Health check

Health check is a standardized inspection metric. Adding a fuchsia.inspect.Health child to an Inspect Node gives that node the contained health information. This information can be aggregated by system-wide health-checking tools.

The layout of the health check node

The following properties and metrics are exported in any health check node:

Name	Type	Description
start_timestamp_nanos	int64	The monotonic clock system timestamp at which this health node was initialized (i.e. first became STARTING UP)
message	String	If status==UNHEALTHY, this includes an optional failure detail message.
status	Enum	STARTING_UP: The health node was initialized but not yet marked running.
		OK: The subsystem reporting to this health node is reporting healthy.
		UNHEALTHY: The subsystem reporting to this health node is reporting unhealthy.

User guide

The following example illustrates the use of iquery for getting information about the component health status.

Examples:

$ iquery show `iquery list`
a.cmx:
  root:
    fuchsia.inspect.Health:
      start_timestamp_nanos = ...
      status = OK
    connections:
      0:
        fuchsia.inspect.Health:
          start_timestamp_nanos = ...
          status = STARTING_UP
    optional_database:
      fuchsia.inspect.Health:
        start_timestamp_nanos = ...
        status = UNHEALTHY
        message = "Cannot open local.file"
b.cmx:
  root:
    fuchsia.inspect.Health:
      start_timestamp_nanos = ...
      status = OK
c.cmx:
  root:
    fuchsia.inspect.Health:
      start_timestamp_nanos = ...
      status = UNHEALTHY
      message = "Failed to connect to fuchsia.example.RequiredService"

$ iquery show a.cmx:root/fuchsia.inspect.Health:status b.cmx:root/fuchsia.inspect.Healh:status c.cmx:root/fuchsia.inspect.Health:status
a:
  root:
    fuchsia.inspectHealth:
      status = Ok
b:
  root:
    fuchsia.inspectHealth:
      status = Ok
c:
  root:
    fuchsia.inspectHealth:
      status = Ok

Using health checks in components

The following sections explain how to use the library in Fuchsia components written in various programming languages.

Rust

use fuchsia_inspect as inspect;
use fuchsia_inspect::health;

fn main() {
  // If you have your own inspector, it's also possible to export its health.

  /* inspector needs to be initialized */
  let inspector = /* ... */
  let mut node = inspector::root();
  let mut health = fuchsia_inspect::health::Node(node);
  // ...
  health.set_ok();
  health.set_unhealthy("I'm not feeling well.");
  health.set_ok();  // The component is healthy again.
}