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Changes to deal with failed session creation by keeping the new session in existence until all related DCBs have closed; minor changes in response to reviews.

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This commit is contained in:
Martin Brampton
2015-09-17 08:15:32 +01:00
parent 30239f395a
commit 0cba9b797f
3 changed files with 65 additions and 46 deletions
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102
server/core/session.c
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@ -27,6 +27,7 @@
* 02/09/13 Massimiliano Pinto Added session refcounter
* 29/05/14 Mark Riddoch Addition of filter mechanism
* 23/08/15 Martin Brampton Tidying; slight improvement in safety
* 17/09/15 Martin Brampton Keep failed session in existence - leave DCBs to close
*
* @endverbatim
*/
@ -82,14 +83,30 @@ session_alloc(SERVICE *service, DCB *client_dcb)
if (session == NULL)
{
char errbuf[STRERROR_BUFLEN];
char errbuf[STRERROR_BUFLEN];
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
"Error : Failed to allocate memory for "
"session object due error %d, %s.",
errno,
strerror_r(errno, errbuf, sizeof(errbuf)))));
session_simple_free(session, client_dcb);
/* Does this possibly need a lock? */
/*
* This is really not the right way to do this. The data in a DCB is
* router specific and should be freed by a function in the relevant
* router. This would be better achieved by placing a function reference
* in the DCB and having dcb_final_free call it to dispose of the data
* at the final destruction of the DCB. However, this piece of code is
* only run following a calloc failure, so the system is probably on
* the point of crashing anyway.
*
*/
if (dcb->data && !DCB_IS_CLONE(dcb))
{
void * clientdata = dcb->data;
dcb->data = NULL;
free(clientdata);
}
return NULL;
}
#if defined(SS_DEBUG)
@ -135,7 +152,7 @@ session_alloc(SERVICE *service, DCB *client_dcb)
session->router_session = service->router->newSession(service->router_instance, session);
if (session->router_session == NULL)
{
session_simple_free(session, client_dcb);
session->state = SESSION_STATE_TO_BE_FREED;
LOGIF(LE, (skygw_log_write_flush(
LOGFILE_ERROR,
@ -145,7 +162,6 @@ session_alloc(SERVICE *service, DCB *client_dcb)
__func__,
service->name)));
return NULL;
}
/*
* Pending filter chain being setup set the head of the chain to
@ -165,53 +181,65 @@ session_alloc(SERVICE *service, DCB *client_dcb)
session->tail.session = session;
session->tail.clientReply = session_reply;
if (service->n_filters > 0)
if (SESSION_STATE_TO_BE_FREED != session->state
&& service->n_filters > 0
&& !session_setup_filters(session))
{
if (!session_setup_filters(session))
{
session_simple_free(session, client_dcb);
session->state = SESSION_STATE_TO_BE_FREED;
LOGIF(LE, (skygw_log_write(
LOGFILE_ERROR,
"Error : Setting up filters failed. "
"Terminating session %s.",
service->name)));
return NULL;
}
}
}
session->state = SESSION_STATE_ROUTER_READY;
if (SESSION_STATE_TO_BE_FREED != session->state)
{
session->state = SESSION_STATE_ROUTER_READY;
if (session->client->user == NULL)
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started session [%lu] for %s service ",
session->ses_id,
service->name)));
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started %s client session [%lu] for '%s' from %s",
service->name,
session->ses_id,
session->client->user,
session->client->remote)));
}
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Start %s client session [%lu] for '%s' from %s failed, will be "
"closed as soon as all related DCBs have been closed.",
service->name,
session->ses_id,
session->client->user,
session->client->remote)));
}
spinlock_acquire(&session_spin);
/** Assign a session id and increase, insert session into list */
session->ses_id = ++session_id;
session->next = allSessions;
allSessions = session;
spinlock_release(&session_spin);
if (session->client->user == NULL)
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started session [%lu] for %s service ",
session->ses_id,
service->name)));
}
else
{
LOGIF(LT, (skygw_log_write(
LOGFILE_TRACE,
"Started %s client session [%lu] for '%s' from %s",
service->name,
session->ses_id,
session->client->user,
session->client->remote)));
}
atomic_add(&service->stats.n_sessions, 1);
atomic_add(&service->stats.n_current, 1);
CHK_SESSION(session);
client_dcb->session = session;
return session;
return SESSION_STATE_TO_BE_FREED == session->state ? NULL : session;
}
/**
@ -240,13 +268,6 @@ session_set_dummy(DCB *client_dcb)
memset(&session->stats, 0, sizeof(SESSION_STATS));
session->stats.connect = 0;
session->state = SESSION_STATE_DUMMY;
/*<
* Associate the session to the client DCB and set the reference count on
* the session to indicate that there is a single reference to the
* session. There is no need to protect this or use atomic add as the
* session has not been made available to the other threads at this
* point.
*/
session->data = NULL;
session->refcount = 1;
session->ses_id = 0;
@ -352,6 +373,9 @@ int session_unlink_dcb(
/**
* Deallocate the specified session, minimal actions during session_alloc
* Since changes to keep new session in existence until all related DCBs
* have been destroyed, this function is redundant. Just left until we are
* sure of the direction taken.
*
* @param session The session to deallocate
*/
@ -402,7 +426,7 @@ session_free(SESSION *session)
* Remove one reference. If there are no references left,
* free session.
*/
if (atomic_add(&session->refcount, -1) - 1)
if (atomic_add(&session->refcount, -1) > 1)
{
/* Must be one or more references left */
return false;