README (dbi-dbrc)

Last Update: Thu Aug 02 11:04:22 -0600 2007

Description

This is a supplement to the dbi module, allowing you to avoid hard-coding passwords in your programs that make database connections.

Requirements

Ruby 1.8.2 or later
sys-admin
win32-file (MS Windows only)
win32-dir (MS Windows only)

Synopsis

   
   require 'dbi/dbrc'
   include DBI

   dbrc = DBRC.new('mydb')

   or

   dbrc = DBRC.new('mydb', 'someUser')

   puts dbrc.db
   puts dbrc.user
   puts dbrc.driver
   puts dbrc.timeout
   puts dbrc.max_reconn
   puts dbrc.interval
   puts dbrc.dsn

   dbh = DBI.connect(dbrc.dsn, dbrc.user, dbrc.password)

Installation

rake test (optional)
rake install (non-gem) or rake install_gem (gem)

Notes on the .dbrc file

This module relies on a file in your home directory called ".dbrc", and it is meant to be analogous to the ".netrc" file used by programs such as telnet. The .dbrc file has several conditions that must be met by the module or it will fail:
  • Permissions must be set to 600 (Unix only).
  • Must be hidden (MS Windows only).
  • Must be owned by the current user.
  • Must have database, user and password. Other fields are optional.
  • Must be in the following space-separated format (in the 'plain' version): 
   database user password driver timeout maximum_reconnects interval

   e.g. mydb     dan    mypass     oracle   10        2         30

You may include comments in the .dbrc file by starting the line with a "#" symbol.

A failure in any of the rules mentioned above will result in a DBRC::Error being raised. In addition, the file may also be encrypted on MS Windows systems, in which case the file will automatically be (temporarily) decrypted.

The format for XML (using the example above) is as follows: 


   <dbrc>
      <database name="mydb">
         <user>dan</user>
         <password>mypass</password>
         <driver>oracle</driver>
         <interval>30</interval>
         <timeout>10</timeout>
         <maximum_reconnects>2</maximum_reconnects>
      </database>
   </dbrc>
The format for YAML is as follows: 

   - mydb:
      user: dan
      password: mypass
      driver: oracle
      interval: 30
      timeout: 10
      max_reconn: 2

Constants

VERSION

The current version of this packages, returned as a String.

Class Methods

DBRC.new(db, user=nil, dir=nil)

The constructor takes one to three arguments. The first argument is the database name. This *must* be provided. If only the database name is passed, the module will look for the first database entry in the .dbrc file that matches.

The second argument, a user name, is optional. If it is passed, the module will look for the first entry in the .dbrc file where both the database *and* user name match.

The third argument, also optional, specifies the directory where DBRC will look for the .dbrc file. By default, it looks in the pwuid (blockquotesent working user id) home directory. The rules for a .dbrc file still apply.

MS Windows users should read the "Notes" section for how your home directory is determined.

Instance Methods

DBRC#database

The name of the database. Note that the same entry can appear more than once, blockquotesumably because you have multiple user id's for the same database.

DBRC#db

An alias for DBRC#database.

DBRC#database=(database)

Sets the database to +database+. This is generally discouraged because it does not automatically reset the dsn.

DBRC#db=(database)

An alias for DBRC#database=.

DBRC#user

A valid user name for that database.

DBRC#user=(user)

Sets the user name to +user+.

DBRC#password

The password for that user.

DBRC#passwd

An alias for DBRC#password.

DBRC#password=(password)

Sets the password to +password+.

DBRC#passwd=(password)

An alias for DBRC#password=.

DBRC#driver

The driver type for that database (Oracle, MySql, etc).

DBRC#driver=(driver)

Sets the driver to +driver+. This use is discouraged because it does not reset the dsn.

DBRC#timeout

The timeout period for a connection before the attempt is dropped.

DBRC#time_out

An alias for DBRC#timeout, provided purely for the sake of backwards compatability.

DBRC#timeout=(int)

Sets the timeout value to +int+.

DBRC#maximum_reconnects

The maximum number of reconnect attempts that should be made for the the database. Presumablly, you would use this with a "retry" within a rescue block.

DBRC#max_reconn

An alias for DBRC#maximum_reconnects.

DBRC#maximum_reconnects=(max)

Sets the maximum number of reconnect attempts to +max+.

DBRC#max_reconn=(max)

An alias for DBRC#maximum_reconnects.

DBRC#interval

The number of seconds to wait before attempting to reconnect to the database again should a network/database glitch occur.

DBRC#interval=(int)

Sets the interval seconds between connection attempts.

DBRC#dsn

Returns a string in "dbi:<driver>:<database>" format.

DBRC#dsn=(dsn)

Sets the dsn string to +dsn+. This method is discouraged because it does not automatically reset the driver or database.

Canonical Example

   
   # This is a basic template for how I do things:

   require 'dbi/dbrc'
   require 'timeout'

   db = DBI::DBRC.new("somedb")
   n = db.max_reconn

   begin
      timeout(db.time_out){
         DBI.connect(db.dsn, db.user, db.passwd)
      }
   rescue DBI::Error
      n -= 1
      sleep db.interval if n > 0
      retry if n > 0
      raise
   rescue TimeoutError
      # handle timeout error
   end

Notes for MS Windows Users

The 'home' directory for Win32 users is determined by ENV['USERPROFILE']. If that is not set, ENV['HOME'] is used. If that is not set, then 'C:\Documents and Settings\user_name' is used.

To make your file hidden, right click on the .dbrc file in your Explorer window, select "Properties" and check the "Hidden" checkbox.

I was going to require that the .dbrc file be encrypted on MS Windows, but that may require an official "certificate", assigned to you by a third party, which is a bit much to expect. However, if the file is encrypted, DBRC will attempt to decrypt it, parse it, and encrypt it again when done parsing.

Notes on running the test suite

I cannot guarantee that the .dbrc files under the +examples+ subdirectories maintain the appropriate properties. This can cause failures for the test suite (which uses these files).

The only solution is to perform a 'chmod 600 .dbrc' (on Unix) or set the properties to 'hidden' (on MS Windows) manually, for the file in question.

Summary

These "methods" don't really do anything. They're simply meant as a convenience mechanism for you dbi connections, plus a little bit of obfuscation (for passwords).

Adding your own configuration

If you want to add your own type of configuration file, you can still use the dbi-dbrc package. All you need to do is:

  • subclass DBRC
  • redefine the +parse_dbrc_config_file+ method (a private method).

Take a look at the XML and YML subclasses in dbrc.rb for two examples that you can work from.

Known Bugs

I'm not positive about the dsn strings for databases other than Oracle. If it's not correct, please let me know.

Author

Daniel J. Berger
djberg96 at nospam at gmail dot com
imperator on IRC (irc.freenode.net)

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