* log_buffer: read only ts_ns during metadata-read binary search
readTs ran a full proto.Unmarshal of each LogEntry just to compare
timestamps during ReadFromBuffer's binary search, allocating fresh
slices for the data and key byte fields on every probe. Under
metadata-subscription fan-out this decode churn dominated allocations
and drove heavy GC, inflating filer RSS well past the live heap.
Scan the wire format for ts_ns (field 1) instead and skip the data/key
payloads without copying them. readTs is now zero-alloc; the binary
search no longer touches the event payloads at all.
* log_buffer: alias event payloads instead of copying them on delivery
The subscribe read loops decoded each LogEntry with a full proto.Unmarshal,
allocating fresh slices for the data and key byte fields on every entry
(protobuf consumeBytesNoZero). When many metadata subscribers each re-read
the in-memory log window under a reconnect storm, that per-entry copy was a
large share of allocation churn -- and for entries a subscriber filters out
by prefix, the copied payload was never even looked at.
Decode with a wire scan that points data/key at sub-slices of the source
buffer instead of copying. The aliased slices are valid only for the
duration of the eachLogEntryFn callback; every current subscriber either
re-decodes the event into its own struct or hands it to a synchronous grpc
Send, so none retain them. Per delivered entry the loop decode drops from
176 B / 2 allocs to zero.
