C-Raft¶
C-Raft is a fully asynchronous C implementation of the Raft consensus protocol.
Design¶
The library has modular design: its core part implements only the core Raft algorithm logic, in a fully platform independent way. On top of that, a pluggable interface defines the I/O implementation for networking and disk persistence.
A stock implementation of the I/O interface is provided when building the library with default options. It is based on libuv and should fit the vast majority of use cases.
Features¶
C-Raft implements all the basic features described in the Raft dissertation:
Leader election
Log replication
Log compaction
Membership changes
It also includes a few optional enhancements:
Optimistic pipelining to reduce log replication latency
Writing to leader’s disk in parallel
Automatic stepping down when the leader loses quorum
Leadership transfer extension
Non-voting servers
Quick start¶
Make sure that libuv is installed on your system, then run:
1 autoreconf -i
2 ./configure --enable-example
3 make
Then create a main.c file with this simple test program that just runs a
single raft server and implements a basic state machine for incrementing a
counter:
1 #include <raft.h>
2 #include <raft/uv.h>
3
4 static raft_id id = 12345;
5 static const char *address = "127.0.0.1:8080";
6 static const char *dir = "/tmp/raft-quick-start";
7 static struct uv_loop_s loop;
8 static struct raft_uv_transport transport;
9 static struct raft_io io;
10 static struct raft_fsm fsm;
11 static struct raft raft;
12 static struct raft_configuration conf;
13 static struct uv_timer_s timer;
14 static struct raft_apply apply;
15 static unsigned counter = 0;
16 static uint64_t command;
17
18 static int applyCommand(struct raft_fsm *fsm,
19 const struct raft_buffer *buf,
20 void **result) {
21 counter += *(uint64_t *)buf->base;
22 printf("counter: %u\n", counter);
23 return 0;
24 }
25
26 static void submitCommand(uv_timer_t *timer) {
27 struct raft_buffer buf;
28 command = uv_now(timer->loop) % 10;
29 buf.len = sizeof command;
30 buf.base = &command;
31 raft_apply(&raft, &apply, &buf, 1, NULL);
32 }
33
34 int main() {
35 mkdir(dir, 0755);
36 uv_loop_init(&loop);
37 raft_uv_tcp_init(&transport, &loop);
38 raft_uv_init(&io, &loop, dir, &transport);
39 fsm.apply = applyCommand;
40 raft_init(&raft, &io, &fsm, id, address);
41 raft_configuration_init(&conf);
42 raft_configuration_add(&conf, id, address, RAFT_VOTER);
43 raft_bootstrap(&raft, &conf);
44 raft_start(&raft);
45 uv_timer_init(&loop, &timer);
46 uv_timer_start(&timer, submitCommand, 0, 1000);
47 uv_run(&loop, UV_RUN_DEFAULT);
48 }
You can compile and run it with:
1 cc main.c -o main -lraft -luv && ./main