bb6e0767cc
MXS_WORKER is an abstraction of a worker aka worker thread. It has a pipe whose read descriptor is added to the worker/thread specific poll set and a write descriptor used for sending messages to the worker. The worker exposes a function mxs_worker_post_message using which messages can be sent to the worker. These messages can be sent from any thread but will be delivered on the thread dedicated for the worker. To illustrate how it works, maxadmin has been provided with a new command "ping workers" that sends a message to every worker, which then logs a message to the log. Additional refactoring are needed, since there currently are overlaps and undesirable interactions between the poll mechanism, the thread mechanism and the worker mechanism. This is visible currently, for instance, by it not being possible to shut down MaxScale. The reason is that the workers should be shut down first, then the poll mechanism and finally the threads. The shutdown need to be arranged so that a shutdown message is sent to the workers who then cause the polling loop to exit, which will cause the threads to exit. That can be arranged cleanly by making poll_waitevents() a "method" of the worker, which implies that the poll set becomes a "member variable" of the worker. To be continued.
75 lines
2.1 KiB
C
75 lines
2.1 KiB
C
#pragma once
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/*
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* Copyright (c) 2016 MariaDB Corporation Ab
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*
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* Use of this software is governed by the Business Source License included
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* in the LICENSE.TXT file and at www.mariadb.com/bsl11.
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*
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* Change Date: 2019-07-01
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*
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* On the date above, in accordance with the Business Source License, use
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* of this software will be governed by version 2 or later of the General
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* Public License.
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*/
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#include <maxscale/cdefs.h>
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#include <maxscale/poll.h>
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MXS_BEGIN_DECLS
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typedef struct mxs_worker
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{
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MXS_POLL_DATA poll; /*< The poll data used by the polling mechanism. */
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int id; /*< The id of the worker. */
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int read_fd; /*< The file descriptor the worked reads from. */
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int write_fd; /*< The file descriptor used for sending data to the worker. */
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} MXS_WORKER;
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enum mxs_worker_msg_id
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{
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/**
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* Ping message.
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*
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* arg1: 0
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* arg2: NULL or pointer to dynamically allocated NULL-terminated string,
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* to be freed by worker.
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*/
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MXS_WORKER_MSG_PING
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};
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/**
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* Initialize the worker mechanism.
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*
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* To be called once at process startup. This will cause as many workers
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* to be created as the number of threads defined.
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*/
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void mxs_worker_init();
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/**
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* Return the worker associated with the provided worker id.
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*
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* @param worker_id A worker id.
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*
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* @return The corresponding worker instance, or NULL if the id does
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* not correspond to a worker.
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*/
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MXS_WORKER* mxs_worker_get(int worker_id);
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/**
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* Post a message to a worker.
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*
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* @param worker The worker to whom the message should be sent.
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* @param msg_id The message id.
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* @param arg1 Message specific first argument.
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* @param arg2 Message specific second argument.
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*
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* @return True if the message could be sent, false otherwise. If the message
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* posting fails, errno is set appropriately.
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*
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* @attention The return value tells *only* whether the message could be sent,
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* *not* that it has reached the worker.
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*/
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bool mxs_worker_post_message(MXS_WORKER* worker, int msg_id, int64_t arg1, void* arg2);
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MXS_END_DECLS
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