6.9 KiB
Using the 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 and put $GOPATH/bin in your $PATH.
Next, install the abci-cli tool and example applications:
go get -u github.com/tendermint/abci/cmd/...
If this fails, you may need to use glide to get vendored dependencies:
go get github.com/Masterminds/glide
cd $GOPATH/src/github.com/tendermint/abci
glide install
go install ./cmd/...
Now run abci-cli --help to see the list of commands:
COMMANDS:
batch Run a batch of ABCI commands against an application
console Start an interactive console for multiple commands
echo Have the application echo a message
info Get some info about the application
set_option Set an option on the application
deliver_tx Append a new tx to application
check_tx Validate a tx
commit Get application Merkle root hash
help, h Shows a list of commands or help for one command
GLOBAL OPTIONS:
--address "tcp://127.0.0.1:46658" address of application socket
--help, -h show help
--version, -v print the version
First Example - Dummy
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.
Let's start a dummy application, which was installed at the same time as abci-cli above. The dummy just stores transactions in a merkle tree:
dummy
In another terminal, run
abci-cli echo hello
abci-cli info
The application should echo hello and give you some information about itself.
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
-> data: hello
> info
-> data: {"size":0}
> commit
-> data: 0x
> deliver_tx "abc"
-> code: OK
> info
-> data: {"size":1}
> commit
-> data: 0x750502FC7E84BBD788ED589624F06CFA871845D1
> query "abc"
-> code: OK
-> data: {"index":0,"value":"abc","exists":true}
> deliver_tx "def=xyz"
-> code: OK
> commit
-> data: 0x76393B8A182E450286B0694C629ECB51B286EFD5
> query "def"
-> code: OK
-> data: {"index":1,"value":"xyz","exists":true}
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.
Another Example - Counter
Now that we've got the hang of it, let's try another application, the "counter" app.
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 dummy application, and start the counter app:
counter
In another window, start the abci-cli console:
> set_option serial on
-> data: serial=on
> 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
-> data: {"hashes":0,"txs":2}
This is a very simple application, but between counter and dummy, 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.
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!
Notes
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 introductory guide.