title: Remote Service Admin SHM
Remote Service Admin SHM
The Celix Remote Service Admin SHM bundle implement OSGi remote service using shared memory. In order to reuse the (de)serialization features of remote service admin, the remote service admin will be realized by ‘rsa_shm’ and ‘rsa_json_rpc’(see Remote Service Admin RPC Using JSON) bundles. The ‘rsa_shm’ bundle is used to realize ‘remote_service_admin_service_t’ and IPC. The ‘rsa_json_rpc’ bundle is used to realize (de)serialization and creating service endpoint/proxy.
Supported Platform
- Linux
Properties/Configuration
| Properties | Type | Description | Default value |
|---|---|---|---|
| CELIX_RSA_SHM_POOL_SIZE | long | The RSA SHM pool size in bytes. Its value should be greater than or equal to 8192 bytes. | 256KB |
| CELIX_RSA_SHM_MSG_TIMEOUT | long | The timeout of remote service invocation in seconds. | default 30s |
| CELIX_RSA_SHM_MAX_CONCURRENT_INVOCATIONS_NUM | long | The maximum concurrent invocations of the same service. If there are more concurrent invocations than its value, service invocation will fail. | 32 |
The value of RSA_SHM_POOL_SIZE should be greater than or equal to 8192 bytes, because current memory pool ctrl block(control_t) size is 6536 bytes.
Supported service.exported.configs
- celix.remote.admin.shm : The IPC type is shared memory, and the default serialization type is json. And remote service can use
celix.remote.admin.shm.rpc_typeproperty to configure the serialization type(Current only implement json serialization in celix project).The value ofcelix.remote.admin.shm.rpc_typeproperty should be equal to the value ofcelix.remote.admin.rpc_typeproperty ofrsa_rpc_factory_t.
Conan Option
build_rsa_remote_service_admin_shm_v2=True Default is False
CMake Option
RSA_REMOTE_SERVICE_ADMIN_SHM_V2=ON Default is OFF
Software Design
The Relationship Between RSA_SHM And Other RSA Bundles
If you need to complete a remote procedure call, multiple different bundles need to work together, as shown in the figure below:
RSA_SHM (Remote Service Admin SHM) has implemented data transmission based on shared memory, and provides a remote service admin service (remote_service_admin_service_t), and a remote request sending service (rsa_request_sender_service_t).
RSA_RPC (Remote Service Admin RPC) implements the serialization and deserialization for interactive data, and provides an endpoint/proxy factory service (rsa_rpc_factory_t) of remote service, as well as a remote request handler service (rsa_request_handler_service_t).
During imports/exports remote services, the topology manager imports/exports the remote service endpoint by remote_service_admin_service_t. At the same time, RSA_SHM creates a remote service proxy/endpoint by rsa_rpc_factory_t.
When a remote procedure call occurs, the remote service proxy use rsa_request_sender_service_t to send the request to the remote service endpoint. And the remote service endpoint uses rsa_request_handler_service_t to convert the request into a local service call.
The Remote Service Invocation Sequence
When the user uses the remote service, the user directly calls the proxy service. The proxy service will send the request to the remote service endpoint via shared memory. The remote service endpoint will convert the request into a local service call. The sequence diagram for remote invocation is as follows:
The Shared Memory Communication Sequence
In order to dynamically allocate shared memory only on the client. The client will transmit the shared memory id and shared memory offset to the server using a domain datagram socket. And response will reuse the shared memory of request.
Example
See the cmake target remote-services-shm-server and remote-services-shm-client.