scripts: refactored daemon-stack.sh (#2496)

* refactored `daemon-stack.sh`

A new method was introduced to uniformaly start daemons and log output
accordingly. The methods for daemon start were renamed (plural ->
singular), therefore the adjustments in `start-mailserver.sh`.

* cleaned Fetchmail setup from `daemon-stack.sh`

Not sure why, but the Fetchmail setup was somehow happening in
`daemon-stack.sh` - this is not supposed to be the case. I relocated the
setup into `setup-stack.sh`, where it belong.

* delete old, unnecessary script in `target/bin/`

These are unused leftovers from the last commit, that relocated the
setup of Fetchmail into `setup.stack.sh`.

* corrected changedetector function name

* Apply suggestions from code review

* adjusted `debug-fetchmail` script

It is absolutely fine to source `setup-stack.sh` because sourcing the
script does not execute a single function (by desing of the script).
This way, we retain functionality.

* praise be ShellCheck

* added `log.sh` to `debug-fetchmail` as a dependency

* final cleanup

Co-authored-by: Brennan Kinney <5098581+polarathene@users.noreply.github.com>
Co-authored-by: Casper <casperklein@users.noreply.github.com>

target/scripts/startup/setup-stack.sh

@@ -1160,3 +1160,106 @@ function _setup_dnsbl_disable
   postconf -e "postscreen_dnsbl_action = ignore"
   postconf -e "postscreen_dnsbl_sites = "
 }
+
+function _setup_fetchmail
+{
+  _log 'trace' 'Preparing Fetchmail configuration'
+
+  local CONFIGURATION FETCHMAILRC
+
+  CONFIGURATION='/tmp/docker-mailserver/fetchmail.cf'
+  FETCHMAILRC='/etc/fetchmailrc'
+
+  if [[ -f ${CONFIGURATION} ]]
+  then
+    cat /etc/fetchmailrc_general "${CONFIGURATION}" >"${FETCHMAILRC}"
+  else
+    cat /etc/fetchmailrc_general >"${FETCHMAILRC}"
+  fi
+
+  chmod 700 "${FETCHMAILRC}"
+  chown fetchmail:root "${FETCHMAILRC}"
+}
+
+function _setup_fetchmail_parallel
+{
+  _log 'trace' 'Setting up Fetchmail parallel'
+  mkdir /etc/fetchmailrc.d/
+
+  # Split the content of /etc/fetchmailrc into
+  # smaller fetchmailrc files per server [poll] entries. Each
+  # separate fetchmailrc file is stored in /etc/fetchmailrc.d
+  #
+  # The sole purpose for this is to work around what is known
+  # as the Fetchmail IMAP idle issue.
+  function _fetchmailrc_split
+  {
+    local FETCHMAILRC='/etc/fetchmailrc'
+    local FETCHMAILRCD='/etc/fetchmailrc.d'
+    local DEFAULT_FILE="${FETCHMAILRCD}/defaults"
+
+    if [[ ! -r ${FETCHMAILRC} ]]
+    then
+      _log 'warn' "File '${FETCHMAILRC}' not found"
+      return 1
+    fi
+
+    if [[ ! -d ${FETCHMAILRCD} ]]
+    then
+      if ! mkdir "${FETCHMAILRCD}"
+      then
+        _log 'warn' "Unable to create folder '${FETCHMAILRCD}'"
+        return 1
+      fi
+    fi
+
+    local COUNTER=0 SERVER=0
+    while read -r LINE
+    do
+      if [[ ${LINE} =~ poll ]]
+      then
+        # If we read "poll" then we reached a new server definition
+        # We need to create a new file with fetchmail defaults from
+        # /etc/fetcmailrc
+        COUNTER=$(( COUNTER + 1 ))
+        SERVER=1
+        cat "${DEFAULT_FILE}" >"${FETCHMAILRCD}/fetchmail-${COUNTER}.rc"
+        echo "${LINE}" >>"${FETCHMAILRCD}/fetchmail-${COUNTER}.rc"
+      elif [[ ${SERVER} -eq 0 ]]
+      then
+        # We have not yet found "poll". Let's assume we are still reading
+        # the default settings from /etc/fetchmailrc file
+        echo "${LINE}" >>"${DEFAULT_FILE}"
+      else
+        # Just the server settings that need to be added to the specific rc.d file
+        echo "${LINE}" >>"${FETCHMAILRCD}/fetchmail-${COUNTER}.rc"
+      fi
+    # delete commented lines before parsing
+    done < <(sed '/^[[:space:]]*#/d' "${FETCHMAILRC}")
+
+    rm "${DEFAULT_FILE}"
+  }
+
+  _fetchmailrc_split
+
+  local COUNTER=0
+  for RC in /etc/fetchmailrc.d/fetchmail-*.rc
+  do
+    COUNTER=$(( COUNTER + 1 ))
+    cat >"/etc/supervisor/conf.d/fetchmail-${COUNTER}.conf" << EOF
+[program:fetchmail-${COUNTER}]
+startsecs=0
+autostart=false
+autorestart=true
+stdout_logfile=/var/log/supervisor/%(program_name)s.log
+stderr_logfile=/var/log/supervisor/%(program_name)s.log
+user=fetchmail
+command=/usr/bin/fetchmail -f ${RC} -v --nodetach --daemon %(ENV_FETCHMAIL_POLL)s -i /var/lib/fetchmail/.fetchmail-UIDL-cache --pidfile /var/run/fetchmail/%(program_name)s.pid
+EOF
+    chmod 700 "${RC}"
+    chown fetchmail:root "${RC}"
+  done
+
+  supervisorctl reread
+  supervisorctl update
+}