Using ABCI-CLI

To facilitate testing and debugging of ABCI servers and simple apps, we built a CLI, the abci-cli, for sending ABCI messages from the command line.

Install

Make sure you have Go installed.

Next, install the abci-cli tool and example applications:

go get -u github.com/tendermint/abci/cmd/abci-cli

If this fails, you may need to use dep to get vendored dependencies:

cd $GOPATH/src/github.com/tendermint/abci
make get_tools
make get_vendor_deps
make install

Now run abci-cli to see the list of commands:

Usage:
  abci-cli [command]

Available Commands:
  batch       Run a batch of abci commands against an application
  check_tx    Validate a tx
  commit      Commit the application state and return the Merkle root hash
  console     Start an interactive abci console for multiple commands
  counter     ABCI demo example
  deliver_tx  Deliver a new tx to the application
  kvstore       ABCI demo example
  echo        Have the application echo a message
  help        Help about any command
  info        Get some info about the application
  query       Query the application state
  set_option  Set an options on the application

Flags:
      --abci string      socket or grpc (default "socket")
      --address string   address of application socket (default "tcp://127.0.0.1:26658")
  -h, --help             help for abci-cli
  -v, --verbose          print the command and results as if it were a console session

Use "abci-cli [command] --help" for more information about a command.

KVStore - First Example

The abci-cli tool lets us send ABCI messages to our application, to help build and debug them.

The most important messages are deliver_tx, check_tx, and commit, but there are others for convenience, configuration, and information purposes.

We’ll start a kvstore application, which was installed at the same time as abci-cli above. The kvstore just stores transactions in a merkle tree.

Its code can be found here and looks like:

func cmdKVStore(cmd *cobra.Command, args []string) error {
    logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout))

    // Create the application - in memory or persisted to disk
    var app types.Application
    if flagPersist == "" {
        app = kvstore.NewKVStoreApplication()
    } else {
        app = kvstore.NewPersistentKVStoreApplication(flagPersist)
        app.(*kvstore.PersistentKVStoreApplication).SetLogger(logger.With("module", "kvstore"))
    }

    // Start the listener
    srv, err := server.NewServer(flagAddrD, flagAbci, app)
    if err != nil {
        return err
    }
    srv.SetLogger(logger.With("module", "abci-server"))
    if err := srv.Start(); err != nil {
        return err
    }

    // Wait forever
    cmn.TrapSignal(func() {
        // Cleanup
        srv.Stop()
    })
    return nil
}

Start by running:

abci-cli kvstore

And in another terminal, run

abci-cli echo hello
abci-cli info

You’ll see something like:

-> data: hello
-> data.hex: 68656C6C6F

and:

-> data: {"size":0}
-> data.hex: 7B2273697A65223A307D

An ABCI application must provide two things:

  • a socket server
  • a handler for ABCI messages

When we run the abci-cli tool we open a new connection to the application’s socket server, send the given ABCI message, and wait for a response.

The server may be generic for a particular language, and we provide a reference implementation in Golang. See the list of other ABCI implementations for servers in other languages.

The handler is specific to the application, and may be arbitrary, so long as it is deterministic and conforms to the ABCI interface specification.

So when we run abci-cli info, we open a new connection to the ABCI server, which calls the Info() method on the application, which tells us the number of transactions in our Merkle tree.

Now, since every command opens a new connection, we provide the abci-cli console and abci-cli batch commands, to allow multiple ABCI messages to be sent over a single connection.

Running abci-cli console should drop you in an interactive console for speaking ABCI messages to your application.

Try running these commands:

> echo hello
-> code: OK
-> data: hello
-> data.hex: 0x68656C6C6F

> info
-> code: OK
-> data: {"size":0}
-> data.hex: 0x7B2273697A65223A307D

> commit
-> code: OK
-> data.hex: 0x0000000000000000

> deliver_tx "abc"
-> code: OK

> info
-> code: OK
-> data: {"size":1}
-> data.hex: 0x7B2273697A65223A317D

> commit
-> code: OK
-> data.hex: 0x0200000000000000

> query "abc"
-> code: OK
-> log: exists
-> height: 0
-> value: abc
-> value.hex: 616263

> deliver_tx "def=xyz"
-> code: OK

> commit
-> code: OK
-> data.hex: 0x0400000000000000

> query "def"
-> code: OK
-> log: exists
-> height: 0
-> value: xyz
-> value.hex: 78797A

Note that if we do deliver_tx "abc" it will store (abc, abc), but if we do deliver_tx "abc=efg" it will store (abc, efg).

Similarly, you could put the commands in a file and run abci-cli --verbose batch < myfile.

Counter - Another Example

Now that we’ve got the hang of it, let’s try another application, the “counter” app.

Like the kvstore app, its code can be found here and looks like:

func cmdCounter(cmd *cobra.Command, args []string) error {

    app := counter.NewCounterApplication(flagSerial)

    logger := log.NewTMLogger(log.NewSyncWriter(os.Stdout))

    // Start the listener
    srv, err := server.NewServer(flagAddrC, flagAbci, app)
    if err != nil {
        return err
    }
    srv.SetLogger(logger.With("module", "abci-server"))
    if err := srv.Start(); err != nil {
        return err
    }

    // Wait forever
    cmn.TrapSignal(func() {
        // Cleanup
        srv.Stop()
    })
    return nil
}

The counter app doesn’t use a Merkle tree, it just counts how many times we’ve sent a transaction, asked for a hash, or committed the state. The result of commit is just the number of transactions sent.

This application has two modes: serial=off and serial=on.

When serial=on, transactions must be a big-endian encoded incrementing integer, starting at 0.

If serial=off, there are no restrictions on transactions.

We can toggle the value of serial using the set_option ABCI message.

When serial=on, some transactions are invalid. In a live blockchain, transactions collect in memory before they are committed into blocks. To avoid wasting resources on invalid transactions, ABCI provides the check_tx message, which application developers can use to accept or reject transactions, before they are stored in memory or gossipped to other peers.

In this instance of the counter app, check_tx only allows transactions whose integer is greater than the last committed one.

Let’s kill the console and the kvstore application, and start the counter app:

abci-cli counter

In another window, start the abci-cli console:

> set_option serial on
-> code: OK
-> log: OK (SetOption doesn't return anything.)

> check_tx 0x00
-> code: OK

> check_tx 0xff
-> code: OK

> deliver_tx 0x00
-> code: OK

> check_tx 0x00
-> code: BadNonce
-> log: Invalid nonce. Expected >= 1, got 0

> deliver_tx 0x01
-> code: OK

> deliver_tx 0x04
-> code: BadNonce
-> log: Invalid nonce. Expected 2, got 4

> info
-> code: OK
-> data: {"hashes":0,"txs":2}
-> data.hex: 0x7B22686173686573223A302C22747873223A327D

This is a very simple application, but between counter and kvstore, its easy to see how you can build out arbitrary application states on top of the ABCI. Hyperledger’s Burrow also runs atop ABCI, bringing with it Ethereum-like accounts, the Ethereum virtual-machine, Monax’s permissioning scheme, and native contracts extensions.

But the ultimate flexibility comes from being able to write the application easily in any language.

We have implemented the counter in a number of languages see the example directory.

To run the Node JS version, cd to example/js and run

node app.js

(you’ll have to kill the other counter application process). In another window, run the console and those previous ABCI commands. You should get the same results as for the Go version.

Bounties

Want to write the counter app in your favorite language?! We’d be happy to add you to our ecosystem! We’re also offering bounties for implementations in new languages!

The abci-cli is designed strictly for testing and debugging. In a real deployment, the role of sending messages is taken by Tendermint, which connects to the app using three separate connections, each with its own pattern of messages.

For more information, see the application developers guide. For examples of running an ABCI app with Tendermint, see the getting started guide. Next is the ABCI specification.