Add a status check for the size of database tables.

[cwebster61083]

Use Case

Have a check to alert if a table is above a certain threshold. For example, the certnames table. It would like this value to have a sane value but also be configurable.

Describe the Solution You Would Like

Alert me if key tables are larger than a set threshold and allow me to configure the threshold where necessary.

[MartyEwings]

The way we have the module is that the facts can not be altered, it's a good.idea but we wouldn't configure the threshold.

What list of tables and sizes do we think we want @cwebster61083

[bastelfreak]

might be related? If not let me know and I create a new issue:
I spent a few hours debugging unresponsive nodes

• they worked fine, but reports weren't stored in PuppetDB
• pe-puppetdb on the compiles was fine, but couldn't write into postgresql
• postgresql was overloaded because autovacuum was too conservative and didn't clean up enough
• dead tuple count was rising -> db size grow -> inserting takes more and more IO
• we were at a point where inserts where aborting because storage wasn't delivering enough IO for the (too) huge database

tl;dr a fact for dead tuples per table would be helpful I think? (and PE should have better defaults for autovacuum)

[MartyEwings]

@bastelfreak seems like a good addition