main->PostmasterMain->ServerLoop:
for(;;){
...
//会阻塞在这,监视文件描述符的变化
selres = select(nSockets, &rmask, NULL, NULL, &timeout);
if (selres > 0){
for (i = 0; i < MAXLISTEN; i++){
//找一个有效的fd
if (ListenSocket[i] == PGINVALID_SOCKET)
break;
if (FD_ISSET(ListenSocket[i], &rmask)){
port = ConnCreate(ListenSocket[i]);->StreamConnection->accept
BackendStartup(port);//fork进程
|-- pid = fork_process();
| if (pid == 0){//child
| InitPostmasterChild();
| ClosePostmasterPorts(false);
| BackendInitialize(port);
| //该函数不会返回
| BackendRun(port);->PostgresMain:
| |-- for (;;){
| | if (send_ready_for_query){
| | ...
| | ReadyForQuery(whereToSendOutput);->pq_flush();->internal_flush->secure_write->secure_raw_write->send
| | send_ready_for_query = false;
| | }
| | firstchar = ReadCommand(&input_message);
| | switch(firstchar):{
| | case 'Q':exec_simple_query(query_string);
| | ...
| | }
| |-- }
| }
| ...father
|-- return STATUS_OK
//关闭father socket
StreamClose(port->sock);
ConnFree(port);
}
}
}
}
文章名称:PostgreSQLserver端接收连接后fork进程
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