Large attachments - Mysql2::Error::ConnectionError: MySQL server has gone away

[arthurzenika]

Describe the bug

SMTP server fails to receive emails with large attachments even though the configuration specifies large attachments

To Reproduce

1. Increase the `max_message_size in the postal configuration, we trie with 50MB

smtp_server:
  max_message_size = "50"

2. Send an email with attachment, our test was with a 20MB PDF
3. No message in the "Incoming messages" in the web ui
4. See the following error in the smtp component logs :

$ postal logs smtp | grep D3VENMVJ
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  Client identified as 209.85.167.53 trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= EHLO mail-lf1-f53.google.com trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250-My capabilities are trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250-STARTTLS trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250 AUTH CRAM-MD5 PLAIN LOGIN trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= STARTTLS trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 220 Ready to start TLS trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= EHLO mail-lf1-f53.google.com trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250-My capabilities are trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250 AUTH CRAM-MD5 PLAIN LOGIN trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= MAIL FROM:<user@example.org> trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250 OK trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= RCPT TO:<destination@example.org> trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  Added route 129 to recipients (tag: nil) trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 250 OK trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= DATA trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  => 354 Go ahead trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  <= Received: by mail-lf1-f53.google.com with SMTP id 2adb3069b0e04-54fd1650b83so1368775e87.2 trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:39 +0000 DEBUG  Not logging further message data. trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  An error occurred while processing data from a client. trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  Mysql2::Error::ConnectionError: MySQL server has gone away trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/mysql2-0.5.6/lib/mysql2/client.rb:151:in `_query' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/mysql2-0.5.6/lib/mysql2/client.rb:151:in `block in query' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/mysql2-0.5.6/lib/mysql2/client.rb:150:in `handle_interrupt' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/mysql2-0.5.6/lib/mysql2/client.rb:150:in `query' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/database.rb:326:in `query_on_connection' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/database.rb:234:in `block in insert' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/connection_pool.rb:20:in `use' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/database.rb:345:in `with_mysql' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/database.rb:233:in `insert' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/database.rb:126:in `insert_raw_message' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/message.rb:278:in `save_raw_message' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/lib/postal/message_db/message.rb:208:in `save' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/models/route.rb:144:in `create_messages' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/client.rb:533:in `block in finished' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/client.rb:490:in `each' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/client.rb:490:in `finished' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/client.rb:429:in `block in data' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/client.rb:72:in `handle' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:204:in `block (2 levels) in run_event_loop' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:106:in `select' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:106:in `block in run_event_loop' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:104:in `loop' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:104:in `run_event_loop' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:39:in `block in run' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/klogger-logger-1.4.0/lib/klogger/group_set.rb:18:in `call_without_id' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /usr/local/bundle/gems/klogger-logger-1.4.0/lib/klogger/logger.rb:72:in `tagged' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  /opt/postal/app/app/lib/smtp_server/server.rb:37:in `run' trace_id=D3VENMVJ component=smtp-server
smtp-1  | 2025-05-12 08:01:43 +0000 ERROR  script/smtp_server.rb:13:in `<main>' trace_id=D3VENMVJ component=smtp-server

Expected behaviour

The SMTP server should receive and store the email in the database. Or at least answer that the email has not been received correctly (it seems that the sending server thinks the email went through correctly).

Environment details

• OS: n/a
• Browser n/a
• Version : 3.3.4
• Type : n/a

[willpower232]

You can see in the stack trace MySQL server has gone away which implies the database server crashed or blocked your request.

Have you changed settings on it yet? I think there is something like max_allowed_packet_size and a few others which are mentioned somewhere around here.