[native] Add Prestissimo documentation page to Developer Guide

Adding a new documentation page for Prestissimo to the Developer Guide,
and adding some of the configuration parameters for remote function
execution.

presto-docs/src/main/sphinx/develop/presto-native.rst

@@ -0,0 +1,95 @@
+===========================
+Presto Native - Prestissimo
+===========================
+
+Prestissimo is a C++ drop-in replacement for Presto workers based on the Velox
+library. It implements the same RESTful endpoints as Java workers using the
+Proxygen C++ HTTP framework. Since communication with the Java coordinator and
+across workers is only done using the REST endpoints, Prestissimo does not use
+JNI and it is commonly deployed in such a way as to avoid having a JVM process
+on worker nodes.
+
+Prestissimo's codebase is located at `presto-native-execution
+<https://github.com/prestodb/presto/tree/master/presto-native-execution>`_.
+
+
+Endpoints
+---------
+
+HTTP endpoints related to tasks are registered to Proxygen in
+`TaskResource.cpp`. Important endpoints implemented include:
+
+* POST: v1/task: This processes a `TaskUpdateRequest`
+* GET: v1/task: This returns a serialized `TaskInfo` (used for comprehensive
+  metrics, may be reported less frequently) 
+* GET: v1/task/status: This returns
+  a serialized `TaskStatus` (used for query progress tracking, must be reported
+  frequently)
+
+Other HTTP endpoints include:
+
+* POST: v1/memory
+  * Reports memory, but no assignments are adjusted unlike in Java workers.
+* GET: v1/info
+* GET: v1/status
+
+The request/response flow of Prestissimo is identical to Java workers. The
+tasks or new splits are registered via `TaskUpdateRequest`. Resource
+utilization and query progress are sent to the coordinator via task endpoints.
+
+
+Remote Function Execution
+-------------------------
+
+Prestissimo supports remote execution of scalar functions. This feature is
+useful for cases when the function code is not written in C++, or if for
+security or flexibility reasons the function code cannot be linked to the same
+executable as the main engine.
+
+Remote function signatures need to be provided using a JSON file, following
+the format implemented by `JsonFileBasedFunctionNamespaceManager
+<https://github.com/prestodb/presto/blob/master/presto-function-namespace-managers/src/main/java/com/facebook/presto/functionNamespace/json/JsonFileBasedFunctionNamespaceManager.java>`_.
+The following properties allow the configuration of remote function execution:
+
+``remote-function-server.signature.files.directory.path``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    * **Type:** ``string``
+    * **Default value:** ``""``
+
+    The local filesystem path where JSON files containing remote function
+    signatures are located. If not empty, the Presto native worker will
+    recursively search, open, parse, and register function definitions from
+    these JSON files.
+
+
+``remote-function-server.thrift.address``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    * **Type:** ``string``
+    * **Default value:** ``""``
+
+    The location (ip address or hostname) that hosts the remote function
+    server, if any remote functions were registered using
+    ``remote-function-server.signature.files.directory.path``.
+    If not specified, falls back to the loopback interface (``::1``)
+
+``remote-function-server.thrift.port``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    * **Type:** ``integer``
+    * **Default value:** ``0``
+
+    The port that hosts the remote function server. If not specified and remote
+    functions are trying to be registered, an exception is thrown.
+
+``remote-function-server.thrift.uds-path``
+^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
+
+    * **Type:** ``string``
+    * **Default value:** ``""``
+
+    The UDS (unix domain socket) path to communicate with a local remote
+    function server. If specified, takes precedence over
+    ``remote-function-server.thrift.address`` and 
+    ``remote-function-server.thrift.port``.