This commit addresses issue #44788 where the
`datacoord_stored_binlog_size` metric could become inaccurate when
multiple concurrent `GetMetrics` calls arrived at DataCoord.
### Problem
The original implementation called `Reset()` followed by `Add()`
operations on Prometheus metrics within the `GetQuotaInfo()` method.
When multiple goroutines invoked this method concurrently, race
conditions occurred:
- Thread 1: Reset() → Add(value1)
- Thread 2: Reset() → Add(value2)
- Result: Metrics could be reset multiple times and values added in an
interleaved fashion, leading to inaccurate and inflated metric values
### Solution
Changed the approach from `Reset() + Add()` to aggregating metric values
in local maps first, then using `Set()` to update metrics atomically:
1. Collect segment size data into local maps:
- `storedBinlogSize`: tracks size per collection per segment state
- `binlogFileSize`: tracks total file count per collection
- `coll2DbName`: maps collection IDs to database names
2. After aggregation is complete, use `Set()` (instead of `Add()`) to
update metrics in a single operation per label combination
This ensures that concurrent `GetMetrics` calls don't interfere with
each other, as each invocation works with its own local state and only
updates the final metric value atomically.
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Signed-off-by: Congqi Xia <congqi.xia@zilliz.com>
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