# Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
# Use of this source code is governed by a BSD-style license that can be
# found in the LICENSE file.

description   "Reboot device upon repeated user interface crash."
author        "chromium-os-dev@chromium.org"

# The ui job requires special respawning logic, as the system needs to respond
# differently to different kinds of exits.
#
# 0: Normal exit; respawn forever.
# 2: (Defined in session_manager_service.h) The browser is exiting too much too
#    quickly. In some cases, such as a hung GPU, rebooting the device will allow
#    the system to recover. Respawn up to TOO_CRASHY_LIMIT times in
#    TOO_CRASHY_WINDOW_SECONDS before trying a reboot. Try this up to
#    REBOOT_LIMIT times in REBOOT_WINDOW_SECONDS before giving up and waiting
#    for an AU.
# All nonzero: respawn up to RESPAWN_LIMIT times in RESPAWN_WINDOW_SECONDS,
#              then stop.
start on stopping ui

script
  RESPAWN_LIMIT=6
  RESPAWN_WINDOW_SECONDS=60
  RESPAWN_TIMESTAMP_FILE=/tmp/ui-respawn-timestamps

  CHILD_EXITING_TOO_FAST=2  # Defined in session_manager_service.h
  TOO_CRASHY_LIMIT=1
  TOO_CRASHY_WINDOW_SECONDS=180
  TOO_CRASHY_TIMESTAMP_FILE=/tmp/ui-too-crashy-timestamps

  REBOOT_LIMIT=1
  REBOOT_WINDOW_SECONDS=$(( 3 * TOO_CRASHY_WINDOW_SECONDS ))
  REBOOT_TIMESTAMP_DIR=/var/lib/ui
  REBOOT_TIMESTAMP_FILE="${REBOOT_TIMESTAMP_DIR}"/reboot-timestamps

  # Given a file full of timestamps, appends a timestamp for 'now', and then
  # trims it to include only timestamps in 'now' - |time|.
  # Succeeds if there are <= than |limit| timestamps remaining in |file|
  # after this operation, fails otherwise.
  #  file: the name of the file containing timestamps (in s), one per line.
  #  time: the window of time, prior to now, that we consider.
  #  limit: the number of timestamps we're willing to allow.
  under_limit() {
    local file=$1
    local time=$2
    local limit=$3

    local tfile=$(mktemp)
    local curtime=$(date +%s)
    echo $curtime >>$file  # To ensure the file exists.
    awk "\$0 >= $curtime - $time" $file >$tfile
    mv $tfile $file

    if [ $(wc -l < $file) -gt $limit ]; then
      return 1
    else
      return 0
    fi
  }

  over_ui_crash_limit() {
    ! under_limit $TOO_CRASHY_TIMESTAMP_FILE $TOO_CRASHY_WINDOW_SECONDS \
        $TOO_CRASHY_LIMIT
  }

  under_reboot_limit() {
    under_limit $REBOOT_TIMESTAMP_FILE $REBOOT_WINDOW_SECONDS \
        $REBOOT_LIMIT
  }

  under_respawn_limit() {
    under_limit $RESPAWN_TIMESTAMP_FILE $RESPAWN_WINDOW_SECONDS \
        $RESPAWN_LIMIT
  }

  # Create the directory where reboot timestamps (which must persist across
  # reboots) will live.
  mkdir -p "${REBOOT_TIMESTAMP_DIR}"

  # if ${RESULT} = "ok", that means the job was stopped manually, so we want
  # to avoid respawning. Otherwise, we want to kick in the logic.
  if [ "${RESULT}" != "ok" ]; then
    if [ "${EXIT_STATUS}" = "0" ] ; then
      start -n "${JOB}"  # start ui job again, always.
    else
      if [ "${EXIT_STATUS}" = "${CHILD_EXITING_TOO_FAST}" ]; then
        if over_ui_crash_limit ; then
          if under_reboot_limit ; then
            logger -t ${UPSTART_JOB} "Rebooting to mitigate crashiness."
            reboot
          else
            logger -t ${UPSTART_JOB} "Rebooted too much; running respawn logic."
          fi
        else
          logger -t ${UPSTART_JOB} "Haven't been too crashy too much yet."
        fi
      fi

      if [ -n "${EXIT_STATUS}" ]; then
        logger -t ${UPSTART_JOB} "${JOB} failed with exit status ${EXIT_STATUS}."
      elif [ -n "${EXIT_SIGNAL}" ]; then
        logger -t ${UPSTART_JOB} "${JOB} died on signal ${EXIT_SIGNAL}."
      else
        logger -t ${UPSTART_JOB} "${JOB} died for mysterious and unknown reasons."
      fi

      # Generic respawn handling.
      if under_respawn_limit ; then
        logger -t ${UPSTART_JOB} "Respawning ${JOB}."
        start -n "${JOB}"
      else
        logger -t ${UPSTART_JOB} "Reached respawn limit for ${JOB}."
      fi
    fi
    # TODO(cmasone): http://crbug.com/266153 Show the user a splash
    # screen telling them to keep calm and carry on.
  fi
end script