Inspect codelab

This document contains the codelab for Inspect in C++, Dart and Rust.

The code is available at:

• //examples/diagnostics/inspect/codelab/cpp.
• //examples/diagnostics/inspect/codelab/rust.
• //topaz/public/dart/fuchsia_inspect/codelab.

This codelab is organized into several parts, each with their own subdirectory. The starting point for the codelab is part 1, and the code for each part contains the solution for the previous parts.

• C++ Part 1
• Rust Part 1
• Dart Part 1

When working on this codelab, you may continue adding your solutions to "part_1", or you may skip around by building on the existing solutions.

Prerequisites

Set up your development environment.

This codelab assumes you have completed Getting Started and have:

1. A checked out and built Fuchsia tree.
2. A device or emulator (fx emu) that runs Fuchsia.
3. A workstation to serve components (fx serve) to your Fuchsia device or emulator.

To build and run the examples in this codelab, add the following arguments to your fx set invocation:

fx set core.x64 \
--with //examples/diagnostics/inspect/codelab/cpp \
--with //examples/diagnostics/inspect/codelab/cpp:tests

fx set core.x64 \
--with //examples/diagnostics/inspect/codelab/rust \
--with //examples/diagnostics/inspect/codelab/rust:tests

fx set workstation.x64
--with //topaz/public/dart/fuchsia_inspect/codelab:all

Part 1: A buggy component

There is a component that serves a protocol called Reverser:

// Implementation of a string reverser.
[Discoverable]
protocol Reverser {
    // Returns the input string reversed character-by-character.
    Reverse(string:1024 input) -> (string:1024 response);
};

This protocol has a single method, called "Reverse," that simply reverses any string passed to it. An implementation of the protocol is provided, but it has a critical bug. The bug makes clients who attempt to call the Reverse method see that their call hangs indefinitely. It is up to you to fix this bug.

Run the component

There is a client application that will launch the Reverser component and send the rest of its command line arguments as strings to Reverse:

1. See usage

   C++

   fx shell run inspect_cpp_codelab_client
   

   Rust

   fx shell run inspect_rust_codelab_client
   

   Dart

   fx shell run inspect_dart_codelab_client
   

2. Run part 1 code, and reverse the string "Hello"

   C++

   fx shell run inspect_cpp_codelab_client 1 Hello
   

   Rust

   fx shell run inspect_rust_codelab_client 1 Hello
   

   This command prints some output containing errors.

   Dart

   fx shell run inspect_dart_codelab_client 1 Hello
   

   These commands hang.

3. Press Ctrl+C to stop the client and try running with more arguments:

   C++

   fx shell run inspect_cpp_codelab_client 1 Hello World
   

   Rust

   fx shell run inspect_rust_codelab_client 1 Hello World
   

   Dart

   fx shell run inspect_dart_codelab_client 1 Hello World
   

   This command also prints no outputs.

   These commands also hang.

You are now ready to look through the code to troubleshoot the issue.

Look through the code

Now that you can reproduce the problem, take a look at what the client is doing:

// Repeatedly send strings to be reversed to the other component.
for (int i = 2; i < argc; i++) {
  printf("Input: %s\n", argv[i]);

  std::string output;
  if (ZX_OK != reverser->Reverse(argv[i], &output)) {
    printf("Error: Failed to reverse string.\nPerhaps %s was not found?\n",
           reverser_component_url.c_str());
    exit(1);
  }

  printf("Output: %s\n", output.c_str());
  fflush(stdout);
}

for string in args.strings {
    println!("Input: {}", string);
    match reverser.reverse(&string).await {
        Ok(output) => println!("Output: {}", output),
        Err(e) => println!("Failed to reverse string. Error: {:?}", e),
    }
}

for (int i = 1; i < args.length; i++) {
  print('Input: ${args[i]}');
  final response = await reverser.reverse(args[i]);
  print('Output: $response');
}

In this code snippet, the client calls the Reverse method but never seems to get a response. There doesn't seem to be an error message or output.

Take a look at the server code for this part of the codelab. There is a lot of standard component setup:

See what the reverser definition is:

class Reverser final : public fuchsia::examples::inspect::Reverser {
 public:
  // CODELAB: Create a new constructor for Reverser that takes an Inspect node.

  // Implementation of Reverser.Reverse().
  void Reverse(std::string input, ReverseCallback callback) override;

  // Return a request handler for the Reverser protocol that binds incoming requests to new
  // Reversers.
  static fidl::InterfaceRequestHandler<fuchsia::examples::inspect::Reverser> CreateDefaultHandler();
};

pub struct ReverserServerFactory {}

impl ReverserServerFactory {
    // CODELAB: Create a new() constructor that takes an Inspect node.
    pub fn new() -> Self {
        Self {}
    }

    pub fn spawn_new(&self, stream: ReverserRequestStream) {
        // CODELAB: Add stats about incoming connections.
        ReverserServer::new().spawn(stream);
    }
}

struct ReverserServer {}

impl ReverserServer {
    // CODELAB: Create a new() constructor that takes an Inspect node.
    fn new() -> Self {
        Self {}
    }

    pub fn spawn(self, mut stream: ReverserRequestStream) {
        fasync::Task::local(async move {
            while let Some(request) = stream.try_next().await.expect("serve reverser") {
                // CODELAB: Add stats about incoming requests.
                let ReverserRequest::Reverse { input, responder: _ } = request;
                let _result = input.chars().rev().collect::<String>();
                // Yes, this is silly. Just for codelab purposes.
                fasync::Timer::new(fasync::Time::after(10.hours())).await
            }
        })
        .detach();
    }
}

typedef BindCallback = void Function(InterfaceRequest<fidl_codelab.Reverser>);
typedef VoidCallback = void Function();

class ReverserImpl extends fidl_codelab.Reverser {
  final _binding = fidl_codelab.ReverserBinding();

  // CODELAB: Create a constructor that takes an Inspect node.
  ReverserImpl();

  @override
  Future<String> reverse(String value) async {
    // CODELAB: Add stats about incoming requests.
    print(String.fromCharCodes(value.runes.toList().reversed));
    await Future.delayed(Duration(hours: 10));
    return '';
  }

  static final _bindingSet = <ReverserImpl>{};
  static BindCallback getDefaultBinder() {
    return (InterfaceRequest<fidl_codelab.Reverser> request) {
      // CODELAB: Add stats about incoming connections.
      final reverser = ReverserImpl()..bind(request, onClose: () {});
      _bindingSet.add(reverser);
    };
  }

  void bind(
    InterfaceRequest<fidl_codelab.Reverser> request, {
    @required VoidCallback onClose,
  }) {
    _binding.stateChanges.listen((state) {
      if (state == InterfaceState.closed) {
        dispose();
        onClose();
      }
    });
    _binding.bind(this, request);
  }

  void dispose() {}
}

Add Inspect

Now that you know the code structure, you can start to instrument the code with Inspect to find the problem.

You may have previously debugged programs by printing or logging. While this is often effective, asynchronous Components that run persistently often output numerous logs about their internal state over time. This codelab shows how Inspect provides snapshots of your component's current state without needing to dig through logs.

1. Include Inspect dependencies:

   C++

   In BUILD.gn:

   source_set("lib") {
     sources = [
       "reverser.cc",
       "reverser.h",
     ]
   
     public_deps = [
       "//examples/diagnostics/inspect/codelab/fidl:fuchsia.examples.inspect",
       "//sdk/lib/sys/inspect/cpp",
     ]
   }
   
   

   Rust

   In BUILD.gn in deps under rustc_binary("bin"):

   "//src/lib/diagnostics/inspect/rust",
   "//src/lib/syslog/rust:syslog",
   "//src/lib/zircon/rust:fuchsia-zircon",
   
   

   Dart

   In BUILD.gn in deps under dart_library("lib") and dart_app("bin"):

   "//topaz/public/dart/fuchsia_inspect",
   
   

2. Initialize Inspect:

   C++

   In main.cc:

   #include <lib/sys/inspect/cpp/component.h>
   sys::ComponentInspector inspector(context.get());
   

   Rust

   In main.rs:

   use fuchsia_inspect::component;
   component::inspector().serve(&mut fs)?;
   

   Dart

   In main.dart:

   import 'package:fuchsia_inspect/inspect.dart' as inspect;
   final inspector = inspect.Inspect();
   

   You are now using Inspect.

3. Add a simple "version" property to show which version is running:

   C++

   inspector.root().CreateString("version", "part2", &inspector);
   

   This snippet does the following:

   1. Obtain the "root" node of the Inspect hierarchy.

      The Inspect hierarchy for your component consists of a tree of Nodes, each of which contains any number of properties.

   2. Create a new property using CreateString.

      This adds a new StringProperty on the root. This StringProperty is called "version", and its value is "part1".

   3. Emplace the new property in the inspector.

      The lifetime of a property is tied to an object returned by Create, and destroying the object causes the property to disappear. The optional third parameter emplaces the new property in inspector rather than return it. As a result, the new property lives as long as the inspector itself (the entire execution of the component).

   Rust

   component::inspector().root().record_string("version", "part2");
   

   This snippet does the following:

   1. Obtain the "root" node of the Inspect hierarchy.

   The Inspect hierarchy for your component consists of a tree of Nodes, each of which contains any number of properties.

   1. Create a new property using record_string.

   This adds a new StringProperty on the root. This StringProperty is called "version", and its value is "part1".

   1. It records it in the root node.

   The usual way of creating properties is through create_* methods on nodes. The lifetime of a property created with these methods is tied to the object returned and destroying the object causes the property to disappear. The library provides convinience methods record_* that perform creation of a property and tie the property lifetime to the node on which the method was called. As a result, the new property lives as long as the node itself (in this case, as long as the root node, so the entire execution of the component).

   Dart

   inspector.root.stringProperty('version').setValue('part2');
   

   This snippet does the following:

   1. Obtain the "root" node of the Inspect hierarchy.

   The Inspect hierarchy for your component consists of a tree of Nodes, each of which contains any number of properties.

   1. Create a new property using stringProperty(...).setValue(...).

   This adds a new StringProperty on the root. This StringProperty is called "version", and its value is "part1".

   1. It records it in the root node.

   The lifetime of a property is tied to the lifetime of the node where it was created (in this case root, so the lifetime of the component). To delete the property one would have to call delete() on it.

Reading Inspect data

Now that you have added Inspect to your component, you can read what it says:

1. Rebuild and update the target system

   fx build && fx update
   

2. Run the client:

   C++

   fx run inspect_cpp_codelab_client 1 Hello
   

   Rust

   fx run inspect_rust_codelab_client 1 Hello
   

   Dart

   fx run inspect_dart_codelab_client 1 Hello
   

   Note that these should still hang.

3. Use iquery (Inspect query) to view your output:

   fx iquery
   

   This dumps all of the Inspect data for the entire system, which may be a lot of data.

4. Since iquery supports regex matching, run:

   C++

   $ fx iquery show codelab_\*/inspect_cpp_codelab_part_1.cmx
   # or `fx iquery show --manifest_inspect_cpp_codelab_part_1`
   /hub/r/codelab/1234/c/inspect_cpp_codelab_part_1.cmx/1234/out/diagnostics/root.inspect:
     version = part1
   

   Rust

   $ fx iquery show codelab_\*/inspect_rust_codelab_part_1.cmx
   # or `fx iquery show --manifest_inspect_rust_codelab_part_1`
   /hub/r/codelab/1234/c/inspect_rust_codelab_part_1.cmx/1234/out/diagnostics/root.inspect:
     version = part1
   

   Dart

   $ fx iquery show codelab_\*/inspect_dart_codelab_part_1.cmx
   # or `fx iquery show --manifest_inspect_dart_codelab_part_1`
   /hub/r/codelab/1234/c/inspect_dart_codelab_part_1.cmx/1234/out/diagnostics/root.inspect:
     version = part1
   

5. You can also view the output as JSON:

   C++

   $ fx iquery -f json show codelab_\*/inspect_cpp_codelab_part_1.cmx
   [
       {
           "contents": {
               "root": {
                   "version": "part1"
               }
           },
           "path": "/hub/r/codelab/1234/c/inspect_cpp_codelab_part_1.cmx/1234/out/diagnostics/root.inspect"
       }
   ]
   

   Rust

   $ fx iquery -f json show codelab_\*/inspect_rust_codelab_part_1.cmx
   [
       {
           "contents": {
               "root": {
                   "version": "part1"
               }
           },
           "path": "/hub/r/codelab/1234/c/inspect_rust_codelab_part_1.cmx/1234/out/diagnostics/root.inspect"
       }
   ]
   

   Dart

   $ fx iquery -f json show codelab_\*/inspect_dart_codelab_part_1.cmx
   [
       {
           "contents": {
               "root": {
                   "version": "part1"
               }
           },
           "path": "/hub/r/codelab/1234/c/inspect_dart_codelab_part_1.cmx/1234/out/diagnostics/root.inspect"
       }
   ]
   

Instrumenting the code to find the bug

Now that you have initialized Inspect and know how to read data, you are ready to instrument your code and uncover the bug.

The previous output shows you how the component is actually running and that the component is not hanging completely. Otherwise the Inspect read would hang.

Add new information per-connection to observe if the connection is even being handled by your component.

1. Add a new child to your root node to contain statistics about the reverser service:

   C++

   context->outgoing()->AddPublicService(
       Reverser::CreateDefaultHandler(inspector.root().CreateChild("reverser_service")));
   

   Rust

   let reverser_factory =
       ReverserServerFactory::new(component::inspector().root().create_child("reverser_service"));
   

   Dart

   context.outgoing.addPublicService<fidl_codelab.Reverser>(
     ReverserImpl.getDefaultBinder(inspector.root.child('reverser_service')),
     fidl_codelab.Reverser.$serviceName,
   );
   

2. Update your server to accept this node:

   C++

   Update the definition of CreateDefaultHandler in reverser.h and [reverser.cc][part1-reverser-cc]:

   #include <lib/inspect/cpp/inspect.h>
   fidl::InterfaceRequestHandler<fuchsia::examples::inspect::Reverser> Reverser::CreateDefaultHandler(
       inspect::Node node) {
   

   Rust

   Update ReverserServerFactory::new to accept this node in reverser.rs:

   use fuchsia_inspect as inspect;
   pub struct ReverserServerFactory {
       node: inspect::Node,
       // ...
   }
   
   impl ReverserServerFactory {
       pub fn new(node: inspect::Node) -> Self {
           let request_count = Arc::new(node.create_uint("total_requests", 0));
           let connection_count = node.create_uint("connection_count", 0);
           Self {
               node,
               // ...
           }
       }
   
       // ...
   }
   

   Dart

   Update the definition of getDefaultBinder in reverser.dart and [reverser.cc][part1-reverser-cc]:

   import 'package:fuchsia_inspect/inspect.dart' as inspect;
   static BindCallback getDefaultBinder(inspect.Node node) {
   

3. Add a property to keep track of the number of connections:

   C++

   fidl::InterfaceRequestHandler<fuchsia::examples::inspect::Reverser> Reverser::CreateDefaultHandler(
       inspect::Node node) {
     // ...
   
     // Return a handler for incoming FIDL connections to Reverser.
     //
     // The returned closure contains a binding set, which is used to bind incoming requests to a
     // particular implementation of a FIDL interface. This particular binding set is configured to
     // bind incoming requests to unique_ptr<Reverser>, which means the binding set itself takes
     // ownership of the created Reversers and frees them when the connection is closed.
     return [connection_count = node.CreateUint("connection_count", 0), node = std::move(node),
             // ...
   

   Rust

   pub struct ReverserServerFactory {
       node: inspect::Node,
       // ...
       connection_count: inspect::UintProperty,
   }
   
   impl ReverserServerFactory {
       pub fn new(node: inspect::Node) -> Self {
           // ...
           let connection_count = node.create_uint("connection_count", 0);
           Self {
               node,
               // ...
               connection_count,
           }
       }
   
       pub fn spawn_new(&self, stream: ReverserRequestStream) {
           self.connection_count.add(1);
   

   Dart

   static BindCallback getDefaultBinder(inspect.Node node) {
     // ...
     final glabalConnectionCount = node.intProperty('connection_count')
       ..setValue(0);
     return (InterfaceRequest<fidl_codelab.Reverser> request) {
       glabalConnectionCount.add(1);
   

   This snippet demonstrates creating a new UintProperty (containing a 64 bit unsigned int) called connection_count and setting it to 0. In the handler (which runs for each connection), the property is incremented by 1.

4. Rebuild, re-run your component and then run iquery:

   C++

   $ fx iquery -f json --manifest inspect_cpp_codelab_part_1
   

   Rust

   $ fx iquery -f json --manifest inspect_rust_codelab_part_1
   

   Dart

   $ fx iquery -f json --manifest inspect_dart_codelab_part_1
   

   You should now see:

   ...
   "contents": {
      "root": {
          "reverser_service": {
              "connection_count": 1,
          },
          "version": "part1"
      }
   }
   

The output above demonstrates that the client successfully connected to the service, so the hanging problem must be caused by the Reverser implementation itself. In particular, it will be helpful to know:

1. If the connection is still open while the client is hanging.

2. If the Reverse method was called.

Exercise: Create a child node for each connection, and record "request_count" inside the Reverser.

• Hint: There is a utility function for generating unique names:

  C++

  auto child = node.CreateChild(node.UniqueName("connection-"));
  

  Rust

  let node = self.node.create_child(inspect::unique_name("connection"));
  

  Dart

  final name = inspect.uniqueName('connection');
  

  This will create unique names starting with "connection".

• Hint: You will need to create a member on Reverser to hold the request_count property. Its type will be inspect::UintProperty.

• Follow up: Does request count give you all of the information you need? Add response_count as well.

• Advanced: Can you add a count of all requests on all connections? The Reverser objects must share some state. You may find it helpful to refactor arguments to Reverser into a separate struct (See solution in part 2 for this approach).

After completing this exercise and running iquery, you should see something like this:

...
"contents": {
    "root": {
        "reverser_service": {
            "connection-0x0": {
                "request_count": 1,
            },
            "connection_count": 1,
        },
        "version": "part1"
    }
}

The output above shows that the connection is still open and it received one request.

1. Send the response:

   C++

   // At the end of Reverser::Reverse
   callback(std::move(output));
   

   Rust

   responder.send(&result).expect("send reverse request response");
   

   Dart

   final result = String.fromCharCodes(value.runes.toList().reversed);
   // ...
   return result;
   

2. Run the client again:

   C++

   fx shell run inspect_cpp_codelab_client 1 hello
   Input: hello
   Output: olleh
   Done. Press Ctrl+C to exit
   

   Rust

   fx shell run inspect_rust_codelab_client 1 hello
   Input: hello
   Output: olleh
   Done. Press Ctrl+C to exit
   

   Dart

   fx shell run inspect_dart_codelab_client 1 hello
   Input: hello
   Output: olleh
   Done. Press Ctrl+C to exit
   

   The component continues running until Ctrl+C is pressed to give you a chance to run iquery and observe your output.

This concludes part 1. You may commit your changes so far:

git commit -am "solution to part 1"

Part 2: Diagnosing inter-component problems

You received a bug report. The "FizzBuzz" team is saying they are not receiving data from your component.

In addition to serving the Reverser protocol, the component also reaches out to the "FizzBuzz" service and prints the response:

fuchsia::examples::inspect::FizzBuzzPtr fizz_buzz;
context->svc()->Connect(fizz_buzz.NewRequest());
fizz_buzz->Execute(30, [](std::string result) { FX_LOGS(INFO) << "Got FizzBuzz: " << result; });

let fizzbuzz_fut = async move {
    let fizzbuzz = client::connect_to_service::<FizzBuzzMarker>()
        .context("failed to connect to fizzbuzz")?;
    match fizzbuzz.execute(30u32).await {
        Ok(result) => fx_log_info!("Got FizzBuzz: {}", result),
        Err(_) => {}
    };
    Ok(())
};

final fizzBuzz = fidl_codelab.FizzBuzzProxy();
context.incoming.connectToService(fizzBuzz);
final result = await fizzBuzz.execute(30);

If you see the logs, you will see that this log is never printed.

fx log --tag inspect_cpp_codelab

fx log --tag inspect_rust_codelab

fx log --tag inspect_dart_codelab_part_2

You will need to diagnose and solve this problem.

Diagnose the issue with Inspect

1. Run the component to see what is happening:

   C++

   $ fx shell run inspect_cpp_codelab_client 2 hello
   

   Rust

   $ fx shell run inspect_rust_codelab_client 2 hello
   

   Dart

   $ fx shell run inspect_dart_codelab_client 2 hello
   

   Fortunately the FizzBuzz team instrumented their component using Inspect.

2. Read the FizzBuzz Inspect data using iquery as before, you get:

   "contents": {
       "root": {
           "fizzbuzz_service": {
               "closed_connection_count": 0,
               "incoming_connection_count": 0,
               "request_count": 0,
               ...
   

   This output confirms that FizzBuzz is not receiving any connections.

3. Add Inspect to identify the problem:

   C++

   // CODELAB: Instrument our connection to FizzBuzz using Inspect. Is there an error?
   fuchsia::examples::inspect::FizzBuzzPtr fizz_buzz;
   context->svc()->Connect(fizz_buzz.NewRequest());
   fizz_buzz.set_error_handler([&](zx_status_t status) {
     // CODELAB: Add Inspect here to see if there is a response.
   });
   fizz_buzz->Execute(30, [](std::string result) {
     // CODELAB: Add Inspect here to see if there was a response.
     FX_LOGS(INFO) << "Got FizzBuzz: " << result;
   });
   

   Rust

   let fizzbuzz_fut = async move {
       let fizzbuzz = client::connect_to_service::<FizzBuzzMarker>()
           .context("failed to connect to fizzbuzz")?;
       match fizzbuzz.execute(30u32).await {
           Ok(result) => {
               // CODELAB: Add Inspect here to see if there is a response.
               fx_log_info!("Got FizzBuzz: {}", result);
           }
           Err(_) => {
               // CODELAB: Add Inspect here to see if there is an error
           }
       };
       Ok(())
   };
   

   Dart

   final fizzBuzz = fidl_codelab.FizzBuzzProxy();
   context.incoming.connectToService(fizzBuzz);
   
   fizzBuzz.execute(30).timeout(const Duration(seconds: 2), onTimeout: () {
     throw Exception('timeout');
   }).then((result) {
     // CODELAB: Add Inspect here to see if there is a response.
     log.info('Got FizzBuzz: $result');
   }).catchError((e) {
     // CODELAB: Instrument our connection to FizzBuzz using Inspect. Is there an error?
   });
   

Exercise: Add Inspect to the FizzBuzz connection to identify the problem

• Hint: Use the snippet above as a starting point, it provides an error handler for the connection attempt.

 /*
 "fuchsia.inspect.Health": {
     "status": "STARTING_UP"
 }
 */
 inspector.Health().StartingUp();

 /*
 "fuchsia.inspect.Health": {
     "status": "OK"
 }
 */
 inspector.Health().Ok();

 /*
 "fuchsia.inspect.Health": {
     "status": "UNHEALTHY",
     "message": "Something went wrong!"
 }
 */
 inspector.Health().Unhealthy("Something went wrong!");

/*
"fuchsia.inspect.Health": {
    "status": "STARTING_UP"
}
*/
fuchsia_inspect::component::health().set_starting_up();

/*
"fuchsia.inspect.Health": {
    "status": "OK"
}
*/
fuchsia_inspect::component::health().set_ok();

/*
"fuchsia.inspect.Health": {
    "status": "UNHEALTHY",
    "message": "Something went wrong!"
}
*/
fuchsia_inspect::component::health().set_unhealthy("something went wrong!");

/*
"fuchsia.inspect.Health": {
    "status": "STARTING_UP"
}
*/
inspect.Inspect().health.setStartingUp();

/*
"fuchsia.inspect.Health": {
    "status": "OK"
}
*/
inspect.Inspect().health.setOk();

/*
"fuchsia.inspect.Health": {
    "status": "UNHEALTHY",
    "message": "Something went wrong!"
}
*/
inspect.Inspect().health.setUnhealthy('Something went wrong!');

Once you complete this exercise, you should see that the connection error handler is being called with a "not found" error. Inspect output showed that FizzBuzz is running, so maybe something is misconfigured. Unfortunately not everything uses Inspect (yet!) so look at the logs:

$ fx log --only FizzBuzz
...
... Component fuchsia-pkg://fuchsia.com/inspect_cpp_codelab_part_2.cmx
is not allowed to connect to fuchsia.examples.inspect.FizzBuzz...

$ fx log --only FizzBuzz
...
... Component fuchsia-pkg://fuchsia.com/inspect_rust_codelab_part_2.cmx
is not allowed to connect to fuchsia.examples.inspect.FizzBuzz...

$ fx log --only FizzBuzz
...
... Component fuchsia-pkg://fuchsia.com/inspect_dart_codelab_part_2.cmx
is not allowed to connect to fuchsia.examples.inspect.FizzBuzz...

Sandboxing errors are a common pitfall that are sometimes difficult to uncover.

Looking at the sandbox in part2 meta, you can see it is missing the service:

"sandbox": {
    "services": [
        "fuchsia.logger.LogSink"
    ]
}

Add "fuchsia.examples.inspect.FizzBuzz" to the services array, rebuild, and run again. You should now see FizzBuzz in the logs and an OK status:

$ fx log --tag inspect_cpp_codelab
[inspect_cpp_codelab, part2] INFO: main.cc(57): Got FizzBuzz: 1 2 Fizz
4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz
22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz

$ fx log --tag inspect_rust_codelab
[inspect_rust_codelab, part2] INFO: main.rs(52): Got FizzBuzz: 1 2 Fizz
4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz
22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz

$ fx log --tag inspect_dart_codelab
[inspect_dart_codelab, part2] INFO: main.dart(35): Got FizzBuzz: 1 2 Fizz
4 Buzz Fizz 7 8 Fizz Buzz 11 Fizz 13 14 FizzBuzz 16 17 Fizz 19 Buzz Fizz
22 23 Fizz Buzz 26 Fizz 28 29 FizzBuzz

This concludes Part 2.

You can now commit your solution:

git commit -am "solution for part 2"

Part 3: Unit Testing for Inspect

All code on Fuchsia should be tested, and this applies to Inspect data as well.

While Inspect data is not required to be tested in general, you need to test Inspect data that is depended upon by other tools such as Triage or Feedback.

Reverser has a basic unit test. Run it:

fx test inspect_cpp_codelab_unittests

fx test inspect_rust_codelab_unittests

fx test inspect_dart_codelab_part_3_unittests

The unit test ensures that Reverser works properly (and doesn't hang!), but it does not check that the Inspect output is as expected.

Passing Nodes into constructors is a form of Dependency Injection, which allows you to pass in test versions of dependencies to check their state.

The code to open a Reverser looks like the following:

binding_set_.AddBinding(std::make_unique<Reverser>(ReverserStats::CreateDefault()),
                        ptr.NewRequest());
// Alternatively
binding_set_.AddBinding(std::make_unique<Reverser>(inspect::Node()),
                        ptr.NewRequest());

let (proxy, stream) = fidl::endpoints::create_proxy_and_stream::<ReverserMarker>()?;
let reverser = ReverserServer::new(ReverserServerMetrics::default());
reverser.spawn(stream);

return ReverserImpl(ReverserStats.noop());

A default version of the Inspect Node is passed into the Reverser. This allows the reverser code to run properly in tests, but it does not support asserting on Inspect output.

Follow up: Create multiple reverser connections and test them independently.

Following this exercise, your unit test will set real values in an Inspect hierarchy.

Add code to test the output in Inspect:

#include <lib/inspect/testing/cpp/inspect.h>
fit::result<inspect::Hierarchy> hierarchy;
RunPromiseToCompletion(inspect::ReadFromInspector(inspector).then(
    [&](fit::result<inspect::Hierarchy>& result) { hierarchy = std::move(result); }));
ASSERT_TRUE(hierarchy.is_ok());

auto* global_count =
    hierarchy.value().node().get_property<inspect::UintPropertyValue>("request_count");
ASSERT_TRUE(global_count);
EXPECT_EQ(3u, global_count->value());

auto* connection_0 = hierarchy.value().GetByPath({"connection_0x0"});
ASSERT_TRUE(connection_0);
auto* requests_0 =
    connection_0->node().get_property<inspect::UintPropertyValue>("request_count");
ASSERT_TRUE(requests_0);
EXPECT_EQ(2u, requests_0->value());

fuchsia_inspect::{self, assert_inspect_tree},
let inspector = inspect::Inspector::new();
assert_inspect_tree!(inspector, root: {
    reverser_service: {
        total_requests: 3u64,
        connection_count: 2u64,
        "connection0": {
            request_count: 2u64,
            response_count: 2u64,
        },
        "connection1": {
            request_count: 1u64,
            response_count: 1u64,
        },
    }
});

test('reverser', () async {
  final vmo = FakeVmoHolder(256 * 1024);
  final inspector = inspect.Inspect.forTesting(vmo, 'root.inspect');
  // ...

The snippets above read a snapshot from the underlying virtual memory object (VMO) containing Inspect data and parses it into a readable hierarchy.

Exercise: Add assertions for the rest of your Inspect data.

This concludes Part 3.

You may commit your changes:

git commit -am "solution to part 3"

Part 4: Integration Testing for Inspect

Integration testing is an important part of the software development workflow for Fuchsia. Integration tests allow you to observe the behavior of your actual component when it runs on the system.

Running integration tests

You can run the integration tests for the codelab as follows:

$ fx test inspect_cpp_codelab_integration_tests

$ fx test inspect_rust_codelab_integration_tests

$ fx test inspect_dart_codelab_part_4_integration_tests

View the code

Look at how the integration test is setup:

1. View the component manifest for the integration test:

   C++

   Find the component manifest (cmx) in cpp/meta

   Rust

   Find the component manifest (cmx) in rust/meta

   Dart

   Find the component manifest (cmx) in dart/part_4/meta

   {
       "facets": {
           "fuchsia.test": {
               "injected-services": {
                   "fuchsia.diagnostics.ArchiveAccessor":
                       "fuchsia-pkg://fuchsia.com/archivist-for-embedding#meta/archivist-for-embedding.cmx"
               }
           }
       },
       "program": {
           "binary": "test/integration_part_4"
       },
       "sandbox": {
           "services": [
               "fuchsia.logger.LogSink",
               "fuchsia.sys.Loader",
               "fuchsia.sys.Environment"
               ...
           ]
       }
   }
   

   The important parts of this file are:

   • Injected services: The fuchsia.test facet includes configuration for tests. In this file, the fuchsia.diagnostics.ArchiveAccessor service is injected and points to a component called archivist-for-embedding.cmx. The Archivist collects information from all components in your test environment and provides a reading interface. You can use this information to look at your Inspect output.

   • Sandbox services: Integration tests need to start other components in the test environment and wire them up. For this you need fuchsia.sys.Loader and fuchsia.sys.Environment.

2. Look at the integration test itself. The individual test cases are fairly straightforward:

   C++

   Locate the integration test in part4/tests/integration_test.cc.

   TEST_F(CodelabTest, StartWithFizzBuzz) {
     auto ptr = StartComponentAndConnect({.include_fizzbuzz_service = true});
   
     bool error = false;
     ptr.set_error_handler([&](zx_status_t unused) { error = true; });
   
     bool done = false;
     std::string result;
     ptr->Reverse("hello", [&](std::string value) {
       result = std::move(value);
       done = true;
     });
     RunLoopUntil([&] { return done || error; });
   
     ASSERT_FALSE(error);
     EXPECT_EQ("olleh", result);
   
     // CODELAB: Check that the component was connected to FizzBuzz.
   }
   

   StartComponentAndConnect is responsible for creating a new test environment and starting the codelab component inside of it. The include_fizzbuzz_service option instructs the method to optionally include FizzBuzz. This feature tests that your Inspect output is as expected in case it fails to connect to FizzBuzz as in Part 2.

   Rust

   Locate the integration test in part4/tests/integration_test.rs.

   #[fasync::run_singlethreaded(test)]
   async fn start_with_fizzbuzz() -> Result<(), Error> {
       let mut test = IntegrationTest::start()?;
       let reverser = test.start_component_and_connect(TestOptions::default())?;
       let result = reverser.reverse("hello").await?;
       assert_eq!(result, "olleh");
       // CODELAB: Check that the component was connected to FizzBuzz.
       Ok(())
   }
   

   IntegrationTest::start is responsible for creating a new test environment and starting the codelab component inside of it. The include_fizzbuzz option instructs the method to optionally launch the FizzBuzz component. This feature tests that your Inspect output is as expected in case it fails to connect to FizzBuzz as in Part 2.

   Dart

   Locate the integration test in part_4/test/integration_test.dart.

   setUp(() async {
     env = CodelabEnvironment();
     await env.create();
   });
   
   tearDown(() async {
     env.dispose();
   });
   
   test('start with fizzbuzz', () async {
     final reverser = await startComponentAndConnect(includeFizzbuzz: true);
     final result = await reverser.reverse('hello');
     expect(result, equals('olleh'));
     // CODELAB: Check that the component was connected to FizzBuzz.
   });
   

   env.create() is responsible for creating a new test environment. startComponentAndConnect launches the reverser component and optionally launches the FizzBuzz component. This feature tests that the Inspect output is as expected in case it fails to connect to FizzBuzz as in Part 2.

3. Add the following method to your test fixture to read from the ArchiveAccessor service:

   C++

   #include <rapidjson/document.h>
   #include <rapidjson/pointer.h>
   std::string GetInspectJson() {
     fuchsia::diagnostics::ArchiveAccessorPtr archive;
     real_services()->Connect(archive.NewRequest());
   
     while (true) {
       ContentVector current_entries;
   
       fuchsia::diagnostics::BatchIteratorPtr iterator;
       fuchsia::diagnostics::StreamParameters stream_parameters;
       stream_parameters.set_data_type(fuchsia::diagnostics::DataType::INSPECT);
       stream_parameters.set_stream_mode(fuchsia::diagnostics::StreamMode::SNAPSHOT);
       stream_parameters.set_format(fuchsia::diagnostics::Format::JSON);
   
       {
         std::vector<fuchsia::diagnostics::SelectorArgument> args;
         args.emplace_back();
         args[0].set_raw_selector("sys/inspect_cpp_codelab_part_5.cmx:root");
   
         fuchsia::diagnostics::ClientSelectorConfiguration client_selector_config;
         client_selector_config.set_selectors(std::move(args));
         stream_parameters.set_client_selector_configuration(std::move(client_selector_config));
       }
       archive->StreamDiagnostics(std::move(stream_parameters), iterator.NewRequest());
   
       bool done = false;
       iterator->GetNext([&](auto result) {
         auto res = fit::result<ContentVector, fuchsia::diagnostics::ReaderError>(std::move(result));
         if (res.is_ok()) {
           current_entries = res.take_value();
         }
   
         done = true;
       });
   
       RunLoopUntil([&] { return done; });
   
       // Should be at most one component.
       ZX_ASSERT(current_entries.size() <= 1);
       if (!current_entries.empty()) {
         std::string json;
         fsl::StringFromVmo(current_entries[0].json(), &json);
         // Ensure the component is either OK or UNHEALTHY.
         if (json.find("OK") != std::string::npos || json.find("UNHEALTHY") != std::string::npos) {
           return json;
         }
       }
   
       // Retry with delay until the data appears.
       usleep(150000);
     }
   
     return "";
   }
   

   Rust

   use {
       anyhow::format_err,
       fuchsia_inspect::testing::{assert_inspect_tree, AnyProperty},
       fuchsia_inspect_contrib::reader::{ArchiveReader, ComponentSelector, NodeHierarchy},
   };
   async fn get_inspect_hierarchy(&self) -> Result<NodeHierarchy, Error> {
       ArchiveReader::new()
           .add_selector(ComponentSelector::new(vec![
               self.environment_label.clone(),
               "inspect_rust_codelab_part_5.cmx".to_string(),
           ]))
           .get()
           .await?
           .into_iter()
           .next()
           .and_then(|result| result.payload)
           .ok_or(format_err!("expected one inspect hierarchy"))
   }
   

   Dart

   // NOTE: this test is currently commented out in the BUILD.gn file.
   // TODO(fxb/45831): re-enable
   import 'dart:convert';
   import 'package:fidl_fuchsia_diagnostics/fidl_async.dart';
   import 'package:fidl_fuchsia_mem/fidl_async.dart';
   import 'package:fuchsia_services/services.dart';
   import 'package:zircon/zircon.dart';
   String readBuffer(Buffer buffer) {
     final dataVmo = SizedVmo(buffer.vmo.handle, buffer.size);
     final data = dataVmo.read(buffer.size);
     return utf8.decode(data.bytesAsUint8List());
   }
   
   Future<Map<String, dynamic>> getInspectHierarchy() async {
     final archive = ArchiveProxy();
     StartupContext.fromStartupInfo().incoming.connectToService(archive);
   
     final params = StreamParameters(
         dataType: DataType.inspect,
         streamMode: StreamMode.snapshot,
         format: Format.json,
         selectors: [
           SelectorArgument.withRawSelector(
               '${env.label}/inspect_dart_codelab_part_5.cmx:root'),
         ]);
   
     // ignore: literal_only_boolean_expressions
     while (true) {
       final iterator = BatchIteratorProxy();
       await archive.streamDiagnostics(iterator.ctrl.request(), params);
       final batch = await iterator.getNext();
       for (final entry in batch) {
         final jsonData = readBuffer(entry.json);
         if (jsonData.contains('fuchsia.inspect.Health') &&
             !jsonData.contains('STARTING_UP')) {
           return json.decode(jsonData);
         }
       }
       iterator.ctrl.close();
       await Future.delayed(Duration(milliseconds: 150));
     }
   }
   

4. Exercise. Use the returned data in your tests and add assertions to the returned data:

   C++

   rapidjson::Document document;
   document.Parse(GetInspectJson());
   

   Add assertions on the returned JSON data.

   • Hint: It may help to print the JSON output to view the schema.

   • Hint: You can read values by path as follows:

   • Hint: You can EXPECT_EQ by passing in the expected value as a rapidjson::Value: rapidjson::Value("OK").

   rapidjson::GetValueByPointerWithDefault(
       document, "/payload/root/fuchsia.inspect.Health/status", "")
   

   Rust

   let hierarchy = test.get_inspect_hierarchy().await?;
   

   Add assertions on the returned NodeHierarchy.

   • Hint: It may help to print the JSON output to view the schema.

   Dart

   final inspectData = await getInspectHierarchy();
   

   Add assertions on the returned Map data.

   • Hint: It may help to print the JSON output to view the schema.

Your integration test will now ensure your inspect output is correct.

This concludes Part 4.

You may commit your solution:

git commit -am "solution to part 4"

Part 5: Feedback Selectors

This section is under construction.

• TODO: Writing a feedback selector and adding tests to your integration test.

• TODO: Selectors for Feedback and other pipelines