Documented the Jellyfin and HTTP2 upgrading thingie

Migrations/Forget_Traefik_2023/README.md

@@ -2020,4 +2020,94 @@ This left me some questions, especially **how many things can be affected by thi
 As well the hassle of this issue, provided more reasons to use the `ACME DNS01` challenge instead of the `ACME HTTP01`, which will be configured as soon as available.  
 
 
-### Jellyfin and HTTP2 upgrading
+### Jellyfin and HTTP2 upgrading
+
+I initially set the Jellyfin `DestinationRule` to have the connection upgraded to HTTP2.
+
+I set it up.
+
+All the other services work.
+
+I am also able to listen music and play videos so everything **seems** fine.
+
+```yaml
+apiVersion: networking.istio.io/v1alpha3
+kind: DestinationRule
+metadata:
+  name: jelly
+  namespace: external
+  labels:
+    app: jellyfin
+spec:
+  host: jelly.external.svc.cluster.local
+  trafficPolicy:
+    tls:
+      mode: SIMPLE
+    connectionPool:
+      http:
+        h2UpgradePolicy: UPGRADE
+```
+
+Couple days later, decide to watch some video with a friend.
+
+We notice that things are not syncing.
+
+I try to upgrade version.
+
+I try to downgrade version.
+
+Video still doesn't sync.
+
+I try to use the Jellyfin locally with only Traefik being the Load Balancer in front the Jellyfin service.
+
+I works.
+
+Great, well, "_great_", we confirmed that the issue remains within the Istio LB, but why? Why would Istio LB not work and Traefik yes.
+
+Also, on the Traefik and Istio LB logs everything seems correct...
+
+Searching through different GitHub issues I stumble into a post mentioning that websockets are used for room/group sync.
+
+Searching regarding Istio and websockets, I find [the following post](https://github.com/istio/istio/issues/27078) on the Istio issue, stating that cannot upgrade websocket connection to HTTP2.
+
+On the post it's mentioned that they have deployed an `EnvoyFilter` on their application in order to set `allow_connect: true`.
+
+It's important to notice that they set this with the context `SIDECAR_INBOUND` meaning that will be applied to the ingress traffic towards that service.
+
+I have an issue tho, I don't have the service hosted within the cluster (nor will, it requires a little bit more of horsepower to encode/decode on which I am using a full size PC with its GPU with hardware accelaration.)
+
+What happens if I don't have the service running within the cluster?
+
+- I can't attach a `EnvoyFilter` configuration to a non-cluster deployed resource.
+
+Here there are a couple options:
+
+- Make the Jellyfin host join the cluster as if it was a Virtual Machine, or, install the required resources to join the cluster as a node.   In any case meanwhile some of these options are interesting they will be saved for the future.
+- Remove the HTTP2 upgrade for that service.
+
+> **Note**:\
+> Fore more information regarding the `EnvoyFilter` resource refer to the [pertinent documentation regarding `EnvoyFilter` from Istio](https://istio.io/latest/docs/reference/config/networking/envoy-filter/).
+> 
+> As well, the [following documentation from Envoy Regarding Websocket and HTTP upgrades](https://www.envoyproxy.io/docs/envoy/latest/intro/arch_overview/http/upgrades#websocket-over-http-2-or-http-3-hops) is very helpful and interesting.
+
+Well I disabled the HTTP2 upgrade because I wanted to watch a movie with a friend at that moment, since it's not causing me any issue whatsoever I am not bothered about it, as well I have other matters to prioritize.
+
+The `DestinationRule` configuration result was the following:
+
+```yaml
+apiVersion: networking.istio.io/v1alpha3
+kind: DestinationRule
+metadata:
+  name: jelly
+  namespace: external
+  labels:
+    app: jellyfin
+spec:
+  host: jelly.external.svc.cluster.local
+  trafficPolicy:
+    tls:
+      mode: SIMPLE
+    connectionPool:
+      http:
+        h2UpgradePolicy: DO_NOT_UPGRADE
+```