MXS-1985: Kill connections inside workers
The LocalClient micro-client required a reference to the session that was valid at construction time. This is the reason why the previous implementation used dcb_foreach to first gather the targets and then execute queries on them. By replacing this reference with pointers to the raw data it requires, we lift the requirement of the orignating session being alive at construction time. Now that the LocalClient no longer holds a reference to the session, the killing of the connection does not have to be done on the same thread that started the process. This prevents the deadlock that occurred when concurrect dcb_foreach calls were made. Replaced the unused dcb_foreach_parallel with a version of dcb_foreach that allows iteration of DCBs local to this worker. The dcb_foreach_local is the basis upon which all DCB access outside of administrative tasks should be built on. This change will introduce a regression in functionality: The client will no longer receive an error if no connections match the KILL query criteria. This is done to avoid having to synchronize the workers after they have performed the killing of their own connections.
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@ -367,21 +367,15 @@ static inline void dcb_readq_set(DCB *dcb, GWBUF *buffer)
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bool dcb_foreach(bool (*func)(DCB *dcb, void *data), void *data);
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/**
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* @brief Call a function for each connected DCB
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* @brief Call a function for each connected DCB on the current worker
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*
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* @note This function can call @c func from multiple thread at one time.
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* @param func Function to call. The function should return @c true to continue
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* iteration and @c false to stop iteration earlier. The first parameter
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* is the current DCB.
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*
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* @param func Function to call. The function should return @c true to continue iteration
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* and @c false to stop iteration earlier. The first is a DCB and
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* the second is this thread's value in the @c data array that
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* the user provided.
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*
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* @param data Array of user provided data passed as the second parameter to @c func.
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* The array must have more space for pointers thann the return
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* value of `config_threadcount()`. The value passed to @c func will
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* be the value of the array at the index of the current thread's ID.
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* @param data User provided data passed as the second parameter to @c func
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*/
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void dcb_foreach_parallel(bool (*func)(DCB *dcb, void *data), void **data);
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void dcb_foreach_local(bool (*func)(DCB *dcb, void *data), void *data);
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/**
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* @brief Return the port number this DCB is connected to
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@ -37,8 +37,8 @@ public:
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*
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* @return New virtual client or NULL on error
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*/
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static LocalClient* create(MXS_SESSION* session, SERVICE* service);
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static LocalClient* create(MXS_SESSION* session, SERVER* server);
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static LocalClient* create(MYSQL_session* session, MySQLProtocol* proto, SERVICE* service);
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static LocalClient* create(MYSQL_session* session, MySQLProtocol* proto, SERVER* server);
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/**
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* Queue a new query for execution
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@ -57,8 +57,8 @@ public:
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void self_destruct();
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private:
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static LocalClient* create(MXS_SESSION* session, const char* ip, uint64_t port);
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LocalClient(MXS_SESSION* session, int fd);
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static LocalClient* create(MYSQL_session* session, MySQLProtocol* proto, const char* ip, uint64_t port);
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LocalClient(MYSQL_session* session, MySQLProtocol* proto, int fd);
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static uint32_t poll_handler(struct mxs_poll_data* data, int wid, uint32_t events);
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void process(uint32_t events);
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GWBUF* read_complete_packet();
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