misc/pod-as-a-service#3: Define the interface for app modules

Lets start with the current signature then:

create(k8s_client, apps_api, name, namespace, customer_id) -> dict
create_service(k8s_client, name, namespace, customer_id) -> dict
delete(k8s_client, apps_api, name, namespace) -> void

At some point we'll also want a describe() that returns information about the package.

I guess the answer, then, is to start writing a package for grafana and see what headaches we run into

That wasn't too bad at all.

There's relatively little difference between the two modules:

--- app/apps/influxdbv1.py  2024-11-10 13:34:52.070336719 +0000
+++ app/apps/grafana.py 2024-11-10 14:01:34.709599411 +0000
@@ -8,7 +8,7 @@
 from kubernetes import client

 def getAppName(name):
-    return f"influxdb1x-{name}"
+    return f"grafana-{name}"

 def getDefaultCreds():
     ''' Generate a random password to use for the default user
@@ -27,16 +27,16 @@
     return {"user": "admin", "password": ''.join(p)}

 def create(k8s_client, apps_api, name, namespace, customer_id):
-    ''' Create a new InfluxDB OSS 1.x app in the namespace
-    
+    ''' Create a new Grafana app in the namespace
         args:

-            @k8s_client: The kubernetes client object
+            k8s_client: The kubernetes client object
+            apps_api: the k8s apps api handle
             name: the user provided name for this deployment
             namespace: the namespace to create in,
             customer_id: the customer's internal ID

-        # TODO: persistent volume claim
+            # TODO: do we want to access SMTP credentials?
     '''

     app_name = getAppName(name)
@@ -45,20 +45,20 @@

     # Define the container
     container = client.V1Container(
-        name="influxdb",
-        image="influxdb:1.11.7",
+        name="grafana",
+        image="grafana/grafana:latest",
         image_pull_policy="IfNotPresent",
-        ports=[client.V1ContainerPort(container_port=8086)],
+        ports=[client.V1ContainerPort(container_port=3000)],
         volume_mounts = [
             {
-                "mountPath" : "/var/lib/influxdb",
+                "mountPath" : "/var/lib/grafana",
                 "name" :  "storage",
                 "subPath" : f"paas/{app_name}/data"
             },
             {
-                "mountPath" : "/etc/influxdb",
-                "name" :  "storage",
-                "subPath" : f"paas/{app_name}/config"
+                "mountPath" : "/var/run/grafana_secret",
+                "name" : "grafana-secrets",
+                "readOnly" : True
             }
             ],
             env = [
@@ -67,25 +67,9 @@
                 "value" : "true"
                 },
                 {
-                "name" : "INFLUXDB_ADMIN_PASSWORD",
-                "valueFrom" : {
-                        "secretKeyRef" : {
-                                "name" : app_name,
-                                "key" : "admin_pass",
-                                "optional" : False
-                            }
-                    }
-                },
-                {
-                "name" : "INFLUXDB_ADMIN_USER",
-                "valueFrom" : {
-                        "secretKeyRef" : {
-                                "name" : app_name,
-                                "key" : "admin_user",
-                                "optional" : False
-                            }
-                    }
-                }                
+                 "name" : "GF_SECURITY_ADMIN_PASSWORD__FILE",
+                 "value" : "/var/run/grafana_secret/admin_pass"
+                }
             ]
     )

@@ -93,7 +77,7 @@
     template = client.V1PodTemplateSpec(
         metadata=client.V1ObjectMeta(
             labels={
-                "app": "influxdb1x",
+                "app": "grafana",
                 "name": app_name
             },
             annotations={
@@ -110,6 +94,13 @@
                             "path" : os.getenv("NFS_PATH", "/volume1/kubernetes_misc_mounts"),
                             "readOnly": False
                         }
+                },
+                {
+                    "name" : "grafana-secrets",
+                    "secret" : {
+                            "secretName" : app_name
+                        }
+                    
                 }
                 ]

@@ -123,7 +114,7 @@
         service_name=f"influx1x-{name}",
         selector=client.V1LabelSelector(
             match_labels={
-                "app": "influxdb1x",
+                "app": "grafana",
                 "name" : app_name
             }
         ),
@@ -180,9 +171,9 @@
                 },
             "spec" : {
                 "ports" : [{
-                    "port": 8086,
+                    "port": 3000,
                     "protocol": "TCP",
-                    "targetPort": 8086
+                    "targetPort": 3000
                 }],
                 "selector": {
                     "name" : app_name
@@ -191,7 +182,7 @@
             }
         }
         k8s_client.create_namespaced_service(namespace, service)
-        return {"name" : app_name, "port": 8086}, ""
+        return {"name" : app_name, "port": 3000}, ""
     except Exception as e:
         return False, e

But that's because they're also both quite simple in terms of demands.

One thing I think we need to do, though, is have create include an attribute that can be used to passed a dict of generic config in (for example, if we wanted to add support for SMTP config to grafana).

We should also make sure the signature doesn't need updating to pass some other k8s api handle in

Although I'm not planning on doing anything with it at the moment, I'd like to add a resize_disk() function too.

Most app instances are actually going to be a StateFulSet and you can't simply resize a PV included in the claim template - you have to go through a bit of mischief.

Each module is the authority on how its volumes are defined, so it'd probably be best to give them the (optional) ability to resize.

OK, so that gives us the following

describe() -> dict
resize_disk(clients, name, namespace, customer_id, new_size, config) -> dict, error (but not currently implemented)
create(clients, name, namespace, customer_id, config) -> dict, error
create_service(clients, name, namespace, customer_id, config) -> dict, error
delete(k8s_client, apps_api, name, namespace, config) -> bool, error