Release 5.6.0

[TheJokr]

Added

• The ratelimit! utility macro simplifies the setup required for rate-limiting a code block into a single macro expression. There is also a special ratelimit= prefix syntax for log statements specifically. (Add ratelimit! utility macro #182)
• The sentry metrics hook added in v5.5 now also supports rate-limiting for sentry events. To make use of this feature, call the new foundations::sentry::install_hook_with_settings setup function. (Add configurable rate limiting for sentry events #183)
• The telemetry server implements a /pprof/symbol endpoint now, which can be used for remote symbolization with pprof-compatible tools. (Implement /pprof/symbol #186)
• foundations::telemetry::tracing::span_is_sampled() provides a cheap way to check whether the current trace has been sampled. This allows skipping expensive tag/log formatting code if the values would be discarded anyway. (Expose span_is_sampled for cheap sampling checks #187)
• Secret (string) and RawSecret (bytes) wrappers have been added to aid with confidential values in config files. Both types hide their contents from Debug/Display calls and require an explicit accessors to retrieve the secret. Additionally, they zero their memory when dropped. (Add helpful string/byte wrappers for secrets and external data #188)
• MaybeExternal is a new settings type that can load plain data (strings, bytes, and secrets) from either inline config or external sources (environment variables or file system). (Add helpful string/byte wrappers for secrets and external data #188)

Improved

• serde_yaml was replaced by the new serde-saphyr YAML implementation. serde_yaml has been unmaintained since 2024. (Remove serde yaml, update some deps to the latest version. #181)
• Loggers can now be frozen, meaning any further mutation (such as add_fields!) will lead to an error. This is useful to catch bugs where mutations are applied to the wrong logger instance. (feat(logging): add logger freeze/unfreeze #189)
• The maximum queue size for trace span output can now be limited via telemetry settings. The default has been set at 1 million spans. Additionally, there are new metrics to observe the queue size, total number of spans exported, and how many spans have been dropped. (Prepare foundations for multi-consumer tracing output #190)
• Tracing can now be configured with multiple concurrent output tasks to boost span throughput. The tasks now run independently of the TelemetryDriver to ensure spans are output throughout the lifetime of the process. (Allow multiple concurrent trace exporter tasks #191)

Fixed

• Log rate limiting now correctly applies across set_verbosity calls. (Refactor slog::Drain setup code and fix rate limiting bug #180)

Deprecated

• foundations::sentry::install_hook is deprecated in favor of foundations::sentry::install_hook_with_settings.