Check hippo health

[FrankYang0529]

resolves #562

> ~/Project/spin/target/debug/spin deploy -f spin.toml --deploy-existing-bindle
Error: Hippo server http://localhost:5309/ is unhealthy
# follow nomad tutorial to start nomad
> ~/Project/spin/target/debug/spin deploy -f spin.toml --deploy-existing-bindle
Deployed spin-hello-world version 1.0.0+qb632d35
Available Routes:
  hello: http://spin-deploy.spin-hello-world.hippofactory.io/hello
    A simple component that returns hello.

[lann]

I think this should perhaps be:

Suggested change

	if result == "Unhealthy" {
	if result != "Healthy" {

Unless I'm forgetting how reqwest works, I think this would return Ok on a - for example - 502 Bad Gateway, as long as the body wasn't Unhealthy.

[dicej]

I agree with @lann and would also recommend using error_for_status, e.g.:

        let result = reqwest::get(hippo_healthz_url.to_string())
            .await?
            .error_for_status()?
            .text()
            .await?;

[FrankYang0529]

Hi @dicej and @lann, thanks for the suggestion. If we use error_for_status, it looks like we don't need to check result text.

> curl -k http://localhost:5309/healthz
Unhealthy%

> ~/Project/spin/target/debug/spin deploy -f spin.toml --deploy-existing-bindle
Error: HTTP status server error (503 Service Unavailable) for url (http://localhost:5309/healthz)

# start nomad

> ~/Project/spin/target/debug/spin deploy -f spin.toml --deploy-existing-bindle
Deployed spin-hello-world version 1.0.0+qb632d35
Available Routes:
  hello: http://spin-deploy.spin-hello-world.hippofactory.io/hello
    A simple component that returns hello.

[lann]

I believe Hippo still returns 200 with an Unhealthy status: deislabs/hippo#889

[FrankYang0529]

Thanks for pointing it out. I add the check for result != "Healthy" back.

[lann]

Looks good to me. I'd like @michelleN to sanity-check the behavior.

[bacongobbler]

FYI in the latest version of hippo, /healthz will now return a 503 if something is unhealthy.

[michelleN]

Going to merge and then we can update.