This example demonstrates a simple example of integration between the Fuchsia component framework and an offloaded program that uses Pigweed.
pw_system_demo: A binary that can be built from the Pigweed repo, found at //pw_system. It runs a Pigweed RPC server that exposes an Echo and a Logs service.pw_runner: A Fuchsia component runner that hosts components which bridge between Fuchsia and offloaded programs that serve Pigweed RPC.pw_rpc_server: A Fuchsia component that uses pw_runner, which provides a proxy to pw_system_demo.pw_rpc_client: A Fuchsia component that is the client of pw_rpc_server. It makes an Echo RPC to the server.To bridge between Fuchsia and the offloaded program, pw_runner implements the following functionality:
fidl.example.pigweed/RemoteEndpoint, that clients can use to obtain a connection to the remote endpoint. This protocol is routed from the component using the runner to the client component.Make sure you are running your emulator in Tun/Tap mode, and find your emulator's IPv6 address with:
ip addr show
Replace the entry in the host field in [//examples/components/pw_rpc/server/meta/pw_rpc_server.cml][pw_rpc_server.cml] with this address.
First, you need a Pigweed checkout. You have two options for this:
cd to the submodule that's part of fuchsia.git, //third_party/pigweed/src.After you follow those instructions to setup a checkout, activate the pigweed development environment.
$ cd ${PIGWEED_DIR} $ . ./activate.sh
You'll need to enable multi-endpoint mode on pw_system for the example to work. For more information on this, see Multi-endpoint mode.
$ gn args out # Set build arguments here. See `gn help buildargs`. pw_system_USE_MULTI_ENDPOINT_CONFIG = true
In this terminal, run the following commands to start the Pigweed example binary that we'll use as the remote endpoint:
$ ninja -C out pw_system_demo $ ./out/host_device_simulator.speed_optimized/obj/pw_system/bin/system_example
You should see this in the console to indicate the program is waiting for connections:
Awaiting connections on port 33000
First, make sure the example is in your fx args:
$ fx set core.x64 --with //examples/components/pw_rpc`
Build the tree:
$ cd ${FUCHSIA_DIR} $ fx build
In a terminal (different from the one running pw_system_demo), launch the pw_rpc_realm component, which bundles the client and server together:
ffx component run --recreate -f /core/ffx-laboratory:pw_rpc \ 'fuchsia-pkg://fuchsia.com/pw_rpc_realm#meta/pw_rpc_realm.cm'
The output of ffx component run should include logs that indicate what is happening in the client and server. For example:
[00039.842753][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(90)] Starting up. [00039.853834][pw_runner] INFO: [examples/components/pw_rpc/runner/main.cc(36)] Starting up. [00039.854959][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(106)] Sending echo request. [00039.854977][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(118)] Processing packets. [00039.856143][pw_server] INFO: [pw_system/init.cc(41)] System init [00039.856369][pw_server] INFO: [pw_system/example_user_app_init.cc(28)] Pigweed is fun! [00039.856589][pw_server] INFO: [pw_system/hdlc_rpc_server.cc(113)] Running RPC server [00039.856683][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(110)] Received echo reply msg=Hello, Pigweed [00039.856695][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(121)] Done.
These lines indicates that the client made an RPC and received the response:
[00039.856683][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(110)] Received echo reply msg=Hello, Pigweed [00039.856695][pw_client] INFO: [examples/components/pw_rpc/client/pw_rpc_client.cc(121)] Done.
These lines contain the logs from pw_system_demo Notice how they are attributed to the pw_server proxy component.
[00039.856143][pw_server] INFO: [pw_system/init.cc(41)] System init [00039.856369][pw_server] INFO: [pw_system/example_user_app_init.cc(28)] Pigweed is fun! [00039.856589][pw_server] INFO: [pw_system/hdlc_rpc_server.cc(113)] Running RPC server
Note: the Fuchsia timestamps do not reflect the Pigweed timestamps currently, which is why the server log appears second even though temporally it happened first.
Verify that the server component is still running:
$ ffx component show core/ffx-laboratory:pw_rpc/pw_server Moniker: core/ffx-laboratory:pw_rpc/pw_server URL: pw_rpc_server#meta/pw_rpc_server.cm Environment: pw_env Instance ID: None Component State: Resolved Resolved URL: pw_rpc_server#meta/pw_rpc_server.cm Namespace Capabilities: /svc/fuchsia.logger.LogSink Exposed Capabilities: fidl.examples.pigweed.RemoteEndpoint Merkle root: d16ac772d07caae0b1f2a75a468f324a1c20d4f1801ad3065c3e39c1ccee0a47 Execution State: Running Start reason: 'core/ffx-laboratory:pw_rpc/pw_client' requested capability 'fidl.examples.pigweed.RemoteEndpoint' Outgoing Capabilities: debug fidl.examples.pigweed.RemoteEndpoint Runtime: Unknown
From the terminal running pw_system_demo, you should see a message reporting the client's connection:
$ ./out/host_device_simulator.speed_optimized/obj/pw_system/bin/system_example Awaiting connections on port 33000 Clients connected
You can terminate the pw_system_demo process and verify that gets reflected in the server component:
$ ./out/host_device_simulator.speed_optimized/obj/pw_system/bin/system_example Awaiting connections on port 33000 Clients connected ^C
$ ffx component show core/ffx-laboratory:pw_rpc/pw_server Moniker: core/ffx-laboratory:pw_rpc/pw_server URL: pw_rpc_server#meta/pw_rpc_server.cm Environment: pw_env Instance ID: None Component State: Resolved Resolved URL: pw_rpc_server#meta/pw_rpc_server.cm Namespace Capabilities: /svc/fuchsia.logger.LogSink Exposed Capabilities: fidl.examples.pigweed.RemoteEndpoint Merkle root: d16ac772d07caae0b1f2a75a468f324a1c20d4f1801ad3065c3e39c1ccee0a47 Execution State: Stopped
You should also see a log message from the runner indicating this:
[00044.200376][pw_server] INFO: [examples/components/pw_rpc/runner/log_proxy.cc(247)] Connection to proxy has terminated. Exiting.