wait until the transmission-daemon terminates properly

[0b100100]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description:

We should wait for the termination of the transmission-daemon before the s6 service issues a sigterm to all remaining processes.
Without this delay the s6 sigterms are issued right after the RPC 'transmission-remote --exit'. This leaves not time to properly save the settings.json file, stats.json file, all resume files and showing the closing message 'Closing transmission session... done'.

Benefits of this PR and context:

This PR closes #80.

How Has This Been Tested?

docker-compose.yml:

version: '2'
services:
  transmission:
    image: linuxserver/transmission
    container_name: transmission
    environment:
      - PUID=1000
      - PGID=1000
      - TZ=Europe/London
      - TRANSMISSION_WEB_HOME=/transmission-web-control/
      - USER=username
      - PASS=password
    volumes:
      - /root/transmission_config:/config
      - /root/Downloads/transmission:/downloads
      - /root/Downloads/transmission/watch:/watch
    ports:
      - 9091:9091
      - 51413:51413
      - 51413:51413/udp

Build:

# git clone https://github.com/linuxserver/docker-transmission.git
# cd docker-transmission
# docker build \
  --no-cache \
  --pull \
  -t linuxserver/transmission:latest .

Start:

# docker-compose up -d

Log after issuing docker-compose down without the fix:

# docker logs -f transmission
...
Caught SIGTERM signal!
localhost:9091/transmission/rpc/ responded: "success"
[cont-finish.d] executing container finish scripts...
[cont-finish.d] done.
[s6-finish] waiting for services.
[s6-finish] sending all processes the TERM signal.
[2021-07-09 00:47:24.210] Reloading settings from "/config" (/home/buildozer/aports/community/transmission/src/transmission-3.00/daemon/daemon.c:592)
[2021-07-09 00:47:24.210] RPC Server Serving RPC and Web requests on 0.0.0.0:9091/transmission/ (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/rpc-server.c:1243)
[2021-07-09 00:47:24.210] RPC Server Password required (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/rpc-server.c:1254)
[2021-07-09 00:47:24.210] Saved "/config/settings.json" (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/variant.c:1221)
[2021-07-09 00:47:24.210] DHT Not saving nodes, DHT not ready (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/tr-dht.c:445)
[2021-07-09 00:47:24.210] Port Forwarding Stopped (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/port-forwarding.c:196)
Closing transmission session... done.
[s6-finish] sending all processes the KILL signal and exiting.

Log after issuing docker-compose down with the fix:

...
Caught SIGTERM signal!
Tell the transmission session to shut down.
localhost:9091/transmission/rpc/ responded: "success"
Closing transmission session... done.
[2021-07-09 00:51:07.671] Saved "/config/settings.json" (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/variant.c:1221)
[2021-07-09 00:51:07.671] DHT Not saving nodes, DHT not ready (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/tr-dht.c:445)
[2021-07-09 00:51:07.671] Port Forwarding Stopped (/home/buildozer/aports/community/transmission/src/transmission-3.00/libtransmission/port-forwarding.c:196)
[cont-finish.d] executing container finish scripts...
[cont-finish.d] done.
[s6-finish] waiting for services.
[s6-finish] sending all processes the TERM signal.
[s6-finish] sending all processes the KILL signal and exiting.

Important line in the logs when the saving occurs:
... Saved "/config/settings.json" ...

Without the fix the old settings get reloaded right after the TERM signal by the S6 service.
This prevents saving changed settings from the Web-Interface:
... Reloading settings from "/config" ...

Source / References:

#80 (comment)

[github-actions]

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[LinuxServer-CI]

I am a bot, here are the test results for this PR:
https://ci-tests.linuxserver.io/lspipepr/transmission/3.00-r2-pkg-a91e9ad2-pr-167/index.html
https://ci-tests.linuxserver.io/lspipepr/transmission/3.00-r2-pkg-a91e9ad2-pr-167/shellcheck-result.xml

[aptalca]

Thanks for the PR. Let's get some test results in the issue topic, then we can merge.

In the meantime, please add a changelog entry to readme-vars.yml

[LinuxServer-CI]

I am a bot, here are the test results for this PR:
https://ci-tests.linuxserver.io/lspipepr/transmission/3.00-r2-pkg-a91e9ad2-pr-167/index.html
https://ci-tests.linuxserver.io/lspipepr/transmission/3.00-r2-pkg-a91e9ad2-pr-167/shellcheck-result.xml