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linux-scripts/dokku-exporter.sh
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#!/bin/bash
################################################################################
# Script Name: dokku-exporter.sh
# Version: 1.0
# Description: Prometheus exporter for Dokku PaaS providing operational
# metrics via the Dokku CLI — application status, plugin counts,
# domain configuration, SSL status, and host health
#
# Author: Phil Connor
# Contact: contact@mylinux.work
# Website: https://mylinux.work
# License: MIT
#
# Prerequisites:
# - Dokku installed on the local host
# - Root or dokku user access to run dokku commands
# - netcat (nc) for HTTP mode
#
# Usage:
# # Output to stdout
# ./dokku-exporter.sh
#
# # HTTP server mode
# ./dokku-exporter.sh --http -p 9198
#
# # Textfile collector mode
# ./dokku-exporter.sh --textfile
#
# Metrics Exported:
# - dokku_up - Dokku reachability (1=up, 0=down)
# - dokku_info{version} - Dokku version info
# - dokku_apps_total - Total app count
# - dokku_apps_running - Running apps
# - dokku_apps_stopped - Stopped apps
# - dokku_plugins_total - Installed plugin count
# - dokku_domains_app_total - Total app domains configured
# - dokku_ssl_enabled_total - Apps with SSL enabled
# - dokku_exporter_duration_seconds - Script execution time
# - dokku_exporter_last_run_timestamp - Last run timestamp
#
# Configuration:
# Default HTTP port: 9198
# Textfile directory: /var/lib/node_exporter
#
################################################################################
set -euo pipefail
# ============================================================================
# CONFIGURATION VARIABLES
# ============================================================================
TEXTFILE_DIR="/var/lib/node_exporter"
OUTPUT_FILE=""
HTTP_MODE=false
HTTP_PORT=9198
# ============================================================================
# HELPER FUNCTIONS
# ============================================================================
show_usage() {
cat <<EOF
Usage: $0 [OPTIONS]
Export Dokku PaaS statistics as Prometheus metrics via the Dokku CLI.
MODES:
--textfile Write to node_exporter textfile collector
--http Run HTTP server on port $HTTP_PORT
OPTIONS:
-p, --port HTTP port (default: 9198)
-o, --output Output file path
EXAMPLES:
$0 --textfile # Write to textfile collector
$0 --http --port 9198 # Run HTTP server
$0 # Output to stdout
$0 -o /tmp/dokku.prom # Write to custom file
EOF
exit 0
}
parse_args() {
while [[ $# -gt 0 ]]; do
case $1 in
-h|--help) show_usage ;;
--textfile) OUTPUT_FILE="$TEXTFILE_DIR/dokku.prom"; shift ;;
--http) HTTP_MODE=true; shift ;;
-p|--port) HTTP_PORT="$2"; shift 2 ;;
-o|--output) OUTPUT_FILE="$2"; shift 2 ;;
*) echo "Unknown option: $1" >&2; exit 1 ;;
esac
done
}
# Check prerequisites
# Returns: 0 if OK, 1 if error
check_prerequisites() {
if ! command -v dokku >/dev/null 2>&1; then
echo "ERROR: dokku not found" >&2
return 1
fi
return 0
}
# Escape special characters in Prometheus label values
# Args: $1 - string to escape
# Returns: escaped string safe for Prometheus labels
prom_escape() {
local val="$1"
val="${val//\\/\\\\}"
val="${val//\"/\\\"}"
val="${val//$'\n'/}"
echo "$val"
}
# ============================================================================
# METRIC GENERATION
# ============================================================================
# Generate all Prometheus metrics
# Returns: Prometheus text format metrics on stdout
generate_metrics() {
local script_start
script_start=$(date +%s)
# Check prerequisites
if ! check_prerequisites; then
cat <<EOF
# HELP dokku_up Dokku reachability (1=up, 0=down)
# TYPE dokku_up gauge
dokku_up 0
EOF
return
fi
# Verify Dokku is responding
local version_output
version_output=$(dokku version 2>/dev/null)
if [ -z "$version_output" ]; then
cat <<EOF
# HELP dokku_up Dokku reachability (1=up, 0=down)
# TYPE dokku_up gauge
dokku_up 0
EOF
return
fi
# Extract version string (e.g., "dokku version 0.38.0" -> "0.38.0")
local dokku_version
dokku_version=$(echo "$version_output" | awk '{print $NF}')
if [ -z "$dokku_version" ]; then
cat <<EOF
# HELP dokku_up Dokku reachability (1=up, 0=down)
# TYPE dokku_up gauge
dokku_up 0
EOF
return
fi
cat <<EOF
# HELP dokku_up Dokku reachability (1=up, 0=down)
# TYPE dokku_up gauge
dokku_up 1
EOF
echo ""
# ========================================================================
# VERSION INFO
# ========================================================================
cat <<EOF
# HELP dokku_info Dokku version information
# TYPE dokku_info gauge
dokku_info{version="$(prom_escape "$dokku_version")"} 1
EOF
echo ""
# ========================================================================
# APPLICATION METRICS
# ========================================================================
local apps_list
apps_list=$(dokku --quiet apps:list 2>/dev/null || true)
local total_apps=0
local running_apps=0
local stopped_apps=0
if [ -n "$apps_list" ]; then
total_apps=$(echo "$apps_list" | wc -l)
total_apps=${total_apps:-0}
# Count running apps by checking each app's process status
while IFS= read -r app; do
local ps_running
ps_running=$(dokku ps:report "$app" --ps-running 2>/dev/null || echo "false")
if [ "$ps_running" = "true" ]; then
running_apps=$((running_apps + 1))
fi
done <<< "$apps_list"
stopped_apps=$((total_apps - running_apps))
fi
cat <<EOF
# HELP dokku_apps_total Total number of apps
# TYPE dokku_apps_total gauge
dokku_apps_total $total_apps
# HELP dokku_apps_running Running apps
# TYPE dokku_apps_running gauge
dokku_apps_running $running_apps
# HELP dokku_apps_stopped Stopped apps
# TYPE dokku_apps_stopped gauge
dokku_apps_stopped $stopped_apps
EOF
echo ""
# ========================================================================
# PLUGIN METRICS
# ========================================================================
local plugins_count=0
plugins_count=$(dokku plugin:list 2>/dev/null | wc -l)
plugins_count=${plugins_count:-0}
cat <<EOF
# HELP dokku_plugins_total Installed plugins
# TYPE dokku_plugins_total gauge
dokku_plugins_total $plugins_count
EOF
echo ""
# ========================================================================
# DOMAIN METRICS
# ========================================================================
local total_domains=0
if [ -n "$apps_list" ]; then
while IFS= read -r app; do
local app_domains
app_domains=$(dokku domains:report "$app" --domains-app-vhosts 2>/dev/null || true)
if [ -n "$app_domains" ]; then
# Domains are space-separated; count words
local domain_count
domain_count=$(echo "$app_domains" | wc -w)
total_domains=$((total_domains + domain_count))
fi
done <<< "$apps_list"
fi
cat <<EOF
# HELP dokku_domains_app_total Total app domains configured
# TYPE dokku_domains_app_total gauge
dokku_domains_app_total $total_domains
EOF
echo ""
# ========================================================================
# SSL METRICS
# ========================================================================
local ssl_enabled_count=0
if [ -n "$apps_list" ]; then
while IFS= read -r app; do
local ssl_enabled
ssl_enabled=$(dokku certs:report "$app" --certs-ssl-enabled 2>/dev/null || echo "false")
if [ "$ssl_enabled" = "true" ]; then
ssl_enabled_count=$((ssl_enabled_count + 1))
fi
done <<< "$apps_list"
fi
cat <<EOF
# HELP dokku_ssl_enabled_total Apps with SSL enabled
# TYPE dokku_ssl_enabled_total gauge
dokku_ssl_enabled_total $ssl_enabled_count
EOF
echo ""
# ========================================================================
# EXPORTER RUNTIME
# ========================================================================
local script_end script_duration
script_end=$(date +%s)
script_duration=$((script_end - script_start))
cat <<EOF
# HELP dokku_exporter_duration_seconds Time to generate all metrics
# TYPE dokku_exporter_duration_seconds gauge
dokku_exporter_duration_seconds $script_duration
# HELP dokku_exporter_last_run_timestamp Unix timestamp of last successful run
# TYPE dokku_exporter_last_run_timestamp gauge
dokku_exporter_last_run_timestamp $script_end
EOF
echo ""
}
# ============================================================================
# HTTP SERVER MODE
# ============================================================================
# Run simple HTTP server using netcat
# Serves metrics on /metrics endpoint
run_http_server() {
echo "Starting Dokku exporter on port $HTTP_PORT..." >&2
if ! command -v nc >/dev/null 2>&1; then
echo "ERROR: netcat (nc) required for HTTP mode" >&2
exit 1
fi
# Infinite loop accepting HTTP requests
while true; do
{
read -r request
# Check if request is for /metrics endpoint
if [[ "$request" =~ ^GET\ /metrics ]]; then
echo -e "HTTP/1.1 200 OK\r\nContent-Type: text/plain; version=0.0.4\r\n\r"
generate_metrics
else # Serve HTML landing page for other requests
echo -e "HTTP/1.1 200 OK\r\nContent-Type: text/html\r\n\r"
cat <<EOF
<!DOCTYPE html>
<html>
<head><title>Dokku Exporter v1.0</title></head>
<body>
<h1>Dokku Prometheus Exporter v1.0</h1>
<p><a href="/metrics">Metrics</a></p>
<p>Operational metrics from the Dokku CLI.</p>
</body>
</html>
EOF
fi
} | nc -l -p "$HTTP_PORT" -q 1 2>/dev/null
done
}
# ============================================================================
# MAIN EXECUTION
# ============================================================================
# Main entry point - routes to appropriate output mode
main() {
parse_args "$@"
if [ "$HTTP_MODE" = true ]; then
# Run HTTP server (blocks until killed)
run_http_server
elif [ -n "$OUTPUT_FILE" ]; then
# Textfile collector mode: write atomically using temp file
local output_dir
output_dir="$(dirname "$OUTPUT_FILE")"
mkdir -p "$output_dir"
# Create temp file in SAME directory for atomic rename (same filesystem)
local temp_file
temp_file=$(mktemp "${output_dir}/.dokku_metrics.XXXXXX")
# Generate metrics to temp file
if ! generate_metrics > "$temp_file" 2>/dev/null; then
rm -f "$temp_file"
echo "ERROR: Failed to generate metrics" >&2
exit 1
fi
# Validate: file must exist, have content
local file_lines
file_lines=$(wc -l < "$temp_file" 2>/dev/null || echo 0)
if [ "$file_lines" -lt 10 ]; then
rm -f "$temp_file"
echo "ERROR: Metrics file too small ($file_lines lines), keeping previous" >&2
exit 1
fi
# Set permissions before move
chmod 644 "$temp_file"
# Atomic rename - no gap where file is missing
mv -f "$temp_file" "$OUTPUT_FILE"
echo "Metrics written to $OUTPUT_FILE ($file_lines lines)" >&2
else
# Default: output to stdout
generate_metrics
fi
}
# Execute main function with all script arguments
main "$@"