How Cassandra storing Metrics values from Agent ?

[arun2arunraj]

Hi Developers,

    For curious, I would like to know how cassandra collecting values from Agent and pushing it back to Postgresql.

    Please share me the documentation to understand it.

Regards,

ArunRaj.

[jayshaughnessy]

Hi,

In 4.9, the metric collection and reporting from the agent is unchanged from previous versions.  Metrics are collected at scheduled intervals and reports are fed to the RHQ Server(s),  The difference now is that metric data is stored into the RHQ Storage Cluster (i.e. Cassandra) and not the RDB (Postgres or Oracle).  It is *not* pushed from Cassandra to the RDB.  The legacy RDB tables are deprecated.  They are retained for the upgrade purpose of migrating legacy metric data only.  Once migrated those tables will now be unused.

Note that calltime and trait data are still stored in the RDB but that will change in the future.

This is a major step towards meeting the scalability demands of increasingly large RHQ deployments.

[arun2arunraj]

Hi Jay,

    Thank you so much for explaining simply and precisely about RHQ 4.9 Storage.

    Is possible to use Cassandra-cli tool for checking the metrics values in Storage node? If yes , share me the documentation. If no Please suggest me other tool.

Regards,

ArunRaj.

[jayshaughnessy]

Of course it would be possible to use the Cassandra CLI but I wouldn't recommend that approach.  You can still use the same higher level RHQ APIs to pull metric data.  CLI, REST, GUI, these will all behave the same as always, just using a different backend.

Accessing Cassandra directly is equivalent to playing with the RDB directly.  Basically, it's not documented, recommended, supported, or guaranteed to be backward compatible.

[arun2arunraj]

Hi Jay,

    I am completely new to development. I can Understand CLI. But I cant understand the other API . What is that RHQ REST and RHQ GUI ? Could you brief me by specifying documentation ?  

Regards,

ArunRaj.

[jayshaughnessy]

The GUI is just the standard RHQ user interface.   The CLI is the scripting inetrface, which uses our remote API.  That same API can be used via a custom Remote Java Client. The REST API is a separate API (unfortunately, not each approach offers the exact same features) for people wanting a REST interface to RHQ.

Running the RHQ CLI - RHQ - Project Documentation Editor

Best Practices for Remote Clients - RHQ - Project Documentation Editor

Design-REST - RHQ - Project Documentation Editor

There are some other useful REST links, google on RHQ REST API and you can find information on generating the API documentation, paging, etc.

[arun2arunraj]

Hi Jay,

    Thanks for your guidance.

Regards,

ArunRaj.