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MXS-1690: Need Backpressure mechanism (#169)

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* 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
This commit is contained in:
dapeng
2018-03-07 18:34:47 +08:00
committed by Johan Wikman
parent d6b8147119
commit 82bb624981
6 changed files with 185 additions and 2 deletions
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18
include/maxscale/config.h
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@ -168,6 +168,8 @@ extern const char CN_USER[];
extern const char CN_USERS[];
extern const char CN_VERSION_STRING[];
extern const char CN_WEIGHTBY[];
extern const char CN_WRITEQ_HIGH_WATER[];
extern const char CN_WRITEQ_LOW_WATER[];
/**
* The config parameter
@ -233,6 +235,8 @@ typedef struct
bool substitute_variables; /**< Should environment variables be substituted */
char* local_address; /**< Local address to use when connecting */
time_t users_refresh_time; /**< How often the users can be refreshed */
uint32_t writeq_high_water; /**< High water mark of dcb write queue */
uint32_t writeq_low_water; /**< Low water mark of dcb write queue */
} MXS_CONFIG;
/**
@ -503,4 +507,18 @@ bool config_reload(void);
*/
json_t* config_maxscale_to_json(const char* host);
/**
* @brief Get DCB write queue high water mark
*
* @return Number of high water mark in bytes
*/
uint32_t config_writeq_high_water();
/**
* @brief Get DCB write queue low water mark
*
* @return @return Number of low water mark in bytes
*/
uint32_t config_writeq_low_water();
MXS_END_DECLS

7
include/maxscale/dcb.h
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@ -151,7 +151,9 @@ typedef struct dcb
struct servlistener *listener; /**< For a client DCB, the listener data */
MXS_PROTOCOL func; /**< The protocol functions for this descriptor */
MXS_AUTHENTICATOR authfunc; /**< The authenticator functions for this descriptor */
int writeqlen; /**< Current number of byes in the write queue */
uint32_t writeqlen; /**< Current number of byes in the write queue */
uint32_t high_water; /**< High water mark of write queue */
uint32_t low_water; /**< Low water mark of write queue */
GWBUF *writeq; /**< Write Data Queue */
GWBUF *delayq; /**< Delay Backend Write Data Queue */
GWBUF *readq; /**< Read queue for storing incomplete reads */
@ -176,6 +178,7 @@ typedef struct dcb
bool ssl_write_want_read; /*< Flag */
bool ssl_write_want_write; /*< Flag */
bool was_persistent; /**< Whether this DCB was in the persistent pool */
bool high_water_reached; /** High water mark reached, to determine whether need release throttle */
struct
{
struct dcb *next; /**< Next DCB in owning thread's list */
@ -206,7 +209,7 @@ typedef enum
#define DCB_SET_HIGH_WATER(x, hi) (x)->low_water = (hi);
#define DCB_BELOW_LOW_WATER(x) ((x)->low_water && (x)->writeqlen < (x)->low_water)
#define DCB_ABOVE_HIGH_WATER(x) ((x)->high_water && (x)->writeqlen > (x)->high_water)
#define DCB_THROTTLING_ENABLED(x) ((x)->high_water && (x)->low_water)
/**
* @brief DCB system initialization function
*

1
include/maxscale/session.h
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@ -136,6 +136,7 @@ typedef struct session
mxs_session_state_t state; /*< Current descriptor state */
uint64_t ses_id; /*< Unique session identifier */
struct dcb *client_dcb; /*< The client connection */
struct mxs_router_session *router_session; /*< The router instance data */
MXS_SESSION_STATS stats; /*< Session statistics */
struct service *service; /*< The service this session is using */