20210823 Telegraf - experimental branch - PR 3 of 3

1. Implements self-repair functionality by adding `Dockerfile` and
`entrypoint.sh` to the Telegraf template.
2. Removes `telegraf.conf` from Telegraf template. The default
configuration file is now the one supplied with the container
downloaded from DockerHub. In other words, it will always be kept
up-to-date by the container's maintainers.
3. Alters service definition to:

	* use a persistent storage area in `./volumes/telegraf`
	* remove the old `./services/telegraf/telegraf.conf` file mapping
	* add explicit mappings for all exposed ports.

Note:

* I made no attempt to follow-up with changes to either `build.js` or
`config.js`.

Author: Paraphraser

.internal/templates/services/telegraf/buildFiles/Dockerfile

@@ -0,0 +1,20 @@
+# Download base image
+FROM telegraf:latest
+
+# Add support tool
+RUN apt update && apt install -y rsync
+
+# where IOTstack template files are stored
+ENV IOTSTACK_DEFAULTS_DIR="iotstack_defaults"
+
+# make a copy of the default config file
+RUN mkdir -p /${IOTSTACK_DEFAULTS_DIR} && \
+    cp /etc/telegraf/telegraf.conf /${IOTSTACK_DEFAULTS_DIR}/
+
+# replace the docker entry-point script with a self-repairing version
+ENV IOTSTACK_ENTRY_POINT="entrypoint.sh"
+COPY ${IOTSTACK_ENTRY_POINT} /${IOTSTACK_ENTRY_POINT}
+RUN chmod 755 /${IOTSTACK_ENTRY_POINT}
+ENV IOTSTACK_ENTRY_POINT=
+
+# EOF

.internal/templates/services/telegraf/buildFiles/entrypoint.sh

@@ -0,0 +1,18 @@
+#!/bin/bash
+set -e
+
+if [ "${1:0:1}" = '-' ]; then
+    set -- telegraf "$@"
+fi
+
+# perform IOTstack self-repair
+U="$(id -u)"
+T="/etc/telegraf"
+if [ "$U" = '0' -a -d "$T" ]; then
+   rsync -arp --ignore-existing /${IOTSTACK_DEFAULTS_DIR}/ "$T"
+   chown -R "$U:$U" "$T"
+fi
+
+exec "$@"
+
+

.internal/templates/services/telegraf/serviceFiles/telegraf.conf

@@ -1,11 +1,18 @@
 telegraf:
   container_name: telegraf
-  image: telegraf
+  build: ./.templates/telegraf/.
   restart: unless-stopped
+  environment:
+    - TZ=Etc/UTC
+  ports:
+    - "8092:8092/udp"
+    - "8094:8094/tcp"
+    - "8125:8125/udp"
   volumes:
-    - ./services/telegraf/telegraf.conf:/etc/telegraf/telegraf.conf:ro
+    - ./volumes/telegraf/:/etc/telegraf
   depends_on:
     - influxdb
     - mosquitto
   networks:
     - iotstack_nw
+