Linux (Ubuntu 16.04), PHP and MS SQL

In the many years I’ve been using the traditional LAMP stack, I’ve successfully managed to avoid having anything to do with MS SQL server. Until 2016. This year I’ve had to work quiet a bit with it – administration, backups and, now, scripted queries from Linux with PHP.

I suspect I’m (a) lucky I haven’t had to do this before now; and (b) that Azure seems to have pushed Microsoft into greater Linux based support for MS SQL. The evidence? This open source Mircosoft repository with a MS SQL PHP binary driver for Linux released just a few months ago.

NB: installing the Microsoft PHP driver is different to installing the Microsoft ODBC driver for SQL Server on Linux. These may even be incompatible.

For me, I just took a standard Ubuntu 16.04 install (64bit obviously) with PHP 7.0 and downloaded the latest MS PHP SQL extension (for me, at time of writing, this was 4.0.6. When you untar the Ubuntu16.tar file, copy the .so files to /usr/lib/php/20151012/ and then create a /etc/php/7.0/mods-available/msphpsql.ini file with contents:

Note that the tar also contains two ‘ts’ versions of these files. Trying to use those resulted in errors. Link this for Apache2 / CLI as required. E.g. for PHP CLI:

You can confirm it’s working via:

And, finally, for using it, following the the sample scripts from the repository worked a charm.

Debugging NFS Slowness

During patching for the recent GHOST bug, I updated all packages (including kernel) on a Ubuntu 14.04 file server (filer). This filer provided static content (mainly tens of thousands of images) to a number of web servers. You can see the effect in the following load graph from the filer:

Load average on the filer
Load average on the filer

You may notice from the above, that there were actually two issues. The first was solved by upgrading the filer from 14.04 to 14.10 based on a number of online references to symptoms and fixes. About an hour after this upgrade, a new form of NFS slowness manifested and, needless to say, sites that rendered in <1sec were now taking >15secs.

Diagnosing the second issue took a while longer but some tips and utilities include:

  • check /var/log and see if any log files are increasing rapidly;
  • check top and check any processes with high / unusual utilisation;
  • use iostat (apt-get install sysstat) and pay particular attention to any devices with high volumes of transactions per second. In my case it was the root filesystem rather than any of the mounted partitions exported by NFS.
  • use iotop (apt-get install iotop) and note any processes with high utilisation (in my case jbd2/xvda1-8 was at 100% and xvda1-8 is my root partition)

The jbd2 process is the ext4 journaling process. At this point you can evaluate fsck’ing your partition but I wanted to see if I could discover what was happening here. I enabled some debugging via:

What I found were lots of:

where every entry related to the same inode number (276278). We found this via:

The solution was to stop nfs_kernal_server, remove that directory entirely, add it back and restart the nfs_kernel_server. We got the permissions wrong on the first attempt but this’ll be obvious from dmesg / kernel log messages such as:

Development Contracts

At Open Solutions, we tend to undertake a lot of fixed price contracts to develop web applications. In fact, clients usually insist on fixed price contracts as they want to know in advance what the bill will be.

However, fixed price contracts have big negatives for both parties:

  • for the client, a fixed price contract can often limit them to their earliest ideas. Now, as a service provider, we want to be flexible and so we’re happy to chop and change as a project develops. But, this leads to:
  • for the service provider, if change and revision requests are not carefully managed agreed and billed for, the service provider could very quickly end up making a loss on the contract and thus find themselves in the position of funding their clients project!

To this end, we’ve recently been reviewing various web development contracts and have found some nice inspiration for basing our own on.

Following the success of Killer Contract, Andy wrote a plain language NDA (also available as a Gist).

Virtual Mail with Ubuntu, Postfix, Dovecot and ViMbAdmin

As part of pushing our new release of ViMbAdmin, I wrote up a mini how-to for setting up a virtual email system on Ubuntu where the components are:

  • Postfix as the SMTP engine;
  • Dovecot for IMAP. POP3, Sieve and LMTP;
  • ViMbAdmin as the domain / mailbox / alias management system via web interface.

It supports a number of features including mailbox archival and deletion, quota support and display of mailbox sizes (as well as per domain totals).

Find the how-to at:

Querying Cisco MST Port Roles via SNMP with OSS_SNMP

OSS_SNMP is a PHP SNMP library written by myself for people who hate SNMP. After a customer migration from PVST to MST (Multiple Spanning Tree), I have added a number of MST functions / MIBs to OSS_SNMP:

During a fairly significant network migration involving breaking / connecting a number of links, I wanted to be able to monitor the MST port role of significant ports at a glance. For this purpose, I wrote the mst-port-roles.php script and have committed it as an example to OSS_SNMP. First, here is what it looks like when run on the command line (with hostnames obfuscated):

MST Port RolesFrom a very simple array of port details at the top of the script, it will poll all switches and for each port print:

  • device and port name;
  • port state and speed;
  • port role for each applicable MST instance.

I run it on bash and use bash colouring. The script is well documented and can easily be repurposed for other networks. You’ll find the source here.