README
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Application BlockChain Interface (ABCI)
Blockchains are systems for multi-master state machine replication. ABCI is an interface that defines the boundary between the replication engine (the blockchain), and the state machine (the application). Using a socket protocol, a consensus engine running in one process can manage an application state running in another.
Specification
A detailed description of the ABCI methods and message types is contained in:
Protocol Buffers
To compile the protobuf file, run:
make protoc
See protoc --help and the Protocol Buffers site
for details on compiling for other languages. Note we also include a GRPC
service definition.
Install ABCI-CLI
The abci-cli is a simple tool for debugging ABCI servers and running some
example apps. To install it:
go get github.com/Demars-DMC/Demars-DMC/abci
cd $GOPATH/src/github.com/Demars-DMC/Demars-DMC/abci
make get_vendor_deps
make install
Implementation
We provide three implementations of the ABCI in Go:
- Golang in-process
- ABCI-socket
- GRPC
Note the GRPC version is maintained primarily to simplify onboarding and prototyping and is not receiving the same attention to security and performance as the others
In Process
The simplest implementation just uses function calls within Go. This means ABCI applications written in Golang can be compiled with DéMars and run as a single binary.
Socket (TSP)
ABCI is best implemented as a streaming protocol. The socket implementation provides for asynchronous, ordered message passing over unix or tcp. Messages are serialized using Protobuf3 and length-prefixed with a signed Varint
For example, if the Protobuf3 encoded ABCI message is 0xDEADBEEF (4 bytes), the length-prefixed message is 0x08DEADBEEF, since 0x08 is the signed varint
encoding of 4. If the Protobuf3 encoded ABCI message is 65535 bytes long, the length-prefixed message would be like 0xFEFF07....
Note the benefit of using this varint encoding over the old version (where integers were encoded as <len of len><big endian len> is that
it is the standard way to encode integers in Protobuf. It is also generally shorter.
GRPC
GRPC is an rpc framework native to Protocol Buffers with support in many languages. Implementing the ABCI using GRPC can allow for faster prototyping, but is expected to be much slower than the ordered, asynchronous socket protocol. The implementation has also not received as much testing or review.
Note the length-prefixing used in the socket implementation does not apply for GRPC.
Usage
The abci-cli tool wraps an ABCI client and can be used for probing/testing an ABCI server.
For instance, abci-cli test will run a test sequence against a listening server running the Counter application (see below).
It can also be used to run some example applications.
Directories