Storage Engine API

Classes
struct	item_observer_cb_data
struct	server_handle_v1_t
struct	feature_info
struct	engine_info
struct	engine_interface_v1

Macros
#define	ENGINE_INTERFACE_VERSION   1

Typedefs
typedef void(*	ADD_STAT )(const char *key, const uint16_t klen, const char *val, const uint32_t vlen, const void *cookie)
typedef bool(*	ADD_RESPONSE )(const void *key, uint16_t keylen, const void *ext, uint8_t extlen, const void *body, uint32_t bodylen, uint8_t datatype, uint16_t status, uint64_t cas, const void *cookie)
typedef tap_event_t(*	TAP_ITERATOR )(ENGINE_HANDLE *handle, const void *cookie, item **item, void **engine_specific, uint16_t *nengine_specific, uint8_t *ttl, uint16_t *flags, uint32_t *seqno, uint16_t *vbucket)
typedef ENGINE_ERROR_CODE(*	CREATE_INSTANCE )(uint64_t interface, GET_SERVER_API get_server_api, ENGINE_HANDLE **handle)
typedef struct engine_interface_v1	ENGINE_HANDLE_V1

Enumerations
enum	tap_event_t {   TAP_MUTATION = 1, TAP_DELETION, TAP_FLUSH, TAP_OPAQUE,   TAP_VBUCKET_SET, TAP_ACK, TAP_DISCONNECT, TAP_NOOP,   TAP_PAUSE, TAP_CHECKPOINT_START, TAP_CHECKPOINT_END }
enum	engine_feature_t {   ENGINE_FEATURE_CAS, ENGINE_FEATURE_PERSISTENT_STORAGE, ENGINE_FEATURE_SECONDARY_ENGINE, ENGINE_FEATURE_ACCESS_CONTROL,   ENGINE_FEATURE_MULTI_TENANCY, ENGINE_FEATURE_LRU }

Detailed Description

Most interesting here is to implement engine_interface_v1 for your engine.

Typedef Documentation

typedef bool(* ADD_RESPONSE)(const void *key, uint16_t keylen, const void *ext, uint8_t extlen, const void *body, uint32_t bodylen, uint8_t datatype, uint16_t status, uint64_t cas, const void *cookie)

Callback for adding a response backet

Parameters

key	The key to put in the response
keylen	The length of the key
ext	The data to put in the extended field in the response
extlen	The number of bytes in the ext field
body	The data body
bodylen	The number of bytes in the body
datatype	This is currently not used and should be set to 0
status	The status code of the return packet (see in protocol_binary for the legal values)
cas	The cas to put in the return packet
cookie	The cookie provided by the frontend

Returns

true if return message was successfully created, false if an error occured that prevented the message from being sent

Definition at line 80 of file engine.h.

typedef void(* ADD_STAT)(const char *key, const uint16_t klen, const char *val, const uint32_t vlen, const void *cookie)

Callback for any function producing stats.

Parameters

key	the stat's key
klen	length of the key
val	the stat's value in an ascii form (e.g. text form of a number)
vlen	length of the value
cookie	magic callback cookie

Definition at line 60 of file engine.h.

typedef ENGINE_ERROR_CODE(* CREATE_INSTANCE)(uint64_t interface, GET_SERVER_API get_server_api, ENGINE_HANDLE **handle)

The signature for the "create_instance" function exported from the module.

This function should fill out an engine inteface structure according to the interface parameter (Note: it is possible to return a lower version number).

Parameters

interface	The highest interface level the server supports
get_server_api	function to get the server API from
Where	to store the interface handle

Returns

See description of ENGINE_ERROR_CODE

Definition at line 166 of file engine.h.

typedef struct engine_interface_v1 ENGINE_HANDLE_V1

Definition of the first version of the engine interface

typedef tap_event_t(* TAP_ITERATOR)(ENGINE_HANDLE *handle, const void *cookie, item **item, void **engine_specific, uint16_t *nengine_specific, uint8_t *ttl, uint16_t *flags, uint32_t *seqno, uint16_t *vbucket)

An iterator for the tap stream. The memcached core will keep on calling this function as long as a tap client is connected to the server. Each event returned by the iterator will be encoded in the binary protocol with the appropriate command opcode.

If the engine needs to store extra information in the tap stream it should do so by returning the data through the engine_specific pointer. This data should be valid for the core to use (read only) until the next invocation of the iterator, of if the connection is closed.

Parameters

handle	the engine handle
cookie	identification for the tap stream
item	item to send returned here (check tap_event_t)
engine_specific	engine specific data returned here
nengine_specific	number of bytes of engine specific data
ttl	ttl for this item (Tap stream hops)
flags	tap flags for this object
seqno	sequence number to send
vbucket	the virtual bucket id

Returns

the tap event to send (or TAP_PAUSE if there isn't any events)

Definition at line 144 of file engine.h.

Enumeration Type Documentation

enum engine_feature_t

Enumerator:

ENGINE_FEATURE_CAS	has compare-and-set operation
ENGINE_FEATURE_PERSISTENT_STORAGE	has persistent storage support
ENGINE_FEATURE_SECONDARY_ENGINE	performs as pseudo engine
ENGINE_FEATURE_ACCESS_CONTROL	has access control feature

Definition at line 170 of file engine.h.