feat: update rockcraft with new non root solution

canonical/seldon-core-operator#133

Summary of changes:
- Updated rockcraft.yaml with new run-user option to run as non-root.
- Updated import procedure.
- Tested with integration tests on the branch.

sklearnserver/rockcraft.yaml

@@ -1,25 +1,27 @@
+# Based on https://github.com/SeldonIO/seldon-core/tree/master/servers/sklearnserver/sklearnserver
 name: sklearnserver
 summary: An image for Seldon SKLearn Server
 description: |
   This image is used as part of the Charmed Kubeflow product. The SKLearn Server serves
   models which have been stored as pickles.
-version: v1.16.0_20.04_1 # <upstream-version>-<base-version>_<Charmed-KF-version>
+version: v1.16.0_20.04_1 # <upstream-version>_<base-version>_<Charmed-KF-version>
 license: Apache-2.0
 base: ubuntu:20.04
+run-user: _daemon_
 services:
   sklearnserver:
     override: replace
     summary: "sklearnserver service"
     startup: enabled
     # Yet again, use a subshell to jam conda into a working state. Can't use bashrc, because it immediately
-    # exits if PS1 isn't set, so no-go from scripts
-    command: bash -c 'cd /microservice && export PATH=/opt/conda/bin/${PATH} && eval $(/opt/conda/bin/conda shell.bash hook 2> /dev/null) && source /opt/conda/etc/profile.d/conda.sh && conda activate && seldon-core-microservice $MODEL_NAME --service-type $SERVICE_TYPE --persistence $PERSISTENCE'
+    # exits if PS1 isn't set, so no-go from scripts.
+    command: bash -c 'cd /microservice && export PATH=/opt/conda/bin/:${PATH} && eval $(/opt/conda/bin/conda shell.bash hook 2> /dev/null) && source /opt/conda/etc/profile.d/conda.sh && conda activate && seldon-core-microservice ${MODEL_NAME} --service-type ${SERVICE_TYPE} &> /tmp/log.txt'
     environment:
+      # the following environment variables are taken from:
+      # https://github.com/SeldonIO/seldon-core/blob/master/servers/sklearnserver/environment
+      # NOTE: PERSISTENCE is omitted because it is depricated
       MODEL_NAME: "SKLearnServer"
       SERVICE_TYPE: "MODEL"
-      PERSISTENCE: "0"
-    user: ubuntu
-
 platforms:
   amd64:
 
@@ -78,13 +80,6 @@ parts:
       # but it does need to match pebble's workdir
       install -D -m 755 ${CRAFT_STAGE}/microservice/SKLearnServer.py microservice/SKLearnServer.py
 
-  non-root-user:
-    plugin: nil
-    overlay-script: |
-      # Create a user in the $CRAFT_OVERLAY chroot
-      groupadd -R $CRAFT_OVERLAY -g 1001 ubuntu
-      useradd -R $CRAFT_OVERLAY -M -r -u 1001 -g ubuntu ubuntu
-
   security-team-requirement:
     plugin: nil
     after: [sklearnserver]

sklearnserver/tests/test_rock.py

@@ -32,7 +32,10 @@ def test_rock(ops_test: OpsTest, rock_test_env):
     """Test rock."""
     check_rock = CheckRock("rockcraft.yaml")
     container_name = rock_test_env
-    LOCAL_ROCK_IMAGE = check_rock.get_image_name()
+    LOCAL_ROCK_IMAGE = f"{check_rock.get_image_name()}:{check_rock.get_version()}"
 
     # verify that all artifacts are in correct locations
     subprocess.run(["docker", "run", LOCAL_ROCK_IMAGE, "exec", "ls", "-la", "/microservice/SKLearnServer.py"], check=True)
+
+    # verify that rockcraft.yaml contains correct image name for PREDICTIVE_UNIT_IMAGE environment variable
+    #assert CheckRock.get_environment()["PREDICTIVE_UNIT_IMAGE"].contains(LOCAL_ROCK_IMAGE)

sklearnserver/tox.ini

@@ -66,11 +66,12 @@ commands =
                     print(CheckRock("rockcraft.yaml").get_version())'\'') && \
              sudo skopeo --insecure-policy copy oci-archive:$ROCK.rock docker-daemon:$ROCK:$VERSION && \
              docker save $ROCK > $ROCK.tar && \
-             microk8s ctr image import $ROCK.tar && \
+             microk8s ctr image import $ROCK.tar --digests=true && \
 	     predictor_servers=$(yq e ".data.predictor_servers" {env:LOCAL_CHARM_DIR}/src/templates/configmap.yaml.j2) && \
              predictor_servers=$(jq --arg jq_rock $ROCK -r '\''.SKLEARN_SERVER.protocols.seldon.image=$jq_rock'\'' <<< $predictor_servers) && \
              predictor_servers=$(jq --arg jq_version $VERSION -r '\''.SKLEARN_SERVER.protocols.seldon.defaultImageVersion=$jq_version'\'' <<< $predictor_servers) yq e -i ".data.predictor_servers=strenv(predictor_servers)" {env:LOCAL_CHARM_DIR}/src/templates/configmap.yaml.j2'
     # replace yq safe placeholder with original value
     sed -i "s/namespace: YQ_SAFE/namespace: {{ namespace }}/" {env:LOCAL_CHARM_DIR}/src/templates/configmap.yaml.j2
     # run charm integration test with rock
     tox -c {env:LOCAL_CHARM_DIR} -e integration
+