f74f67540f
reworked the reference count mechanism on the session. Introduced a FREE state for the session and alter the session destruction flow so that we only remove the session when all the DCB's have singled they have finished processing events for the DCB rather than when the first thread decides to clsoe the DCB.
316 lines
8.5 KiB
C
316 lines
8.5 KiB
C
/*
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* This file is distributed as part of the SkySQL Gateway. It is free
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* software: you can redistribute it and/or modify it under the terms of the
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* GNU General Public License as published by the Free Software Foundation,
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* version 2.
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*
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* This program is distributed in the hope that it will be useful, but WITHOUT
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* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
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* FOR A PARTICULAR PURPOSE. See the GNU General Public License for more
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* details.
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*
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* You should have received a copy of the GNU General Public License along with
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* this program; if not, write to the Free Software Foundation, Inc., 51
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* Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
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*
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* Copyright SkySQL Ab 2013
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*/
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/**
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* @file session.c - A representation of the session within the gateway.
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*
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* @verbatim
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* Revision History
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*
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* Date Who Description
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* 17/06/13 Mark Riddoch Initial implementation
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* 02/09/13 Massimiliano Pinto Added session refcounter
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*
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* @endverbatim
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*/
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#include <string.h>
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#include <errno.h>
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#include <session.h>
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#include <service.h>
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#include <router.h>
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#include <dcb.h>
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#include <spinlock.h>
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#include <atomic.h>
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#include <skygw_utils.h>
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#include <log_manager.h>
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static SPINLOCK session_spin = SPINLOCK_INIT;
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static SESSION *allSessions = NULL;
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/**
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* Allocate a new session for a new client of the specified service.
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*
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* Create the link to the router session by calling the newSession
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* entry point of the router using the router instance of the
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* service this session is part of.
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*
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* @param service The service this connection was established by
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* @param client The client side DCB
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* @return The newly created session or NULL if an error occured
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*/
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SESSION *
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session_alloc(SERVICE *service, DCB *client)
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{
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SESSION *session;
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session = (SESSION *)calloc(1, sizeof(SESSION));
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ss_info_dassert(session != NULL, "Allocating memory for session failed.");
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if (session == NULL) {
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int eno = errno;
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errno = 0;
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skygw_log_write_flush(
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LOGFILE_ERROR,
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"%lu [session_alloc] Allocating memory for session "
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"object failed. Errno %d, %s.",
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pthread_self(),
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eno,
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strerror(eno));
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return NULL;
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}
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session->ses_chk_top = CHK_NUM_SESSION;
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session->ses_chk_tail = CHK_NUM_SESSION;
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spinlock_init(&session->ses_lock);
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/**
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* Prevent backend threads from accessing before session is completely
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* initialized.
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*/
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spinlock_acquire(&session->ses_lock);
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session->service = service;
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session->client = client;
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memset(&session->stats, 0, sizeof(SESSION_STATS));
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session->stats.connect = time(0);
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session->state = SESSION_STATE_ALLOC;
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/**
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* Associate the session to the client DCB and set the reference count on
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* the session to indicate that there is a single reference to the session.
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* There is no need to protect this or use atomic add as the session has not
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* been made available to the other threads at this point.
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*/
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session->data = client->data;
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client->session = session;
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session->refcount = 1;
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/** Release session lock */
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spinlock_release(&session->ses_lock);
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/*
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* Only create a router session if we are not the listening
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* DCB. Creating a router session may create a connection to a
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* backend server, depending upon the router module implementation
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* and should be avoided for the listener session
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*
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* Router session creation may create other DCBs that link to the
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* session, therefore it is important that the session lock is relinquished
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* beforethe router call.
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*/
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if (client->state != DCB_STATE_LISTENING)
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{
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session->router_session =
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service->router->newSession(service->router_instance, session);
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}
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spinlock_acquire(&session_spin);
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session->next = allSessions;
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allSessions = session;
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spinlock_release(&session_spin);
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/** This indicates that session is ready to be shared with backend DCBs. */
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session->state = SESSION_STATE_READY;
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atomic_add(&service->stats.n_sessions, 1);
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atomic_add(&service->stats.n_current, 1);
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CHK_SESSION(session);
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return session;
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}
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/**
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* Link a session to a DCB.
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*
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* @param session The session to link with the dcb
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* @param dcb The DCB to be linked
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* @return True if the session was sucessfully linked to the DCB
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*/
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bool
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session_link_dcb(SESSION *session, DCB *dcb)
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{
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spinlock_acquire(&session->ses_lock);
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if (session->state == SESSION_STATE_FREE)
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{
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spinlock_release(&session->ses_lock);
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return false;
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}
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atomic_add(&session->refcount, 1);
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dcb->session = session;
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spinlock_release(&session->ses_lock);
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return true;
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}
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/**
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* Deallocate the specified session
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*
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* @param session The session to deallocate
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*/
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void
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session_free(SESSION *session)
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{
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SESSION *ptr;
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CHK_SESSION(session);
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spinlock_acquire(&session->ses_lock);
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if (atomic_add(&session->refcount, -1) > 1)
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{
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/*
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* There are still other references to the session
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* so we simply return after decrementing the session
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* count.
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*/
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spinlock_release(&session->ses_lock);
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return;
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}
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session->state = SESSION_STATE_FREE;
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spinlock_release(&session->ses_lock);
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/* First of all remove from the linked list */
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spinlock_acquire(&session_spin);
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if (allSessions == session)
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{
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allSessions = session->next;
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}
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else
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{
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ptr = allSessions;
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while (ptr && ptr->next != session)
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{
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ptr = ptr->next;
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}
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if (ptr)
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ptr->next = session->next;
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}
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spinlock_release(&session_spin);
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atomic_add(&session->service->stats.n_current, -1);
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/* Clean up session and free the memory */
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free(session);
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}
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/**
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* Print details of an individual session
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*
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* @param session Session to print
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*/
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void
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printSession(SESSION *session)
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{
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printf("Session %p\n", session);
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printf("\tState: %s\n", session_state(session->state));
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printf("\tService: %s (%p)\n", session->service->name, session->service);
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printf("\tClient DCB: %p\n", session->client);
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printf("\tConnected: %s", asctime(localtime(&session->stats.connect)));
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}
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/**
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* Print all sessions
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*
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* Designed to be called within a debugger session in order
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* to display all active sessions within the gateway
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*/
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void
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printAllSessions()
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{
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SESSION *ptr;
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spinlock_acquire(&session_spin);
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ptr = allSessions;
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while (ptr)
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{
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printSession(ptr);
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ptr = ptr->next;
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}
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spinlock_release(&session_spin);
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}
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/**
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* Print all sessions to a DCB
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*
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* Designed to be called within a debugger session in order
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* to display all active sessions within the gateway
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*
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* @param dcb The DCB to print to
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*/
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void
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dprintAllSessions(DCB *dcb)
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{
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SESSION *ptr;
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spinlock_acquire(&session_spin);
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ptr = allSessions;
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while (ptr)
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{
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dcb_printf(dcb, "Session %p\n", ptr);
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dcb_printf(dcb, "\tState: %s\n", session_state(ptr->state));
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dcb_printf(dcb, "\tService: %s (%p)\n", ptr->service->name, ptr->service);
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dcb_printf(dcb, "\tClient DCB: %p\n", ptr->client);
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if (ptr->client && ptr->client->remote)
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dcb_printf(dcb, "\tClient Address: %s\n", ptr->client->remote);
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dcb_printf(dcb, "\tConnected: %s", asctime(localtime(&ptr->stats.connect)));
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ptr = ptr->next;
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}
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spinlock_release(&session_spin);
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}
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/**
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* Print a particular session to a DCB
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*
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* Designed to be called within a debugger session in order
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* to display all active sessions within the gateway
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*
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* @param dcb The DCB to print to
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* @param ptr The session to print
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*/
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void
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dprintSession(DCB *dcb, SESSION *ptr)
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{
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dcb_printf(dcb, "Session %p\n", ptr);
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dcb_printf(dcb, "\tState: %s\n", session_state(ptr->state));
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dcb_printf(dcb, "\tService: %s (%p)\n", ptr->service->name, ptr->service);
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dcb_printf(dcb, "\tClient DCB: %p\n", ptr->client);
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if (ptr->client && ptr->client->remote)
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dcb_printf(dcb, "\tClient Address: %s\n", ptr->client->remote);
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dcb_printf(dcb, "\tConnected: %s", asctime(localtime(&ptr->stats.connect)));
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}
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/**
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* Convert a session state to a string representation
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*
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* @param state The session state
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* @return A string representation of the session state
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*/
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char *
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session_state(int state)
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{
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switch (state)
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{
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case SESSION_STATE_ALLOC:
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return "Session Allocated";
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case SESSION_STATE_READY:
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return "Session Ready";
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case SESSION_STATE_LISTENER:
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return "Listener Session";
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case SESSION_STATE_LISTENER_STOPPED:
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return "Stopped Listener Session";
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default:
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return "Invalid State";
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}
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}
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