feat(lnm): switch to epoll

CHANGELOG.md

@@ -18,6 +18,8 @@ and this project adheres to [Semantic Versioning](https://semver.org/spec/v2.0.0
         * Better API for adding routes
         * State machine HTTP loop
     * Automatically support HEAD requests for all GET requests
+    * Event loop uses `epoll` instead of `poll`
+    * Configurable multithreading using `epoll`
 * Landerctl
     * `-c` flag to use custom config file (useful for testing)
 

lnm/include/lnm/http/loop.h

@@ -81,7 +81,7 @@ lnm_err lnm_http_route_init_regex(lnm_http_route **out, lnm_http_method method,
  */
 lnm_err lnm_http_loop_route_add(lnm_http_loop *hl, lnm_http_route *route);
 
-lnm_err lnm_http_loop_run(lnm_http_loop *hl, uint16_t port);
+lnm_err lnm_http_loop_run(lnm_http_loop *hl, uint16_t port, int thread_count);
 
 void lnm_http_loop_set_api_key(lnm_http_loop *hl, const char *api_key);
 

lnm/include/lnm/loop.h

@@ -1,13 +1,13 @@
 #ifndef LNM_LOOP
 #define LNM_LOOP
 
+#include <stdatomic.h>
 #include <stdint.h>
 #include <stdlib.h>
 
 #include "lnm/common.h"
 
 #define LNM_LOOP_BUF_SIZE 2048
-#define LNM_LOOP_INITIAL_CONNS 16
 
 typedef enum {
   lnm_loop_state_req = 0,
@@ -32,11 +32,8 @@ typedef struct lnm_loop_conn {
 
 typedef struct lnm_loop {
   int listen_fd;
-  struct {
+  int epoll_fd;
-    lnm_loop_conn **arr;
+  atomic_int open;
-    size_t len;
-    size_t open;
-  } conns;
   void *gctx;
   lnm_err (*ctx_init)(void **out, void *gctx);
   void (*ctx_free)(void *ctx);
@@ -52,6 +49,6 @@ lnm_err lnm_loop_init(lnm_loop **out, void *gctx,
 
 lnm_err lnm_loop_setup(lnm_loop *l, uint16_t port);
 
-lnm_err lnm_loop_run(lnm_loop *l);
+lnm_err lnm_loop_run(lnm_loop *l, int thread_count);
 
 #endif

lnm/src/http/lnm_http_loop.c

@@ -122,9 +122,9 @@ lnm_err lnm_http_loop_route_add(lnm_http_loop *hl, lnm_http_route *route) {
   return lnm_err_ok;
 }
 
-lnm_err lnm_http_loop_run(lnm_http_loop *hl, uint16_t port) {
+lnm_err lnm_http_loop_run(lnm_http_loop *hl, uint16_t port, int thread_count) {
   LNM_RES(lnm_loop_setup(hl, port));
-  return lnm_loop_run(hl);
+  return lnm_loop_run(hl, thread_count);
 }
 
 void lnm_http_loop_set_api_key(lnm_http_loop *hl, const char *api_key) {

lnm/src/loop/lnm_loop.c

@@ -1,12 +1,14 @@
 #include <fcntl.h>
 #include <netinet/in.h>
-#include <poll.h>
+#include <pthread.h>
 #include <stdio.h>
 #include <string.h>
+#include <sys/epoll.h>
 #include <unistd.h>
 
 #include "lnm/common.h"
 #include "lnm/log.h"
+#include "lnm/loop.h"
 #include "lnm/loop_internal.h"
 
 static const char *section = "loop";
@@ -47,35 +49,18 @@ lnm_err lnm_loop_accept(lnm_loop *l) {
   flags |= O_NONBLOCK;
   fcntl(conn_fd, F_SETFL, flags);
 
-  // Append connection to list of connections
-  if ((size_t)conn_fd >= l->conns.len) {
-    // We always calloc as a realloc might introduce unitialized values in the
-    // array
-    lnm_loop_conn **new = calloc(sizeof(lnm_loop_conn *), conn_fd + 1);
-
-    if (new == NULL) {
-      close(conn_fd);
-
-      return lnm_err_failed_alloc;
-    }
-
-    if (l->conns.len > 0) {
-      memcpy(new, l->conns.arr, l->conns.len * sizeof(lnm_loop_conn *));
-      free(l->conns.arr);
-    }
-
-    l->conns.arr = new;
-    l->conns.len = conn_fd + 1;
-  }
-
   lnm_loop_conn *conn;
   LNM_RES2(lnm_loop_conn_init(&conn, l), close(conn_fd));
 
-  l->conns.arr[conn_fd] = conn;
   conn->fd = conn_fd;
   conn->state = lnm_loop_state_req;
 
-  l->conns.open++;
+  struct epoll_event event = {.data.ptr = conn,
+                              .events = EPOLLIN | EPOLLET | EPOLLONESHOT};
+
+  epoll_ctl(l->epoll_fd, EPOLL_CTL_ADD, conn_fd, &event);
+
+  l->open++;
 
   lnm_ldebug(section, "connection opened with fd %i", conn_fd);
 
@@ -115,96 +100,133 @@ lnm_err lnm_loop_setup(lnm_loop *l, uint16_t port) {
   int flags = fcntl(listen_fd, F_GETFL);
   fcntl(listen_fd, F_SETFL, flags | O_NONBLOCK);
 
+  int epoll_fd = epoll_create1(0);
+
+  if (epoll_fd < 0) {
+    return lnm_err_failed_network;
+  }
+
+  struct epoll_event event = {
+      // The listening socket is marked using a NULL data field
+      .data.ptr = NULL,
+      .events = EPOLLIN | EPOLLET | EPOLLONESHOT};
+
+  res = epoll_ctl(epoll_fd, EPOLL_CTL_ADD, listen_fd, &event);
+
+  if (res < 0) {
+    return lnm_err_failed_network;
+  }
+
   l->listen_fd = listen_fd;
+  l->epoll_fd = epoll_fd;
 
   return lnm_err_ok;
 }
 
-lnm_err lnm_loop_run(lnm_loop *l) {
+typedef struct lnm_loop_thread_args {
-  if (l->listen_fd == 0) {
+  lnm_loop *l;
-    return lnm_err_not_setup;
+  int id;
-  }
+  int thread_count;
+} lnm_loop_thread_args;
 
-  struct pollfd *poll_args =
+lnm_err lnm_loop_run_thread(lnm_loop_thread_args *args) {
-      calloc(LNM_LOOP_INITIAL_CONNS + 1, sizeof(struct pollfd));
+  lnm_loop *l = args->l;
-  size_t poll_args_cap = LNM_LOOP_INITIAL_CONNS + 1;
+  int thread_id = args->id;
+  int thread_count = args->thread_count;
 
-  if (poll_args == NULL) {
+  struct epoll_event *events = calloc(1, sizeof(struct epoll_event));
+  int events_cap = 1;
+
+  if (events == NULL) {
     return lnm_err_failed_alloc;
   }
 
-  // First argument is listening socket
+  lnm_linfo(section, "thread %i started", thread_id);
-  poll_args[0].fd = l->listen_fd;
-  poll_args[0].events = POLLIN;
 
-  lnm_linfo(section, "started on fd %i", l->listen_fd);
+  struct epoll_event listen_event = {
+      .data.ptr = NULL, .events = EPOLLIN | EPOLLET | EPOLLONESHOT};
 
   while (1) {
-    nfds_t poll_args_len = 1;
+    int polled = epoll_wait(l->epoll_fd, events, events_cap, -1);
-
+    lnm_ldebug(section, "polled (thread %i): %i", thread_id, polled);
-    // Add all open connections to the poll command
-    for (size_t i = 0; i < l->conns.len && poll_args_len < l->conns.open + 1;
-         i++) {
-      const lnm_loop_conn *conn = l->conns.arr[i];
-
-      if (conn == NULL) {
-        continue;
-      }
-
-      poll_args[poll_args_len].fd = conn->fd;
-      poll_args[poll_args_len].events =
-          ((conn->state == lnm_loop_state_req) ? POLLIN : POLLOUT) | POLLERR;
-
-      poll_args_len++;
-    }
-
-    int polled = poll(poll_args, poll_args_len, -1);
 
     if (polled < 0) {
       return lnm_err_failed_poll;
     }
 
-    if (poll_args[0].revents) {
+    for (int i = 0; i < polled; i++) {
+      if (events[i].data.ptr == NULL) {
         lnm_loop_accept(l);
-      polled--;
-    }
-
-    for (size_t i = 1; i < poll_args_len && polled > 0; i++) {
-      if (poll_args[i].revents) {
-        lnm_loop_conn *conn = l->conns.arr[poll_args[i].fd];
 
+        epoll_ctl(l->epoll_fd, EPOLL_CTL_MOD, l->listen_fd, &listen_event);
+      } else {
+        lnm_loop_conn *conn = events[i].data.ptr;
         lnm_loop_conn_io(l, conn);
 
         if (conn->state == lnm_loop_state_end) {
-          l->conns.arr[conn->fd] = NULL;
+          int conn_fd = conn->fd;
-          close(conn->fd);
-
-          l->conns.open--;
-          lnm_ldebug(section, "connection closed with fd %i", conn->fd);
 
           lnm_loop_conn_free(l, conn);
-        }
+          close(conn_fd);
+          l->open--;
 
-        polled--;
+          epoll_ctl(l->epoll_fd, EPOLL_CTL_DEL, conn_fd, NULL);
+
+          lnm_ldebug(section, "connection closed with fd %i", conn_fd);
+        } else {
+          struct epoll_event event = {
+              .data.ptr = conn,
+              .events =
+                  (conn->state == lnm_loop_state_req ? EPOLLIN : EPOLLOUT) |
+                  EPOLLET | EPOLLONESHOT};
+          epoll_ctl(l->epoll_fd, EPOLL_CTL_MOD, conn->fd, &event);
+        }
       }
     }
 
-    if (poll_args_cap < l->conns.open + 1) {
+    int open = l->open;
-      struct pollfd *buf = calloc(l->conns.open + 1, sizeof(struct pollfd));
+    int cap_per_thread =
+        open + 1 > thread_count ? (open + 1) / thread_count : 1;
 
-      if (buf == NULL) {
+    if (cap_per_thread > events_cap) {
+      struct epoll_event *new_events =
+          malloc(cap_per_thread * sizeof(struct epoll_event));
+
+      if (new_events == NULL) {
         return lnm_err_failed_alloc;
       }
 
-      buf[0].fd = l->listen_fd;
+      free(events);
-      buf[0].events = POLLIN;
+      events = new_events;
-
+      events_cap = cap_per_thread;
-      free(poll_args);
-      poll_args = buf;
-
-      poll_args_cap = l->conns.open + 1;
     }
   }
 
   return lnm_err_ok;
 }
+
+lnm_err lnm_loop_run(lnm_loop *l, int thread_count) {
+  if (l->epoll_fd == 0) {
+    return lnm_err_not_setup;
+  }
+
+  lnm_loop_thread_args args[thread_count];
+
+  for (int i = 1; i < thread_count; i++) {
+    args[i].l = l;
+    args[i].id = i;
+    args[i].thread_count = thread_count;
+
+    pthread_t thread;
+    pthread_create(&thread, NULL, (void *(*)(void *))lnm_loop_run_thread,
+                   &args[i]);
+  }
+
+  args[0].l = l;
+  args[0].id = 0;
+  args[0].thread_count = thread_count;
+
+  lnm_loop_run_thread(&args[0]);
+
+  return lnm_err_ok;
+}

src/lander/lander_get.c

@@ -3,8 +3,8 @@
 
 #include "lnm/http/consts.h"
 #include "lnm/http/loop.h"
-#include "lnm/loop.h"
 #include "lnm/log.h"
+#include "lnm/loop.h"
 #include "lsm/store.h"
 
 #include "lander.h"
@@ -40,7 +40,8 @@ lnm_http_step_err lander_get_redirect(lnm_http_conn *conn) {
   // This shouldn't be able to happen
   if (lsm_entry_attr_get(&url_attr_val, c_ctx->entry, lander_attr_type_url) !=
       lsm_error_ok) {
-    lnm_lerror("lander", "%s", "Entry of type redirect detected without URL attribute");
+    lnm_lerror("lander", "%s",
+               "Entry of type redirect detected without URL attribute");
 
     ctx->res.status = lnm_http_status_internal_server_error;
     lsm_entry_close(c_ctx->entry);

src/main.c

@@ -104,7 +104,7 @@ int main() {
   lnm_linfo("main", "Store loaded containing %lu entries",
             lsm_store_size(c_gctx->store));
   lnm_http_loop *hl = loop_init(c_gctx, api_key);
-  lnm_http_loop_run(hl, port);
+  lnm_http_loop_run(hl, port, 1);
 
   /* http_loop *hl = http_loop_init( */
   /*     lander_routes, sizeof(lander_routes) / sizeof(lander_routes[0]),