Johnathan Kong

Recursive Query Using CTE

admin — Sat, 17 Mar 2012 20:56:31 +0000

For one of my projects I had to write a crawler that would crawl up a table that referenced itself, it was a table that stored directory structure. My initial logic was to just loop through and spit out folder sizes. Unfortunately this was AWFUL. Fortunately one of my managers gave me a recursive query using CTE to create a view that we could query and get files sizes on.

WITH MyFolder(FolderID, ParentFolderID, FolderName, Sku, Level, Path)
AS
(
	SELECT FolderID, ParentFolderID, FolderName, Sku, 0 AS Level, cast(FolderID AS varchar(100)) AS Path
	FROM Folder f
	WHERE ParentFolderID IS NULL
	UNION ALL
	SELECT f.FolderID, f.ParentFolderID, f.FolderName, f.Sku, (p.level + 1) AS Level, cast(p.Path + '/' + cast(f.FolderID AS varchar) AS varchar(100)) AS Path
	FROM Folder f
	INNER JOIN MyFolder p ON f.ParentFolderID = p.FolderID
)
SELECT f.FolderID, f.ParentFolderID, f.FolderName, f.sku, f.Path, f.Level, count(d.documentID) AS FileCount, isnull(sum(d.size), 0) AS FileSize
FROM myFolder f
	LEFT OUTER JOIN FolderFile ff ON f.FolderID = ff.FolderID
	LEFT OUTER JOIN Document d ON ff.DocumentID = d.DocumentID
GROUP BY f.FolderID, f.ParentFolderID, f.FolderName, f.Sku, f.Path, f.Level

unable to qualify my own domain name (production)

admin — Sat, 17 Mar 2012 20:49:13 +0000

While trying to solve an issue with my sendmail, I stumbled upon an error that was filling up my mail.err logs. The error is as follows:

Mar 7 06:26:37 production sendmail[11539]: My unqualified host name (production) unknown; sleeping for retry
Mar 7 06:27:37 production sendmail[11539]: unable to qualify my own domain name (production) — using short name

What apparently happened was that while setting up a second ip address I set my ip address to point to “production” in the host file, /etc/hosts. My line looked like this:

127.0.0.1 production localhost

Apparently this was causing the error because send mail seems to like it as a valid domain name format, like mydomain.com. The fix was simple; I just had to add mydomain.com in front of production. Please note that it has to be in front of production. After that I restarted networking and sendmail:

/etc/init.d/networking restart
/etc/init.d/sendmail restart

Send out email with sendmail from command line

admin — Sat, 17 Mar 2012 20:40:44 +0000

/usr/sbin/sendmail -t < testing.txt

contents of testing.txt:
Date: Thu Nov 11 08:41:54 2007
To: johnathankong@gmail.com
Subject: The subject of the message
From: jared@razoredgelabs.com
Body of message goes herev

your host may have disabled the mail() function…

admin — Sat, 17 Mar 2012 20:39:44 +0000

Recently after trying to get our server off of the blacklisting, we had an issue with WordPress giving us your host may have disabled the mail() function… This turned out to not be centralized to WP, but to sendmail. It wasn’t the fact that sendmail wasn’t able to send emails out properly, because the fact was that we were able to send mails anywhere EXCEPT to our main domain; so we were able to send emails out to gmail, yeahoo, etc., but unable to send to johnathankong.ca only. In looking at the logs for the sendmail (/var/log/mail.stats) I noticed that we were getting a lot of “DSN: User unknown” errors. after stumbling through multiple sites, I realized that the change I made to the sendmail.cf file was causing the issue. Apparently when I set the Dj to point to my main domain, it disabled all emails to that domain through sendmail. My solution, workaround, was that I created a production.mydomain.com and put it in place there. Now all my emails are up and running perfectly.

HELO Error

admin — Sat, 17 Mar 2012 20:32:50 +0000

Recently after setting up my linode servers we realized that we were getting blacklisted. The error that we were getting when blacklisted was:

This IP address is HELO’ing as “localhost.localdomain” which violates the relevant standards (specifically: RFC5321).

After searching around for a solution, we came upon this page, http://cbl.abuseat.org/sendmailhelp.html. Apparently we didn’t setup our sendmail.cf file properly. To sum up the solution, we needed to do the following steps:

1. open /etc/mail/sendmail.cf
2. search for #Djlocalhost.localdomain
3. uncomment #Djlocalhost.localdomain and replace localhost.localdomain with your domain. For example, in my case it would be Djjohnathankong.ca
4. restart sendmail /etc/init.d/sendmail restart

After doing those steps, we automatically removed from the blacklist

Unmap Network Drive

admin — Tue, 06 Mar 2012 02:41:04 +0000

This will remove the login information from a mapped drive

net use \\ /delete

Could not reliably determine the server’s fully qualified domain name

admin — Tue, 06 Mar 2012 02:37:34 +0000

A while back I was getting the error message

Could not reliably determine the server’s fully qualified domain name, using 127.0.1.1 for ServerName
… waiting apache2: Could not reliably determine the server’s fully qualified domain name, using 127.0.1.1 for ServerName

every time I restarted Apache. Apparently to fix this issue you have to edit the /etc/apache2/httpd.conf. To resolve this issue, open up the httpd.conf (this will be empty by default) and add ServerName localhost. After you’ve added that entry, restart the Apache server and everything should work.

Setup Curl

admin — Tue, 06 Mar 2012 02:26:17 +0000

apt-get install curl libcurl3 libcurl3-dev php5-curl

Setup Send Mail

admin — Tue, 06 Mar 2012 02:25:44 +0000

apt-get install sendmail

Change Ubuntu Hostname

admin — Tue, 06 Mar 2012 02:21:10 +0000

Change the host name of the ubuntu server:

echo > /etc/hostname
hostname -F /etc/hostname
vi /etc/hosts
add the host name to the 127.0.0.1 entry

Note: if you are using Linode, you have to comment out SET_HOSTNAME=’yes’ in /etc/default/dhcpcd