clear

Drop every metric series this exporter holds and delete its five persisted keys (#2208).

Local-only, and it cannot be otherwise. GCounter and HyperLogLog are monotonic join-semilattices: a merge takes the element-wise maximum, so a peer holding the pre-clear state restores it. LWWRegister has no "cleared" value to write. Unlike WarpLogRecordExporter.clear and WarpSpanExporter.clear, which suppress the state they drop, this one only forgets it locally. On a replica that does not gossip its metrics — the case this exists for — the distinction never arises.

The keys are deleted rather than rewritten empty: there is no retained context to preserve here, so deleting reclaims the bytes and recover treats an absent key as empty.

Never throws. A refused delete returns MetricExportResult.Failure; the in-memory maps are cleared either way, so a retry converges.

Holds writeMutex across the whole turn, so a mutation that encoded the pre-clear map cannot land its stale bytes after the deletes. Without that fence the resurrection is permanent: nothing rewrites a deleted key unless that metric kind is used afresh, so a restart brings back every pre-clear series (#2232).