DogstatsdExporter: `max_payload_len` behavior difference

[nappairam]

Thanks for taking time to review my PR for global labels, namespace.
#555

I observed another difference today, when compared to the v0.8 of dogstatsd exporter.
Each metric is send in a separate UDP packets, instead of aggregating.

Version 0.8 supported a parameter max_packet_size. The exporter will aggregate the metrics and split based on the above size and send as UDP packets.
https://github.com/dialtone/metrics-exporter-dogstatsd/blob/a623e5c1463f063c1377386b2754f1e79cc5435a/src/builder.rs#L466

Current version 0.9 has a similar parameter maximum_payload_length

metrics/metrics-exporter-dogstatsd/src/builder.rs

Line 183 in e113ab4

pub fn with_maximum_payload_length(

But instead of aggregating the metrics in a single packet, it simply restricts the maximum size of the single metric.

Aggregating metrics is very useful to servers with large amount of metrics, since exporter do not need to spam UDP packets and waste CPU cycles.

Could you consider adding this aggregation support ?

[tobz]

Payload-level aggregation is definitely on the roadmap... just haven't gotten to it yet.

I'll keep this issue open to track it. 👍🏻

[nappairam]

Attempting this on #561