comparison src/capnproto-0.6.0/doc/roadmap.md @ 62:0994c39f1e94

Cap'n Proto v0.6 + build for OSX

+---
+layout: page
+title: Road Map
+---
+
+# Road Map
+
+This is a list of big ideas we'd like to implement in Cap'n Proto. We don't know in what order
+these will actually happen; as always, real work is driven by real-world needs.
+
+### Language Features
+
+* **Inline lists:**  Lets you define a field composed of a fixed number of elements of the same
+  type, and have those elements be stored directly within the struct rather than as a separate
+  object.  Useful mainly to avoid the need to validate list lengths when the length should always
+  be the same.  Also saves a pointer's worth of space.
+* **Type aliases:**  Ability to define a type which is just an alias of some other type, and
+  have it show up as e.g. a `typedef` in languages that support that.  (The current `using`
+  keyword is intended only for local use and does not affect code generation.)
+* **Doc comments:**  Harvest doc comments from schema files and use them to generate doc comments
+  on generated code.  Also make them available in the compiled schema so that a documentation
+  generator could use them.
+* **Encapsulated types:**  This will allow you to create a hand-written wrapper around a
+  type which will be automatically injected into the generated code, so that you can provide a
+  nicer interface which encapsulates the type's inner state.
+* **Maps:**  Based on encapsulated and parameterized types.
+
+### RPC Protocol Features
+
+* **Dynamic schema transmission:**  Allow e.g. Python applications to obtain schemas directly from
+  the RPC server so that they need not have a local copy.  Great for interactive debugging.
+* **Three-way introductions (level 3 RPC):**  Allow RPC interactions between more than two parties,
+  with new connections formed automatically as needed.
+* **Bulk and Realtime**: Add features that make it easier to design Cap'n Proto APIs for bulk
+  data transfers (with flow control) and realtime communications (where it's better to drop
+  messages than to deliver them late).
+* **UDP transport**: Cap'n Proto RPC could benefit from implementing a UDP transport, in order
+  to achieve zero-round-trip three-party introductions and to implement "realtime" APIs (see
+  "bulk and realtime", above).
+* **Encrypted transport**: Cap'n Proto RPC should support an encrypted transport which uses
+  capability-based authorization (not PKI), can accomplish zero-round-trip three-party
+  introductions (via a pre-shared key from the introducer) and based on modern crypto. TLS is
+  not designed for this, but we don't want to invent new crypto; we intend to build on
+  [libsodium](https://github.com/jedisct1/libsodium) and the
+  [Noise Protocol Framework](http://noiseprotocol.org/) as much as possible.
+
+### C++ Cap'n Proto API Features
+
+* **Plain Old C Structs:** The code generator should also generate a POCS type corresponding
+  to each struct type. The POCS type would use traditional memory allocation, thus would not
+  support zero-copy, but would support a more traditional and easy-to-use C++ API, including
+  the ability to mutate the object over time without convoluted memory management. POCS types
+  could be extracted from an inserted into messages with a single copy, allowing them to be
+  used easily in non-performance-critical code.
+* **Multi-threading:**  It should be made easy to assign different Cap'n Proto RPC objects
+  to different threads and have them be able to safely call each other. Each thread would still
+  have an anyschronous event loop serving the objects that belong to it.
+* **Shared memory RPC:**  Zero-copy inter-process communication.
+* **JSON codec customization:**  Extend the JSON library to support customizing the JSON
+  representation using annotations. For example, a field could be given a different name in
+  JSON than it is in Cap'n Proto. The goal of these features would be to allow any reasonable
+  pre-existing JSON schema to be representable as a Cap'n Proto type definition, so that
+  servers implementing JSON APIs can use Cap'n Proto exclusively on the server side.
+* **LZ4 integration:**  Integrate LZ4 compression into the API to further reduce bandwidth needs
+  with minimal CPU overhead.
+* **Annotations API:**  For each annotation definition, generate code which assists in extracting
+  that annotation from schema objects in a type-safe way.
+
+### C++ KJ API Features
+
+KJ is a framework library that is bundled with Cap'n Proto, but is broadly applicable to C++
+applications even if they don't use Cap'n Proto serialization.
+
+* **Fiber-based concurrency:**  The C++ runtime's event loop concurrency model will be augmented
+  with support for fibers, which are like threads except that context switches happen only at
+  well-defined points (thus avoiding the need for mutex locking).  Fibers essentially provide
+  syntax sugar on top of the event loop model.
+* **TLS bindings:** Write bindings for e.g. OpenSSL to make it easy to integrate with the KJ
+  I/O framework, Cap'n Proto RPC, and the KJ HTTP library.
+* **Modern crypto bindings:** A thin wrapper around
+  [libsodium](https://github.com/jedisct1/libsodium) with a nice C++ API, e.g. representing
+  keys using fixed-size, trivially-copyable classes.
+* **Event loop integrations:** We should provide off-the-shelf integrations with popular event
+  loop libraries, such as libuv, libev, libevent, boost::asio, and others, so that it's easier
+  to use Cap'n Proto RPC in applications that already use another event framework.
+
+### Storage
+
+* **ORM interface:**  Define a standard interface for capabilities that represent remotely-stored
+  objects, with get, put, publish, and subscribe methods.  Ideally, parameterize this interface
+  on the stored type.
+* **mmap-friendly mutable storage format:**  Define a standard storage format that is friendly
+  to mmap-based use while allowing modification.  (With the current serialization format, mmap
+  is only useful for read-only structures.)  Possibly based on the ORM interface, updates only
+  possible at the granularity of a whole ORM entry.
+
+### Tools
+
+* **Schema compatibility checker:**  Add a `capnp` command which, given two schemas, verifies
+  that the latter is a compatible upgrade from the former.  This could be used as a git hook
+  to prevent submission of schema changes that would break wire compatibility.
+* **RPC debugger:**  Add a `capnp` command which sends an RPC from the command line and prints
+  the result.  Useful for debugging RPC servers.
+
+## Quality Assurance
+
+These things absolutely must happen before any 1.0 release.  Note that it's not yet decided when
+a 1.0 release would happen nor how many 0.x releases might precede it.
+
+* **Expand test coverage:**  There are lots of tests now, but some important scenarios, such as
+  handling invalid of invalid input, need better testing.
+* **Performance review:**  Performance is already very good compared to competitors, but at some
+  point we need to break out the profiler and really hone down on the details.
+* **Security review:**  We need a careful security review to make sure malicious input cannot
+  crash an application or corrupt memory.
+
+### Infrastructure
+
+Note:  These are very large projects.
+
+* **JSON-HTTP proxy:**  Develop a web server which can expose a Cap'n Proto RPC backend as a
+  JSON-over-HTTP protocol.
+* **Database:**  A fast storage database based on Cap'n Proto which implements the ORM interface
+  on top of the mmap storage format.