6th August 2010

Plesk-based hosting can often suffer from a resilience problem: failure of the DNS for sites it hosts if the server goes down for any reason.

Ideally a zone should have a number of domain name servers located in different places. A zone is basically a domain and all its sub-domains. The zone record tells other servers where to find everything for that domain – where the websites are, the main servers etc.

Plesk run on a server or virtual server (VPS) generally provides two name servers. They will be configured automatically when websites are set up on the server, and are very convenient to use. Plesk also allows some customisation of the domain records so that, for example, a sub-domain can point to another server, or the mail server points to your office server.

The problem comes when the server running Plesk is down or inaccessible. A mail server trying to send an email to your domain will suddenly find there is no record anywhere of that domain – it has basically dissappeared.

The way around this is to use external name servers. By setting up the external name servers as a slave servers, they can be made to automatically keep themselves updated from your master name servers on your hosting machine.

For our domain, I used www.zoneedit.com to set up a slave for one of our zones. The slave was pointed at our hosting server (using its IP address) and that was it for that end – the zoneedit slave just fetches updates when it is appropriate and updates its own records, putting them onto two geographically-separated name servers of its own.

Back to the domain registration settings, I then needed to add the zoneedit name servers to the domain, giving me four in total (the two on our Plesk hosting and the two on zoneedit). There is no priority assigned to any of these name servers, so a server looking for our website or mail server could go to any of these sources. It is therefore very important to ensure they are all synchronised identically.

One last step was to tell Plesk to allow these name servers to fetch a copy of the zone records. This is not so obvious but is in Plesk under the option:

Server -> DNS Settings -> Common ACL

In here I added the IP addresses of the two zoneedit name servers assigned to my zone, and then the updates simply went ahead.

You can test this works using nslookup command from another server. Create a new sub-domain, then check it can be seen on your Plesk server:

nslookup new.sub-domain.example.com ns.plask-server.example.net

Then try the same command but pointed at the external name server. You will find the external name server cannot see the sub-domain immediately. Try again in an hour – and it should be there. If not, check your setting and TTL etc.

Hopefully that will give you more resilience; even if your website is down, other severs that your zone points to are still locatable.

One thing that I am still looking for a solution to, is domain aliases. A domain alias for a domain set up in Plesk will not get transferred to the slave name server. Even if the alias is a sub-domain of the main domain, it does not get transferred. So the hosting server will correctly return the IP address for example.com for the alias myalias.example.com, but the slave name servers will not. This is not just a problem for when your hosting server goes down, because there is no priority on the name servers – all and any could be used at any time for a server to locate your alias domain, and depending on which name server it hits, it is pot luck as to whether it finds it or not. I’m looking for a solution to this, so any hints appreciated.

I’m also looking for a decent and cheap slave name server service. zoneedit is good and reliable, and easy to use, but could get costly when we have scores of domains to sync up. Any suggestions?

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8th July 2010

Was on the hunt for some software that would let me take multiple screengrabs. Eventually settled on Grab them all, a Firefox extension. Here’s the story!

Step 1 was to create a list of URLs that needed screengrabs. I wrote an small PHP that printed a list of URLs (one per line) which I then saved to a text file:

http://www.siteroom.co.uk/

http://www.consil.co.uk/

The first tool I came across was WebShot. The GUI interface is simple, but there’s far more flexibility using the command line. This is the command I used to run a batch of screenshots listed in the text file I created earlier

webshotcmd.exe /in "C:\screenshots.txt"

The tool worked well and uses Internet Explorer to render the web pages (so make sure you have the latest version!). You can also add parameters to your batch list too. I wanted the width of the image to be 1280px wide, rather than defaulting to the width of the web page, and also to use custom file names.

/url "http://www.siteroom.co.uk/" /bwidth "1280" /out "C:\screenshots\siteroom.jpg"
/url "http://www.consil.co.uk/" /bwidth "1280" /out "C:\screenshots\consil.jpg"

Unfortunately the free version only renders screengrabs in black and white.

I settled on Grab them all – a Firefox addon. Although it doesn’t have advanced features like watermarking, it does boast enough options for my needs. You’ve also got the benefit of Firefox’s web page rendering engine, which means screengrabbing the page with all the good-looking CSS3 features.

Options can be tweaked by going:

Tools > Add-ons > Extensions > Grab them all ‘Options’ button

I was able to change the filename from Base64 to the URL and set the width of the window. To run the program go to:

Tools >> Grab them all

Pass it the simple list of URLs (one URL per line) and let it run its magic!

6th February 2010

nlite logoI came across this neat Windows application today. It is basically a tool for creating customised Windows installation disks.

I’ve seen similar tools for slip-streaming service packs into disks, but this one goes a step further and makes it dead easy to include drivers and various other Windows tweaks. It is all very straight-forward to use:

  1. Point it at the original Windows disk.
  2. Tell it what you want to change (point it at service packs, drivers, etc.)
  3. Tell it to generate an ISO.
  4. Press GO.

The application will then spit out an ISO image that you burn to CDROM. I’m sure there are ways to install it over the network without burning a CD too.

I found it while looking for a way to reinstall XP onto Dell machine with a SATA device that the default Windows disk did not recognise.

nlite – http://www.nliteos.com/ – a great application for your toolbox.

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17th November 2008

I was recently tasked with transferring files from a failed laptop. The laptop kind of worked, but some bad sectors had started to appear in a number of vital system files, so it was very unstable.

This was an old WIndows 98 system, and I could not simply plug in a USB drive, because there were no Windows 98 drivers around for the external USB drives that I had. In the end the disk had to be removed, and connected up to a working machine with a flying lead.

Since then, I have come across Puppy Linux. It seems to be ideal for this type of thing. By booting it directly from CDROM or USB key, it is possible to have a working Linux box in 60 seconds flat. It is then a simple matter of mounting the local drive, plugging in a USB drive, and transferring the files across.

Puppy Linux is not something I have ever come across before, but it is now a part of my standard toolbox. It also looks like the ideal platform for building custom appliances, such as video players and thin clients.

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25th September 2008

This search has gone on for years. I am looking for a newsletter system that is easy to install (to most likely LAMP-based), allows sign-up to multiple newsletters, and is reliable and flexible.

The most important thing is that once configired, I need to be able to hand over the keys to a client so that they can manage it from that point on. That is the hardest part, because no matter what I try, there are always highly technical aspects to sending out a newsletter that really stump the non-technical clients.

This is what I have come up with (and tried) so far:

PHPlist (Tincan)

PHPlist Logo

PHPlist Logo

This has some lovely features, but some pretty dire ‘gotchas’ that can trap an unwary user. For a start the admin screens are as ugly as hell, and the terminology can make it hard to fathom out what each option does (for example, to create a draft newsletter, you need to use the ‘send a message’ option). It is just not intuitive.

Problems for end users involve its uncanny ability to drop stylesheets when editing templates. Another is signing lists of imported users up to text-only e-mails even when ‘HTML’ is selected. Yes these can be worked around, but only if you know the problems exist.

On the plus side, the e-mail sending system is brilliant. You queue messages to send, and leave it to do its job. If it fails (and anything that involves a browser window staying open will fail) then you just start it again and it carries on from where it left off. It keeps track of who a newsletter has been sent to, so you can requeue a newsletter every day until the next newsletter is ready, and it will send just to new subscribers.

The ability to pick of bounces from an IMAP or POP3 mail box is also great. Each bounce will increment a counter, and subscribers can be disabled when a preset number of bounces is reached.

This system also supports tracking, counting each individual e-mail as it is opened, using an image embedded in HTML e-mails.

Another downside is the lack of APIs, making integration difficult. Signing users up to a list automatically, while they are signing up to a CMS, is impossible without some major hacking.

The problems with PHPlist stem from it being around a long time. It has grown and grown over the years, but is creaking at the seams. Everything it does is great, but the way it does it is not so hot. It is time, IMO, to throw away the old code and start again, with all the same features, an established framework (e.g. Zend or CakePHP) and it will be a killer application.

I must also add that I believe PHPlist got the data schema right from the start. Most other newsletter systems I have looked at have gone for a much more simplistic approach, that makes it much harder for them to advance their products beyond very simple functionality.

With all that it is, I do use it, and find it great at what it does. What I can’t do, howver, is roll it out to clients, because it results in nothing but hassle from the non-technical users who just can’t get to grips with its mix of high-level features, and low-level ‘black art’ knowledge that is needed.

poMMo

poMMo logo

poMMo logo

This one has to get the award for ‘hardest to find mailing list manager’. It was formally the bMail project and is hosted on SourceForge. Trying to find it when you can’t quite remember its ‘web 2.0′ name is quite an effort, but the result is well worth it.

Checking the project’s subversion repository, it does not seem there has been any activity on this project since August 2008, which is not very encouraging.

First of all, the admin screens are lovely. They are smooth, AJAX/jQuery-based, clear and well designed. The whole thing feels smooth – it works with you.

The first thing to note is that it does not support multiple mailing lists. In fact, it does not support any ‘mailing lists’ at all. However, what it does provide is a means to mail out to groups of users depending on attributes of those users.

For example, you could provide a series of checkboxes for a subscriber to select what subjects they are interested in. When sending out a newsletter, the author would send it to all subscribers who have expressed an interest in the subject of that newsletter. Now, that does sound rather like a multiple newslist system, but the subtle difference is that there is no ‘newslist’ object in the database – anything that looks like a newslist subscription is specified by the administrator, and not enforced as any kind of fundamental part of the system’s structure.

I think that approach works well. The system is simpler, and the flexibility is increased. There are a few downsides though.

The first downside is that without a newslist for a user to subscribe to, there is no place in which you can find out exactly when a user subscribed to that newslist. That means sending out additional copies of a newsletter to late subscribers simply cannot be done. Remember PHPlist knows who subscribed to what and when, and so is able to send out ‘catchup’ newsletters so a subscriber will always get the latest newsletter very soon after subscribing.

The other downside is in organisation. Without being able to group newsletters into newslists, it is much harder to provide archives organised by subject. On the other hand, the archives are there, with very easy access to the newsletters from a web-based front end.

The e-mail sending backend is both genius and a little frightening for a control-freak such as myself. It also misses a few tricks, I think.

In order to send e-mails, the system first creates a list of who to send to (in a text file, I believe). It then spawns a process through the HTTP protocal to send as many e-mails as it can in the PHP timeout period (you would set this to as long as possible). Before that script times out, it spawns another process to carry on where it left off, and so on until all the e-mails have been sent, whereupon a lock file created right at the start is released.

This is genious in that the developers have worked out a way to run a background script that can keep going even when the browser window is closed. It is frightening for much the same reason. I just don’t feel comfortable letting something like that loose on my server. It could be running all night in some kind of endless loop, and I would never know until I get irate e-mails from subscribers saying that I have filled up their inboxes.

Another minor flaw in the e-mail sending is that no record is kept of who each newsletter has been sent to. Doing that would make it very easy to sort out who has received a copy and who needs a catch-up copy sent. Following from that, without records of e-mails sent, there is no place to hang any flags to say whether that e-mail has been opened and read, so e-mail tracking is out. Clients need to know these things: how well read are those newsletters? Everyone has a master up the chain to report to, and someone up that line, often holding the purse-strings, likes simple measures of performance.

My ideal newsletter system would contain the database and functional features of PHPlist, with the administration front-end of poMMo.

Other Systems

I’ll add a few more when I get the time. I’m mainly looking at Open Source newsletter systems, aimed at sending to self-subscribed users (i.e. not bulk spam systems). Integration with an existing site or CMS is high on the priority list, along with ease of use for non-technical users. Other systems we will be evaluating are:

  • ListMessenger – Free light version, but dirt cheap Pro version with all the features you would want. This one seems to include captchas for registration.
  • Dada Mail – Old, well known, Perl-based, and it looks like a pain to install.
  • Sympa – Again, Perl. This one seems to have been designed by engineers. That is to say the system looks very robust and complete, but there is little gloss to the system. Like Data Mail, you need root access to install it, so you have to be careful about dependances with other modules on your server.

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