Refactored parquet exporters, dynamic selection of output columns

[T0mexX]

Summary

Added output configuration, that can be defined in the scenario .json file, that allows to select which columns are to be included in the raw output files host.parquet, server.parquet and service.parquet.

Implementation Notes ⚒️

Columns

The 'default' columns are defined in DfltHostExportcolumns, DfltServerExportColumns and DfltServiceExportColumns. Any number of additional columns can be definied anywhere (ExportColumn<Exportable>) and it is going to be deserializable as long as it is loaded by the jvm.

Deserialization

Each ExportColumn has a Regex, used for deserialization. If no custom regex is provided, the default one is used. The default regex matches the column name in case-insensitive manner, either with _ as separator (as in the name) or with (blank space).

E.g.:
column name = "cpu_count"
default column regex = "\\s*(?:cpu_count|cpu count)\\s*" (case-insensitive)
matches = "cpu_count", "cpu count", "CpU_cOuNt" etc.

JSON Schema

// scenario.json
{
	...
	"computeExportConfig": {
		"type": "object",
		"properties": {
			"hostExportColumns": { "type": "array" }, 
			"serverExportColumns": { "type": "array" } ,
			"serviceExportColumns": { "type": "array" } ,
			"required": [ /* NONE REQUIRED */ ]
		}
	},
	...
	"required": [
		...
		// NOT REQUIRED
	]
}

Bad Formatting Cases

• If a column name (and type) does not match any deserializable column, the entry is ignored and error message is logged.
• If an empty list of columns is provided or those that are provided were not deserializable, then all loaded columns for that Exportable are used, and a warning message is logged.
• If no list is provided, then all loaded columns for that Exportable are used.

Example

// scenario.json
{
	...
	"computeExportConfig": {
		"hostExportColumns": ["timestamp", "timestamp_absolute", "invalid-entry", "guests_invalid"],
		"serverExportColumns": ["invalid-entry"],
		"serviceExportColumns": ["timestamp", "servers_active", "servers_pending"]
	},
	...

// console output
10:51:56.561 [ERROR] ColListSerializer - no match found for column "invalid-entry", ignoring...
10:51:56.563 [ERROR] ColListSerializer - no match found for column "invalid-entry", ignoring...
10:51:56.564 [WARN] ComputeExportConfig - deserialized list of export columns for exportable ServerTableReader produced empty list, falling back to all loaded columns
10:51:56.584 [INFO] ScenariosSpec - 
| === Compute Export Config ===
| Host columns    : timestamp, timestamp_absolute, guests_invalid
| Server columns  : timestamp, timestamp_absolute, server_id, server_name, cpu_count, mem_capacity, cpu_limit, cpu_time_active, cpu_time_idle, cpu_time_steal, cpu_time_lost, uptime, downtime, provision_time, boot_time, boot_time_absolute
| Service columns : timestamp, servers_active, servers_pending

host.parquet

server.parquet
not included cause too large

service.parquet

External Dependencies 🍀

• N/A

Breaking API Changes ⚠️

• N/A

[T0mexX]

I force-pushed to change the commit messages to all use the past tense, since I saw that most of the commits use it.