Process management with supervisor in Raspberry Pi - Step-by-Step Execution

Concept Flow - Process management with supervisor

Start Supervisor

↓

Read Config File

↓

Launch Managed Processes

↓

Monitor Processes

↓

Process Stops?

Yes→Restart Process

↓

Supervisor Running

Supervisor starts, reads config, launches processes, monitors them, and restarts if they stop.

Execution Sample

Raspberry Pi

[program:myapp]
command=/usr/bin/myapp
autostart=true
autorestart=true

supervisorctl status

This config tells supervisor to start and restart 'myapp' automatically; 'supervisorctl status' checks process state.

Execution Table

Step	Action	Evaluation	Result
1	Start supervisor service	Service not running	Supervisor starts and reads config
2	Read config for 'myapp'	autostart=true, autorestart=true	Prepare to launch 'myapp'
3	Launch 'myapp' process	Process not running	'myapp' starts running
4	Monitor 'myapp'	'myapp' running	No action needed
5	Simulate 'myapp' crash	'myapp' stopped unexpectedly	Supervisor detects stop
6	Restart 'myapp'	autorestart=true	'myapp' restarts automatically
7	Check status with 'supervisorctl status'	Process running	Output shows 'myapp' RUNNING

💡 Supervisor keeps running, managing processes continuously

Variable Tracker

Variable	Start	After Step 3	After Step 5	After Step 6	Final
supervisor_status	stopped	running	running	running	running
myapp_process	not running	running	stopped	running	running

Key Moments - 2 Insights

Why does supervisor restart 'myapp' automatically after it stops?

Because 'autorestart=true' is set in the config, as shown in execution_table step 6 where supervisor detects the stop and restarts the process.

What happens if 'autostart' is set to false?

Supervisor will not start the process automatically on supervisor start, so in step 3 the process would not launch unless started manually.

Visual Quiz - 3 Questions

Look at the execution_table at step 5, what does supervisor detect?

A Supervisor stopped

B 'myapp' is running normally

C 'myapp' stopped unexpectedly

D Config file changed

💡 Hint

Check the 'Evaluation' column at step 5 in execution_table

At which step does 'myapp' process restart automatically?

A Step 4

B Step 6

C Step 5

D Step 7

💡 Hint

Look for 'Restart' action in the 'Action' column in execution_table

If 'autorestart' was false, what would change in variable_tracker after step 6?

A 'myapp_process' would remain stopped

B 'myapp_process' would restart anyway

C 'supervisor_status' would stop

D No change at all

💡 Hint

Refer to 'myapp_process' values in variable_tracker after step 6

Concept Snapshot

Supervisor manages processes by reading config files.
Processes with autostart=true launch automatically.
autorestart=true makes supervisor restart crashed processes.
Use 'supervisorctl status' to check process states.
Supervisor runs continuously to monitor and manage processes.

Full Transcript

Process management with supervisor on Raspberry Pi involves starting the supervisor service, which reads configuration files specifying processes to manage. Processes marked with autostart=true launch automatically when supervisor starts. If a process stops unexpectedly and autorestart=true is set, supervisor restarts it automatically. The supervisor continuously monitors processes to keep them running. Commands like 'supervisorctl status' help check the current state of managed processes. This visual trace showed supervisor starting, launching a process, detecting a crash, and restarting it, demonstrating how supervisor ensures process reliability.