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MXS-1376 Close a connection in dcb_close

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As each client/server connection will be handled by a specific
thread, all closing activity can take place directly when the
connection is closed and not later when the zombie queue is
processed.

In a subsequent commit the zombie queue will be removed.
This commit is contained in:
Johan Wikman 2017-08-25 11:06:48 +03:00
parent 170e03fd23
commit c11d8fa328
1 changed files with 78 additions and 22 deletions
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100
server/core/dcb.cc
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@ -1175,13 +1175,15 @@ static void log_illegal_dcb(DCB *dcb)
*
*
*/
void
dcb_close(DCB *dcb)
void dcb_close(DCB *dcb)
{
CHK_DCB(dcb);
if (DCB_STATE_UNDEFINED == dcb->state
|| DCB_STATE_DISCONNECTED == dcb->state)
// With one thread manipulating each client and backend DCB, dcb_close() should
// be called at most once per DCB.
ss_dassert(!dcb->dcb_is_zombie);
if ((DCB_STATE_UNDEFINED == dcb->state) || (DCB_STATE_DISCONNECTED == dcb->state))
{
log_illegal_dcb(dcb);
raise(SIGABRT);
@ -1193,6 +1195,7 @@ dcb_close(DCB *dcb)
*/
if (dcb->state == DCB_STATE_ALLOC && dcb->fd == DCBFD_CLOSED)
{
// A freshly created dcb that was closed before it was taken into use.
dcb_final_free(dcb);
}
/*
@ -1200,12 +1203,24 @@ dcb_close(DCB *dcb)
*/
else if (dcb->persistentstart > 0)
{
// A DCB in the persistent pool.
// TODO: This dcb will now actually be closed when dcb_persistent_clean_count() is
// TODO: called by either dcb_maybe_add_persistent() - another dcb is added to the
// TODO: persistent pool - or server_get_persistent() - get a dcb from the persistent
// TODO: pool - is called. There is no reason not to just remove this dcb from the
// TODO: persistent pool here and now, and then close it immediately.
dcb->dcb_errhandle_called = true;
}
else if (!dcb->dcb_is_zombie)
else
{
if (DCB_ROLE_BACKEND_HANDLER == dcb->dcb_role && 0 == dcb->persistentstart
&& dcb->server && DCB_STATE_POLLING == dcb->state)
bool should_close = true;
if (dcb->dcb_role == DCB_ROLE_BACKEND_HANDLER && // Backend DCB
dcb->state == DCB_STATE_POLLING && // Being polled
dcb->persistentstart == 0 && // Not already in (> 0) or being evicted from (-1)
// the persistent pool.
dcb->server) // And has a server
{
/* May be a candidate for persistence, so save user name */
const char *user;
@ -1214,25 +1229,66 @@ dcb_close(DCB *dcb)
{
dcb->user = MXS_STRDUP_A(user);
}
if (dcb_maybe_add_persistent(dcb))
{
should_close = false;
}
}
/*<
* Add closing dcb to the top of the list, setting zombie marker
*/
int owner = dcb->poll.thread.id;
dcb->dcb_is_zombie = true;
dcb->memdata.next = zombies[owner];
zombies[owner] = dcb;
nzombies[owner]++;
if (nzombies[owner] > maxzombies)
if (should_close)
{
maxzombies = nzombies[owner];
if (dcb->state == DCB_STATE_POLLING)
{
dcb_stop_polling_and_shutdown(dcb);
}
if (dcb->dcb_role == DCB_ROLE_CLIENT_HANDLER)
{
// TODO: If the role of the dcb is that of a client handler,
// TODO: then dcb->service should be non-NULL, so there should
// TODO: be no need for an if. Let's add an assert to see if
// TODO: such a situation exists.
ss_dassert(dcb->service);
if (dcb->service)
{
atomic_add(&dcb->service->client_count, -1);
}
}
if (dcb->server)
{
// This is now a DCB_ROLE_BACKEND_HANDLER.
// TODO: Make decisions according to the role and assert
// TODO: that what the role implies is preset.
atomic_add(&dcb->server->stats.n_current, -1);
}
if (dcb->fd > 0)
{
// TODO: How could we get this far with a dcb->fd <= 0?
if (close(dcb->fd) < 0)
{
int eno = errno;
errno = 0;
MXS_ERROR("Failed to close socket %d on dcb %p: %d, %s",
dcb->fd, dcb, eno, mxs_strerror(eno));
}
else
{
dcb->fd = DCBFD_CLOSED;
MXS_DEBUG("Closed socket %d on dcb %p.", dcb->fd, dcb);
}
}
dcb->state = DCB_STATE_DISCONNECTED;
dcb_remove_from_list(dcb);
dcb_final_free(dcb);
}
}
else
{
/** DCBs in the zombie queue can still receive events which means that
* a DCB can be closed multiple times while it's in the zombie queue. */
}
}
/**