go-dqlite 
This repository provides the go-dqlite Go package, containing bindings for the
dqlite C library and a pure-Go
client for the dqlite wire protocol.
Usage
The best way to understand how to use the go-dqlite package is probably by
looking at the source code of the demo
program and
use it as example.
In general your application will use code such as:
dir := "/path/to/data/directory"
address := "1.2.3.4:666" // Unique node address
cluster := []string{...} // Optional list of existing nodes, when starting a new node
app, err := app.New(dir, app.WithAddress(address), app.WithCluster(cluster))
if err != nil {
// ...
}
db, err := app.Open(context.Background(), "my-database")
if err != nil {
// ...
}
// db is a *sql.DB object
if _, err := db.Exec("CREATE TABLE my_table (n INT)"); err != nil
// ...
}
Build
In order to use the go-dqlite package in your application, you'll need to have
the dqlite C library installed on your
system, along with its dependencies. You then need to pass the -tags
argument to the Go tools when building or testing your packages, for example:
go build -tags libsqlite3
go test -tags libsqlite3
Documentation
The documentation for this package can be found on Godoc.
Demo
To see dqlite in action, either install the Debian package from the PPA:
sudo add-apt-repository -y ppa:dqlite/stable
sudo apt install dqlite libdqlite-dev
or build the dqlite C library and its dependencies from source, as described
here, and then run:
go install -tags libsqlite3 ./cmd/dqlite-demo
from the top-level directory of this repository.
This builds a demo dqlite application, which exposes a simple key/value store
over an HTTP API.
Once the dqlite-demo binary is installed (normally under ~/go/bin),
start three nodes of the demo application:
dqlite-demo --api 127.0.0.1:8001 --db 127.0.0.1:9001 &
dqlite-demo --api 127.0.0.1:8002 --db 127.0.0.1:9002 --join 127.0.0.1:9001 &
dqlite-demo --api 127.0.0.1:8003 --db 127.0.0.1:9003 --join 127.0.0.1:9001 &
The --api flag tells the demo program where to expose its HTTP API.
The --db flag tells the demo program to use the given address for internal
database replication.
The --join flag is optional and should be used only for additional nodes after
the first one. It informs them about the existing cluster, so they can
automatically join it.
Now we can start using the cluster. Let's insert a key pair:
curl -X PUT -d my-key http://127.0.0.1:8001/my-value
and then retrive it from the database:
curl http://127.0.0.1:8001/my-value
Currently the first node is the leader. If we stop it and then try to query the
key again curl will fail, but we can simply change the endpoint to another node
and things will work since an automatic failover has taken place:
kill -TERM %1; curl http://127.0.0.1:8002/my-value
Shell
A basic SQLite-like dqlite shell can be built with:
go install -tags libsqlite3 ./cmd/dqlite
You can test it with the dqlite-demo with:
dqlite -s 127.0.0.1:9001
It supports normal SQL queries plus the special .cluster and .leader
commands to inspect the cluster members and the current leader.