1#include <inttypes.h>
2#include <stdio.h>
3#include <stdlib.h>
4#include <string.h>
5#include <uv.h>
6
7uv_loop_t *loop;
8
9struct child_worker {
10    uv_process_t req;
11    uv_process_options_t options;
12    uv_pipe_t pipe;
13} *workers;
14
15int round_robin_counter;
16int child_worker_count;
17
18uv_buf_t dummy_buf;
19char worker_path[500];
20
21void close_process_handle(uv_process_t *req, int64_t exit_status, int term_signal) {
22    fprintf(stderr, "Process exited with status %" PRId64 ", signal %d\n", exit_status, term_signal);
23    uv_close((uv_handle_t*) req, NULL);
24}
25
26void alloc_buffer(uv_handle_t *handle, size_t suggested_size, uv_buf_t *buf) {
27  buf->base = malloc(suggested_size);
28  buf->len = suggested_size;
29}
30
31void on_new_connection(uv_stream_t *server, int status) {
32    if (status == -1) {
33        // error!
34        return;
35    }
36
37    uv_tcp_t *client = (uv_tcp_t*) malloc(sizeof(uv_tcp_t));
38    uv_tcp_init(loop, client);
39    if (uv_accept(server, (uv_stream_t*) client) == 0) {
40        uv_write_t *write_req = (uv_write_t*) malloc(sizeof(uv_write_t));
41        dummy_buf = uv_buf_init("a", 1);
42        struct child_worker *worker = &workers[round_robin_counter];
43        uv_write2(write_req, (uv_stream_t*) &worker->pipe, &dummy_buf, 1, (uv_stream_t*) client, NULL);
44        round_robin_counter = (round_robin_counter + 1) % child_worker_count;
45    }
46    else {
47        uv_close((uv_handle_t*) client, NULL);
48    }
49}
50
51void setup_workers() {
52    size_t path_size = 500;
53    uv_exepath(worker_path, &path_size);
54    strcpy(worker_path + (strlen(worker_path) - strlen("multi-echo-server")), "worker");
55    fprintf(stderr, "Worker path: %s\n", worker_path);
56
57    char* args[2];
58    args[0] = worker_path;
59    args[1] = NULL;
60
61    round_robin_counter = 0;
62
63    // ...
64
65    // launch same number of workers as number of CPUs
66    uv_cpu_info_t *info;
67    int cpu_count;
68    uv_cpu_info(&info, &cpu_count);
69    uv_free_cpu_info(info, cpu_count);
70
71    child_worker_count = cpu_count;
72
73    workers = calloc(cpu_count, sizeof(struct child_worker));
74    while (cpu_count--) {
75        struct child_worker *worker = &workers[cpu_count];
76        uv_pipe_init(loop, &worker->pipe, 1);
77
78        uv_stdio_container_t child_stdio[3];
79        child_stdio[0].flags = UV_CREATE_PIPE | UV_READABLE_PIPE;
80        child_stdio[0].data.stream = (uv_stream_t*) &worker->pipe;
81        child_stdio[1].flags = UV_IGNORE;
82        child_stdio[2].flags = UV_INHERIT_FD;
83        child_stdio[2].data.fd = 2;
84
85        worker->options.stdio = child_stdio;
86        worker->options.stdio_count = 3;
87
88        worker->options.exit_cb = close_process_handle;
89        worker->options.file = args[0];
90        worker->options.args = args;
91
92        uv_spawn(loop, &worker->req, &worker->options);
93        fprintf(stderr, "Started worker %d\n", worker->req.pid);
94    }
95}
96
97int main() {
98    loop = uv_default_loop();
99
100    setup_workers();
101
102    uv_tcp_t server;
103    uv_tcp_init(loop, &server);
104
105    struct sockaddr_in bind_addr;
106    uv_ip4_addr("0.0.0.0", 7000, &bind_addr);
107    uv_tcp_bind(&server, (const struct sockaddr *)&bind_addr, 0);
108    int r;
109    if ((r = uv_listen((uv_stream_t*) &server, 128, on_new_connection))) {
110        fprintf(stderr, "Listen error %s\n", uv_err_name(r));
111        return 2;
112    }
113    return uv_run(loop, UV_RUN_DEFAULT);
114}
115