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.

User Guide

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

Examples:

$ iquery --recursive `iquery --find` .
a/root.inspect:
  fuchsia.inspect.Health:
    status = OK
  connections:
    0:
      fuchsia.inspect.Health:
        status = STARTING_UP
  optional_database:
    fuchsia.inspect.Health:
      status = UNHEALTHY
      message = "Cannot open local.file"
b/root.inspect:
  fuchsia.inspect.Health:
    status = OK
c/root.inspect:
  fuchsia.inspect.Health:
    status = UNHEALTHY
    message = "Failed to connect to fuchsia.example.RequiredService"

$ iquery --health a/root.inspect b/root.inspect c/root.inspect
a/root.inspect = OK
b/root.inspect = OK
c/root.inspect = UNHEALTHY (Failed to connect to fuchsia.example.RequiredService)

$ iquery --health --summary a/root.inspect b/root.inspect c/root.inspect
c/root.inspect = UNHEALTHY (Failed to connect to fuchsia.example.RequiredService)

$ iquery --health --summary a/root.inspect b/root.inspect not_found/root.inspect
not_found/root.inspect = NOT_FOUND

$ iquery --health --recursive a/root.inspect b/root.inspect c/root.inspect
a/root.inspect = HEALTHY
a/root.inspect#connections/0 = STARTING_UP
a/root.inspect#optional_database = UNHEALTHY (Cannot open local.file)
b/root.inspect = OK
c/root.inspect = UNHEALTHY (Failed to connect to fuchsia.example.RequiredService)

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.
}