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MXS-2196: Remove the dummy session

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As each connection now immediately gets a session the dummy session is no
longer required. The next step would be to combine parts of the session
and the client DCB into one entity. This would prevent the possibility of
a client DCB with no associated session. Backend DCBs are different as
they can move from one session to another when the persistent connection
pool is in use.
This commit is contained in:
Markus Mäkelä
2018-12-03 13:18:42 +02:00
parent a2f5cc9d09
commit 692127a2cb
9 changed files with 70 additions and 161 deletions
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110
server/core/session.cc
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@ -69,18 +69,8 @@ struct
SESSION_DUMP_STATEMENTS_NEVER
};
static MXS_SESSION dummy_session()
{
MXS_SESSION session = {};
session.state = SESSION_STATE_DUMMY;
session.refcount = 1;
return session;
}
}
static MXS_SESSION session_dummy_struct = dummy_session();
static void session_initialize(void* session);
static int session_setup_filters(MXS_SESSION* session);
static void session_simple_free(MXS_SESSION* session, DCB* dcb);
@ -98,50 +88,33 @@ static void session_deliver_response(MXS_SESSION* session);
*/
static int session_reply(MXS_FILTER* inst, MXS_FILTER_SESSION* session, GWBUF* data);
MXS_SESSION::MXS_SESSION(DCB* client_dcb)
: state(SESSION_STATE_READY)
, ses_id(session_get_next_id())
, client_dcb(client_dcb)
, router_session(nullptr)
, stats{time(0)}
, service(client_dcb->service)
, head{}
, tail{}
, refcount(1)
, trx_state(SESSION_TRX_INACTIVE)
, autocommit(config_get_global_options()->qc_sql_mode == QC_SQL_MODE_ORACLE ? false : true)
, client_protocol_data(0)
, qualifies_for_pooling(false)
, response{}
, close_reason(SESSION_CLOSE_NONE)
, load_active(false)
{
}
MXS_SESSION::~MXS_SESSION()
{
}
MXS_SESSION* session_alloc(SERVICE* service, DCB* client_dcb)
{
Session* session = new (std::nothrow) Session(service);
if (session == nullptr)
{
return NULL;
}
session->state = SESSION_STATE_READY;
session->ses_id = session_get_next_id();
session->client_dcb = client_dcb;
session->router_session = NULL;
session->stats.connect = time(0);
session->service = service;
memset(&session->head, 0, sizeof(session->head));
memset(&session->tail, 0, sizeof(session->tail));
session->load_active = false;
/*<
* 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.
*
* Note: Strictly speaking, we do have to increment it with a relaxed atomic
* operation but in practice it doesn't matter.
*/
session->refcount = 1;
session->trx_state = SESSION_TRX_INACTIVE;
MXS_CONFIG* config = config_get_global_options();
// If MaxScale is running in Oracle mode, then autocommit needs to
// initially be off.
bool autocommit = (config->qc_sql_mode == QC_SQL_MODE_ORACLE) ? false : true;
session_set_autocommit(session, autocommit);
session->client_protocol_data = 0;
session->qualifies_for_pooling = false;
memset(&session->response, 0, sizeof(session->response));
session->close_reason = SESSION_CLOSE_NONE;
return session;
return new(std::nothrow) Session(service, client_dcb);
}
bool session_start(MXS_SESSION* session)
@ -200,21 +173,6 @@ bool session_start(MXS_SESSION* session)
return true;
}
/**
* Allocate a dummy session so that DCBs can always have sessions.
*
* Only one dummy session exists, it is statically declared
*
* @param client_dcb The client side DCB
* @return The dummy created session
*/
MXS_SESSION* session_set_dummy(DCB* client_dcb)
{
MXS_SESSION* session = &session_dummy_struct;
client_dcb->session = session;
return session;
}
void session_link_backend_dcb(MXS_SESSION* session, DCB* dcb)
{
mxb_assert(dcb->dcb_role == DCB_ROLE_BACKEND_HANDLER);
@ -255,11 +213,7 @@ static void session_simple_free(MXS_SESSION* session, DCB* dcb)
}
if (session)
{
if (SESSION_STATE_DUMMY == session->state)
{
return;
}
if (session && session->router_session)
if (session->router_session)
{
session->service->router->freeSession(session->service->router_instance,
session->router_session);
@ -402,8 +356,7 @@ void printAllSessions()
/** Callback for dprintAllSessions */
bool dprintAllSessions_cb(DCB* dcb, void* data)
{
if (dcb->dcb_role == DCB_ROLE_CLIENT_HANDLER
&& dcb->session->state != SESSION_STATE_DUMMY)
if (dcb->dcb_role == DCB_ROLE_CLIENT_HANDLER)
{
DCB* out_dcb = (DCB*)data;
dprintSession(out_dcb, dcb->session);
@ -520,9 +473,6 @@ const char* session_state(mxs_session_state_t state)
case SESSION_STATE_ALLOC:
return "Session Allocated";
case SESSION_STATE_DUMMY:
return "Dummy Session";
case SESSION_STATE_READY:
return "Session Ready";
@ -765,7 +715,7 @@ MXS_SESSION* session_get_ref(MXS_SESSION* session)
void session_put_ref(MXS_SESSION* session)
{
if (session && session->state != SESSION_STATE_DUMMY)
if (session)
{
/** Remove one reference. If there are no references left, free session */
if (mxb::atomic::add(&session->refcount, -1) == 1)
@ -904,7 +854,6 @@ void session_qualify_for_pool(MXS_SESSION* session)
bool session_valid_for_pool(const MXS_SESSION* session)
{
mxb_assert(session->state != SESSION_STATE_DUMMY);
return session->qualifies_for_pooling;
}
@ -1148,7 +1097,8 @@ const char* session_get_close_reason(const MXS_SESSION* session)
}
}
Session::Session(SERVICE* service)
Session::Session(SERVICE* service, DCB* client_dcb)
: MXS_SESSION(client_dcb)
{
if (service->retain_last_statements != -1) // Explicitly set for the service
{