82bb624981
* implication of backpressure * fix typo and refactor * misc refactor * misc fix * add function session_unlink_backend_dcb and more comments * misc fix * refactor, move all throttling logic into dcb.cc * misc fix * misc fix
419 lines
16 KiB
C
419 lines
16 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: 2020-01-01
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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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/**
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* @file dcb.h The Descriptor Control Block
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*/
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#include <maxscale/cdefs.h>
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#include <maxscale/spinlock.h>
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#include <maxscale/buffer.h>
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#include <maxscale/protocol.h>
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#include <maxscale/authenticator.h>
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#include <maxscale/ssl.h>
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#include <maxscale/modinfo.h>
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#include <maxscale/poll_core.h>
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#include <netinet/in.h>
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MXS_BEGIN_DECLS
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#define ERRHANDLE
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struct session;
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struct server;
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struct service;
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struct servlistener;
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struct dcb;
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#define DCBFD_CLOSED -1
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/**
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* The statistics gathered on a descriptor control block
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*/
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typedef struct dcbstats
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{
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int n_reads; /*< Number of reads on this descriptor */
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int n_writes; /*< Number of writes on this descriptor */
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int n_accepts; /*< Number of accepts on this descriptor */
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int n_buffered; /*< Number of buffered writes */
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int n_high_water; /*< Number of crosses of high water mark */
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int n_low_water; /*< Number of crosses of low water mark */
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} DCBSTATS;
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#define DCBSTATS_INIT {0}
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/* DCB states */
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typedef enum
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{
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DCB_STATE_UNDEFINED, /*< State variable with no state */
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DCB_STATE_ALLOC, /*< Memory allocated but not populated */
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DCB_STATE_POLLING, /*< Waiting in the poll loop */
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DCB_STATE_WAITING, /*< Client wanting a connection */
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DCB_STATE_LISTENING, /*< The DCB is for a listening socket */
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DCB_STATE_DISCONNECTED, /*< The socket is now closed */
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DCB_STATE_NOPOLLING, /*< Removed from poll mask */
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} dcb_state_t;
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typedef enum
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{
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DCB_ROLE_SERVICE_LISTENER, /*< Receives initial connect requests from clients */
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DCB_ROLE_CLIENT_HANDLER, /*< Serves dedicated client */
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DCB_ROLE_BACKEND_HANDLER, /*< Serves back end connection */
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DCB_ROLE_INTERNAL /*< Internal DCB not connected to the outside */
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} dcb_role_t;
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#define DCB_STRTYPE(dcb) (dcb->dcb_role == DCB_ROLE_CLIENT_HANDLER ? "Client DCB" : \
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dcb->dcb_role == DCB_ROLE_BACKEND_HANDLER ? "Backend DCB" : \
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dcb->dcb_role == DCB_ROLE_SERVICE_LISTENER ? "Listener DCB" : \
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dcb->dcb_role == DCB_ROLE_INTERNAL ? "Internal DCB" : "Unknown DCB")
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/**
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* Callback reasons for the DCB callback mechanism.
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*/
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typedef enum
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{
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DCB_REASON_CLOSE, /*< The DCB is closing */
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DCB_REASON_DRAINED, /*< The write delay queue has drained */
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DCB_REASON_HIGH_WATER, /*< Cross high water mark */
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DCB_REASON_LOW_WATER, /*< Cross low water mark */
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DCB_REASON_ERROR, /*< An error was flagged on the connection */
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DCB_REASON_HUP, /*< A hangup was detected */
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DCB_REASON_NOT_RESPONDING /*< Server connection was lost */
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} DCB_REASON;
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/**
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* Callback structure - used to track callbacks registered on a DCB
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*/
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typedef struct dcb_callback
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{
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DCB_REASON reason; /*< The reason for the callback */
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int (*cb)(struct dcb *dcb, DCB_REASON reason, void *userdata);
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void *userdata; /*< User data to be sent in the callback */
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struct dcb_callback *next; /*< Next callback for this DCB */
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} DCB_CALLBACK;
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/**
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* State of SSL connection
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*/
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typedef enum
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{
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SSL_HANDSHAKE_UNKNOWN, /*< The DCB has unknown SSL status */
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SSL_HANDSHAKE_REQUIRED, /*< SSL handshake is needed */
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SSL_HANDSHAKE_DONE, /*< The SSL handshake completed OK */
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SSL_ESTABLISHED, /*< The SSL connection is in use */
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SSL_HANDSHAKE_FAILED /*< The SSL handshake failed */
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} SSL_STATE;
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/**
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* Descriptor Control Block
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*
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* A wrapper for a network descriptor within the gateway, it contains all the
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* state information necessary to allow for the implementation of the asynchronous
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* operation of the protocol and gateway functions. It also provides links to the service
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* and session data that is required to route the information within the gateway.
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*
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* It is important to hold the state information here such that any thread within the
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* gateway may be selected to execute the required actions when a network event occurs.
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*
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* Note that the first few fields (up to and including "entry_is_ready") must
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* precisely match the LIST_ENTRY structure defined in the list manager.
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*/
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typedef struct dcb
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{
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MXS_POLL_DATA poll;
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skygw_chk_t dcb_chk_top;
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bool dcb_errhandle_called; /*< this can be called only once */
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dcb_role_t dcb_role;
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int fd; /**< The descriptor */
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dcb_state_t state; /**< Current descriptor state */
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SSL_STATE ssl_state; /**< Current state of SSL if in use */
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int flags; /**< DCB flags */
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char *remote; /**< Address of remote end */
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char *user; /**< User name for connection */
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struct sockaddr_storage ip; /**< remote IPv4/IPv6 address */
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char *protoname; /**< Name of the protocol */
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void *protocol; /**< The protocol specific state */
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size_t protocol_packet_length; /**< How long the protocol specific packet is */
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size_t protocol_bytes_processed; /**< How many bytes of a packet have been read */
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struct session *session; /**< The owning session */
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struct servlistener *listener; /**< For a client DCB, the listener data */
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MXS_PROTOCOL func; /**< The protocol functions for this descriptor */
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MXS_AUTHENTICATOR authfunc; /**< The authenticator functions for this descriptor */
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uint32_t writeqlen; /**< Current number of byes in the write queue */
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uint32_t high_water; /**< High water mark of write queue */
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uint32_t low_water; /**< Low water mark of write queue */
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GWBUF *writeq; /**< Write Data Queue */
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GWBUF *delayq; /**< Delay Backend Write Data Queue */
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GWBUF *readq; /**< Read queue for storing incomplete reads */
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GWBUF *fakeq; /**< Fake event queue for generated events */
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uint32_t fake_event; /**< Fake event to be delivered to handler */
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DCBSTATS stats; /**< DCB related statistics */
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struct dcb *nextpersistent; /**< Next DCB in the persistent pool for SERVER */
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time_t persistentstart; /**< 0: Not in the persistent pool.
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-1: Evicted from the persistent pool and being closed.
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non-0: Time when placed in the persistent pool.
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*/
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struct service *service; /**< The related service */
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void *data; /**< Specific client data, shared between DCBs of this session */
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void *authenticator_data; /**< The authenticator data for this DCB */
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DCB_CALLBACK *callbacks; /**< The list of callbacks for the DCB */
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int64_t last_read; /*< Last time the DCB received data */
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struct server *server; /**< The associated backend server */
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SSL* ssl; /*< SSL struct for connection */
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bool ssl_read_want_read; /*< Flag */
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bool ssl_read_want_write; /*< Flag */
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bool ssl_write_want_read; /*< Flag */
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bool ssl_write_want_write; /*< Flag */
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bool was_persistent; /**< Whether this DCB was in the persistent pool */
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bool high_water_reached; /** High water mark reached, to determine whether need release throttle */
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struct
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{
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struct dcb *next; /**< Next DCB in owning thread's list */
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struct dcb *tail; /**< Last DCB in owning thread's list */
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} thread;
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uint32_t n_close; /** How many times dcb_close has been called. */
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char *path; /** If a Unix socket, the path it was bound to. */
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skygw_chk_t dcb_chk_tail;
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} DCB;
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/**
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* The DCB usage filer used for returning DCB's in use for a certain reason
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*/
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typedef enum
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{
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DCB_USAGE_CLIENT,
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DCB_USAGE_LISTENER,
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DCB_USAGE_BACKEND,
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DCB_USAGE_INTERNAL,
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DCB_USAGE_ALL
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} DCB_USAGE;
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/* A few useful macros */
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#define DCB_SESSION(x) (x)->session
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#define DCB_PROTOCOL(x, type) (type *)((x)->protocol)
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#define DCB_WRITEQLEN(x) (x)->writeqlen
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#define DCB_SET_LOW_WATER(x, lo) (x)->low_water = (lo);
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#define DCB_SET_HIGH_WATER(x, hi) (x)->low_water = (hi);
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#define DCB_BELOW_LOW_WATER(x) ((x)->low_water && (x)->writeqlen < (x)->low_water)
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#define DCB_ABOVE_HIGH_WATER(x) ((x)->high_water && (x)->writeqlen > (x)->high_water)
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#define DCB_THROTTLING_ENABLED(x) ((x)->high_water && (x)->low_water)
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/**
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* @brief DCB system initialization function
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*
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* This function needs to be the first function call into this system.
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*/
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void dcb_global_init();
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int dcb_write(DCB *, GWBUF *);
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DCB *dcb_accept(DCB *listener);
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DCB *dcb_alloc(dcb_role_t, struct servlistener *);
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DCB *dcb_connect(struct server *, struct session *, const char *);
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int dcb_read(DCB *, GWBUF **, int);
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int dcb_drain_writeq(DCB *);
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void dcb_close(DCB *);
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/**
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* @brief Close DCB in the thread that owns it.
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*
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* @param dcb The dcb to be closed.
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*
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* @note Even if the calling thread owns the dcb, the closing will
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* still be made via the event loop.
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*/
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void dcb_close_in_owning_thread(DCB *dcb);
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/**
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* Add a DCB to the owner's list
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*
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* @param dcb DCB to add
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*/
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void dcb_add_to_list(DCB *dcb);
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void printAllDCBs(); /* Debug to print all DCB in the system */
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void printDCB(DCB *); /* Debug print routine */
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void dprintDCBList(DCB *); /* Debug print DCB list statistics */
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void dprintAllDCBs(DCB *); /* Debug to print all DCB in the system */
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void dprintOneDCB(DCB *, DCB *); /* Debug to print one DCB */
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void dprintDCB(DCB *, DCB *); /* Debug to print a DCB in the system */
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void dListDCBs(DCB *); /* List all DCBs in the system */
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void dListClients(DCB *); /* List al the client DCBs */
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const char *gw_dcb_state2string(dcb_state_t); /* DCB state to string */
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void dcb_printf(DCB *, const char *, ...) __attribute__((format(printf, 2, 3))); /* DCB version of printf */
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void dcb_hashtable_stats(DCB *, void *); /**< Print statisitics */
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int dcb_add_callback(DCB *, DCB_REASON, int (*)(struct dcb *, DCB_REASON, void *), void *);
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int dcb_remove_callback(DCB *, DCB_REASON, int (*)(struct dcb *, DCB_REASON, void *), void *);
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int dcb_count_by_usage(DCB_USAGE); /* Return counts of DCBs */
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int dcb_persistent_clean_count(DCB *, int, bool); /* Clean persistent and return count */
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void dcb_hangup_foreach (struct server* server);
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uint64_t dcb_get_session_id(DCB* dcb);
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char *dcb_role_name(DCB *); /* Return the name of a role */
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int dcb_accept_SSL(DCB* dcb);
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int dcb_connect_SSL(DCB* dcb);
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int dcb_listen(DCB *listener, const char *config, const char *protocol_name);
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void dcb_enable_session_timeouts();
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void dcb_process_idle_sessions(int thr);
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/**
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* @brief Append a buffer the DCB's readqueue
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*
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* Usually data is stored into the DCB's readqueue when not enough data is
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* available and the processing needs to be deferred until more data is available.
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*
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* @param dcb The DCB to be appended to.
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* @param buffer The buffer to append.
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*/
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static inline void dcb_readq_append(DCB *dcb, GWBUF *buffer)
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{
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dcb->readq = gwbuf_append(dcb->readq, buffer);
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}
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/**
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* @brief Returns the read queue of the DCB.
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*
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* @note The read queue remains the property of the DCB.
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*
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* @return A buffer of NULL if there is no read queue.
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*/
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static GWBUF* dcb_readq_get(DCB* dcb)
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{
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return dcb->readq;
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}
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/**
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* @brief Returns whether a DCB currently has a read queue.
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*
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* @return True, if the DCB has a read queue, otherwise false.
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*/
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static inline bool dcb_readq_has(DCB* dcb)
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{
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return dcb->readq != NULL;
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}
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/**
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* @brief Returns the current length of the read queue
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*
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* @return Length of read queue
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*/
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static unsigned int dcb_readq_length(DCB* dcb)
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{
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return dcb->readq ? gwbuf_length(dcb->readq) : 0;
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}
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/**
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* @brief Prepend a buffer the DCB's readqueue
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*
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* @param dcb The DCB to be prepended to.
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* @param buffer The buffer to prepend
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*/
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static inline void dcb_readq_prepend(DCB *dcb, GWBUF *buffer)
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{
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dcb->readq = gwbuf_append(buffer, dcb->readq);
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}
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/**
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* @brief Returns the read queue of the DCB and sets the read queue to NULL.
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*
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* @note The read queue becomes the property of the caller.
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*
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* @return A buffer of NULL if there is no read queue.
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*/
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static GWBUF* dcb_readq_release(DCB* dcb)
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{
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GWBUF* readq = dcb->readq;
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dcb->readq = NULL;
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return readq;
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}
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/**
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* @brief Set read queue of a DCB
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*
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* The expectation is that there is no readqueue when this is done.
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* The ownership of the provided buffer moved to the DCB.
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*
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* @param dcb The DCB to be reset.
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* @param buffer The buffer to reset with
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*/
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static inline void dcb_readq_set(DCB *dcb, GWBUF *buffer)
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{
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if (dcb->readq)
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{
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MXS_ERROR("Read-queue set when there already is a read-queue.");
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// TODO: Conceptually this should be freed here. However, currently
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// TODO: the code just assigns without checking, so we do the same
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// TODO: for now. If this is not set to NULL when it has been consumed,
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// TODO: we would get a double free.
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// TODO: gwbuf_free(dcb->readq);
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dcb->readq = NULL;
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}
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dcb->readq = buffer;
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}
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/**
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* @brief Call a function for each connected DCB
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*
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* @deprecated You should not use this function, use dcb_foreach_parallel instead
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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 parameter is a DCB and the second
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* is the value of @c data that the user provided.
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* @param data User provided data passed as the second parameter to @c func
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* @return True if all DCBs were iterated, false if the callback returned false
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*/
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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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*
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* @note This function can call @c func from multiple thread at one time.
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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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*/
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void dcb_foreach_parallel(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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*
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* @param dcb DCB to inspect
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* @return Port number the DCB is connected to or -1 if information is not available
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*/
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int dcb_get_port(const DCB *dcb);
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/**
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* @brief Return the DCB currently being handled by the calling thread.
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*
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* @return A DCB, or NULL if the calling thread is not currently handling
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* a DCB or if the calling thread is not a polling/worker thread.
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*/
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DCB* dcb_get_current();
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/**
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* DCB flags values
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*/
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#define DCBF_HUNG 0x0002 /*< Hangup has been dispatched */
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#define DCBF_REPLIED 0x0004 /*< DCB was written to */
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#define DCB_REPLIED(d) ((d)->flags & DCBF_REPLIED)
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MXS_END_DECLS
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