfg.Size {
+		return fmt.Errorf("payload size exceeds configured size")
+	}
+	return nil
+}
+
+func (f *ClientFactory) NewClient(cfg loadtest.Config) (loadtest.Client, error) {
+	return &TxGenerator{
+		conns: uint64(cfg.Connections),
+		rate:  uint64(cfg.Rate),
+		size:  uint64(cfg.Size),
+	}, nil
+}
+
+func (c *TxGenerator) GenerateTx() ([]byte, error) {
+	return payload.NewBytes(&payload.Payload{
+		Connections: c.conns,
+		Rate:        c.rate,
+		Size:        c.size,
+	})
+}