before.sh.erb

# This script (`before.sh.erb`) is sourced directly into the main Bash script
# that is run when the batch job starts up. It is called before the `script.sh`
# is forked off into a separate process.
#
# There are some helpful Bash functions that are made available to this script
# that encapsulate commonly used routines when initializing a web server:
#
#   - find_port
#       Find available port in range [$1..$2]
#       Default: 2000 65535
#
#   - create_passwd
#       Generate random alphanumeric password with $1 characters
#       Default: 32
#
# We **MUST** supply the following environment variables in this
# `before.sh.erb` script so that a user can connect back to the web server when
# it is running (case-sensitive variable names):
#
#   - $host (already defined earlier, so no need to define again)
#       The host that the web server is listening on
#
#   - $port
#       The port that the web server is listening on
#
#   - $password
#       The plain text password used to authenticate to the web server with

# Export the module function if it exists
[[ $(type -t module) == "function" ]] && export -f module

# Find available port to run server on
port=$(find_port)

# Generate SHA1 encrypted password (requires OpenSSL installed)
SALT="$(create_passwd 16)"
password="$(create_passwd 16)"
PASSWORD_SHA1="$(echo -n "${password}${SALT}" | openssl dgst -sha1 | awk '{print $NF}')"

# The `$CONFIG_FILE` environment variable is exported as it is used in the main
# `script.sh.erb` file when launching the Jupyter Notebook server.
export CONFIG_FILE="${PWD}/config.py"

# Generate Jupyter configuration file with secure file permissions
(
umask 077
cat > "${CONFIG_FILE}" << EOL
c.NotebookApp.ip = '*'
c.NotebookApp.port = ${port}
c.NotebookApp.port_retries = 0
c.NotebookApp.password = u'sha1:${SALT}:${PASSWORD_SHA1}'
c.NotebookApp.base_url = '/node/${host}/${port}/'
c.NotebookApp.open_browser = False
c.NotebookApp.allow_origin = '*'
c.NotebookApp.notebook_dir = '${HOME}'
c.NotebookApp.disable_check_xsrf = True
EOL
)