Introduce security.BearerPrefix ("Bearer ", RFC 6750) and use it
everywhere an "Authorization: Bearer <token>" header is constructed,
replacing the scattered "BEARER "/"Bearer " string literals. SeaweedFS
matches the scheme case-insensitively when parsing (security.GetJwt), so
behavior is unchanged; this removes the magic string and settles the
casing on the standard form. The parser's upper-case comparison stays as
is on purpose.
A Canceled/DeadlineExceeded from the caller's per-request context was
treated like a dead channel: it closed the shared cached ClientConn and
cancelled every other in-flight RPC on it with "the client connection is
closing". Under a burst of concurrent chunk assigns (e.g. a large S3
multipart upload) one slow assign hitting its 10s attempt timeout could
poison the connection for all the rest, cascading into a flood of 500s.
Thread the caller's context into shouldInvalidateConnection and only
invalidate on Canceled/DeadlineExceeded while that context is still live,
which isolates the genuine stale-channel signal (a peer restart behind a
k8s Service VIP). To carry the context, add a ctx parameter to the
existing WithGrpcClient, WithMasterClient, and WithMasterServerClient; the
master assign and volume-lookup paths pass their per-attempt context and
every other caller passes context.Background().
When jwt.filer_signing.key is set, the filer's IamGrpcServer requires
a Bearer token on every IAM RPC. The shell's s3.* IAM commands dialed
without that header and failed with Unauthenticated. Route them through
a small helper that mints a token from the same key viper-loaded from
security.toml and appends it as outgoing metadata, matching the credential
grpc_store pattern.