Refactor diags and write into internal database

[otoolep]

No description provided.

[otoolep]

This is a significant refactor that splits out the common diags code into its own file, allowing it to be used by other types of nodes (brokers). The actual code is mostly the same, but diags types (as well as the server) can now convert diags data to InfluxQL rows. As rows, the latest diags data can be returned to the user as a query set, as well as easily written back into the database for monitoring.

This allows historical monitoring of all diagnostics. Of particular interest will be GC performance, memory usage, number of shards and shard groups on the cluster, index points, amongst other important data

[otoolep]

For example, here is a memory query from the internal database:

$ curl -G http://localhost:8086/query?pretty=true --data-urlencode "db=internal" --data-urlencode "q=SELECT * FROM server_memory LIMIT 1"
{
    "results": [
        {
            "series": [
                {
                    "name": "server_memory",
                    "columns": [
                        "time",
                        "alloc",
                        "frees",
                        "heapAlloc",
                        "heapIdle",
                        "heapInUse",
                        "heapObjects",
                        "heapReleased",
                        "heapSys",
                        "lookups",
                        "mallocs",
                        "numGG",
                        "pauseTotalNs",
                        "sys",
                        "totalAlloc"
                    ],
                    "values": [
                        [
                            "2015-03-26T08:08:54.214372053Z",
                            431184,
                            2878,
                            431184,
                            925696,
                            712704,
                            3161,
                            0,
                            1.6384e+06,
                            61,
                            6039,
                            7,
                            2.115413e+06,
                            3.999992e+06,
                            743328
                        ]
                    ]
                }
            ]
        }
    ]
}

[toddboom]

👍

so awesome.