(ITS#7775) LMDB terminates Postfix daemon process without logfile record

[wietse@porcupine.org]

Full_Name: Wietse Venema
Version: All LMDB versions
OS: Linux, BSD
URL: ftp://ftp.openldap.org/incoming/
Submission from: (NULL) (70.104.130.26)


Subject: LMDB terminates Postfix daemon process without logfile record

The LMDB library uses assert() which will abort() the program after
writing a message to stderr.  In the case of the Postfix MTA, the
symptom is a that a daemon process falls out of the sky without
logfile record.

- This frustrates sysadmins (no logfile message).

- This frustrates my efforts to make Postfix automatically recover
  from non-catastrophic error. In many cases the database is only 
  a cache, a mere optimization. I want the option to just blow it
  away when LMDB has a problem with it.

- Library modules should not abort programs after error. They should
  return an error result such as EINVAL, or use some other strategy 
  that leaves control with the application.

- Writing diagnostics to stderr is not useful for daemon programs 
  in the general case.

To fix this problem I suggest that LMDB provide way to notify the
application that it was unable to complete a request, so that the 
application can make proper arrangements.

A few alternatives:

- When a request fails, return a distinct error code such as 
  MDB_PANIC, and allow the application to look up the text for the
  error.       

- Invoke an application call-back function with the error code and 
  problem description text.  If the error code is MDB_PANIC then
  the application knows that it needs to make final arrangements.
  
The second option preserves 100% backwards compatibility. The first
option may cause functions to return a result that they didn't
return previously.

        Wietse