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Reset persistent MySQL connections

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When a persistent connection is taken from the pool, the state is reset
with a COM_CHANGE_USER on the next write. This allows reuse of persistent
connections without having to worry about the state of the MySQL session.
This commit is contained in:
Markus Makela 2016-10-28 11:57:52 +03:00
parent e8e2933b56
commit 5085b41d20
5 changed files with 102 additions and 20 deletions
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1
include/maxscale/dcb.h
View File

@ -276,6 +276,7 @@ typedef struct dcb
bool ssl_write_want_read; /*< Flag */
bool ssl_write_want_write; /*< Flag */
int dcb_port; /**< port of target server */
bool was_persistent; /**< Whether this DCB was in the persistent pool */
skygw_chk_t dcb_chk_tail;
} DCB;

37
include/maxscale/protocol/mysql.h
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@ -262,28 +262,25 @@ typedef struct server_command_st
typedef struct
{
#if defined(SS_DEBUG)
skygw_chk_t protocol_chk_top;
skygw_chk_t protocol_chk_top;
#endif
int fd; /*< The socket descriptor */
struct dcb *owner_dcb; /*< The DCB of the socket
* we are running on */
SPINLOCK protocol_lock;
mysql_server_cmd_t current_command; /**< Current command being executed */
server_command_t protocol_command; /*< session command list */
server_command_t* protocol_cmd_history; /*< session command history */
mxs_auth_state_t protocol_auth_state; /*< Authentication status */
mysql_protocol_state_t protocol_state; /*< Protocol struct status */
uint8_t scramble[MYSQL_SCRAMBLE_LEN]; /*< server scramble,
* created or received */
uint32_t server_capabilities; /*< server capabilities,
* created or received */
uint32_t client_capabilities; /*< client capabilities,
* created or received */
unsigned long tid; /*< MySQL Thread ID, in
* handshake */
unsigned int charset; /*< MySQL character set at connect time */
int fd; /*< The socket descriptor */
struct dcb* owner_dcb; /*< The DCB of the socket we are running on */
SPINLOCK protocol_lock; /*< Protocol lock */
mysql_server_cmd_t current_command; /*< Current command being executed */
server_command_t protocol_command; /*< session command list */
server_command_t* protocol_cmd_history; /*< session command history */
mxs_auth_state_t protocol_auth_state; /*< Authentication status */
mysql_protocol_state_t protocol_state; /*< Protocol struct status */
uint8_t scramble[MYSQL_SCRAMBLE_LEN]; /*< server scramble, created or received */
uint32_t server_capabilities; /*< server capabilities, created or received */
uint32_t client_capabilities; /*< client capabilities, created or received */
unsigned long tid; /*< MySQL Thread ID, in handshake */
unsigned int charset; /*< MySQL character set at connect time */
bool ignore_reply; /*< If the reply should be discarded */
GWBUF* stored_query; /*< Temporarily stored queries */
#if defined(SS_DEBUG)
skygw_chk_t protocol_chk_tail;
skygw_chk_t protocol_chk_tail;
#endif
} MySQLProtocol;

3
server/core/dcb.c
View File

@ -772,6 +772,7 @@ dcb_connect(SERVER *server, SESSION *session, const char *protocol)
MXS_DEBUG("%lu [dcb_connect] Reusing a persistent connection, dcb %p\n",
pthread_self(), dcb);
dcb->persistentstart = 0;
dcb->was_persistent = true;
return dcb;
}
else
@ -867,6 +868,8 @@ dcb_connect(SERVER *server, SESSION *session, const char *protocol)
dcb->dcb_server_status = server->status;
dcb->dcb_port = server->port;
dcb->was_persistent = false;
/**
* backend_dcb is connected to backend server, and once backend_dcb
* is added to poll set, authentication takes place as part of

77
server/modules/protocol/MySQL/MySQLBackend/mysql_backend.c
View File

@ -759,6 +759,41 @@ gw_read_and_write(DCB *dcb)
}
}
MySQLProtocol *proto = (MySQLProtocol *)dcb->protocol;
spinlock_acquire(&dcb->authlock);
if (proto->ignore_reply)
{
/** The reply to a COM_CHANGE_USER is in packet */
GWBUF *query = proto->stored_query;
uint8_t result = *((uint8_t*)GWBUF_DATA(read_buffer) + 4);
proto->stored_query = NULL;
proto->ignore_reply = false;
gwbuf_free(read_buffer);
spinlock_release(&dcb->authlock);
int rval = 0;
if (result == MYSQL_REPLY_OK)
{
rval = query ? dcb->func.write(dcb, query) : 1;
}
else if (query)
{
/** The COM_CHANGE USER failed, generate a fake hangup event to
* close the DCB and send an error to the client. */
gwbuf_free(query);
poll_fake_hangup_event(dcb);
}
return rval;
}
spinlock_release(&dcb->authlock);
/**
* If protocol has session command set, concatenate whole
* response into one buffer.
@ -911,6 +946,48 @@ static int gw_MySQLWrite_backend(DCB *dcb, GWBUF *queue)
CHK_DCB(dcb);
spinlock_acquire(&dcb->authlock);
if (dcb->was_persistent)
{
/**
* This is a DCB that was just taken out of the persistent connection pool.
* We need to sent a COM_CHANGE_USER query to the backend to reset the
* session state.
*/
if (backend_protocol->stored_query)
{
/** It is possible that the client DCB is closed before the COM_CHANGE_USER
* response is received. */
gwbuf_free(backend_protocol->stored_query);
}
dcb->was_persistent = false;
backend_protocol->ignore_reply = true;
backend_protocol->stored_query = queue;
spinlock_release(&dcb->authlock);
GWBUF *buf = gw_create_change_user_packet(dcb->session->client_dcb->data, dcb->protocol);
return dcb_write(dcb, buf) ? 1 : 0;
}
else if (backend_protocol->ignore_reply)
{
if (MYSQL_IS_COM_QUIT((uint8_t*)GWBUF_DATA(queue)))
{
gwbuf_free(queue);
}
else
{
/**
* We're still waiting on the reply to the COM_CHANGE_USER, append the
* buffer to the stored query. This is possible if the client sends
* BLOB data on the first command.
*/
backend_protocol->stored_query = gwbuf_append(backend_protocol->stored_query, queue);
}
spinlock_release(&dcb->authlock);
return 1;
}
/**
* Pick action according to state of protocol.
* If auth failed, return value is 0, write and buffered write

4
server/modules/protocol/MySQL/mysql_common.c
View File

@ -102,6 +102,7 @@ MySQLProtocol* mysql_protocol_init(DCB* dcb, int fd)
p->protocol_command.scom_cmd = MYSQL_COM_UNDEFINED;
p->protocol_command.scom_nresponse_packets = 0;
p->protocol_command.scom_nbytes_to_read = 0;
p->stored_query = NULL;
#if defined(SS_DEBUG)
p->protocol_chk_top = CHK_NUM_PROTOCOL;
p->protocol_chk_tail = CHK_NUM_PROTOCOL;
@ -145,6 +146,9 @@ void mysql_protocol_done(DCB* dcb)
MXS_FREE(scmd);
scmd = scmd2;
}
gwbuf_free(p->stored_query);
p->protocol_state = MYSQL_PROTOCOL_DONE;
retblock: