Revert "Revert "DVT-1057 replace block data structure with LRU cache …

…to fix memory leak (#148)""

This reverts commit f174e63.

README.md

@@ -148,6 +148,9 @@ You can then generate some load to make sure that blocks with transactions are b
 $ polycli loadtest --verbosity 700 --chain-id 1337 --concurrency 1 --requests 1000 --rate-limit 5 --mode c --rpc-url http://127.0.0.1:8545
 ```
 
+## Monitor Debug
+`polycli monitor --rpc-url http://34.117.145.249:80 -v 700 &> log.txt`
+
 # Contributing
 
 - If you add a new loadtest mode, don't forget to update the loadtest mode string by running the following command: `cd cmd/loadtest && stringer -type=loadTestMode`. You can install [stringer](https://pkg.go.dev/golang.org/x/tools/cmd/stringer) with `go install golang.org/x/tools/cmd/stringer@latest`.

cmd/monitor/cmd.go

@@ -15,9 +15,10 @@ var (
 	usage string
 
 	// flags
-	rpcUrl         string
-	batchSizeValue string
-	intervalStr    string
+	rpcUrl          string
+	batchSizeValue  string
+	blockCacheLimit int
+	intervalStr     string
 )
 
 // MonitorCmd represents the monitor command
@@ -37,6 +38,7 @@ var MonitorCmd = &cobra.Command{
 func init() {
 	MonitorCmd.PersistentFlags().StringVarP(&rpcUrl, "rpc-url", "r", "http://localhost:8545", "The RPC endpoint url")
 	MonitorCmd.PersistentFlags().StringVarP(&batchSizeValue, "batch-size", "b", "auto", "Number of requests per batch")
+	MonitorCmd.PersistentFlags().IntVarP(&blockCacheLimit, "cache-limit", "c", 100, "Number of cached blocks for the LRU block data structure (Min 100)")
 	MonitorCmd.PersistentFlags().StringVarP(&intervalStr, "interval", "i", "5s", "Amount of time between batch block rpc calls")
 }
 
@@ -66,5 +68,10 @@ func checkFlags() (err error) {
 		}
 	}
 
+	// Check batch-size flag.
+	if blockCacheLimit < 100 {
+		return fmt.Errorf("block-cache can't be less than 100")
+	}
+
 	return nil
 }