Fix classic snap (#80)

* Refactor to reduce errors
* Revert to building classic on core20

make-classic.sh

@@ -1,13 +1,11 @@
 #!/bin/sh
 
+# The classic snap needs to be built on core20 because of libc6 dependency:
+# A core22 snap needs glibc 2.32+, but in a 20.04 charm we have glibc 2.31.
 sed -i 's/base: core22/base: core20/g' snap/snapcraft.yaml
 sed -i 's/confinement: strict/confinement: classic/g' snap/snapcraft.yaml
 sed -i 's/CRAFT_PART_INSTALL/SNAPCRAFT_PART_INSTALL/g' snap/snapcraft.yaml
 sed -i '/libbpfcc/d' snap/snapcraft.yaml
 sed -i '/bpfcc-tools/d' snap/snapcraft.yaml
 yq -i 'del(.apps.grafana-agent.plugs) | del(.plugs)' snap/snapcraft.yaml
-cat << "EOF" > snap/local/agent-wrapper
-#!/bin/sh
-
-exec "${SNAP}/agent" -config.expand-env -config.file "/etc/grafana-agent.yaml"
-EOF
+sed -i 's/agent-wrapper.strict/agent-wrapper.classic/g' snap/snapcraft.yaml

snap/local/agent-wrapper.classic

@@ -0,0 +1,12 @@
+#!/bin/sh
+
+if [ "$(snapctl get reporting-enabled)" = "0" ]
+then
+  echo "Launched with reporting disabled" | systemd-cat
+  REPORTING_ARG="-disable-reporting"
+else
+  echo "Launched with reporting enabled" | systemd-cat
+  REPORTING_ARG=""
+fi
+
+exec "${SNAP}/agent" -config.expand-env -config.file "/etc/grafana-agent.yaml" "${REPORTING_ARG}"

snap/snapcraft.yaml

@@ -51,7 +51,7 @@ parts:
     source: ./snap/local
     source-type: local
     override-build: |
-      cp agent-wrapper $CRAFT_PART_INSTALL/
+      cp agent-wrapper.strict $CRAFT_PART_INSTALL/agent-wrapper
   grafana-agent:
     plugin: go
     source: https://github.com/grafana/agent