Hazelcast

Hazelcast is a great in-memory data grid. Much like Redis, but has way better clustering model.

Strange conf file location

The installation of Hazelcast is stellar, you set up the APT repository and run

# apt-get install hazelcast

to install it. However, the conf file isn't under /etc as you would expect, but is instead to be found under this path:

/usr/lib/hazelcast/hazelcast-5.0/config/hazelcast.xml

Having it to listen on something else than the loopback device

Change:

<interfaces enabled="true">
  <interface>127.0.0.1</interface>
</interfaces>

to the IP of the interface on which you want Hazelcast to listen:

<interfaces enabled="true">
  <interface>10.196.166.239</interface>
</interfaces>

Restart the Hazelcast instance with:

$ hz restart

Enable REST API

Hazelcast has a nice, simple REST API. You can enable it by adding the <rest-api> element:

<hazelcast ..>
..
  <network>
    <rest-api enabled="true">
      <endpoint-group name="DATA" enabled="true"/>
    </rest-api>
    ..
  </network>
..
</hazelcast>

Good error messages

Here, I've asked it to use LRUs eviction strategy instead of LRU 🤦:

Caused by: org.xml.sax.SAXParseException; lineNumber: 271;
columnNumber: 79; cvc-enumeration-valid: Value 'LRUs' is not
facet-valid with respect to enumeration '[NONE, LRU, LFU, RANDOM]'. It
must be a value from the enumeration.