// stdlib
#include <assert.h>
#include <stdint.h>
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <errno.h>
#include <math.h> // isnan
// system
#include <time.h>
#include <fcntl.h>
#include <poll.h>
#include <unistd.h>
#include <arpa/inet.h>
#include <sys/socket.h>
#include <netinet/ip.h>
// C++
#include <string>
#include <vector>
// proj
#include "common.h"
#include "hashtable.h"
#include "zset.h"
#include "list.h"
#include "heap.h"
static void msg(const char *msg) {
fprintf(stderr, "%s\n", msg);
}
static void msg_errno(const char *msg) {
fprintf(stderr, "[errno:%d] %s\n", errno, msg);
}
static void die(const char *msg) {
fprintf(stderr, "[%d] %s\n", errno, msg);
abort();
}
static uint64_t get_monotonic_msec() {
struct timespec tv = {0, 0};
clock_gettime(CLOCK_MONOTONIC, &tv);
return uint64_t(tv.tv_sec) * 1000 + tv.tv_nsec / 1000 / 1000;
}
static void fd_set_nb(int fd) {
errno = 0;
int flags = fcntl(fd, F_GETFL, 0);
if (errno) {
die("fcntl error");
return;
}
flags |= O_NONBLOCK;
errno = 0;
(void)fcntl(fd, F_SETFL, flags);
if (errno) {
die("fcntl error");
}
}
const size_t k_max_msg = 32 << 20; // likely larger than the kernel buffer
typedef std::vector<uint8_t> Buffer;
// append to the back
static void buf_append(Buffer &buf, const uint8_t *data, size_t len) {
buf.insert(buf.end(), data, data + len);
}
// remove from the front
static void buf_consume(Buffer &buf, size_t n) {
buf.erase(buf.begin(), buf.begin() + n);
}
struct Conn {
int fd = -1;
// application's intention, for the event loop
bool want_read = false;
bool want_write = false;
bool want_close = false;
// buffered input and output
Buffer incoming; // data to be parsed by the application
Buffer outgoing; // responses generated by the application
// timer
uint64_t last_active_ms = 0;
DList idle_node;
};
// global states
static struct {
HMap db;
// a map of all client connections, keyed by fd
std::vector<Conn *> fd2conn;
// timers for idle connections
DList idle_list;
// timers for TTLs
std::vector<HeapItem> heap;
} g_data;
// application callback when the listening socket is ready
static int32_t handle_accept(int fd) {
// accept
struct sockaddr_in client_addr = {};
socklen_t addrlen = sizeof(client_addr);
int connfd = accept(fd, (struct sockaddr *)&client_addr, &addrlen);
if (connfd < 0) {
msg_errno("accept() error");
return -1;
}
uint32_t ip = client_addr.sin_addr.s_addr;
fprintf(stderr, "new client from %u.%u.%u.%u:%u\n",
ip & 255, (ip >> 8) & 255, (ip >> 16) & 255, ip >> 24,
ntohs(client_addr.sin_port)
);
// set the new connection fd to nonblocking mode
fd_set_nb(connfd);
// create a `struct Conn`
Conn *conn = new Conn();
conn->fd = connfd;
conn->want_read = true;
conn->last_active_ms = get_monotonic_msec();
dlist_insert_before(&g_data.idle_list, &conn->idle_node);
// put it into the map
if (g_data.fd2conn.size() <= (size_t)conn->fd) {
g_data.fd2conn.resize(conn->fd + 1);
}
assert(!g_data.fd2conn[conn->fd]);
g_data.fd2conn[conn->fd] = conn;
return 0;
}
static void conn_destroy(Conn *conn) {
(void)close(conn->fd);
g_data.fd2conn[conn->fd] = NULL;
dlist_detach(&conn->idle_node);
delete conn;
}
const size_t k_max_args = 200 * 1000;
static bool read_u32(const uint8_t *&cur, const uint8_t *end, uint32_t &out) {
if (cur + 4 > end) {
return false;
}
memcpy(&out, cur, 4);
cur += 4;
return true;
}
static bool
read_str(const uint8_t *&cur, const uint8_t *end, size_t n, std::string &out) {
if (cur + n > end) {
return false;
}
out.assign(cur, cur + n);
cur += n;
return true;
}
// +------+-----+------+-----+------+-----+-----+------+
// | nstr | len | str1 | len | str2 | ... | len | strn |
// +------+-----+------+-----+------+-----+-----+------+
static int32_t
parse_req(const uint8_t *data, size_t size, std::vector<std::string> &out) {
const uint8_t *end = data + size;
uint32_t nstr = 0;
if (!read_u32(data, end, nstr)) {
return -1;
}
if (nstr > k_max_args) {
return -1; // safety limit
}
while (out.size() < nstr) {
uint32_t len = 0;
if (!read_u32(data, end, len)) {
return -1;
}
out.push_back(std::string());
if (!read_str(data, end, len, out.back())) {
return -1;
}
}
if (data != end) {
return -1; // trailing garbage
}
return 0;
}
// error code for TAG_ERR
enum {
ERR_UNKNOWN = 1, // unknown command
ERR_TOO_BIG = 2, // response too big
ERR_BAD_TYP = 3, // unexpected value type
ERR_BAD_ARG = 4, // bad arguments
};
// data types of serialized data
enum {
TAG_NIL = 0, // nil
TAG_ERR = 1, // error code + msg
TAG_STR = 2, // string
TAG_INT = 3, // int64
TAG_DBL = 4, // double
TAG_ARR = 5, // array
};
// help functions for the serialization
static void buf_append_u8(Buffer &buf, uint8_t data) {
buf.push_back(data);
}
static void buf_append_u32(Buffer &buf, uint32_t data) {
buf_append(buf, (const uint8_t *)&data, 4);
}
static void buf_append_i64(Buffer &buf, int64_t data) {
buf_append(buf, (const uint8_t *)&data, 8);
}
static void buf_append_dbl(Buffer &buf, double data) {
buf_append(buf, (const uint8_t *)&data, 8);
}
// append serialized data types to the back
static void out_nil(Buffer &out) {
buf_append_u8(out, TAG_NIL);
}
static void out_str(Buffer &out, const char *s, size_t size) {
buf_append_u8(out, TAG_STR);
buf_append_u32(out, (uint32_t)size);
buf_append(out, (const uint8_t *)s, size);
}
static void out_int(Buffer &out, int64_t val) {
buf_append_u8(out, TAG_INT);
buf_append_i64(out, val);
}
static void out_dbl(Buffer &out, double val) {
buf_append_u8(out, TAG_DBL);
buf_append_dbl(out, val);
}
static void out_err(Buffer &out, uint32_t code, const std::string &msg) {
buf_append_u8(out, TAG_ERR);
buf_append_u32(out, code);
buf_append_u32(out, (uint32_t)msg.size());
buf_append(out, (const uint8_t *)msg.data(), msg.size());
}
static void out_arr(Buffer &out, uint32_t n) {
buf_append_u8(out, TAG_ARR);
buf_append_u32(out, n);
}
static size_t out_begin_arr(Buffer &out) {
out.push_back(TAG_ARR);
buf_append_u32(out, 0); // filled by out_end_arr()
return out.size() - 4; // the `ctx` arg
}
static void out_end_arr(Buffer &out, size_t ctx, uint32_t n) {
assert(out[ctx - 1] == TAG_ARR);
memcpy(&out[ctx], &n, 4);
}
// value types
enum {
T_INIT = 0,
T_STR = 1, // string
T_ZSET = 2, // sorted set
};
// KV pair for the top-level hashtable
struct Entry {
struct HNode node; // hashtable node
std::string key;
// for TTL
size_t heap_idx = -1; // array index to the heap item
// value
uint32_t type = 0;
// one of the following
std::string str;
ZSet zset;
};
static Entry *entry_new(uint32_t type) {
Entry *ent = new Entry();
ent->type = type;
return ent;
}
static void entry_set_ttl(Entry *ent, int64_t ttl_ms);
static void entry_del(Entry *ent) {
if (ent->type == T_ZSET) {
zset_clear(&ent->zset);
}
entry_set_ttl(ent, -1); // remove from the heap data structure
delete ent;
}
struct LookupKey {
struct HNode node; // hashtable node
std::string key;
};
// equality comparison for the top-level hashstable
static bool entry_eq(HNode *node, HNode *key) {
struct Entry *ent = container_of(node, struct Entry, node);
struct LookupKey *keydata = container_of(key, struct LookupKey, node);
return ent->key == keydata->key;
}
static void do_get(std::vector<std::string> &cmd, Buffer &out) {
// a dummy struct just for the lookup
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
// hashtable lookup
HNode *node = hm_lookup(&g_data.db, &key.node, &entry_eq);
if (!node) {
return out_nil(out);
}
// copy the value
Entry *ent = container_of(node, Entry, node);
if (ent->type != T_STR) {
return out_err(out, ERR_BAD_TYP, "not a string value");
}
return out_str(out, ent->str.data(), ent->str.size());
}
static void do_set(std::vector<std::string> &cmd, Buffer &out) {
// a dummy struct just for the lookup
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
// hashtable lookup
HNode *node = hm_lookup(&g_data.db, &key.node, &entry_eq);
if (node) {
// found, update the value
Entry *ent = container_of(node, Entry, node);
if (ent->type != T_STR) {
return out_err(out, ERR_BAD_TYP, "a non-string value exists");
}
ent->str.swap(cmd[2]);
} else {
// not found, allocate & insert a new pair
Entry *ent = entry_new(T_STR);
ent->key.swap(key.key);
ent->node.hcode = key.node.hcode;
ent->str.swap(cmd[2]);
hm_insert(&g_data.db, &ent->node);
}
return out_nil(out);
}
static void do_del(std::vector<std::string> &cmd, Buffer &out) {
// a dummy struct just for the lookup
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
// hashtable delete
HNode *node = hm_delete(&g_data.db, &key.node, &entry_eq);
if (node) { // deallocate the pair
entry_del(container_of(node, Entry, node));
}
return out_int(out, node ? 1 : 0);
}
static void heap_delete(std::vector<HeapItem> &a, size_t pos) {
// swap the erased item with the last item
a[pos] = a.back();
a.pop_back();
// update the swapped item
if (pos < a.size()) {
heap_update(a.data(), pos, a.size());
}
}
static void heap_upsert(std::vector<HeapItem> &a, size_t pos, HeapItem t) {
if (pos < a.size()) {
a[pos] = t; // update an existing item
} else {
pos = a.size();
a.push_back(t); // or add a new item
}
heap_update(a.data(), pos, a.size());
}
// set or remove the TTL
static void entry_set_ttl(Entry *ent, int64_t ttl_ms) {
if (ttl_ms < 0 && ent->heap_idx != (size_t)-1) {
// setting a negative TTL means removing the TTL
heap_delete(g_data.heap, ent->heap_idx);
ent->heap_idx = -1;
} else if (ttl_ms >= 0) {
// add or update the heap data structure
uint64_t expire_at = get_monotonic_msec() + (uint64_t)ttl_ms;
HeapItem item = {expire_at, &ent->heap_idx};
heap_upsert(g_data.heap, ent->heap_idx, item);
}
}
static bool str2int(const std::string &s, int64_t &out) {
char *endp = NULL;
out = strtoll(s.c_str(), &endp, 10);
return endp == s.c_str() + s.size();
}
// PEXPIRE key ttl_ms
static void do_expire(std::vector<std::string> &cmd, Buffer &out) {
int64_t ttl_ms = 0;
if (!str2int(cmd[2], ttl_ms)) {
return out_err(out, ERR_BAD_ARG, "expect int64");
}
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
HNode *node = hm_lookup(&g_data.db, &key.node, &entry_eq);
if (node) {
Entry *ent = container_of(node, Entry, node);
entry_set_ttl(ent, ttl_ms);
}
return out_int(out, node ? 1: 0);
}
// PTTL key
static void do_ttl(std::vector<std::string> &cmd, Buffer &out) {
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
HNode *node = hm_lookup(&g_data.db, &key.node, &entry_eq);
if (!node) {
return out_int(out, -2); // not found
}
Entry *ent = container_of(node, Entry, node);
if (ent->heap_idx == (size_t)-1) {
return out_int(out, -1); // no TTL
}
uint64_t expire_at = g_data.heap[ent->heap_idx].val;
uint64_t now_ms = get_monotonic_msec();
return out_int(out, expire_at > now_ms ? (expire_at - now_ms) : 0);
}
static bool cb_keys(HNode *node, void *arg) {
Buffer &out = *(Buffer *)arg;
const std::string &key = container_of(node, Entry, node)->key;
out_str(out, key.data(), key.size());
return true;
}
static void do_keys(std::vector<std::string> &, Buffer &out) {
out_arr(out, (uint32_t)hm_size(&g_data.db));
hm_foreach(&g_data.db, &cb_keys, (void *)&out);
}
static bool str2dbl(const std::string &s, double &out) {
char *endp = NULL;
out = strtod(s.c_str(), &endp);
return endp == s.c_str() + s.size() && !isnan(out);
}
// zadd zset score name
static void do_zadd(std::vector<std::string> &cmd, Buffer &out) {
double score = 0;
if (!str2dbl(cmd[2], score)) {
return out_err(out, ERR_BAD_ARG, "expect float");
}
// look up or create the zset
LookupKey key;
key.key.swap(cmd[1]);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
HNode *hnode = hm_lookup(&g_data.db, &key.node, &entry_eq);
Entry *ent = NULL;
if (!hnode) { // insert a new key
ent = entry_new(T_ZSET);
ent->key.swap(key.key);
ent->node.hcode = key.node.hcode;
hm_insert(&g_data.db, &ent->node);
} else { // check the existing key
ent = container_of(hnode, Entry, node);
if (ent->type != T_ZSET) {
return out_err(out, ERR_BAD_TYP, "expect zset");
}
}
// add or update the tuple
const std::string &name = cmd[3];
bool added = zset_insert(&ent->zset, name.data(), name.size(), score);
return out_int(out, (int64_t)added);
}
static const ZSet k_empty_zset;
static ZSet *expect_zset(std::string &s) {
LookupKey key;
key.key.swap(s);
key.node.hcode = str_hash((uint8_t *)key.key.data(), key.key.size());
HNode *hnode = hm_lookup(&g_data.db, &key.node, &entry_eq);
if (!hnode) { // a non-existent key is treated as an empty zset
return (ZSet *)&k_empty_zset;
}
Entry *ent = container_of(hnode, Entry, node);
return ent->type == T_ZSET ? &ent->zset : NULL;
}
// zrem zset name
static void do_zrem(std::vector<std::string> &cmd, Buffer &out) {
ZSet *zset = expect_zset(cmd[1]);
if (!zset) {
return out_err(out, ERR_BAD_TYP, "expect zset");
}
const std::string &name = cmd[2];
ZNode *znode = zset_lookup(zset, name.data(), name.size());
if (znode) {
zset_delete(zset, znode);
}
return out_int(out, znode ? 1 : 0);
}
// zscore zset name
static void do_zscore(std::vector<std::string> &cmd, Buffer &out) {
ZSet *zset = expect_zset(cmd[1]);
if (!zset) {
return out_err(out, ERR_BAD_TYP, "expect zset");
}
const std::string &name = cmd[2];
ZNode *znode = zset_lookup(zset, name.data(), name.size());
return znode ? out_dbl(out, znode->score) : out_nil(out);
}
// zquery zset score name offset limit
static void do_zquery(std::vector<std::string> &cmd, Buffer &out) {
// parse args
double score = 0;
if (!str2dbl(cmd[2], score)) {
return out_err(out, ERR_BAD_ARG, "expect fp number");
}
const std::string &name = cmd[3];
int64_t offset = 0, limit = 0;
if (!str2int(cmd[4], offset) || !str2int(cmd[5], limit)) {
return out_err(out, ERR_BAD_ARG, "expect int");
}
// get the zset
ZSet *zset = expect_zset(cmd[1]);
if (!zset) {
return out_err(out, ERR_BAD_TYP, "expect zset");
}
// seek to the key
if (limit <= 0) {
return out_arr(out, 0);
}
ZNode *znode = zset_seekge(zset, score, name.data(), name.size());
znode = znode_offset(znode, offset);
// output
size_t ctx = out_begin_arr(out);
int64_t n = 0;
while (znode && n < limit) {
out_str(out, znode->name, znode->len);
out_dbl(out, znode->score);
znode = znode_offset(znode, +1);
n += 2;
}
out_end_arr(out, ctx, (uint32_t)n);
}
static void do_request(std::vector<std::string> &cmd, Buffer &out) {
if (cmd.size() == 2 && cmd[0] == "get") {
return do_get(cmd, out);
} else if (cmd.size() == 3 && cmd[0] == "set") {
return do_set(cmd, out);
} else if (cmd.size() == 2 && cmd[0] == "del") {
return do_del(cmd, out);
} else if (cmd.size() == 3 && cmd[0] == "pexpire") {
return do_expire(cmd, out);
} else if (cmd.size() == 2 && cmd[0] == "pttl") {
return do_ttl(cmd, out);
} else if (cmd.size() == 1 && cmd[0] == "keys") {
return do_keys(cmd, out);
} else if (cmd.size() == 4 && cmd[0] == "zadd") {
return do_zadd(cmd, out);
} else if (cmd.size() == 3 && cmd[0] == "zrem") {
return do_zrem(cmd, out);
} else if (cmd.size() == 3 && cmd[0] == "zscore") {
return do_zscore(cmd, out);
} else if (cmd.size() == 6 && cmd[0] == "zquery") {
return do_zquery(cmd, out);
} else {
return out_err(out, ERR_UNKNOWN, "unknown command.");
}
}
static void response_begin(Buffer &out, size_t *header) {
*header = out.size(); // messege header position
buf_append_u32(out, 0); // reserve space
}
static size_t response_size(Buffer &out, size_t header) {
return out.size() - header - 4;
}
static void response_end(Buffer &out, size_t header) {
size_t msg_size = response_size(out, header);
if (msg_size > k_max_msg) {
out.resize(header + 4);
out_err(out, ERR_TOO_BIG, "response is too big.");
msg_size = response_size(out, header);
}
// message header
uint32_t len = (uint32_t)msg_size;
memcpy(&out[header], &len, 4);
}
// process 1 request if there is enough data
static bool try_one_request(Conn *conn) {
// try to parse the protocol: message header
if (conn->incoming.size() < 4) {
return false; // want read
}
uint32_t len = 0;
memcpy(&len, conn->incoming.data(), 4);
if (len > k_max_msg) {
msg("too long");
conn->want_close = true;
return false; // want close
}
// message body
if (4 + len > conn->incoming.size()) {
return false; // want read
}
const uint8_t *request = &conn->incoming[4];
// got one request, do some application logic
std::vector<std::string> cmd;
if (parse_req(request, len, cmd) < 0) {
msg("bad request");
conn->want_close = true;
return false; // want close
}
size_t header_pos = 0;
response_begin(conn->outgoing, &header_pos);
do_request(cmd, conn->outgoing);
response_end(conn->outgoing, header_pos);
// application logic done! remove the request message.
buf_consume(conn->incoming, 4 + len);
// Q: Why not just empty the buffer? See the explanation of "pipelining".
return true; // success
}
// application callback when the socket is writable
static void handle_write(Conn *conn) {
assert(conn->outgoing.size() > 0);
ssize_t rv = write(conn->fd, &conn->outgoing[0], conn->outgoing.size());
if (rv < 0 && errno == EAGAIN) {
return; // actually not ready
}
if (rv < 0) {
msg_errno("write() error");
conn->want_close = true; // error handling
return;
}
// remove written data from `outgoing`
buf_consume(conn->outgoing, (size_t)rv);
// update the readiness intention
if (conn->outgoing.size() == 0) { // all data written
conn->want_read = true;
conn->want_write = false;
} // else: want write
}
// application callback when the socket is readable
static void handle_read(Conn *conn) {
// read some data
uint8_t buf[64 * 1024];
ssize_t rv = read(conn->fd, buf, sizeof(buf));
if (rv < 0 && errno == EAGAIN) {
return; // actually not ready
}
// handle IO error
if (rv < 0) {
msg_errno("read() error");
conn->want_close = true;
return; // want close
}
// handle EOF
if (rv == 0) {
if (conn->incoming.size() == 0) {
msg("client closed");
} else {
msg("unexpected EOF");
}
conn->want_close = true;
return; // want close
}
// got some new data
buf_append(conn->incoming, buf, (size_t)rv);
// parse requests and generate responses
while (try_one_request(conn)) {}
// Q: Why calling this in a loop? See the explanation of "pipelining".
// update the readiness intention
if (conn->outgoing.size() > 0) { // has a response
conn->want_read = false;
conn->want_write = true;
// The socket is likely ready to write in a request-response protocol,
// try to write it without waiting for the next iteration.
return handle_write(conn);
} // else: want read
}
const uint64_t k_idle_timeout_ms = 5 * 1000;
static uint32_t next_timer_ms() {
uint64_t now_ms = get_monotonic_msec();
uint64_t next_ms = (uint64_t)-1;
// idle timers using a linked list
if (!dlist_empty(&g_data.idle_list)) {
Conn *conn = container_of(g_data.idle_list.next, Conn, idle_node);
next_ms = conn->last_active_ms + k_idle_timeout_ms;
}
// TTL timers using a heap
if (!g_data.heap.empty() && g_data.heap[0].val < next_ms) {
next_ms = g_data.heap[0].val;
}
// timeout value
if (next_ms == (uint64_t)-1) {
return -1; // no timers, no timeouts
}
if (next_ms <= now_ms) {
return 0; // missed?
}
return (int32_t)(next_ms - now_ms);
}
static bool hnode_same(HNode *node, HNode *key) {
return node == key;
}
static void process_timers() {
uint64_t now_ms = get_monotonic_msec();
// idle timers using a linked list
while (!dlist_empty(&g_data.idle_list)) {
Conn *conn = container_of(g_data.idle_list.next, Conn, idle_node);
uint64_t next_ms = conn->last_active_ms + k_idle_timeout_ms;
if (next_ms >= now_ms) {
break; // not expired
}
fprintf(stderr, "removing idle connection: %d\n", conn->fd);
conn_destroy(conn);
}
// TTL timers using a heap
const size_t k_max_works = 2000;
size_t nworks = 0;
const std::vector<HeapItem> &heap = g_data.heap;
while (!heap.empty() && heap[0].val < now_ms) {
Entry *ent = container_of(heap[0].ref, Entry, heap_idx);
HNode *node = hm_delete(&g_data.db, &ent->node, &hnode_same);
assert(node == &ent->node);
// fprintf(stderr, "key expired: %s\n", ent->key.c_str());
// delete the key
entry_del(ent);
if (nworks++ >= k_max_works) {
// don't stall the server if too many keys are expiring at once
break;
}
}
}
int main() {
// initialization
dlist_init(&g_data.idle_list);
// the listening socket
int fd = socket(AF_INET, SOCK_STREAM, 0);
if (fd < 0) {
die("socket()");
}
int val = 1;
setsockopt(fd, SOL_SOCKET, SO_REUSEADDR, &val, sizeof(val));
// bind
struct sockaddr_in addr = {};
addr.sin_family = AF_INET;
addr.sin_port = ntohs(1234);
addr.sin_addr.s_addr = ntohl(0); // wildcard address 0.0.0.0
int rv = bind(fd, (const sockaddr *)&addr, sizeof(addr));
if (rv) {
die("bind()");
}
// set the listen fd to nonblocking mode
fd_set_nb(fd);
// listen
rv = listen(fd, SOMAXCONN);
if (rv) {
die("listen()");
}
// the event loop
std::vector<struct pollfd> poll_args;
while (true) {
// prepare the arguments of the poll()
poll_args.clear();
// put the listening sockets in the first position
struct pollfd pfd = {fd, POLLIN, 0};
poll_args.push_back(pfd);
// the rest are connection sockets
for (Conn *conn : g_data.fd2conn) {
if (!conn) {
continue;
}
// always poll() for error
struct pollfd pfd = {conn->fd, POLLERR, 0};
// poll() flags from the application's intent
if (conn->want_read) {
pfd.events |= POLLIN;
}
if (conn->want_write) {
pfd.events |= POLLOUT;
}
poll_args.push_back(pfd);
}
// wait for readiness
int32_t timeout_ms = next_timer_ms();
int rv = poll(poll_args.data(), (nfds_t)poll_args.size(), timeout_ms);
if (rv < 0 && errno == EINTR) {
continue; // not an error
}
if (rv < 0) {
die("poll");
}
// handle the listening socket
if (poll_args[0].revents) {
handle_accept(fd);
}
// handle connection sockets
for (size_t i = 1; i < poll_args.size(); ++i) { // note: skip the 1st
uint32_t ready = poll_args[i].revents;
if (ready == 0) {
continue;
}
Conn *conn = g_data.fd2conn[poll_args[i].fd];
// update the idle timer by moving conn to the end of the list
conn->last_active_ms = get_monotonic_msec();
dlist_detach(&conn->idle_node);
dlist_insert_before(&g_data.idle_list, &conn->idle_node);
// handle IO
if (ready & POLLIN) {
assert(conn->want_read);
handle_read(conn); // application logic
}
if (ready & POLLOUT) {
assert(conn->want_write);
handle_write(conn); // application logic
}
// close the socket from socket error or application logic
if ((ready & POLLERR) || conn->want_close) {
conn_destroy(conn);
}
} // for each connection sockets
// handle timers
process_timers();
} // the event loop
return 0;
}redis/13/13_server.cpp
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