metrics formatting: preserve trailing whitespace

[macfarla]

The newline character is required at the end of this string.
Any other whitespace is ignored as per https://prometheus.io/docs/instrumenting/exposition_formats/ so no need to trim
Signed-off-by: Sally MacFarlane [email protected]

I have tested this locally and get the following response from
curl localhost:8581/metrics
Before ie without this change:

tessera_P2P_GET_getPartyInfo_MinTime_ms 0
tessera_P2P_GET_getPartyInfo_MaxTime_ms 0
...
tessera_THIRD_PARTY_GET_getVersion_RequestRate_requestsPerSeconds 0.0
tessera_THIRD_PARTY_GET_getVersion_RequestCount 0%

^ no new line at end of string

After ie with this change:

tessera_P2P_GET_getPartyInfo_MinTime_ms 0
tessera_P2P_GET_getPartyInfo_MaxTime_ms 0
...
tessera_THIRD_PARTY_GET_getVersion_RequestRate_requestsPerSeconds 0.0
tessera_THIRD_PARTY_GET_getVersion_RequestCount 0

so there is a newline at the end. Prometheus serves up the list of metrics.

[chris-j-h]

It's worth mentioning that Prometheus does correctly ingest and parse metrics without the trailing newline (checked with v2.28.1). However, as the Prometheus spec does state that "The last line must end with a line feed character", third party tools may enforce this (as seen in the linked issue), and future versions of Prometheus may not correctly handle no trailing newline.