Supervise SafeSquid Processes With Monit

Monit automatically monitors SafeSquid and restarts it if it crashes or becomes unresponsive. It also performs housekeeping tasks like log rotation and temporary file cleanup. Why you need this: Without Monit, a SafeSquid crash requires manual intervention. In production, this means downtime until someone notices and restarts the service.

Prerequisites

:::note Before You Start

Linux host with systemd
Root or sudo access
SafeSquid installed and running
Log storage capacity for Monit logs

:::

Installation and Configuration

1. Install Monit

Debian/Ubuntu:

sudo apt update
sudo apt install -y monit

RHEL/Rocky/CentOS:

sudo dnf install -y monit

Verify installation:

monit -V

Expected result: This is Monit version 5.34.3 (the number varies by release), followed by the build options.

2. Enable Monit Service

sudo systemctl enable --now monit
systemctl is-active monit
systemctl is-enabled monit

Expected result: systemctl is-active monit prints active and systemctl is-enabled monit prints enabled.

3. Configure Monit HTTP Interface (Local Only)

Edit /etc/monit/monitrc:

sudo nano /etc/monit/monitrc

Add or uncomment:

set httpd port 2812 and
  use address localhost
  allow localhost

Save and reload:

sudo monit reload

Verify:

curl -s http://localhost:2812 | head -n1

Expected result: the first line of an HTML page that starts with <!DOCTYPE html> and contains the title Monit: followed by the hostname.

4. Add SafeSquid Process and Port Checks

Create /etc/monit/conf.d/safesquid:

sudo nano /etc/monit/conf.d/safesquid

Add:

check process safesquid with pidfile /var/run/safesquid/safesquid.pid
  start program = "/bin/systemctl start safesquid"
  stop  program = "/bin/systemctl stop safesquid"
  if failed port 8080 protocol http then restart
  if 3 restarts within 5 cycles then alert

Explanation:

Monitors SafeSquid process via PID file
Checks port 8080 for HTTP responsiveness
Auto-restarts if port check fails
Alerts if SafeSquid restarts 3+ times in 5 cycles (possible persistent issue)

Reload and verify:

sudo monit reload
sudo monit status safesquid

Expected result: status shows Running and OK.

5. Add Housekeeping Checks

Log Rotation Trigger: Create /etc/monit/conf.d/safesquid-logs:

sudo nano /etc/monit/conf.d/safesquid-logs

Add:

check file ss-log-size with path /var/log/safesquid/extended/extended.log
  if size > 500 MB then exec "/usr/sbin/logrotate -f /etc/logrotate.d/safesquid"

Temporary Files Cleanup: Add to the same file:

check directory ss-tmp with path /tmp
  if timestamp > 24 hours then exec "/usr/bin/find /tmp -type f -mtime +1 -delete"

:::caution Cleanup Script Risk The temp file cleanup example deletes files older than 1 day in /tmp. Adjust the path and age to match your environment to avoid deleting needed files. ::: Reload:

sudo monit reload
sudo monit status

6. Add Update Orchestration (Optional)

If you want Monit to trigger SafeSquid upgrades when an upgrade flag file appears: Create /etc/monit/conf.d/safesquid-upgrade:

sudo nano /etc/monit/conf.d/safesquid-upgrade

Add:

check file ss-upgrade-flag with path /var/lib/safesquid/upgrade.flag
  if changed checksum then exec "/usr/local/bin/safesquid-upgrade"

Note: You’ll need to create the /usr/local/bin/safesquid-upgrade script separately.

7. Reload and Validate All Checks

sudo monit reload
sudo monit summary
sudo monit status

Expected:

monit summary shows all checks
monit status shows all checks as Running and OK

Verify Monit is Working

Test Auto-Restart

Simulate SafeSquid crash:

sudo systemctl stop safesquid

Wait 1-2 minutes (one Monit check cycle), then check:

systemctl status safesquid

Expected: SafeSquid is running again (Monit restarted it automatically). Check Monit logs:

sudo tail -20 /var/log/monit.log

Expected log entries:

[UTC] info     : 'safesquid' process is not running
[UTC] info     : 'safesquid' trying to restart
[UTC] info     : 'safesquid' process started

View Monit Dashboard

From the SafeSquid server:

curl http://localhost:2812

Or open in a browser on the server (if GUI available): http://localhost:2812 Expected: Monit dashboard showing SafeSquid status as green/running.

Troubleshooting

Issue	Likely Cause	Fix
Monit won’t start	Incorrect permissions on `/etc/monit/monitrc`	`sudo chmod 600 /etc/monit/monitrc && sudo monit reload`
Checks not loading	Missing `include` directive	Add `include /etc/monit/conf.d/*` to `/etc/monit/monitrc`
Port 8080 check fails	SafeSquid on different port	Update `if failed port` to actual port in config
Frequent restarts (3+ in 5 cycles)	Resource exhaustion or dependency failure	Check `journalctl -u safesquid` and system resources (CPU, memory, disk)
Monit dashboard not accessible	HTTP interface not configured	Verify `set httpd port 2812` in `/etc/monit/monitrc`

Still not working?

Check Monit configuration syntax:
sudo monit -t
Should return: Control file syntax OK
Check Monit logs:
sudo tail -50 /var/log/monit.log
Verify SafeSquid PID file location:
ps aux | grep safesquid cat /var/run/safesquid/safesquid.pid
If PID file doesn’t exist, update the Monit check to use process name instead.

Source register

Topic	Status	Source
Monit restart / port checks for SafeSquid	Confirmed	This guide, `monitrc` examples
Threat-intelligence housekeeping mentions	Draft	CTO: confirm which jobs Monit triggers per product build

Next Steps

BIND - Configure local DNS resolver
NTP - Ensure accurate time synchronization
Audit & Forensics - Monitor SafeSquid logs and events

Application Ecosystem

Supporting Services

Policy Management Console

Files and Folders

Monit Service Governance

Supervise SafeSquid Processes With Monit

Prerequisites

Installation and Configuration

1. Install Monit

2. Enable Monit Service

3. Configure Monit HTTP Interface (Local Only)

4. Add SafeSquid Process and Port Checks

5. Add Housekeeping Checks

6. Add Update Orchestration (Optional)

7. Reload and Validate All Checks

Verify Monit is Working

Test Auto-Restart

View Monit Dashboard

Troubleshooting

Source register

Next Steps

​Supervise SafeSquid Processes With Monit

​Prerequisites

​Installation and Configuration

​1. Install Monit

​2. Enable Monit Service

​3. Configure Monit HTTP Interface (Local Only)

​4. Add SafeSquid Process and Port Checks

​5. Add Housekeeping Checks

​6. Add Update Orchestration (Optional)

​7. Reload and Validate All Checks

​Verify Monit is Working

​Test Auto-Restart

​View Monit Dashboard

​Troubleshooting

​Source register

​Next Steps

Supervise SafeSquid Processes With Monit

Prerequisites

Installation and Configuration

1. Install Monit

2. Enable Monit Service

3. Configure Monit HTTP Interface (Local Only)

4. Add SafeSquid Process and Port Checks

5. Add Housekeeping Checks

6. Add Update Orchestration (Optional)

7. Reload and Validate All Checks

Verify Monit is Working

Test Auto-Restart

View Monit Dashboard

Troubleshooting

Source register

Next Steps