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MXS-2196: Allocate a session before allocating DCBs

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Allocating the session before a DCB guarantees that at no point will a DCB
have a null session. This further clarifies the concept of the session and
also allows the listener reference to be moved there.

Ideally, the session itself would allocate and assign the client DCB but
since the Listener is the only one who does it, it's acceptable for now.
This commit is contained in:
Markus Mäkelä
2018-12-03 19:25:26 +02:00
parent 692127a2cb
commit 43c33e9f4a
20 changed files with 106 additions and 115 deletions
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29
server/core/session.cc
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@ -77,7 +77,7 @@ static void session_simple_free(MXS_SESSION* session, DCB* dcb);
static void session_add_to_all_list(MXS_SESSION* session);
static MXS_SESSION* session_find_free();
static void session_final_free(MXS_SESSION* session);
static void session_deliver_response(MXS_SESSION* session);
static void session_deliver_response(MXS_SESSION* session);
/**
* The clientReply of the session.
@ -88,13 +88,14 @@ 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)
MXS_SESSION::MXS_SESSION(const SListener& listener)
: state(SESSION_STATE_READY)
, ses_id(session_get_next_id())
, client_dcb(client_dcb)
, client_dcb(nullptr)
, listener(listener)
, router_session(nullptr)
, stats{time(0)}
, service(client_dcb->service)
, service(listener ? listener->service() : nullptr)
, head{}
, tail{}
, refcount(1)
@ -112,11 +113,6 @@ MXS_SESSION::~MXS_SESSION()
{
}
MXS_SESSION* session_alloc(SERVICE* service, DCB* client_dcb)
{
return new(std::nothrow) Session(service, client_dcb);
}
bool session_start(MXS_SESSION* session)
{
session->router_session = session->service->router->newSession(session->service->router_instance,
@ -179,7 +175,6 @@ void session_link_backend_dcb(MXS_SESSION* session, DCB* dcb)
mxb::atomic::add(&session->refcount, 1);
dcb->session = session;
dcb->service = session->service;
/** Move this DCB under the same thread */
dcb->owner = session->client_dcb->owner;
@ -1097,10 +1092,10 @@ const char* session_get_close_reason(const MXS_SESSION* session)
}
}
Session::Session(SERVICE* service, DCB* client_dcb)
: MXS_SESSION(client_dcb)
Session::Session(const SListener& listener)
: MXS_SESSION(listener)
{
if (service->retain_last_statements != -1) // Explicitly set for the service
if (service->retain_last_statements != -1) // Explicitly set for the service
{
m_retain_last_statements = service->retain_last_statements;
}
@ -1124,6 +1119,13 @@ Session::~Session()
}
}
void Session::set_client_dcb(DCB* dcb)
{
mxb_assert(client_dcb == nullptr);
mxb_assert(dcb->dcb_role == DCB_ROLE_CLIENT_HANDLER);
client_dcb = dcb;
}
namespace
{
@ -1172,7 +1174,6 @@ bool get_cmd_and_stmt(GWBUF* pBuffer, const char** ppCmd, char** ppStmt, int* pL
return deallocate;
}
}
void Session::dump_statements() const