Crate fuchsia_inspect

fuchsia-inspect

Components in Fuchsia may expose structured information about themselves conforming to the Inspect API. This crate is the core library for writing inspect data in Rust components.

For a comprehensive guide on how to start using inspect, please refer to the codelab.

Library concepts

There’s two types of inspect values: nodes and properties. These have the following characteristics:

• A Node may have any number of key/value pairs called Properties.
• A Node may have any number of children, which are also Nodes.
• Properties and nodes are created under a parent node. Inspect is already initialized with a root node.
• The key for a value in a Node is always a UTF-8 string, the value may be one of the supported types (a node or a property of any type).
• Nodes and properties have strict ownership semantics. Whenever a node or property is created, it is written to the backing VMO and whenever it is dropped it is removed from the VMO.
• Inspection is best effort, if an error occurs, no panic will happen and nodes and properties might become No-Ops. For example, when the VMO becomes full, any further creation of a property or a node will result in no changes in the VMO and a silent failure. However, mutation of existing properties in the VMO will continue to work.
• All nodes and properties are thread safe.

Creating vs Recording

There are two functions each for initializing nodes and properties:

• create_*: returns the created node/property and it’s up to the caller to handle its lifetime.
• record_*: creates the node/property but doesn’t return it and ties its lifetime to the node where the function was called.

Lazy value support

Lazy (or dynamic) values are values that are created on demand, this is, whenever they are read. Unlike regular nodes, they don’t take any space on the VMO until a reader comes and requests its data.

There’s two ways of creating lazy values:

• Lazy node: creates a child node of root with the given name. The callback returns a future for an Inspector whose root node is spliced into the parent node when read.
• Lazy values: works like the previous one, except that all properties and nodes under the future root node node are added directly as children of the parent node.

Quickstart

Add the following to your component main:

use fuchsia_inspect::component;
use inspect_runtime;

let _inspect_server_task = inspect_runtime::publish(
    component::inspector(),
    inspect_runtime::PublishOptions::default(),
);

// Now you can create nodes and properties anywhere!
let child = component::inspector().root().create_child("foo");
child.record_uint("bar", 42);

Modules

• component
  Component inspection utilities
• health
  Health-checking inspect node.
• hierarchy
• reader
  Reading inspect data
• stats
  Inspect stats node.
• types

Structs

• BoolProperty
  Inspect API Bool Property data type.
• BytesProperty
  Inspect Bytes Property data type.
• DoubleArrayProperty
  Inspect double array data type.
• DoubleExponentialHistogramProperty
  An exponential histogram property for double values.
• DoubleLinearHistogramProperty
  A linear histogram property for double values.
• DoubleProperty
  Inspect double property type.
• ExponentialHistogramParams
  The parameters of an exponential histogram.
• Inspector
  Root of the Inspect API. Through this API, further nodes can be created and inspect can be served.
• InspectorConfig
  Classic builder pattern object for constructing an Inspector.
• IntArrayProperty
  Inspect int array data type.
• IntExponentialHistogramProperty
  An exponential histogram property for int values.
• IntLinearHistogramProperty
  A linear histogram property for integer values.
• IntProperty
  Inspect int property data type.
• LazyNode
  Inspect Lazy Node data type. NOTE: do not rely on PartialEq implementation for true comparison. Instead leverage the reader.
• LinearHistogramParams
  The parameters of a linear histogram.
• Node
  Inspect Node data type.
• Stats
  Statistics about the current inspect state.
• StringArrayProperty
• StringProperty
  Inspect String Property data type.
• StringReference
  StringReference is a type that can be constructed and passed into the Inspect API as a name of a Node. If this is done, only one reference counted instance of the string will be allocated per Inspector. They can be safely used with LazyNodes.
• UintArrayProperty
  Inspect uint array data type.
• UintExponentialHistogramProperty
  An exponential histogram property for uint values.
• UintLinearHistogramProperty
  A linear histogram property for unsigned integer values.
• UintProperty
  Inspect uint property data type.
• ValueList
  Holds a list of inspect types that won’t change.

Enums

• Error
  Errors that Inspect API functions can return.

Constants

• DIAGNOSTICS_DIR
  Directiory within the outgoing directory of a component where the diagnostics service should be added.

Traits

• ArithmeticArrayProperty
• ArrayProperty
  Trait implemented by all array properties providing common operations on arrays.
• DiagnosticsHierarchyGetter
  A type which can function as a “view” into a diagnostics hierarchy, optionally allocating a new instance to service a request.
• HistogramProperty
  Trait implemented by all histogram properties providing common operations.
• InspectType
  Trait implemented by all inspect types.
• InspectTypeReparentable
  Trait allowing a Node to adopt any Inspect type as its child, removing it from the original parent’s tree.
• Length
  Get the usable length of a type.
• NumericProperty
  Trait implemented by numeric properties providing common operations.
• Property
  Trait implemented by properties.

Functions

• unique_name
  Generates a unique name that can be used in inspect nodes and properties that will be prefixed by the given prefix.