<a id="configure-hostname-and-check-go-import"></a>

# How to configure hostname

Correct hostname metadata lets Go clients discover source through the stable
`gopkg.in` import path. Set the workload hostname, then query a package
path to verify the generated `go-import` metadata.

Two settings carry a hostname. `service-hostname`, on
`nginx-ingress-integrator`, decides which incoming requests reach the
application. `hostname`, on `gopkg-k8s`, is the name the workload
writes into its `go-import` metadata and package links. This guide changes
the second one and queries the service through the first.
[Ingress](https://canonical.com/juju/docs/gopkg-charm/latest/explanation/ingress/index.html.md#ingress) explains why they are separate settings.

## Prerequisites

This guide changes a running deployment, so it needs:

- `gopkg-k8s` and `nginx-ingress-integrator` deployed and integrated
- the integrator’s `service-hostname` set to the hostname clients use
- that same hostname exported as `INGRESS_HOST`, which every command below
  reuses

The deployment steps of [Deploy and verify gopkg-k8s on Kubernetes](https://canonical.com/juju/docs/gopkg-charm/latest/tutorials/deploy-and-verify-on-kubernetes/index.html.md#deploy-and-verify-on-kubernetes) leave the
first two in place, using `gopkg.example.com`. Export it:

```bash
export INGRESS_HOST=gopkg.example.com
```

For local verification, requests are routed to `127.0.0.1` with
`--resolve`.

## Change the hostname configuration

```bash
juju config gopkg-k8s hostname=staging.example.com
```

The charm applies the new value by restarting the workload in place, which
usually takes a couple of minutes. Wait until the application is active
again:

<!-- SPREAD SKIP -->
```bash
juju status --watch 2s
```

<!-- SPREAD SKIP END -->
<!-- SPREAD
juju wait-for application gopkg-k8s \
  --query='status=="active"' --timeout=15m -->
<!-- SPREAD END -->

## Confirm the stored value

```bash
juju config gopkg-k8s hostname
```

The command prints `staging.example.com`.

## Verify the change

Check that the service still answers through ingress:

```bash
curl --fail --silent --show-error --retry 30 --retry-delay 2 \
   --retry-all-errors \
 http://${INGRESS_HOST}/health-check \
 --resolve ${INGRESS_HOST}:80:127.0.0.1 | grep -Fx ok
```

Expected output is `ok`.

Then check the metadata the service serves to Go clients. The restart means
the old value can be served for a few more seconds, so query until the new
value appears (the loop gives up after two minutes):

```bash
timeout 120 bash -c '
  until curl --fail --silent --show-error \
      "http://${INGRESS_HOST}/yaml.v2?go-get=1" \
      --resolve "${INGRESS_HOST}:80:127.0.0.1" \
      | grep "go-import.*staging.example.com"; do
    sleep 5
  done
'
```

The output contains a `go-import` meta tag reflecting the configured
hostname.