Whether to store data in SQL as key value pairs

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It can be tempting to store unstructured data as key value pairs to avoid lots of schema changes and capture dynamic data.  But it can lead to problems.

  • Overly complex queries/reporting
  • No type support

This article explains some of the issues.

My conclusion is that it is fine if you will only be accessing the data rather than querying it, or as a temporary capture means until you’ve identified where the data really belongs.

If you have another way to query, like a Lucene index it may also be perfectly fine.

Update:

A key value store NoSQL solution may be appropriate, but that brings with it other baggage.  Depending on the NoSQL solution you choose, you may have to do some extra work to get the type of search you need or use a Lucene style indexing solution anyway.

If you are using PostgreSQL, you can get much of the best of both worlds using hstore.

And you can easily use it with rails!

This will have the drawback of not being portable to other SQL backends, but that may be a tradeoff worth making.

With the PostgreSQL solution, you can retain one datastore and still allow some ability to store unstructured key values.  Then as needed, you can integrate these back into the schema to permanent normalized columns.

dockutil 1.1 released

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Version 1.1 of dockutil is out:

  • fixes many issues with paths (should now work with Default User Template and other paths with spaces)
  • adds option to not restart the dock (–no-restart)
  • fixes issue where item would be added multiple times (use –replacing to update an existing item)
  • resolves deprecation warnings
  • adds option to remove all items (–remove all)
  • fixes issue with removals when a url exists in a dock
  • adds option –version to output version

Get and use secure supported LDAP SASL authentication mechanisms

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You don’t have to use insecure clear text Simple BIND authentication for accessing your LDAP servers.

Get list of supported authentication mechanisms:

ldapsearch -h example.com -x -b "" -s base -LLL supportedSASLMechanisms

Kerberos GSSAPI Example:

kinit
ldapsearch -v -Y GSSAPI -h example.com -b "DC=example,DC=com" "(sAMAccountName=someusername)"

DIGEST-MD5 Example:

ldapsearch -v -Y DIGEST-MD5 -h example.com -U someusername -R example.com -b "DC=example,DC=com"\
 "(sAMAccountName=someusername)"
Note: For Active Directory Digest Authentication to work, you may need to enable Reversible encryption on the account’s password and change the user’s password once.

Fix Apache mod_jk or mod_proxy serving stale content

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If your web app starts serving stale cached content when run behind mod_jk or mod_proxy with apache, it may be due to apache inserting a default expiration header.

You can confirm this by comparing the headers returned from apache and directly from your web app.  curl -i will show response headers:

curl -i http://example.com | head -20

To disable apache’s content expirations, add the following to your virtual host:

ExpiresActive Off

Here is the official Apache Documentation.

Inspect Running Mac OS X Applications with F-Script

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Objective C is a Dynamic Runtime, so you can load code like plugins during runtime. This dynamic runtime can be very useful for exploring what applications are doing. I use this to assess the security of applications for example.

F-Script provides an easy way to inject itself into a running app and explore around.

Download F-Script here

Launch the app you want to explore.

Then find the process id number of the app in a Terminal shell:

ps auxww | grep “App Name”

Load the F-Script Framework into the app and insert its menu using:

sudo gdb --pid AppNameProcessID --batch --nx --command=/dev/stdin << EOT
p (char)[[NSBundle bundleWithPath:@"path/to/Library/Frameworks/FScript.framework"] load]
p (void)[FScriptMenuItem insertInMainMenu]
EOT

I found the above snippet by reviewing this automator service.

Note that sudo is only required if you are not in the _developer group.

At this point, switch to your running application.  You will notice an F-Script Menu is added to the menu bar.

Choose Console from the F-Script menu and type:

del := NSApplication sharedApplication delegate

This will give you a reference to the application delegate.  The application delegate is a top level class of the application, so it should provide a good starting point.

Next, choose Open Object Browser from the F-Script menu.

Now you should have a nice GUI window to explore the app.

Click on del in the Workspace to explore the app delegate.  You can call methods, change values, etc.

See the F-Script documentation for more details.

Enjoy

MIME type issue with Apache mod_jk and mod_proxy serving plain text

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Some apps do not properly set mime types of content they serve, but still may work properly when served standalone because client applications like browsers are able to interpret the type of the content.  But when served behind Apache, these apps will not behave correctly because Apache will provide a default type of text/plain.

The solution is to add a DefaultType None line to your apache virtual host for these web apps:

DefaultType None

Here are the docs