Weekly Snap: Load balancing with Cluster IP, PHP memory tracking with Memtrack, new ACKP SensorProbe & Pgpool 2

26 – 30 September bid summer farewell with load balancing and PHP tips, the arrival of a new AKCP sensor probe, and developments in the MySQL – PostgreSQL realm.
Bernd bemoaned recent news from Oracle of new extensions for MySQL Enterprise. As announced in the Oracle blog, a new Enterprise Scalability Extension will join the ranks of the Enterprise High Availability and Enterprise Security modules. This follows the trend to offer much needed extensions for large environments only to commercial users, which can alienate the MySQL user community into the arms of competitor software such as PostgreSQL.
Sebastian continued on this thread to look at PostgreSQL replication with Pgpool-II. A third party middleware between PGSQL client and server, Pgpool complements PostgreSQL’s streaming replication (as of version 9) by managing the failover between master and slave. Features include connection pooling, replication, load balancing, limit exceeding connections and parallel queries. More information can be found in both Pgpool 2 and PostgreSQL’s documentation.
Lennart then looked at load balancing on Linux minus the load balancer. With Cluster IP of Netfilter, extensive clusters with multiple nodes can be built by using a common IP address on all nodes. This way, all nodes can respond to the same address. To avoid confusion in ARP querying, Cluster IP uses a Multicast MAC for the cluster IP addresses, so that incoming packets are received by participating nodes. It also uses a hash to distinguish between source IPs or ports etc, ensuring that nodes only answer queries relevant to them.
Following on, Marius shared his tip for monitoring memory capacity in PHP. The PECL extension Memtrack, tracks PHP memory usage and assists in troubleshooting, by enabling deviations in the logs to be detected.
Last but not least, hardware man Martin announced the arrival of AKCP Sensor Probe 4 to our online store. The much awaited device comes with 4 sensor ports in an AKCP Sensor Probe 8-like casing, making it perfect for a 19 inch rack. The AKCP Sensor Probe 4 features Cat 5 sensor connection for many different sensors, simple installation and configuration, Icinga and Nagios plugins, SNMP Trap messaging, 100Mbit network connection and a web interface to send email alerts.