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memcached探索之thread model(2)

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Jun 07, 2016 pm 03:11 PM

memcached model thread 下面我探索

6. 下面我们看看主线程dispatch_thread的事件处理设置。在memcached.c中的main函数中 /* create unix mode sockets after dropping privileges */ if ( settings . socketpath ! = NULL ) { errno = 0 ; if ( server_socket_unix ( settings . socketpath ,

6. 下面我们看看主线程dispatch_thread的事件处理设置。在memcached.c中的main函数中

/* create unix mode sockets after dropping privileges */ if (settings.socketpath != NULL) { errno = 0; if (server_socket_unix(settings.socketpath,settings.access)) { vperror("failed to listen on UNIX socket: %s", settings.socketpath); exit(EX_OSERR); } } /* create the listening socket, bind it, and init */ if (settings.socketpath == NULL) { int udp_port; const char *portnumber_filename = getenv("MEMCACHED_PORT_FILENAME"); char temp_portnumber_filename[PATH_MAX]; FILE *portnumber_file = NULL; if (portnumber_filename != NULL) { snprintf(temp_portnumber_filename, sizeof(temp_portnumber_filename), "%s.lck", portnumber_filename); portnumber_file = fopen(temp_portnumber_filename, "a"); if (portnumber_file == NULL) { fprintf(stderr, "Failed to open \"%s\": %s\n", temp_portnumber_filename, strerror(errno)); } } errno = 0; if (settings.port && server_socket(settings.port, tcp_transport, portnumber_file)) { vperror("failed to listen on TCP port %d", settings.port); exit(EX_OSERR); } /* * initialization order: first create the listening sockets * (may need root on low ports), then drop root if needed, * then daemonise if needed, then init libevent (in some cases * descriptors created by libevent wouldn't survive forking). */ udp_port = settings.udpport ? settings.udpport : settings.port; /* create the UDP listening socket and bind it */ errno = 0; if (settings.udpport && server_socket(settings.udpport, udp_transport, portnumber_file)) { vperror("failed to listen on UDP port %d", settings.udpport); exit(EX_OSERR); } if (portnumber_file) { fclose(portnumber_file); rename(temp_portnumber_filename, portnumber_filename); } } /* Drop privileges no longer needed */ drop_privileges(); /* enter the event loop */ event_base_loop(main_base, 0); //主线程(dispatcher_thread)的事件监听循环。。。

 

7. 继续跟踪server_socket函数（memcached.c中）

/** * Create a socket and bind it to a specific port number * @param port the port number to bind to * @param transport the transport protocol (TCP / UDP) * @param portnumber_file A filepointer to write the port numbers to * when they are successfully added to the list of ports we * listen on. */ static int server_socket(int port, enum network_transport transport, FILE *portnumber_file) { int sfd; struct linger ling = {0, 0}; struct addrinfo *ai; struct addrinfo *next; struct addrinfo hints = { .ai_flags = AI_PASSIVE, .ai_family = AF_UNSPEC }; char port_buf[NI_MAXSERV]; int error; int success = 0; int flags =1; hints.ai_socktype = IS_UDP(transport) ? SOCK_DGRAM : SOCK_STREAM; if (port == -1) { port = 0; } snprintf(port_buf, sizeof(port_buf), "%d", port); error= getaddrinfo(settings.inter, port_buf, &hints, &ai); if (error != 0) { if (error != EAI_SYSTEM) fprintf(stderr, "getaddrinfo(): %s\n", gai_strerror(error)); else perror("getaddrinfo()"); return 1; } for (next= ai; next; next= next->ai_next) { conn *listen_conn_add; if ((sfd = new_socket(next)) == -1) { //creat socket /* getaddrinfo can return "junk" addresses, * we make sure at least one works before erroring. */ continue; } #ifdef IPV6_V6ONLY if (next->ai_family == AF_INET6) { error = setsockopt(sfd, IPPROTO_IPV6, IPV6_V6ONLY, (char *) &flags, sizeof(flags)); if (error != 0) { perror("setsockopt"); close(sfd); continue; } } #endif //setsockopt
 setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void *)&flags, sizeof(flags)); if (IS_UDP(transport)) { maximize_sndbuf(sfd); } else { error = setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, (void *)&flags, sizeof(flags)); if (error != 0) perror("setsockopt"); error = setsockopt(sfd, SOL_SOCKET, SO_LINGER, (void *)&ling, sizeof(ling)); if (error != 0) perror("setsockopt"); error = setsockopt(sfd, IPPROTO_TCP, TCP_NODELAY, (void *)&flags, sizeof(flags)); if (error != 0) perror("setsockopt"); } //bind if (bind(sfd, next->ai_addr, next->ai_addrlen) == -1) { if (errno != EADDRINUSE) { perror("bind()"); close(sfd); freeaddrinfo(ai); return 1; } close(sfd); continue; } else { success++;

//TCP listen if (!IS_UDP(transport) && listen(sfd, settings.backlog) == -1) { perror("listen()"); close(sfd); freeaddrinfo(ai); return 1; } if (portnumber_file != NULL && (next->ai_addr->sa_family == AF_INET || next->ai_addr->sa_family == AF_INET6)) { union { struct sockaddr_in in; struct sockaddr_in6 in6; } my_sockaddr; socklen_t len = sizeof(my_sockaddr); if (getsockname(sfd, (struct sockaddr*)&my_sockaddr, &len)==0) { if (next->ai_addr->sa_family == AF_INET) { fprintf(portnumber_file, "%s INET: %u\n", IS_UDP(transport) ? "UDP" : "TCP", ntohs(my_sockaddr.in.sin_port)); } else { fprintf(portnumber_file, "%s INET6: %u\n", IS_UDP(transport) ? "UDP" : "TCP", ntohs(my_sockaddr.in6.sin6_port)); } } } } if (IS_UDP(transport)) {

 //UDP 的处理中不需要accept,所以直接派发connection到工作线程。 int c; for (c = 0; c settings.num_threads; c++) { /* this is guaranteed to hit all threads because we round-robin */ dispatch_conn_new(sfd, conn_read, EV_READ | EV_PERSIST, UDP_READ_BUFFER_SIZE, transport); } } else {

//TCP的处理(注意，这里dispatcher_thread同样调用了conn_new来绑定conn_event到其main_base. 并且此时conn的初始状态为conn_listening, 事件为持久可读，而在conn_new中注册了conn_event的回调函数为event_handler,所以，dispatche_thread在当前listen的socket可读时就会调用event_handler,进而调用driver_machine(c) 进入状态机。而在driver_machine中如果是主线程(dispatcher_thread)则会在accept socket后调用dispatch_new_conn函数来给各worker_thread派发connection...) if (!(listen_conn_add = conn_new(sfd, conn_listening, EV_READ | EV_PERSIST, 1, transport, main_base))) { fprintf(stderr, "failed to create listening connection\n"); exit(EXIT_FAILURE); } listen_conn_add->next = listen_conn; listen_conn = listen_conn_add; } } freeaddrinfo(ai); /* Return zero iff we detected no errors in starting up connections */ return success == 0; }

8. 看看UDP和TCP模式下dispatcher_thread都会调用的dispatch_new_conn函数(在thread.c中)

/* * Dispatches a new connection to another thread. This is only ever called * from the main thread, either during initialization (for UDP) or because * of an incoming connection. */ void dispatch_conn_new(int sfd, enum conn_states init_state, int event_flags, int read_buffer_size, enum network_transport transport) { CQ_ITEM *item = cqi_new(); int tid = (last_thread + 1) % settings.num_threads; //轮询的方式找worker_thread LIBEVENT_THREAD *thread = threads + tid; last_thread = tid; item->sfd = sfd; item->init_state = init_state; item->event_flags = event_flags; item->read_buffer_size = read_buffer_size; item->transport = transport; //push conn到worker_thread的CQ中
 cq_push(thread->new_conn_queue, item); MEMCACHED_CONN_DISPATCH(sfd, thread->thread_id); if (write(thread->notify_send_fd, "", 1) != 1) { perror("Writing to thread notify pipe"); } }

9. 先看看unix domain socket模式下主线程的事件处理设置。（在上面的6中调用的 server_socket_unix函数）

static int server_socket_unix(const char *path, int access_mask) { int sfd; struct linger ling = {0, 0}; struct sockaddr_un addr; struct stat tstat; int flags =1; int old_umask; if (!path) { return 1; } if ((sfd = new_socket_unix()) == -1) { return 1; } /* * Clean up a previous socket file if we left it around */ if (lstat(path, &tstat) == 0) { if (S_ISSOCK(tstat.st_mode)) unlink(path); } setsockopt(sfd, SOL_SOCKET, SO_REUSEADDR, (void *)&flags, sizeof(flags)); setsockopt(sfd, SOL_SOCKET, SO_KEEPALIVE, (void *)&flags, sizeof(flags)); setsockopt(sfd, SOL_SOCKET, SO_LINGER, (void *)&ling, sizeof(ling)); /* * the memset call clears nonstandard fields in some impementations * that otherwise mess things up. */ memset(&addr, 0, sizeof(addr)); addr.sun_family = AF_UNIX; strncpy(addr.sun_path, path, sizeof(addr.sun_path) - 1); assert(strcmp(addr.sun_path, path) == 0); old_umask = umask( ~(access_mask&0777)); if (bind(sfd, (struct sockaddr *)&addr, sizeof(addr)) == -1) { perror("bind()"); close(sfd); umask(old_umask); return 1; } umask(old_umask); if (listen(sfd, settings.backlog) == -1) { perror("listen()"); close(sfd); return 1; } if (!(listen_conn = conn_new(sfd, conn_listening, //同样是调用conn_new EV_READ | EV_PERSIST, 1, local_transport, main_base))) { fprintf(stderr, "failed to create listening connection\n"); exit(EXIT_FAILURE); } return 0; }

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