Export tier metrics

[krisis]

Community Contribution License

All community contributions in this pull request are licensed to the project maintainers
under the terms of the Apache 2 license.
By creating this pull request I represent that I have the right to license the
contributions to the project maintainers under the Apache 2 license.

Description

• minio_node_tier_ttlb_seconds_distribution - Distribution of time to last byte for streaming objects from warm tier
• minio_node_tier_requests_success - Number of requests to download object from warm tier that were successful
• minio_node_tier_requests_failure - Number of requests to download object from warm tier that failed

Motivation and Context

Observability into remote tier performance

How to test this PR?

Sample output

./mc admin prometheus metrics myminio/ node | grep tier
# HELP minio_node_tier_requests_failure Number of requests to download object from warm tier that failed
# TYPE minio_node_tier_requests_failure counter
minio_node_tier_requests_failure{server="minio3:9000",tier="WARM-1"} 0
# HELP minio_node_tier_requests_success Number of requests to download object from warm tier that were successful
# TYPE minio_node_tier_requests_success counter
minio_node_tier_requests_success{server="minio3:9000",tier="WARM-1"} 1
# HELP minio_node_tier_ttlb_seconds_distribution Distribution of time to last byte for streaming objects from warm tier
# TYPE minio_node_tier_ttlb_seconds_distribution gauge
minio_node_tier_ttlb_seconds_distribution{le="0.010",server="minio3:9000",tier="WARM-1"} 0
minio_node_tier_ttlb_seconds_distribution{le="0.100",server="minio3:9000",tier="WARM-1"} 1
minio_node_tier_ttlb_seconds_distribution{le="1.000",server="minio3:9000",tier="WARM-1"} 1
minio_node_tier_ttlb_seconds_distribution{le="10.000",server="minio3:9000",tier="WARM-1"} 1
minio_node_tier_ttlb_seconds_distribution{le="2.000",server="minio3:9000",tier="WARM-1"} 1
minio_node_tier_ttlb_seconds_distribution{le="5.000",server="minio3:9000",tier="WARM-1"} 1

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Optimization (provides speedup with no functional changes)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• Fixes a regression (If yes, please add commit-id or PR # here)
• Unit tests added/updated
• Internal documentation updated
• Create a documentation update request here

[vadmeste]

LGTM