The Gateway API is used to create and manage a gateway. Modules are added to the gateway, and communication "links" are established between modules via a message broker.
This section details the internal structure defined in the gateway implementation used to track a gateway and the information it contains.
typedef struct GATEWAY_HANDLE_DATA_TAG {
/** @brief Vector of MODULE_DATA modules that the Gateway must track */
VECTOR_HANDLE modules;
/** @brief The message broker used by this gateway */
BROKER_HANDLE broker;
/** @brief Vector of LINK_DATA links that the Gateway must track */
VECTOR_HANDLE links;
} GATEWAY_HANDLE_DATA;
#define GATEWAY_ADD_LINK_RESULT_VALUES \
GATEWAY_ADD_LINK_SUCCESS, \
GATEWAY_ADD_LINK_ERROR, \
GATEWAY_ADD_LINK_INVALID_ARG
DEFINE_ENUM(GATEWAY_ADD_LINK_RESULT, GATEWAY_ADD_LINK_RESULT_VALUES);
#define GATEWAY_START_RESULT_VALUES \
GATEWAY_START_SUCCESS, \
GATEWAY_START_MODULE_FAIL, \
GATEWAY_START_INVALID_ARGS
DEFINE_ENUM(GATEWAY_START_RESULT, GATEWAY_START_RESULT_VALUES);
typedef struct GATEWAY_LINK_ENTRY_TAG
{
const char* module_source;
const char* module_sink;
} GATEWAY_LINK_ENTRY;
typedef struct GATEWAY_HANDLE_DATA_TAG* GATEWAY_HANDLE;
typedef struct GATEWAY_MODULE_LOADER_INFO_TAG
{
const MODULE_LOADER* loader;
void* entrypoint;
} GATEWAY_MODULE_LOADER_INFO;
typedef struct GATEWAY_MODULES_ENTRY_TAG
{
const char* module_name;
GATEWAY_MODULE_LOADER_INFO module_loader_info;
const void* module_configuration;
} GATEWAY_MODULES_ENTRY;
typedef struct GATEWAY_PROPERTIES_DATA_TAG
{
VECTOR_HANDLE gateway_modules;
VECTOR_HANDLE gateway_links;
} GATEWAY_PROPERTIES;
typedef struct GATEWAY_MODULE_INFO_TAG
{
const char* module_name;
VECTOR_HANDLE module_sources;
} GATEWAY_MODULE_INFO;
typedef enum GATEWAY_EVENT_TAG
{
GATEWAY_CREATED = 0,
GATEWAY_STARTED,
GATEWAY_MODULE_LIST_CHANGED,
GATEWAY_DESTROYED,
GATEWAY_EVENTS_COUNT
} GATEWAY_EVENT;
typedef void* GATEWAY_EVENT_CTX;
typedef void(*GATEWAY_CALLBACK)(GATEWAY_HANDLE gateway, GATEWAY_EVENT event_type, GATEWAY_EVENT_CTX context, void* user_param);
extern GATEWAY_HANDLE Gateway_Create(const GATEWAY_PROPERTIES* properties);
extern GATEWAY_START_RESULT Gateway_Start(GATEWAY_HANDLE gw);
extern void Gateway_Destroy(GATEWAY_HANDLE gw);
extern MODULE_HANDLE Gateway_AddModule(GATEWAY_HANDLE gw, const GATEWAY_MODULES_ENTRY* entry);
extern void Gateway_StartModule(GATEWAY_HANDLE gw, MODULE_HANDLE module);
extern void Gateway_RemoveModule(GATEWAY_HANDLE gw, MODULE_HANDLE module);
extern int Gateway_RemoveModuleByName(GATEWAY_HANDLE gw, const char *module_name);
extern void Gateway_AddEventCallback(GATEWAY_HANDLE gw, GATEWAY_EVENT event_type, GATEWAY_CALLBACK callback, void* user_param);
extern VECTOR_HANDLE Gateway_GetModuleList(GATEWAY_HANDLE gw);
extern void Gateway_DestroyModuleList(VECTOR_HANDLE module_list);
extern GATEWAY_ADD_LINK_RESULT Gateway_AddLink(GATEWAY_HANDLE gw, const GATEWAY_LINK_ENTRY* entryLink);
extern void Gateway_RemoveLink(GATEWAY_HANDLE gw, const GATEWAY_LINK_ENTRY* entryLink);
extern GATEWAY_HANDLE Gateway_Create(const GATEWAY_PROPERTIES* properties);
Gateway_Create creates a new gateway using information from the GATEWAY_PROPERTIES struct to create modules and associate them with a message broker.
SRS_GATEWAY_14_001: [ This function shall create a GATEWAY_HANDLE representing the newly created gateway. ]
SRS_GATEWAY_14_002: [ This function shall return NULL upon any failure. ]
SRS_GATEWAY_17_016: [ This function shall initialize the default module loaders. ]
SRS_GATEWAY_17_017: [ This function shall destroy the default module loaders upon any failure. ]
SRS_GATEWAY_14_003: [ This function shall create a new BROKER_HANDLE for the gateway representing this gateway's message broker. ]
SRS_GATEWAY_14_004: [ This function shall return NULL if a BROKER_HANDLE cannot be created. ]
SRS_GATEWAY_17_001: [ This function shall not accept "*" as a module name. ]
SRS_GATEWAY_14_033: [ The function shall create a vector to store each MODULE_DATA. ]
SRS_GATEWAY_04_001: [ The function shall create a vector to store each LINK_DATA ]
SRS_GATEWAY_14_034: [ This function shall return NULL if a VECTOR_HANDLE cannot be created. ]
SRS_GATEWAY_14_035: [ This function shall destroy the previously created BROKER_HANDLE and free the GATEWAY_HANDLE if the VECTOR_HANDLE cannot be created. ]
SRS_GATEWAY_17_015: [ The function shall use the module's specified loader and the module's entrypoint to get each module's MODULE_LIBRARY_HANDLE. ]
SRS_GATEWAY_17_018: [ The function shall construct module configuration from module's entrypoint and module's module_configuration. ]
SRS_GATEWAY_17_020: [ The function shall clean up any constructed resources. ]
SRS_GATEWAY_14_009: [ The function shall use each of GATEWAY_PROPERTIES's gateway_modules to create and add a module to the gateway's message broker. ]
SRS_GATEWAY_14_036: [ If any MODULE_HANDLE is unable to be created from a GATEWAY_MODULES_ENTRY the GATEWAY_HANDLE will be destroyed. ]
SRS_GATEWAY_04_004: [ If a module with the same module_name already exists, this function shall fail and the GATEWAY_HANDLE will be destroyed. ]
SRS_GATEWAY_17_002: [ The gateway shall accept a link with a source of "*" and a sink of a valid module. ]
SRS_GATEWAY_17_003: [ The gateway shall treat a source of "*" as link to the sink module from every other module in gateway. ]
SRS_GATEWAY_04_002: [ The function shall use each GATEWAY_LINK_ENTRY of GATEWAY_PROPERTIES's gateway_links to add a LINK to GATEWAY_HANDLE's broker. ]
SRS_GATEWAY_26_001: [ This function shall initialize attached Event System and report GATEWAY_CREATED event. ]
SRS_GATEWAY_26_002: [ If Event System module fails to be initialized the gateway module shall be destroyed and NULL returned with no events reported. ]
SRS_GATEWAY_26_010: [ This function shall report GATEWAY_MODULE_LIST_CHANGED event. ]
SRS_GATEWAY_04_003: [ If any GATEWAY_LINK_ENTRY is unable to be added to the broker the GATEWAY_HANDLE will be destroyed. ]
extern GATEWAY_START_RESULT Gateway_Start(GATEWAY_HANDLE gw);
Gateway_Start informs all modules that the gateway is ready to operate. This is a best effort attempt, all modules which implement a Module_Start function will be called. The result of the attempt to start all modules will be reported in the GATEWAY_START_RESULT.
SRS_GATEWAY_17_009: [ This function shall return GATEWAY_START_INVALID_ARGS if a NULL gateway is received. ]
SRS_GATEWAY_17_010: [ This function shall call Module_Start for every module which defines the start function. ]
SRS_GATEWAY_17_012: [ This function shall report a GATEWAY_STARTED event. ]
SRS_GATEWAY_17_013: [ This function shall return GATEWAY_START_SUCCESS upon completion. ]
extern void Gateway_Destroy(GATEWAY_HANDLE gw);
Gateway_Destroy destroys a gateway represented by the gw parameter.
SRS_GATEWAY_14_005: [ If gw is NULL the function shall do nothing. ]
SRS_GATEWAY_14_028: [ The function shall remove each module in GATEWAY_HANDLE_DATA's modules vector and destroy GATEWAY_HANDLE_DATA's modules. ]
SRS_GATEWAY_04_014: [ The function shall remove each link in GATEWAY_HANDLE_DATA's links vector and destroy GATEWAY_HANDLE_DATA's link. ]
SRS_GATEWAY_14_037: [ If GATEWAY_HANDLE_DATA's message broker cannot remove a module, the function shall log the error and continue removing modules from the GATEWAY_HANDLE. ]
SRS_GATEWAY_14_006: [ The function shall destroy the GATEWAY_HANDLE_DATA's broker BROKER_HANDLE. ]
SRS_GATEWAY_17_019: [ The function shall destroy the module loader list. ]
SRS_GATEWAY_26_003: [ If the Event System module is initialized, this function shall report GATEWAY_DESTROYED event. ]
SRS_GATEWAY_26_004: [ This function shall destroy the attached Event System. ]
extern MODULE_HANDLE Gateway_AddModule(GATEWAY_HANDLE gw, const GATEWAY_PROPERTIES_ENTRY* entry);
Gateway_AddModule adds a module to the gateway's message broker using the provided GATEWAY_PROPERTIES_ENTRY's loader_configuration, loader_api and module_configuration.
SRS_GATEWAY_14_011: [ If gw, entry, or GATEWAY_MODULES_ENTRY's specified loader or entrypoint is NULL the function shall return NULL. ]
SRS_GATEWAY_14_012: [ The function shall load the module via the module's specified loader and the module's entrypoint to get each module's MODULE_LIBRARY_HANDLE. ]
SRS_GATEWAY_17_021: [ The function shall construct module configuration from module's entrypoint and module's module_configuration. ]
SRS_GATEWAY_17_022: [ The function shall clean up any constructed resources. ]
SRS_GATEWAY_14_031: [ If unsuccessful, the function shall return NULL. ]
SRS_GATEWAY_14_013: [ The function shall get the const MODULE_API* from the MODULE_LIBRARY_HANDLE. ]
SRS_GATEWAY_14_015: [ The function shall use the MODULE_API to create a MODULE_HANDLE using the GATEWAY_MODULES_ENTRY's module_properties. ]
SRS_GATEWAY_14_016: [ If the module creation is unsuccessful, the function shall return NULL. ]
SRS_GATEWAY_14_017: [ The function shall attach the module to the GATEWAY_HANDLE_DATA's broker using a call to Broker_AddModule. ]
SRS_GATEWAY_14_039: [ The function shall increment the BROKER_HANDLE reference count if the MODULE_HANDLE was successfully linked to the GATEWAY_HANDLE_DATA's broker. ]
SRS_GATEWAY_14_018: [ If the function cannot attach the module to the message broker, the function shall return NULL. ]
SRS_GATEWAY_14_029: [ The function shall create a new MODULE_DATA containing the MODULE_HANDLE, MODULE_LOADER_API and MODULE_LIBRARY_HANDLE if the module was successfully linked to the message broker. ]
SRS_GATEWAY_14_032: [ The function shall add the new MODULE_DATA to GATEWAY_HANDLE_DATA's modules if the module was successfully linked to the message broker. ]
SRS_GATEWAY_14_030: [ If any internal API call is unsuccessful after a module is created, the library will be unloaded and the module destroyed. ]
SRS_GATEWAY_14_019: [ The function shall return the newly created MODULE_HANDLE only if each API call returns successfully. ]
SRS_GATEWAY_99_011: [ The function shall assign module_api to MODULE::module_api. ]
SRS_GATEWAY_26_011: [ The function shall report GATEWAY_MODULE_LIST_CHANGED event after successfully adding the module. ]
SRS_GATEWAY_26_020: [ The function shall make a copy of the name of the module for internal use. ]
extern void Gateway_StartModule(GATEWAY_HANDLE gw, MODULE_HANDLE module);
When a module is added to the Gateway after it has been started, Gateway_StartModule informs a module when the broker is ready for the module to send and receive messages (i.e. after Gateway_AddModule and all Gateway_AddLink have been called). This informational to the module, and the module is not required to implement a Module_Start function.
SRS_GATEWAY_17_006: [ If gw is NULL, this function shall do nothing. ]
SRS_GATEWAY_17_007: [ If module is not found in the gateway, this function shall do nothing. ]
SRS_GATEWAY_17_008: [ When module is found, if the Module_Start function is defined for this module, the Module_Start function shall be called. ]
extern void Gateway_RemoveModule(GATEWAY_HANDLE gw, MODULE_HANDLE module);
Gateway_RemoveModule will remove the specified module from the message broker.
SRS_GATEWAY_14_020: [ If gw or module is NULL the function shall return. ]
SRS_GATEWAY_14_023: [ The function shall locate the MODULE_DATA object in GATEWAY_HANDLE_DATA's modules containing module and return if it cannot be found. ]
SRS_GATEWAY_14_021: [ The function shall detach module from the GATEWAY_HANDLE_DATA's broker BROKER_HANDLE. ]
SRS_GATEWAY_14_022: [ If GATEWAY_HANDLE_DATA's broker cannot detach module, the function shall log the error and continue unloading the module from the GATEWAY_HANDLE. ]
SRS_GATEWAY_14_038: [ The function shall decrement the BROKER_HANDLE reference count. ]
SRS_GATEWAY_14_024: [ The function shall use the MODULE_DATA's library_handle to retrieve the MODULE_API and destroy module. ]
SRS_GATEWAY_14_025: [ The function shall unload MODULE_DATA's library_handle. ]
SRS_GATEWAY_14_026: [ The function shall remove that MODULE_DATA from GATEWAY_HANDLE_DATA's modules. ]
SRS_GATEWAY_26_012: [ The function shall report GATEWAY_MODULE_LIST_CHANGED event after successfully removing the module. ]
SRS_GATEWAY_26_018: [ This function shall remove any links that contain the removed module either as a source or sink. ]
int Gateway_RemoveModuleByName(GATEWAY_HANDLE gw, const char *module_name);
SRS_GATEWAY_26_015: [ If gw or module_name is NULL the function shall do nothing and return with non-zero result. ]
SRS_GATEWAY_26_016: [ The function shall return 0 if the module was found. ]
SRS_GATEWAY_26_017: [ If module with module_name name is not found this function shall return non-zero and do nothing. ]
To be consistent with the requirements of Gateway_RemoveModule, any other remove failures other than name not found or NULL parameters, shall follow Gateway_RemoveModule requirements, and thus be silent.
Furthermore, this function follows the removal procedure requirements of Gateway_RemoveModule.
extern void Gateway_AddEventCallback(GATEWAY_HANDLE gw, GATEWAY_EVENT event_type, GATEWAY_CALLBACK callback);
Gateway_AddEventCallback registers callback function to listen to some kind of GATEWAY_EVENT.
When the event happens the callback will be put in a queue and executed in a seperate callback thread in First-In-First-Out order of registration for that event
Also see event_system_requirements.md file for further requirements.
SRS_GATEWAY_26_006: [ This function shall log a failure and do nothing else when gw parameter is NULL. ]
extern VECTOR_HANDLE Gateway_GetModuleList(GATEWAY_HANDLE gw);
SRS_GATEWAY_26_007: [ This function shall return a snapshot copy of information about current gateway modules. ]
SRS_GATEWAY_26_013: [ For each module returned this function shall provide a snapshot copy vector of link sources for that module. ]
SRS_GATEWAY_26_014: [ For each module returned that has '*' as a link source this function shall provide NULL vector pointer as it's sources vector. ]
SRS_GATEWAY_26_008: [ If the gw parameter is NULL, the function shall return NULL handle and not allocate any data. ]
SRS_GATEWAY_26_009: [ This function shall return a NULL handle should any internal callbacks fail. ]
extern void Gateway_DestroyModuleList(VECTOR_HANDLE module_list);
SRS_GATEWAY_26_011: [ This function shall destroy the module_sources list of each GATEWAY_MODULE_INFO ]
SRS_GATEWAY_26_012: [ This function shall destroy the list of GATEWAY_MODULE_INFO ]
extern GATEWAY_ADD_LINK_RESULT Gateway_AddLink(GATEWAY_HANDLE gw, const GATEWAY_LINK_ENTRY* entryLink);
Gateway_AddLink adds a link to the gateway's message broker using the provided GATEWAY_LINK_ENTRY's loader_configuration and GATEWAY_PROPERTIES_ENTRY's module_configuration.
SRS_GATEWAY_04_008: [ If gw , entryLink, entryLink->module_source or entryLink->module_source is NULL the function shall return GATEWAY_ADD_LINK_INVALID_ARG. ]
SRS_GATEWAY_04_009: [ This function shall check if a given link already exists. ]
SRS_GATEWAY_04_010: [ If the entryLink already exists it the function shall return GATEWAY_ADD_LINK_ERROR ]
SRS_GATEWAY_17_004: [ The gateway shall accept a link containing "*" as entryLink->module_source, and a valid module name as a entryLink->module_sink. ]
SRS_GATEWAY_17_005: [ For this link, the sink shall receive all messages publish by other modules. ]
SRS_GATEWAY_04_011: [ If the module referenced by the entryLink->module_source or entryLink->module_sink doesn't exists this function shall return GATEWAY_ADD_LINK_ERROR ]
SRS_GATEWAY_04_012: [ This function shall add the entryLink to the gw->links ]
SRS_GATEWAY_04_013: [ If adding the link succeed this function shall return GATEWAY_ADD_LINK_SUCCESS ]
SRS_GATEWAY_26_019: [ The function shall report GATEWAY_MODULE_LIST_CHANGED event after successfully adding the link. ]
extern void Gateway_RemoveLink(GATEWAY_HANDLE gw, const GATEWAY_LINK_ENTRY* entryLink);
Gateway_RemoveLink will remove the specified link from the message broker.
SRS_GATEWAY_04_005: [ If gw or entryLink is NULL the function shall return. ]
SRS_GATEWAY_04_006: [ The function shall locate the LINK_DATA object in GATEWAY_HANDLE_DATA's links containing link and return if it cannot be found. ]
SRS_GATEWAY_04_007: [ The functional shall remove that LINK_DATA from GATEWAY_HANDLE_DATA's links. ]
SRS_GATEWAY_26_018: [ The function shall report GATEWAY_MODULE_LIST_CHANGED event. ]