README

This is the Thrift serde used to communicate with the Presto coordinator.

The end state for this code will eventually be just the presto_thrift.thrift file and its fbthrift generated code. While in the transition from JSON to Thrift we will need code to convert between the two internal data structures (JSON derrived and Thrift derrived) that presto_cpp will be using.

There is currently only one Thrift root class TaskStatus being used to return the results of the .getTaskStatus endpoint. To accomplish this the JSON derrived TaskStatus must to converted to its corrosponding struct in Thrift. This code gen produces a toThrift function for each Thrift structure that is also in the JSON protocol.

<pre><code> presto_thrift.thrift ---> fbthrift ---> $BUILDDIR/presto_cpp/main/thrift/ProtocolToThrift.[h|cpp] | v thrift2json.py | v presto_thrift.json presto_protocol/presto_protocol.json presto_protocol-to-thrift-json.yml | | | | v | +-------------> presto_protocol-to-thrift-json.py <---------------+ | v presto_protocol-to-thrift-json.json | | ProtocolToThrift-cpp.mustache | | ProtocolToThrift-hpp.mustache | | | | v | v | chevron <-------------+ chevron <-------------+ | | v v ProtocolToThrift.cpp ProtocolToThrift.h </code></pre>

thrift2json.py uses ptsd_jbroll a fork of the ptsd Thrift parser to produce a JSON representation of the presto_thrift.thrift file. This is combined with the presto_protocol.json from the presto_protocol code gen by presto_protocol-to-thrift-json.py to create a JSON description of the conversion from JSON internal srtruct to Thrift structs in presto_protocol-to-thrift-json.json.

presto_protocol-to-thrift-json.json is used by chevron templates ProtocolToThrift-cpp.mustache and ProtocolToThrift-hpp.mustache to produce the actual C++ code in ProtocolToThrift.cpp and ProtocolToThrift.h.