In many cases, you will need to transfer data between processes running on the same machine or send the data via the network. You can use XML or JSON but these formats are inefficient. There are several alternatives (e.g. Protobuf and Avro) you can use instead.
The serialization frameworks define data structures with schemas in their own languages that can be compiled into classes in a variety of programming languages (Java, C++, Python, etc.).
Your goal is to implement an application (Java) which receives data and stores them to classes generated by protobuf and avro serialization frameworks and sends the converted data via TCP to another application (C/C++). This application processes the data (calculates averages) and sends the results back.
You will be given a reference implementation using JSON data format. Use this data classes as a template how the schemas in protobuf and avro should look like. You will not be probably able to create exact counterparts due to some limitations of the serialization protocols; therefore, you will need to find out a workaround.
Steps:
git clone https://gitlab.fel.cvut.cz/cuchymar/serialization-2018-template.git
sudo apt-get install libboost-all-dev libjsoncpp-dev cd src/main/cpp/ mkdir build cd build cmake .. make ./app 12345 jsonor use any IDE.
mvn compile
AppTest.java
protobuf
and avro
schemas as similar as possible to the provided JSON format (package cz.esw.serialization.json.*
). Write the schemas into prepared measurements.proto
and measurements.avsc
files. Hint: Use class names with prefix P
for protobuf
classes (e.g. PDataset
) and A
for avro
classes (e.g. ADataset
).
pom.xml
,readme.txt
and src/
folder without any compiled binaries or generated sources.
The configuration of the application is handled by Maven (pom.xml
) which takes care of all libraries required and compilation of the serialization schemas (you have to run mvn compile
to generate the source codes of the data classes every time you change the serialization schemas).
The application can be compiled and run from the command line with following commands in the project folder:
mvn compile mvn exec:java -Dexec.mainClass="cz.esw.serialization.App" -Dexec.args="localhost 12345 json"
The java app has to accept following three arguments:
app <host> <port> <format>
The application has to accept generated data and convert it to the transfer format and send the data.
The arguments <host>
and <port>
are the address and port of the receiver and <format>
is one of the following enumeration {json, proto, avro}
defining the format for the data transfer over TCP.
A contrary to Java with Maven, where everything is done automatically, in C/C++ we have to compile the schemas manually and add the generated files to the CMakeLists.txt. Or an experienced user of CMake can enhance the build script to do it automatically like Maven. Links with descriptions of how to install the protocol compilers and how to use them are provided in corresponding sections below.
The C/C++ application has to listen on the defined port and receive data in the defined format, process the data (just calculate averages) and send the results back.
The app has to accept following two arguments:
app <port> <format>
The argument <port>
is the port on which the receiver listens and <format>
is one of the following enumeration {json, protobuf, avro}
defining the format of the data transferred over TCP.
json
- sends/receives the data as JSON text
proto
- sends/receives the data as bytes of the protobuf
generated classes
avro
- sends/receives the data as bytes of the avro
generated clases
The implementations of Protobuf and Avro frameworks will not probably be able to recognize ends of messages, therefore the application has to send the message size before the message itself.
The recieving C part should look similar to:
int messageSize = readAndDecodeMessageSize(stream) // your implementation char *buffer = new char[messageSize]; stream.read(buffer, messageSize) ...
The size of Protobuf message is easy to get:
int messageSize = objectToBeSerialized.getSerializedSize(); sendMessageSize(messageSize, outputStream) // your implementation ...
The size of Avro message is not that straightforward to retrieve:
DatumWriter<ADataset> datumWriter = new SpecificDatumWriter<ADataset>(ADataset.class) ByteArrayOutputStream byteArrayOutputStream = new ByteArrayOutputStream(); BinaryEncoder encoder = EncoderFactory.get().binaryEncoder(byteArrayOutputStream , null); datumWriter .write(objectToBeSerialized, encoder); encoder.flush(); int messageSize = byteArrayOutputStream.size(); sendMessageSize(messageSize, outputStream) // your implementation ...
Apache Maven is a project management tool enabling management of library dependencies and building. Some IDEs have Maven integrated but for easy use in command line you will have to download it and add the bin
folder to the PATH
.
There is an option to receive two bonus points: