nginx-0.8.6处理一个index.html请求的源码分析
初始化
在master process中根据配置文件创建listening fd。调用listen和bind：
#0 ngx_open_listening_sockets (cycle=0x9674bf8) at src/core/ngx_connection.c:360
#1 0x08056493 in ngx_init_cycle (old_cycle=0xbfdccd70) at src/core/ngx_cycle.c:569
#2 0x0804b424 in main (argc=1, argv=0xbfdccef4) at src/core/nginx.c:317
s = ngx_socket(ls[i].sockaddr->sa_family, ls[i].type, 0);
...
if (bind(s, ls[i].sockaddr, ls[i].socklen) == -1) {
...
if (listen(s, ls[i].backlog) == -1) {
在worker process中设置listening fd的read event handler是ngx_event_accept：
#0 ngx_event_process_init (cycle=0x8611bf8) at src/event/ngx_event.c:810
#1 0x0806276b in ngx_worker_process_init (cycle=0x8611bf8, priority=<value optimized out>) at src/os/unix/ngx_process_cycle.c:941
#2 0x08062ba3 in ngx_worker_process_cycle (cycle=0x8611bf8, data=0x0) at src/os/unix/ngx_process_cycle.c:699
#3 0x0806148d in ngx_spawn_process (cycle=0x8611bf8, proc=0x8062b8b <ngx_worker_process_cycle>, data=0x0, name=0x8099148 "worker process", respawn=-2)
at src/os/unix/ngx_process.c:194
#4 0x080621ca in ngx_start_worker_processes (cycle=0x8611bf8, n=1, type=-2) at src/os/unix/ngx_process_cycle.c:331
#5 0x080630df in ngx_master_process_cycle (cycle=0x8611bf8) at src/os/unix/ngx_process_cycle.c:123
#6 0x0804b5bc in main (argc=1, argv=0xbf908a24) at src/core/nginx.c:382
ls = cycle->listening.elts;
...
for (i = 0; i < cycle->listening.nelts; i++) {
c = ngx_get_connection(ls[i].fd, cycle->log);
...
rev = c->read;
...
rev->handler = ngx_event_accept;
客户端发起连接
在worker process中调用ngx_event_accept接受连接，得到connection fd：
#0 ngx_event_accept (ev=0x90bec08) at src/event/ngx_event_accept.c:19
#1 0x08063ff5 in ngx_epoll_process_events (cycle=0x9095bf8, timer=4294967295, flags=<value optimized out>) at src/event/modules/ngx_epoll_module.c:518
#2 0x0805ce5a in ngx_process_events_and_timers (cycle=0x9095bf8) at src/event/ngx_event.c:245
#3 0x08062c3c in ngx_worker_process_cycle (cycle=0x9095bf8, data=0x0) at src/os/unix/ngx_process_cycle.c:775
#4 0x0806148d in ngx_spawn_process (cycle=0x9095bf8, proc=0x8062b8b <ngx_worker_process_cycle>, data=0x0, name=0x8099148 "worker process", respawn=-2)
at src/os/unix/ngx_process.c:194
#5 0x080621ca in ngx_start_worker_processes (cycle=0x9095bf8, n=1, type=-2) at src/os/unix/ngx_process_cycle.c:331
#6 0x080630df in ngx_master_process_cycle (cycle=0x9095bf8) at src/os/unix/ngx_process_cycle.c:123
#7 0x0804b5bc in main (argc=1, argv=0xbff988b4) at src/core/nginx.c:382
lc = ev->data;
ls = lc->listening;
s = accept(lc->fd, (struct sockaddr *) sa, &socklen);
...
c = ngx_get_connection(s, ev->log);
...
ls->handler(c);
接着调用这个handler：
ngx_http_init_connection (c=0x90a7cb8) at src/http/ngx_http_request.c:179
rev = c->read;
rev->handler = ngx_http_init_request;
最后把connection fd的read event handler设置为ngx_http_init_request。
HTTP请求/响应
从ngx_http_init_request开始，找到合适的handler处理请求，再经过一系列filter之后发送出去：
#0 ngx_linux_sendfile_chain (c=0x8148cb8, in=0x813ced4, limit=0) at src/os/unix/ngx_linux_sendfile_chain.c:56
#1 0x08071a41 in ngx_http_write_filter (r=0x8136220, in=0xbfa834d8) at src/http/ngx_http_write_filter_module.c:238
#2 0x0807e1e9 in ngx_http_chunked_body_filter (r=0x8136220, in=0x0) at src/http/modules/ngx_http_chunked_filter_module.c:84
#3 0x08082ae4 in ngx_http_gzip_body_filter (r=0x8136220, in=0xbfa834d8) at src/http/modules/ngx_http_gzip_filter_module.c:304
#4 0x08083791 in ngx_http_postpone_filter (r=0x8136220, in=0x0) at src/http/ngx_http_postpone_filter_module.c:82
#5 0x08084579 in ngx_http_charset_body_filter (r=0x8136220, in=0xbfa834d8) at src/http/modules/ngx_http_charset_filter_module.c:552
#6 0x08087193 in ngx_http_ssi_body_filter (r=0x8136220, in=0x8136220) at src/http/modules/ngx_http_ssi_filter_module.c:394
#7 0x0804dd0a in ngx_output_chain (ctx=0x813cedc, in=0xbfa834d8) at src/core/ngx_output_chain.c:67
#8 0x08071d1f in ngx_http_copy_filter (r=0x8136220, in=0xbfa834d8) at src/http/ngx_http_copy_filter_module.c:110
#9 0x0807e479 in ngx_http_range_body_filter (r=0x8136220, in=0xbfa834d8) at src/http/modules/ngx_http_range_filter_module.c:555
#10 0x08066fbe in ngx_http_output_filter (r=0x8136220, in=0xbfa834d8) at src/http/ngx_http_core_module.c:1689
#11 0x0807d7ae in ngx_http_static_handler (r=0x8136220) at src/http/modules/ngx_http_static_module.c:258
#12 0x08069ff4 in ngx_http_core_content_phase (r=0x8136220, ph=0x81457c8) at src/http/ngx_http_core_module.c:1261
#13 0x08066c85 in ngx_http_core_run_phases (r=0x8136220) at src/http/ngx_http_core_module.c:796
#14 0x08066dae in ngx_http_handler (r=0x8136220) at src/http/ngx_http_core_module.c:779
#15 0x08069396 in ngx_http_internal_redirect (r=0x8136220, uri=0xbfa83668, args=0x81363b0) at src/http/ngx_http_core_module.c:2182
#16 0x0807e0ca in ngx_http_index_handler (r=0x8136220) at src/http/modules/ngx_http_index_module.c:264
#17 0x08069ff4 in ngx_http_core_content_phase (r=0x8136220, ph=0x81457b0) at src/http/ngx_http_core_module.c:1261
#18 0x08066c85 in ngx_http_core_run_phases (r=0x8136220) at src/http/ngx_http_core_module.c:796
#19 0x08066dae in ngx_http_handler (r=0x8136220) at src/http/ngx_http_core_module.c:779
#20 0x0806e968 in ngx_http_process_request (r=0x8136220) at src/http/ngx_http_request.c:1576
#21 0x0806ef57 in ngx_http_process_request_headers (rev=0x815fc70) at src/http/ngx_http_request.c:1038
#22 0x0806f3db in ngx_http_process_request_line (rev=0x815fc70) at src/http/ngx_http_request.c:848
#23 0x0806d06e in ngx_http_init_request (rev=0x815fc70) at src/http/ngx_http_request.c:508
#24 0x08063ff5 in ngx_epoll_process_events (cycle=0x8136bf8, timer=60000, flags=<value optimized out>) at src/event/modules/ngx_epoll_module.c:518
#25 0x0805ce5a in ngx_process_events_and_timers (cycle=0x8136bf8) at src/event/ngx_event.c:245
#26 0x08062c3c in ngx_worker_process_cycle (cycle=0x8136bf8, data=0x0) at src/os/unix/ngx_process_cycle.c:775
#27 0x0806148d in ngx_spawn_process (cycle=0x8136bf8, proc=0x8062b8b <ngx_worker_process_cycle>, data=0x0, name=0x8099148 "worker process", respawn=-2)
at src/os/unix/ngx_process.c:194
#28 0x080621ca in ngx_start_worker_processes (cycle=0x8136bf8, n=1, type=-2) at src/os/unix/ngx_process_cycle.c:331
#29 0x080630df in ngx_master_process_cycle (cycle=0x8136bf8) at src/os/unix/ngx_process_cycle.c:123
#30 0x0804b5bc in main (argc=1, argv=0xbfa83ba4) at src/core/nginx.c:382
最后一步ngx_linux_sendfile_chain，传进去的chain list有两个节点，一个是header的buf，一个是index.html的fd，在ngx_linux_sendfile_chain中分别用writev和sendfile发送出去。
(gdb) p *in->buf
$22 = {
pos = 0x813cdec "HTTP/1.1 200 OK\r\nServer: nginx/0.8.6\r\nDate: Mon, 27 Jul 2009 07:16:02 GMT\r\nContent-Type: text/html\r\nContent-Length: 151\r\nLast-Modified: Sun, 26 Jul 2009 13:15:30 GMT\r\nConnection: keep-alive\r\nAccept-Ra"..., last = 0x813cec3 "", file_pos = 0, file_last = 0,
start = 0x813cdec "HTTP/1.1 200 OK\r\nServer: nginx/0.8.6\r\nDate: Mon, 27 Jul 2009 07:16:02 GMT\r\nContent-Type: text/html\r\nContent-Length: 151\r\nLast-Modified: Sun, 26 Jul 2009 13:15:30 GMT\r\nConnection: keep-alive\r\nAccept-Ra"..., end = 0x813ced4 "��\023\b\034�\023\b", tag = 0x0, file = 0x0, shadow = 0x0, temporary = 1, memory = 0,
mmap = 0, recycled = 0, in_file = 0, flush = 0, sync = 0, last_buf = 0, last_in_chain = 0, last_shadow = 0, temp_file = 0, num = 0}
(gdb) p *in->next->buf
$23 = {pos = 0x0, last = 0x0, file_pos = 0, file_last = 151, start = 0x0, end = 0x0, tag = 0x0, file = 0x813cd34, shadow = 0x0, temporary = 0, memory = 0, mmap = 0,
recycled = 0, in_file = 1, flush = 0, sync = 0, last_buf = 1, last_in_chain = 1, last_shadow = 0, temp_file = 0, num = 0}
(gdb) p *in->next->buf.file
$24 = {fd = 12, name = {len = 32, data = 0x813ccc7 "/usr/local/nginx/html/index.html"}, info = {st_dev = 0, __pad1 = 0, __st_ino = 0, st_mode = 0, st_nlink = 0, st_uid = 0,
st_gid = 0, st_rdev = 0, __pad2 = 0, st_size = 0, st_blksize = 0, st_blocks = 0, st_atim = {tv_sec = 0, tv_nsec = 0}, st_mtim = {tv_sec = 0, tv_nsec = 0}, st_ctim = {
tv_sec = 0, tv_nsec = 0}, st_ino = 0}, offset = 0, sys_offset = 0, log = 0x813f948, valid_info = 0, directio = 0}