[Storage] CMS: monitor metrics

[mellelieuwes]

Implement the following metrics:

1. Number of store requests
2. Nr of bytes written to storage.

Note: If the storage is emptied (see: #891) the monitor metrics are not reset. So 2 is this a sum of the total written bytes (traffic volume) not the current stored bytes.

[mellelieuwes]

[mellelieuwes]

@TjerkNan for the future:

1. What extra usage metrics would be useful for a data storage?
2. Can we set thresholds on the metrics to raise awareness by giving them a color (orange or red). Not sure if this applicable since the Monitor is not for us but for the creator.

[TjerkNan]

Maybe add: Total storage used in GB.

Just my opinion:

• you might consider moving the file count to this screen
• Store requests and kb transfered may not be meaningfull information for non-it people and I'm not sure if it tells me anything
• we might set a soft quota on capacity and show how much of X GB is used just to give a sense that storage is not unlimited
• we might set a soft quota on the number of files stored if it turns out during my testing that large file counts may hurt performance.

[mellelieuwes]

@TjerkNan In general Monitor is based on system events. Actual data is not part of the Monitor.

For storage we currently have the following metrics:

• nr of write requests (most of the time the same as nr of files)
• transferred bytes (most of the time the same as stored bytes).

If the files in the storage are deleted, the events are not reset.

In general the Monitor is (only) designed for:

1. Give trust when seeing activity
2. Taking actions if something is not going as expected

For storage the Monitor is not really necessary. But to be consistent with other CMS pages it is added.

[mellelieuwes]

See the follow up improvements:

1. 918

2. 917

[TjerkNan]

@emielvdveen #918 tested, keep this open for #917 when ready

[TjerkNan]

as discussed this can be closed