Discourse Debugging Guide for Docker Role¶

This document explains how to locate and use key log file paths on both the host and inside the container for a Docker-based Discourse installation deployed via the docker-discourse role.

1. Host Paths¶

Discourse log files are stored in the Docker volume named discourse_data. On the host, you can find them at:

Rails Production Log:
```
cat /var/lib/docker/volumes/discourse_data/_data/log/rails/production.log | grep -i mail
```
Filters for email-related entries:
- Queued emails: Email::Sender: queued mail to [email protected]
- Errors: e.g. Net::SMTPAuthenticationError, SMTPConnectionError

Sidekiq Log:

cat /var/lib/docker/volumes/discourse_data/_data/log/sidekiq.log | grep -i mail

Shows asynchronous mail job executions, retries, and failures.

2. Inside the Container¶

To inspect logs within the container, enter it:

cd /var/discourse
./launcher enter app

Logs are mounted under /var/log inside the container:

Rails Production Log:
```
tail -n 200 /var/log/rails/production.log | grep -i mail
```
- Info: I, [timestamp] INFO -- : Email::Sender: queued mail to ...
- Error: E, [timestamp] ERROR -- : Net::SMTPSyntaxError ...
Sidekiq Log:
```
tail -n 200 /var/log/sidekiq.log | grep -i mail
```
- Execution: Mail::MessageJob JID-...
- Retries/Exceptions on delivery failure.

3. Live Streaming Logs¶

For real-time monitoring while reproducing an issue:

# On host:

tail -f \
  /var/lib/docker/volumes/discourse_data/_data/log/rails/production.log \
  /var/lib/docker/volumes/discourse_data/_data/log/sidekiq.log | grep -i mail

# Or inside container:
tail -f /var/log/rails/production.log /var/log/sidekiq.log | grep -i mail

4. Enabling Verbose Email Debugging¶

For detailed SMTP conversation logging:

# Inside container
rails c
> Discourse.debug_email = true

Send a test email:

rails c
> UserMailer.test_email("[email protected]").deliver_now

Then check logs for the full SMTP handshake details.

5. Flushing Redis Cache¶

After configuration changes, clear Redis to remove stale session or cached data:

# Inside container
rails r "Redis.new.flushall"

6. Sidekiq Web UI¶

In the Admin UI under Plugins → Sidekiq, monitor queues, retries, and failed jobs for additional context.

Use this guide to quickly locate and interpret Discourse logs on both host and container, enabling efficient debugging of email delivery and background job issues in a Docker deployment managed by the docker-discourse role.