# Changelog

All notable changes to this project will be documented in this file. The format
is based on [Keep a Changelog](https://keepachangelog.com).

## [Unreleased]

### Added

- The enum `caf::sec` received an additional error code: `connection_closed`.
- The new `byte_span` and `const_byte_span` aliases provide convenient
  definitions when working with sequences of bytes.

### Changed

- When using `CAF_MAIN`, CAF now looks for the correct default config file name,
  i.e., `caf-application.conf`.

### Fixed

- Setting an invalid credit policy no longer results in a segfault (#1140).
- Version 0.18.0-rc.1 introduced a regression that prevented CAF from writing
  parameters parsed from configuration files back to variables. The original
  behavior has been restored, i.e., variables synchronize with user input from
  configuration files and CLI arguments (#1145).
- Restore correct functionality of `middleman::remote_lookup` (#1146). This
  fixes a regression introduced in version 0.18.0-rc.1
- Fixed an endless recursion when using the `default_inspector` from `inspect`
  overloads (#1147).
- CAF 0.18 added support for `make_behavior` in state classes. However, CAF
  erroneously picked this member function over running the function body when
  spawning function-based actors (#1149).
- When passing `nullptr` or custom types with implicit conversions to
  `const char*` to `deep_to_string`, CAF could run into a segfault in the former
  case or do unexpected things in the latter case. The stringification inspector
  now matches precisely on pointer types to stop the compiler from doing
  implicit conversions in the first place.
- Building executables that link to CAF on 32-bit Linux versions using GCC
  failed due to undefined references to `__atomic_fetch` symbols. Adding a CMake
  dependency for `caf_core` to libatomic gets executables to compile and link as
  expected (#1153).

## [0.18.0-rc.1] - 2020-09-09

### Added

- The new `fan_out_request` function streamlines fan-out/fan-in work flows (see
  the new example in `examples/message_passing/fan_out_request.cpp` as well as
  the new manual entry). The policy-based design further allows us to support
  more use cases in the future (#932, #964).
- We introduced the lightweight template class `error_code` as an alternative to
  the generic but more heavyweight class `error`. The new error code abstraction
  simply wraps an enumeration type without allowing users to add additional
  context such as error messages. However, whenever such information is
  unneeded, the new class is much more efficient than using `error`.
- Tracing messages in distributed systems is a common practice for monitoring
  and debugging message-based systems. The new `tracing_data` abstraction in CAF
  enables users to augment messages between actors with arbitrary meta data.
  This is an experimental API that requires building CAF with the CMake option
  `CAF_ENABLE_ACTOR_PROFILER` (#981).
- Add compact `from..to..step` list notation in configuration files. For
  example, `[1..3]` expands to `[1, 2, 3]` and `[4..-4..-2]` expands to
  `[4, 2, 0, -2, -4]` (#999).
- Allow config keys to start with numbers (#1014).
- The `fan_out_request` function got an additional policy for picking just the
  fist result: `select_any` (#1012).
- Run-time type information in CAF now uses 16-bit type IDs. Users can assign
  this ID by specializing `type_id` manually (not recommended) or use the new
  API for automatically assigning ascending IDs inside `CAF_BEGIN_TYPE_ID_BLOCK`
  and `CAF_END_TYPE_ID_BLOCK` code blocks.
- The new typed view types `typed_message_view` and `const_typed_message_view`
  make working with `message` easier by providing a `std::tuple`-like interface
  (#1034).
- The class `exit_msg` finally got its missing `operator==` (#1039).
- The class `node_id` received an overload for `parse` to allow users to convert
  the output of `to_string` back to the original ID (#1058).
- Actors can now `monitor` and `demonitor` CAF nodes (#1042). Monitoring a CAF
  node causes the actor system to send a `node_down_msg` to the observer when
  losing connection to the monitored node.
- In preparation of potential future API additions/changes, CAF now includes an
  RFC4122-compliant `uuid` class.
- The new trait class `is_error_code_enum` allows users to enable conversion of
  custom error code enums to `error` and `error_code`.
- CAF now enables users to tap into internal CAF metrics as well as adding their
  own instrumentation! Since this addition is too large to cover in a changelog
  entry, please have a look at the new *Metrics* Section of the manual to learn
  more.

### Deprecated

- The `to_string` output for `error` now renders the error code enum by default.
  This renders the member functions `actor_system::render` and
  `actor_system_config::render` obsolete.
- Actors that die due to an unhandled exception now use `sec::runtime_error`
  consistently. This makes `exit_reason::unhandled_exception` obsolete.

### Changed

- CAF now requires C++17 to build.
- On UNIX, CAF now uses *visibility hidden* by default. All API functions and
  types that form the ABI are explicitly exported using module-specific macros.
  On Windows, this change finally enables building native DLL files.
- We switched our coding style to the C++17 nested namespace syntax.
- CAF used to generate the same node ID when running on the same machine and
  only differentiates actors systems by their process ID. When running CAF
  instances in a container, this process ID is most likely the same for each
  run. This means two containers can produce the same node ID and thus
  equivalent actor IDs. In order to make it easier to use CAF in a containerized
  environment, we now generate unique (random) node IDs (#970).
- We did a complete redesign of all things serialization. The central class
  `data_processor` got removed. The two classes for binary serialization no
  longer extend the generic interfaces `serializer` and `deserializer` in order
  to avoid the overhead of dynamic dispatching as well as the runtime cost of
  `error` return values. This set of changes leads so some code duplication,
  because many CAF types now accept a generic `(de)serializer` as well as a
  `binary_(de)serializer` but significantly boosts performance in the hot code
  paths of CAF (#975).
- With C++17, we no longer support compilers without support for `thread_local`.
  Consequently, we removed all workarounds and switched to the C++ keyword
  (#996).
- Our manual now uses `reStructuredText` instead of `LaTeX`. We hope this makes
  extending the manual easier and lowers the barrier to entry for new
  contributors.
- A `stateful_actor` now forwards excess arguments to the `State` rather than to
  the `Base`. This enables states with non-default constructors. When using
  `stateful_actor<State>` as pointer type in function-based actors, nothing
  changes (i.e. the new API is backwards compatible for this case). However,
  calling `spawn<stateful_actor<State>>(xs...)` now initializes the `State` with
  the argument pack `xs...` (plus optionally a `self` pointer as first
  argument). Furthermore, the state class can now provide a `make_behavior`
  member function to initialize the actor (this has no effect for function-based
  actors).
- In order to stay more consistent with naming conventions of the standard
  library, we have renamed some values of the `pec` enumeration:
  + `illegal_escape_sequence` => `invalid_escape_sequence`
  + `illegal_argument` => `invalid_argument`
  + `illegal_category` => `invalid_category`
- CAF no longer automagically flattens `tuple`, `optional`, or `expected` when
  returning these types from message handlers. Users can simply replace
  `std::tuple<A, B, C>` with `caf::result<A, B, C>` for returning more than one
  value from a message handler.
- A `caf::result` can no longer represent `skip`. Whether a message gets skipped
  or not is now only for the default handler to decide. Consequently, default
  handlers now return `skippable_result` instead of `result<message>`. A
  skippable result is a variant over `delegated<message>`, `message`, `error`,
  or `skip_t`. The only good use case for message handlers that skip a message
  in their body was in typed actors for getting around the limitation that a
  typed behavior always must provide all message handlers (typed behavior assume
  a complete implementation of the interface). This use case received direct
  support: constructing a typed behavior with `partial_behavior_init` as first
  argument suppresses the check for completeness.
- In order to reduce complexity of typed actors, CAF defines interfaces as a set
  of function signatures rather than using custom metaprogramming facilities.
  Function signatures *must* always wrap the return type in a `result<T>`. For
  example: `typed_actor<result<double>(double)>`. We have reimplemented the
  metaprogramming facilities `racts_to<...>` and `replies_to<...>::with<...>`
  as an alternative way of writing the function signature.
- All parsing functions in `actor_system_config` that take an input stream
  exclusively use the new configuration syntax (please consult the manual for
  details and examples for the configuration syntax).
- The returned string of `name()` must not change during the lifetime of an
  actor. Hence, `stateful_actor` now only considers static `name` members in its
  `State` for overriding this function. CAF always assumed names belonging to
  *types*, but did not enforce it because the name was only used for logging.
  Since the new metrics use this name for filtering now, we enforce static names
  in order to help avoid hard-to-find issues with the filtering mechanism.
- The type inspection API received a complete overhaul. The new DSL for writing
  `inspect` functions exposes the entire structure of an object to CAF. This
  enables inspectors to read and write a wider range of data formats. In
  particular human-readable, structured data such as configuration files, JSON,
  XML, etc. The inspection API received too many changes to list them here.
  Please refer to the manual section on type inspection instead.

### Removed

- A vendor-neutral API for GPGPU programming sure sounds great. Unfortunately,
  OpenCL did not catch on in the way we had hoped. At this point, we can call
  OpenCL dead and gone. There is only legacy support available and recent
  versions of the standard were never implemented in the first place.
  Consequently, we've dropped the `opencl` module.
- The old `duration` type is now superseded by `timespan` (#994).
- The enum `match_result` became obsolete. Individual message handlers can no
  longer skip messages. Hence, message handlers can only succeed (match) or not.
  Consequently, invoking a message handler or behavior now returns a boolean.
- All member functions of `scheduled_actor` for adding stream managers (such as
  `make_source`) were removed in favor their free-function equivalent, e.g.,
  `attach_stream_source`
- The configuration format of CAF has come a long way since first starting to
  allow user-defined configuration via `.ini` files. Rather than sticking with
  the weird hybrid that evolved over the years, we finally get rid of the last
  pieces of INI syntax and go with the much cleaner, scoped syntax. The new
  default file name for configuration files is `caf-application.conf`.

### Fixed

- Fix uninstall target when building CAF as CMake subdirectory.
- Using `inline_all_enqueues` in deterministic unit tests could result in
  deadlocks when calling blocking functions in message handlers. This function
  now behaves as expected (#1016).
- Exceptions while handling requests now trigger error messages (#1055).
- The member function `demonitor` falsely refused typed actor handles. Actors
  could monitor typed actors but not demonitoring it again. This member function
  is now a template that accepts any actor handle in the same way `monitor`
  already did.
- The `typed_actor_view` decorator lacked several member functions such as
  `link_to`, `send_exit`, etc. These are now available.
- Constructing a `typed_actor` handle from a pointer view failed du to a missing
  constructor overload. This (explicit) overload now exists and the conversion
  should work as expected.
- Sending floating points to remote actors changed `infinity` and `NaN` to
  garbage values (#1107). The fixed packing / unpacking routines for IEEE 754
  values keep these non-numeric values intact now. It is worth mentioning that
  the new algorithm downgrades signaling NaN values to silent NaN values,
  because the standard API does not provide predicates to distinguish between the
  two. This should have no implications for real-world applications, because
  actors that produce a signaling NaN trigger trap handlers before sending
  the result to another actor.
- The URI parser stored IPv4 addresses as strings (#1123). Users can now safely
  assume that the parsed URI for `tcp://127.0.0.1:8080` returns an IP address
  when calling `authority().host`.

## [0.17.7] - Unreleased

### Fixed

- Datagram servants of UDP socket managers were not added as children to their
  parent broker on creation, which prevented proper system shutdown in some
  cases. Adding all servants consistently to the broker should make sure UDP
  brokers terminate correctly (#1133).
- Backport stream manager fix from CAF 0.18 for fused downstream managers that
  prevent loss of messages during regular actor shutdown.

## [0.17.6] - 2020-07-24

### Fixed

- Trying to connect to an actor published via the OpenSSL module with the I/O
  module no longer hangs indefinitely (#1119). Instead, the OpenSSL module
  immediately closes the socket if initializing the SSL session fails.

## [0.17.5] - 2020-05-13

### Added

- In order to allow users to start migrating towards upcoming API changes, CAF
  0.17.5 includes a subset of the CAF 0.18 `type_id` API. Listing all
  user-defined types between `CAF_BEGIN_TYPE_ID_BLOCK` and
  `CAF_END_TYPE_ID_BLOCK` assigns ascending type IDs. Only one syntax for
  `CAF_ADD_ATOM` exists, since the atom text is still mandatory. Assigning type
  IDs has no immediate effect by default. However, the new function
  `actor_system_config::add_message_types` accepts an ID block and adds
  runtime-type information for all types in the block.
- In order to opt into the compile-time checks for all message types, users can
  set the `CAF_ENABLE_TYPE_ID_CHECKS` CMake flag to `ON` (pass
  `--enable-type-id-checks` when using the `configure` script). Building CAF
  with this option causes compiler errors when sending a type without a type ID.
  This option in conjunction with the new `add_message_types` function removes a
  common source of bugs: forgetting to call `add_message_type<T>` for all types
  that can cross the wire.

### Changed

- Our manual now uses `reStructuredText` instead of `LaTeX` (backport from
  [0.18.0]).

### Fixed

- Fix handling of OS-specific threading dependency in CMake.
- Fix uninstall target when building CAF as CMake subdirectory (backport from
  [0.18.0]).
- Fix potential deadlock with `inline_all_enqueues` (backport from [0.18.0]).
- Exceptions while handling requests now trigger error messages (backport from
  [0.18.0]).
- Fix build on GCC 7.2
- Fix build error in the OpenSSL module under some MSVC configurations
- Serializer and deserializer now accept `std::chrono::time_point` for all clock
  types instead of hard-wiring `std::system_clock`.
- In some edge cases, actors failed to shut down properly when hosting a stream
  source (#1076). The handshake process for a graceful shutdown has been fixed.
- Fixed a compiler error on Clang 10 (#1077).
- Setting lists and dictionaries on the command line now properly overrides
  default values and values from configuration files instead of appending to
  them (#942).
- Using unquoted strings in command-line arguments inside lists now works as
  expected. For example, `--foo=abc,def` is now equivalent to
  `--foo=["abc", "def"]`.
- Fixed a type mismatch in the parameter `middleman.heartbeat-interval` (#1095).
  CAF consistently uses `timespan` for this parameter now.

## [0.17.4] - 2019-02-08

### Added

- The class `exit_msg` finally got its missing `operator==` (#1039, backport
  from [0.18.0]).

### Changed

- Make sure actors that receive stream input shut down properly (#1019).
- Improve `to_string` output for `caf::error` (#1021).
- Properly report errors to users while connecting two CAF nodes (#1023).
- Simplify crosscompilation: remove build dependency on code generators (#1026).
- Leave CXX settings to the (CMake) parent when building as subdirectory (#1032).
- Build without documentation in subdirectory mode (#1037).
- Allow parents to set `OPENSSL_INCLUDE_DIR` in subdirectory mode (#1037).
- Add `-pthread` flag on UNIX when looking for `libc++` support (#1038).
- Avoid producing unexpected log files (#1024).

### Fixed

- Accept numbers as keys in the config syntax (#1014).
- Fix undesired function hiding in `fused_downstream_manager` (#1020).
- Fix behavior of `inline_all_enqueues` in the testing DSL (#1016).
- Fix path recognition in the URI parser, e.g., `file:///` is now valid (#1013).

## [0.17.3] - 2019-11-11

### Added

- Add support for OpenBSD (#955).
- Provide uniform access to actor properties (#958).
- Add missing `to_string(pec)` (#940).

### Fixed

- Fix bug in stream managers that caused finalizers to get called twice (#937).
- Fix verbosity level with disabled console output (#953).
- Fix excessive buffering in stream stages (#952).

## [0.17.2] - 2019-10-20

### Added

- Add `scheduled_send` for delayed sends with absolute timeout (#901).
- Allow actors based on composable behaviors to use the streaming API (#902).
- Support arbitrary list and map types in `config_value` (#925).
- Allow users to extend the `config_value` API (#929, #938).

### Changed

- Reduce stack usage of serializers (#912).
- Use default installation directories on GNU/Linux (#917).

### Fixed

- Fix memory leak when deserializing `node_id` (#905).
- Fix composition of statically typed actors using streams (#908).
- Fix several warnings on GCC and Clang (#915).
- Fix `holds_alternative` and `get_if` for `settings` (#920).
- Fix silent dropping of errors in response handlers (#935).
- Fix stall in `remote_group` on error (#933).

## [0.17.1] - 2019-08-31

### Added

- Support nesting of group names in .ini files (#870).
- Support all alphanumeric characters in config group names (#869).

### Changed

- Improve CMake setup when building CAF as subfolder (#866).
- Properly set CLI remainder (#871).

### Fixed

- Fix endless loop in config parser (#894).
- Fix debug build with Clang 7 on Linux (#861).
- Fix type-specific parsing of config options (#814).
- Fix potential deadlock in proxy registry (#880).
- Fix output of --dump-config (#876).
- Fix potential segfault when using streams with trace logging enabled (#878).
- Fix handling of containers with user-defined types (#867).
- Fix `defaulted_function_deleted` warning on Clang (#859).

## [0.17.0] - 2019-07-27

### Added

- Add marker to make categories optional on the CLI. Categories are great at
  organizing program options. However, on the CLI they get in the way quickly.
  This change allows developers to prefix category names with `?` to make it
  optional on the CLI.
- Add conversion from `nullptr` to intrusive and COW pointer types.
- Support move-only behavior functions.
- Allow users to omit `global` in config files.
- Allow IPO on GCC/Clang.

### Changed

- Parallelize deserialization of messages received over the network (#821).
  Moving the deserialization out of the I/O loop significantly increases
  performance. In our benchmark, CAF now handles up to twice as many messages
  per second.
- Relax ini syntax for maps by making `=` for defining maps and `,` for
  separating key-value pairs optional. For example, this change allows to
  rewrite an entry like this:
  ```ini
  logger = {
    console-verbosity='trace',
    console='colored'
  }
  ```
  to a slightly less noisy version such as this:
  ```ini
  logger {
    console-verbosity='trace'
    console='colored'
  }
  ```
- Allow apps to always use the `logger`, whether or not CAF was compiled with
  logging enabled.
- Streamline direct node-to-node communication and support multiple app
  identifiers.
- Reimplement `binary_serializer` and `binary_deserializer` without STL-style
  stream buffers for better performance.

### Fixed

- Fix performance of the thread-safe actor clock (#849). This clock type is used
  whenever sending requests, delayed messages, receive timeouts etc. With this
  change, CAF can handle about 10x more timeouts per second.
- Fix multicast address detection in `caf::ipv4_address.cpp` (#853).
- Fix disconnect issue / WSAGetLastError usage on Windows (#846).
- Fix `--config-file` option (#841).
- Fix parsing of CLI arguments for strings and atom values.

## [0.16.5] - 2019-11-11

### Added

- Support for OpenBSD.

## [0.16.4] - 2019-11-11

### Fixed

- Backport parser fixes from the CAF 0.17 series.
- Silence several compiler warnings on GCC and Clang.

## [0.16.3] - 2018-12-27

### Added

- The new class `cow_tuple` provides an `std::tuple`-like interface for a
  heap-allocated, copy-on-write tuple.
- Missing overloads for `dictionary`.
- The new `to_lowercase` function for atoms allows convenient conversion without
  having to convert between strings and atoms.

### Changed

- Printing timestamps now consistently uses ISO 8601 format.
- The logger now uses a bounded queue. This change in behavior will cause the
  application to slow down when logging faster than the logger can do I/O, but
  the queue can no longer grow indefinitely.
- Actors now always try to dequeue from the high-priority queue first.

### Fixed

- Solved linker errors related to `socket_guard` in some builds.
- Fix the logger output for class names.
- Deserializing into non-empty containers appended to the content instead of
  overriding it. The new implementation properly clears the container before
  filling it.
- The `split` function from the string algorithms header now works as the
  documentation states.
- Silence several compiler warnings on GCC and Clang.

## [0.16.2] - 2018-11-03

### Fixed

- The copy-on-write pointer used by `message` failed to release memory in some
  cases. The resulting memory leak is now fixed.

## [0.16.1] - 2018-10-31

### Added

- Adding additional flags for the compiler when using the `configure` script is
  now easier thanks to the `--extra-flags=` option.
- The actor clock now supports non-overriding timeouts.
- The new `intrusive_cow_ptr` is a smart pointer for copy-on-write access.

### Changed

- Improve `noexcept`-correctness of `variant`.
- CAF threads now have recognizable names in a debugger.
- The middleman now passes `CLOEXEC` on `socket`/`accept`/`pipe` calls.
- Users can now set the log verbosity for file and console output separately.

### Fixed

- A `dictionary` now properly treats C-strings as strings when using `emplace`.
- Eliminate a potential deadlock in the thread-safe actor clock.
- Added various missing includes and forward declarations.

## [0.16.0] - 2018-09-03

### Added

- As part of [CE-0002](https://git.io/Jvoo5), `config_value` received support
  for lists, durations and dictionaries. CAF now exposes the content of an actor
  system config as a dictionary of `config_value`. The free function `get_or`
  offers convenient access to configuration parameters with hard-coded defaults
  as fallback.
- The C++17-compatible `string_view` class enables us to make use of recent
  standard addition without having to wait until it becomes widely available.
- In preparation of plans for future convenience API, we've added `uri`
  according to [RFC 3986](https://tools.ietf.org/html/rfc3986) as well as
  `ipv6_address` and `ipv4_address`.
- A new, experimental streaming API. Please have a look at the new manual
  section for more details.

### Deprecated

- Going forward, the preferred way to access configuration parameters is using
  the new `get_or` API. Hence, these member variables are now deprecated in
  `actor_system_config`:
  + `scheduler_policy`
  + `scheduler_max_threads`
  + `scheduler_max_throughput`
  + `scheduler_enable_profiling`
  + `scheduler_profiling_ms_resolution`
  + `scheduler_profiling_output_file`
  + `work_stealing_aggressive_poll_attempts`
  + `work_stealing_aggressive_steal_interval`
  + `work_stealing_moderate_poll_attempts`
  + `work_stealing_moderate_steal_interval`
  + `work_stealing_moderate_sleep_duration_us`
  + `work_stealing_relaxed_steal_interval`
  + `work_stealing_relaxed_sleep_duration_us`
  + `logger_file_name`
  + `logger_file_format`
  + `logger_console`
  + `logger_console_format`
  + `logger_verbosity`
  + `logger_inline_output`
  + `middleman_network_backend`
  + `middleman_app_identifier`
  + `middleman_enable_automatic_connections`
  + `middleman_max_consecutive_reads`
  + `middleman_heartbeat_interval`
  + `middleman_detach_utility_actors`
  + `middleman_detach_multiplexer`
  + `middleman_cached_udp_buffers`
  + `middleman_max_pending_msgs`

### Removed

- The `boost::asio` was part of an initiative to contribute CAF as
  `boost::actor`. Since there was little interest by the Boost community, this
  backend now serves no purpose.

### Fixed

- Setting the log level to `quiet` now properly suppresses any log output.
- Configuring colored terminal output should now print colored output.

[Unreleased]: https://github.com/actor-framework/actor-framework/compare/0.18.0-rc.1...master
[0.18.0-rc.1]: https://github.com/actor-framework/actor-framework/releases/0.18.0-rc.1
[0.17.7]: https://github.com/actor-framework/actor-framework/compare/0.17.6...release/0.17
[0.17.6]: https://github.com/actor-framework/actor-framework/releases/0.17.6
[0.17.5]: https://github.com/actor-framework/actor-framework/releases/0.17.5
[0.17.4]: https://github.com/actor-framework/actor-framework/releases/0.17.4
[0.17.3]: https://github.com/actor-framework/actor-framework/releases/0.17.3
[0.17.2]: https://github.com/actor-framework/actor-framework/releases/0.17.2
[0.17.1]: https://github.com/actor-framework/actor-framework/releases/0.17.1
[0.17.0]: https://github.com/actor-framework/actor-framework/releases/0.17.0
[0.16.5]: https://github.com/actor-framework/actor-framework/releases/0.16.5
[0.16.4]: https://github.com/actor-framework/actor-framework/releases/0.16.4
[0.16.3]: https://github.com/actor-framework/actor-framework/releases/0.16.3
[0.16.2]: https://github.com/actor-framework/actor-framework/releases/0.16.2
[0.16.1]: https://github.com/actor-framework/actor-framework/releases/0.16.1
[0.16.0]: https://github.com/actor-framework/actor-framework/releases/0.16.0
