---
title: A workaround when scaling out TAP GUI
tags: ["Kubernetes", "TAP GUI", "Tanzu", "TAP", "ytt"]
categories: ["Dev", "CaaS", "Kubernetes", "TAP"]
date: 2022-12-21T00:52:59Z
updated: 2022-12-21T00:52:59Z
---

Starting with TAP 1.3, scaling out TAP GUI is supported. You can set replicas in `tap-values.yaml` like bellow:

```yaml
tap_gui:
  deployment:
    replicas: 3
```

But since sessions are not shared across instances,
If you have authentication enabled for the TAP GUI, scaling out will make requests round-robin and
A successful login can be routed to an instance that is not logged in and then display an authentication error.

Until the TAP GUI fixes this issue, using Contour's [Session Affinity](https://projectcontour.io/docs/v1.22.0/config/request-routing/#session-affinity), you can the same logged-in user should be routed to the same instance.
Create the following overlay to enable Session Affinity for HTTPProxy in TAP GUI.

```yaml
cat EOF > tap-gui-session-affinity.yaml
#@ load("@ytt:overlay", "overlay")
#@overlay/match by=overlay.subset({"kind":"HTTPProxy","metadata":{"name":"tap-gui"}})
---
spec:
  routes:  
  #@overlay/match by=overlay.subset({"services": [{"name": "server"}]}) 
  - services: []
    #@overlay/match missing_ok=True
    loadBalancerPolicy:
      strategy: Cookie
EOF
```

Create a Secret for the overlay

```
kubectl -n tap-install create secret generic tap-gui-session-affinity \
  -o yaml \
  --dry-run=client \
  --from-file=tap-gui-session-affinity.yaml\
  | kubectl apply -f-
```

Set the secret name of the created overlay to package_overlays in tap-values.yaml as follows:

```
package_overlays:
# ...
- name: tap-gui
  secrets:
  - name: tap-gui-session-affinity
  # ...
```

Then, update package install

```
tanzu package installed update -n tap-install tap -f tap-values.yaml
```