Expand section about network

Author: rgaiacs

source/examples/valkey0/play.yml

@@ -4,10 +4,10 @@ metadata:
   name: client-entrypoint
 data:
   entrypoint.sh: |
-    valkey-cli set counter 0
+    valkey-cli -h server set counter 0
     while [ -z "" ]
     do
-      valkey-cli incr counter
+      valkey-cli -h server incr counter
       sleep 5s
     done
 ---

source/examples/valkey1/play.yml

@@ -0,0 +1,47 @@
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: client-entrypoint
+data:
+  entrypoint.sh: |
+    valkey-cli -h valkey1-server set counter 0
+    while [ -z "" ]
+    do
+      valkey-cli -h valkey1-server incr counter
+      sleep 5s
+    done
+---
+apiVersion: v1
+kind: Pod
+metadata:
+  labels:
+    app: valkey
+  name: valkey1-server
+spec:
+  containers:
+    - name: server
+      image: docker.io/valkey/valkey:8.0.2-alpine
+---
+apiVersion: v1
+kind: Pod
+metadata:
+  labels:
+    app: valkey
+  name: valkey1-client
+spec:
+  containers:
+    - name: client
+      image: docker.io/valkey/valkey:8.0.2-alpine
+      command:
+        - /bin/sh
+        - /opt/entrypoint.sh
+      volumeMounts:
+        - mountPath: /opt
+          name: client-entrypoint-volume
+  volumes:
+    - configMap:
+        name: client-entrypoint
+        items:
+          - key: "entrypoint.sh"
+            path: "entrypoint.sh"
+      name: client-entrypoint-volume

source/k8s-network.rst

@@ -1,32 +1,42 @@
 Pod and Network
 ===============
 
-Normally, we want for one container to access the program running on another container.
+Normally, we want for one container to access the program running on another container. Two scenarios are possible: containers run on the same pod or containers run on different pods.
 
-.. mermaid::
-   :align: center
-   :alt: Diagram of network.
-   :caption: Diagram of network.
+Containers on the same Pod
+--------------------------
 
-    graph LR;
-        browser[Web browser] --> flask[Flask];
-        flask .-> postgres[PostgreSQL];
+.. mermaid::
+    :align: center
+    :alt: Diagram of containers running on the same pod.
+    :caption: Diagram of containers running on the same pod.
 
+    flowchart 
         subgraph pod[Pod]
         flask
         postgres
         end
 
+        subgraph network[Network]
+        pod
+        end
+
         subgraph host[Host]
         browser
+        network
+        pod
         end
 
-The container can be reached by another container if they are part of the same pod of if they are part of the same network.
+        browser[Web browser] --> flask[Flask];
+        flask .-> postgres[PostgreSQL];
 
-Containers in the same Pod
---------------------------
+        classDef classPod fill:lightblue,stroke:blue
+        class pod classPod;
+
+        classDef classNetwork stroke:black,stroke-dasharray: 5 5
+        class network classNetwork;
 
-Containers in the same pod share the IP addresses, MAC addresses and port mappings. This allows the container to be reached by another container using ``localhost:port``.
+Containers in the same pod share the IP addresses, MAC addresses and port mappings. This allows the container to be reached by another container using ``localhost`` or the name of the container.
 
 Example
 ^^^^^^^
@@ -43,5 +53,65 @@ running ::
 
 creates a pod named ``valkey0`` with a container named ``server`` running the `Valkey <https://valkey.io/>`_ server and another container named ``client`` running a small Bash script that increases a counter every 5 seconds.
 
-Containers in the same Network
-------------------------------
+Containers on different pods
+----------------------------
+
+.. mermaid::
+    :align: center
+    :alt: Diagram of containers running on different pods.
+    :caption: Diagram of containers running on different pods.
+
+    flowchart 
+        subgraph pod1[Pod 1]
+        flask
+        end
+
+        subgraph pod2[Pod 2]
+        postgres
+        end
+
+        subgraph network[Network]
+        pod1
+        pod2
+        end
+
+        subgraph host[Host]
+        browser
+        network
+        pod1
+        pod2
+        end
+
+        browser[Web browser] --> flask[Flask];
+        flask .-> postgres[PostgreSQL];
+
+        classDef classPod fill:lightblue,stroke:blue
+        class pod1,pod2 classPod;
+
+        classDef classNetwork stroke:black,stroke-dasharray: 5 5
+        class network classNetwork;
+
+The container can be reached by another container if they are part of the same pod of if they are part of the same network.
+
+Example
+^^^^^^^
+
+.. important::
+
+    When no network option is specified and host network mode is not configured in the YAML file, a new network stack is created and pods are attached to it making possible pod to pod communication.
+
+First, create a new network by running ::
+
+    podman network valkey1
+
+Given the following Kubernetes manifest file
+
+.. literalinclude:: examples/valkey1/play.yml
+   :language: yaml
+   :caption: play.yml
+
+running ::
+
+    podman kube play --net valkey1 play.yml
+
+creates a pod named ``valkey1-server`` connected to the network ``valkey1`` with a container named ``server`` running the `Valkey <https://valkey.io/>`_ server and another pod named ``valkey1-client`` connected to the network ``valkey1`` with a container named ``client`` running a small Bash script that increases a counter every 5 seconds.