#!/usr/bin/env bash
# Munin plugin for ILIAS

: << =cut

=head1 NAME

ilias_session - Munin plugin to monitor L<ILIAS|https://ilias.de/> open source
learning management system's sessions

=head1 DESCRIPTION

Reads session and user statistcs from any ILIAS MySQL/MariaDB database.

https://ilias.de/ | http://gallery.munin-monitoring.org/contrib/cms-index.html

Requirements:

bash version 4 is required for associative array support.
This plugin requires mysql CLI or a compatible client being available.

In order to get precise results, please ensure your MySQL server has the same
time as your ILIAS application server. Timezone does not matter.

=head1 CONFIGURATION

The plugin needs the following configuration settings e.g. in
/etc/munin/plugin-conf.d/ilias.conf

    [ilias_session]
        env.ildbuser ilias
        env.ildbpassword youriliaspasword
        env.ildb ilias
        env.ildbhost localhost
        env.ildbport 3306

WARNING: Setting env.ildbpassword will possibly expose the database password
to other processes and might be insecure.

=head1 AUTHOR

Copyright 2018 L<Felix Pahlow|https://wohlpa.de/>
               (L<email|mailto:felix.pahlow@wohlpa.de>)

=head1 LICENSE

Licensed under the MIT license:
https://opensource.org/licenses/MIT

=head1 CONTRIBUTE

Find this plugin on L<GitHub
|https://github.com/munin-monitoring/contrib/tree/master/plugins/ilias>

=head1 MAGIC MARKERS

 #%# family=auto
 #%# capabilities=autoconf

=head1 VERSION

    2.0

=head1 CHANGELOG

=head2 2.0 - 2018/04/20

    first sh release

=head2 1.0 - 2018/03/19

    first release

=cut

# Include plugin.sh
# shellcheck source=/dev/null
. "${MUNIN_LIBDIR:-}/plugins/plugin.sh"

# Shell options
set -o nounset  # Like perl use strict;

# Graph settings
global_attr="
    graph_title ILIAS session and logins
    graph_category cms
    graph_args --lower-limit 0
    graph_vlabel occurrences
    graph_info Number of active ILIAS user sessions and logins
"

declare -A d_attr=( \
    [0,field]=iltotal1day \
    [0,type]=GAUGE \
    [0,draw]=LINE \
    [0,label]='users logged in within day' \
    [0,sql]="SELECT COUNT( usr_id ) AS C
           FROM \`usr_data\`
           WHERE last_login >= DATE_SUB( NOW( ) , INTERVAL 1 DAY )
    " \
    [1,field]=ilsessions \
    [1,type]=GAUGE \
    [1,draw]=LINE \
    [1,label]='active sessions' \
    [1,sql]="SELECT COUNT( user_id ) AS C
           FROM usr_session
           WHERE \`expires\` > UNIX_TIMESTAMP( NOW( ) ) AND user_id != 0
    " \
    [2,field]=il60minavg \
    [2,type]=GAUGE \
    [2,draw]=LINE \
    [2,label]='sessions created/updated within 1h' \
    [2,sql]="SELECT COUNT( user_id ) AS C
           FROM usr_session
           WHERE 60 * 60 > UNIX_TIMESTAMP( NOW( ) ) - ctime AND user_id != 0
    " \
    [3,field]=il5minavg \
    [3,type]=GAUGE \
    [3,draw]=LINE \
    [3,label]='sessions created/updated within 5min' \
    [3,sql]="SELECT COUNT( user_id ) AS C
           FROM usr_session
           WHERE 5 * 60 > UNIX_TIMESTAMP( NOW( ) ) - ctime AND user_id != 0
    " \
)

# Read the environment and apply defaults
DB_CLI_TOOL="${ildbcli:-mysql}"
DB_CLI_CMD="$(command -v "${DB_CLI_TOOL}")"
DB_HOST="${ildbhost:-localhost}"
DB_PORT="${ildbport:-3306}"
DB="${ildb:-ilias}"
DB_USER="${ildbuser:-root}"
DB_PASSWORD="${ildbpassword:-}"

# Functions

autoconf() {
    if command -v "${DB_CLI_TOOL}" >/dev/null ; then
        echo yes
    else
        echo "no (failed to find executable '${DB_CLI_TOOL}')"
    fi
}

config() {
    local label_max_length=45
    local i=0

    # print global attributes
    echo "$global_attr" | sed -e 's/^  *//' -e '/^$/d'

    i=0
    # -v varname
    # True if the shell variable varname is set (has been assigned a value).
    # https://stackoverflow.com/a/45385463/2683737
    # shellcheck disable=SC2102
    while [[ -v d_attr[$i,field] ]]; do
       field=${d_attr[$i,field]}
       echo "$field.type ${d_attr[$i,type]}"
       echo "$field.draw ${d_attr[$i,draw]}"
       echo "$field.label ${d_attr[$i,label]:0:${label_max_length}}"
       echo "$field.min 0"
       ((++i))
    done
}

# Join a bash array $1 is the glue
join_by() {
    local d=$1
    shift
    echo -n "$1"
    shift
    printf "%s" "${@/#/$d}"
}

fetch() {
    local i=0
    local query=()
    local query_string=""
    declare -a results

    # create an array of queries
    i=0
    # shellcheck disable=SC2102
    while [[ -v d_attr[$i,field] ]]; do
        query+=("${d_attr[$i,sql]}")
        ((++i))
    done

    # build query by joining the array elements
    query_string=$(join_by " UNION ALL " "${query[@]}")

    # obtain result using CLI call; don't supply password through
    # command line; note that MySQL considers it insecure using
    # an environment variable:
    # >This method of specifying your MySQL password must
    # >be considered extremely insecure and should not be used.
    # >Some versions of ps include an option to display the
    # >environment of running processes. [...]
    result=$(MYSQL_PWD="$DB_PASSWORD" \
             "$DB_CLI_CMD" \
            --skip-column-names \
            -h "$DB_HOST" \
            -u "$DB_USER" \
            -P "$DB_PORT" \
            "$DB" \
            -e "$query_string" )

    # initialize array
    mapfile -t results  <<< "$result"

    # extract result and echo it to stdout, which is
    # captured by Munin
    i=0
    # shellcheck disable=SC2102
    while [[ -v d_attr[$i,field] ]]; do
        echo "${d_attr[$i,field]}.value ${results[$i]}"
        ((++i))
    done
}


# Main
case ${1:-} in
autoconf)
    autoconf
    ;;
config)
    config
    [ "${MUNIN_CAP_DIRTYCONFIG:-}" = "1" ] && fetch
    ;;
*)
    fetch
    ;;
esac

exit 0