If you have an application which does distributed computing, i.e. means connects to other servers and send data, it is interesting to monitor the connection handling. Therefore collectd provides the plugin tcpconns, that allows to monitor dedicated ports. This data can be send to logstash, where it can have graphite or elasticsearch as output. Having the data in a metrics storage, visualization with Kibana or Grafana is a piece of cake.
Marvel is the monitoring plugin for Elasticsearch and Kibana. If you do maintenance in Elasticsearch, and therefore close indices, you might stumble over some ERROR messages in the elasticsearch log. (Update: elastic rebranded it as x-pack monitoring)
Monit has the capability to check for a process name. The process itself can also provided a service on a dedicated port, in this Kibana in Production, which uses SSL and expose its service on port 5601.
Using Windows command line is sometimes challenging. Especially if you want to check if a special port is up and running (listening). This post demonstrates how.
A long time ago (seems like ages to me) I have programming in Java and let my projects analyze with Sonarqube. I always remembered that every Sonarqube upgrade wasn’t quick to made. Since Docker I now have the possibility to run the latest stable Sonarqube version. No manual upgrades anymore. Sounds wonderful. Following installation was made on my Linux Box running Ubuntu 16.04.01 LTS with Docker 1.11.2 and PostgreSQL 9.5.
If you build docker containers, ensure that you don’t write any data within the containers. Therefore you can use mapped volumes or data containers. Basically your docker containers that hosts the application or service should be immutable. I won’t go into details why, but how to check that a docker container does not grow.
If you use Dropwizard Metrics and the Metrics Reporter you might come into the situation, that the max value is not reported as long value. If it is reported as double Elasticsearch will complain you have an invalid mapping type, since a previous one has the type long. To avoid the situation, you can define in the index template, the type Elasticsearch for new indices from that template.
Having a Rasbperry Pi Cluster allows you to learn, test and experiment concepts about distributed computing. The first challenge is always how to keep the pi’s up to date. Having four nodes seems still manageable, but what about 64 nodes? Although it is a little bit repetitive, to enter the exact same commands over and over again. Another friend would see just write a bash script that executes the exact command on each node via SSH. Hmm, wait, there is Ansible that does exactly that for you. So a quick jump into Ansible under Ubuntu.