k3s/vendor/github.com/canonical/go-dqlite

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.

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/v1
sudo apt install dqlite

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.

Once the dqlite-demo binary is installed, start three nodes of the demo application, respectively with IDs 1, 2, and 3:

dqlite-demo start 1 &
dqlite-demo start 2 &
dqlite-demo start 3 &

The node with ID 1 automatically becomes the leader of a single node cluster, while the nodes with IDs 2 and 3 are waiting to be notified what cluster they belong to. Let's make nodes 2 and 3 join the cluster:

dqlite-demo add 2
dqlite-demo add 3

Now we can start using the cluster. The demo application is just a simple key/value store that stores data in a SQLite table. Let's insert a key pair:

dqlite-demo update my-key my-value

and then retrive it from the database:

dqlite-demo query my-key

Currently node 1 is the leader. If we stop it and then try to query the key again we'll notice that the query command hangs for a bit waiting for the failover to occur and for another node to step up as leader:

kill -TERM %1; sleep 0.1; dqlite-demo query my-key