horizon/ingest: http archive requests need a metric and user-agent correction

[sreuland]

What version are you using?

2.27.0

What did you do?

run horizon with forward/live ingestion enabled, ingest=true which is enabled. by default.

What did you expect to see?

• outbound http archive url requests initiated by horizon ingestion should have the http header User-Agent: "horizon/<horizon_version> golang/<go_mod_version>
• outbound http archive url requests initiated by horizon captive core runner(created from NewCaptive()) should have the http header User-Agent: "horizon/<horizon_version> golang/<go_mod_version>
• a prometheus metric is emitted for the history archive request

What did you see instead?

the outbound archive url request has the default golang http header instead User-Agent: "Go-http-client

[sreuland]

I believe this bug was present up to release 2.27.0 due to the user agent config being dropped from the config sent to archive pool here:

https://github.com/stellar/go/blob/horizon-v2.27.0/historyarchive/archive_pool.go#L36-L39

however, looking at latest on master, this issue appears to now be obsolete as the entire config including user agent is now sent to the archive pool creation:

https://github.com/stellar/go/blob/master/historyarchive/archive_pool.go#L34-L36

this change was merged recently as part of exp: Add the Zenith (Light Horizon) prototype #4352, and will result in archive url requests from horizon ingestion to now emit http header User-Agent: horizon/<horizon_version> golang/<go_mod_version> and will land on next release upcoming of 2.28.0.

[sreuland]

related to #5163, at least for identifying an archive request coming from horizon based on user-agent.

[sreuland]

will patch this on 2.28.0 release branch, since latest master which has a fix from a larger feature dev effort related to ledgerexporter, #4352, will not be included on 2.28.0 release.

[sreuland]

#5166 merged