* volume: count EC reads that fall back to reconstruction
When a needle read can't read an EC shard interval directly (the shard isn't
mounted here and no holder answers), both volume servers rebuild it from the
other shards and the read still succeeds, with nothing to show for it.
Count those fallbacks in SeaweedFS_volumeServer_ec_degraded_read_total{result}
(success, failure), one per interval, at the one place each server falls back:
Go readOneEcShardInterval, Rust fetch_one_interval. Corruption repair and scrub
aren't counted. A line binding each one to the needle and the volume's encode
generation is logged at V(3) in Go and debug in Rust.
* volume: name the EC counter for what it counts
Reed-Solomon reconstruction can't tell corrupt inputs from good ones, and the
needle is validated later, so "success" only ever meant the reconstruction
produced data. Rename the counter to
SeaweedFS_volumeServer_ec_reconstructed_interval_total and the log line to
"ec reconstructed interval", say so in the help text, and pin the behaviour
with a test: an interval rebuilt from corrupt parity counts success while the
read itself fails.
* storage: restore stderr when the log-line test stops early
A fixture failure in readEcNeedle ends the test through t.Fatalf, which
skipped restoring os.Stderr and closing the pipe, so later tests wrote
into a pipe nobody read.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---------
Co-authored-by: Chris Lu <chrislusf@users.noreply.github.com>
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
