path: root/verigraph/src/main/java/it/polito/grpc/README.md

.. This work is licensed under a Creative Commons Attribution 4.0 International License.
.. http://creativecommons.org/licenses/by/4.0

gRPC Project
============

This project contains the interfaces for a web service based on gRPC.

How to install:
---------------

For gRPC interface, add to your ``pom.xml`` (in the project this part is
already present):

::

        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-netty</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-protobuf</artifactId>
            <version>${grpc.version}</version>
        </dependency>
        <dependency>
            <groupId>io.grpc</groupId>
            <artifactId>grpc-stub</artifactId>
            <version>${grpc.version}</version>
        </dependency>

For protobuf-based codegen integrated with the Maven build system, you
can use protobuf-maven-plugin :

::

        <build>
            <extensions>
                <extension>
                    <groupId>kr.motd.maven</groupId>
                    <artifactId>os-maven-plugin</artifactId>
                    <version>1.4.1.Final</version>
                </extension>
            </extensions>
            <plugins>
                <plugin>
                    <groupId>org.xolstice.maven.plugins</groupId>
                    <artifactId>protobuf-maven-plugin</artifactId>
                    <version>0.5.0</version>
                    <configuration>
                        <protocArtifact>com.google.protobuf:protoc:3.1.0:exe:${os.detected.classifier}</protocArtifact>
                        <pluginId>grpc-java</pluginId>
                        <pluginArtifact>io.grpc:protoc-gen-grpc-java:${grpc.version}:exe:${os.detected.classifier}</pluginArtifact>
                    </configuration>
                    <executions>
                        <execution>
                            <goals>
                                <goal>compile</goal>
                                <goal>compile-custom</goal>
                            </goals>
                        </execution>
                    </executions>
                </plugin>
            </plugins>
        </build>

| In order to run the gRPC server and the junit test, you need to download the Manven Ant Task library
  from `here <https://mvnrepository.com/artifact/org.apache.maven/maven-ant-tasks/2.1.3>`__
  and copy into ``[verigraph]/lib/``

| Due to the fact that the project is intended for Eclipse, you need to
  install an additional Eclipse plugin because
  `m2e <https://www.eclipse.org/m2e/>`__ does not evaluate the extension
  specified in a ``pom.xml``. `Download
  ``os-maven-plugin-1.5.0.Final.jar`` <http://repo1.maven.org/maven2/kr/motd/maven/os-maven-plugin/1.5.0.Final/os-maven-plugin-1.5.0.Final.jar>`__
  and put it into the ``<ECLIPSE_HOME>/plugins`` directory.
| (As you might have noticed, ``os-maven-plugin`` is a Maven extension,
  a Maven plugin, and an Eclipse plugin.)

If you are using IntelliJ IDEA, you should not have any problem.

If you are using other IDEs such as NetBeans, you need to set the system
properties ``os-maven-plugin`` sets manually when your IDE is launched.
You usually use JVM's ``-D`` flags like the following:

    | -Dos.detected.name=linux
    | -Dos.detected.arch=x86\_64
    | -Dos.detected.classifier=linux-x86\_64

Included files:
---------------

Here you can find a brief description about useful files for the gRPC
interface:

**src/main/java:**

-  *it.polito.grpc:*

This package includes 2 classes that represent the client and server.

    **Client.java:**

    | Client of gRPC application. It implements all possible methods
      necessary for communicate with server.
    | It prints out the received response.
    | Moreover it provides some static methods that are used for
      creating the instances of requests.

    **Service.java:**

    | Server of gRPC application. It implements all possible methods
      necessary for communicate with client.
    | It saves the received request on log.
    | This server could be accessed by multiple clients, because
      synchronizes concurrent accesses.
    | Each method that is possible to call is has the equivalent
      operation in REST-interface.

    **GrpcUtils.java:**

    | This class provides some static methods that are used by
      ``Service.java`` in order to translate a request into a class that
      is accepted by Verigraph.
    | Other methods are used to translate the class of Verigraph in the
      proper gRPC response.
    | These functionalities are exploited by test classes.
    | Furthermore this set of methods is public, so in your application
      you could call them, even if this should not be useful because
      ``Client.java`` provides other high-level functions.

-  *it.polito.grpc.test:*

   This package includes classes for testing the gRPC application.

    **GrpcServerTest.java:**

    | For each possible method we test if works correctly.
    | We create a fake client (so this test doesn't use the method that
      are present in client class) and test if it receives the expected
      response.
    | In a nutshell, it tests the methods of Client in case of a fake
      server.
    | Please notice that the test prints some errors but this is
      intentional, because the program tests also error case.
    | Indeed, not all methods are tested, because we have another class
      (ReachabilityTest.java) that is specialized for testing the
      verification method.

    **GrpcTest.java:**

    | This set of tests is intended to control the most common use
      cases, in particular all methods that are callable in Client and
      Service class, apart from verifyPolicy for the same reason as
      before.
    | It tries also to raise an exception and verify if the behavior is
      as expected.

    **MultiThreadTest.java:**

    | This test creates multiple clients that connect to the server and
      verify is the result is correct. These methods test the
      synchronization on
    | server-side.

    **ReachabilityTest.java:**

    | This file tests the verification method, it exploits the test case
      already present in the project and consequently has the certainty
      of testing not so simple case. In particular it reads the file in
      "src/main/webapp/json" and use this as starting point.
    | Some exceptions are thrown in order to verify if they are handled
      in a correct way.

**src/main/proto:**

    **verigraph.proto:**

    | File containing the description of the service. This includes the
      definition of all classes used in the application.
    | Moreover contains the definition of the methods that is possible
      to call.
    | Each possible method called by REST API is mapped on a proper gRPC
      method.
    | In case of error a message containing the reason is returned to
      the client.
    | More details are available in the section about Proto Buffer.

**taget/generated-sources/protobuf/java:**

-  *io.grpc.verigraph:*

   This package includes all classes generated from verigraph.proto by
   means of protoc. For each object you can find 2 classes :

       **{NameObject}Grpc.java**

       **{NameObject}GrpcOrBuilder.java**

       The first is the real implementation, the second is the
       interface.

**taget/generated-sources/protobuf/grpc-java:**

-  *io.grpc.verigraph:*

   This package includes a single class generated from verigraph.proto
   by means of protoc.

       **VerigraphGrpc.java:**

       This is useful in order to create the stubs that are necessary to
       communicate both for client and server.

**lib:**

This folder includes a jar used for compiling the project with Ant.

    \*\*maven-ant-tasks-2.1.3.\ jar:**

    This file is used by build.xml in order to include the maven
    dependencies.

**pom.xml:**

| Modified in order to add all necessary dependencies. It contains also
  the build tag used for create the generated-sources folders.
| This part is added according to documentation of gRPC for java as
  explained above in How To Install section.
| For further clarification go to `this
  link <https://github.com/grpc/grpc-java/blob/master/README.md>`__.

**build.xml:**

This ant file permit to run and compile the program in a simple way, it
exploits the maven-ant-tasks-2.1.3.jar already present in project.

It contains 3 fundamental tasks for gRPC interface:

-  **build:** compile the program

-  **run:** run both client and server

-  **run-client :** run only client

-  **run-server :** run only server

-  **run-test :** launch all tests that are present in the package,
   prints out the partial results and global result.

Note that the execution of these tests may take up to 1-2 minutes when
successful, according to your computer architecture.

More Information About Proto Buffer:
------------------------------------

Further clarification about verigraph.proto:

-  A ``simple RPC`` where the client sends a request to the server using
   the stub and waits for a response to come back, just like a normal
   function call.

   .. code:: xml

       // Obtains a graph
       rpc GetGraph (RequestID) returns (GraphGrpc) {}

In this case we send a request that contains the id of the graph and the
response is a Graph.

-  A ``server-side streaming RPC`` where the client sends a request to
   the server and gets a stream to read a sequence of messages back. The
   client reads from the returned stream until there are no more
   messages. As you can see in our example, you specify a server-side
   streaming method by placing the stream keyword before the response
   type.

   .. code:: xml


       // Obtains a list of Nodes
       rpc GetNodes (RequestID) returns (stream NodeGrpc) {}

In this case we send a request that contains the id of the graph and the
response is a list of Nodes that are inside graph.

Further possibilities are available but in this project are not
expolied. If you are curious see
`here <http://www.grpc.io/docs/tutorials/basic/java.html#defining-the-service>`__.

Our ``.proto`` file also contains protocol buffer message type
definitions for all the request and response types used in our service
methods - for example, here’s the ``RequestID`` message type:

.. code:: xml

        message RequestID {
            int64 idGraph = 1;
            int64 idNode = 2;
            int64 idNeighbour = 3;
        }   

The " = 1", " = 2" markers on each element identify the unique "tag"
that field uses in the binary encoding. Tag numbers 1-15 require one
less byte to encode than higher numbers, so as an optimization you can
decide to use those tags for the commonly used or repeated elements,
leaving tags 16 and higher for less-commonly used optional elements.
Each element in a repeated field requires re-encoding the tag number, so
repeated fields are particularly good candidates for this optimization.

Protocol buffers are the flexible, efficient, automated solution to
solve exactly the problem of serialization. With protocol buffers, you
write a .proto description of the data structure you wish to store. From
that, the protocol buffer compiler creates a class that implements
automatic encoding and parsing of the protocol buffer data with an
efficient binary format. The generated class provides getters and
setters for the fields that make up a protocol buffer and takes care of
the details of reading and writing the protocol buffer as a unit.
Importantly, the protocol buffer format supports the idea of extending
the format over time in such a way that the code can still read data
encoded with the old format.

::

    syntax = "proto3";

    package verigraph;

    option java_multiple_files = true;
    option java_package = "io.grpc.verigraph";
    option java_outer_classname = "VerigraphProto";
    ```

This .proto file works for protobuf 3, that is slightly different from
the version 2, so be careful if you have code already installed.

The .proto file starts with a package declaration, which helps to
prevent naming conflicts between different projects. In Java, the
package name is used as the ``Java package`` unless you have explicitly
specified a java\_package, as we have here. Even if you do provide a
``java_package``, you should still define a normal ``package`` as well
to avoid name collisions in the Protocol Buffers name space as well as
in non-Java languages.

| After the package declaration, you can see two options that are
  Java-specific: ``java_package`` and ``java_outer_classname``.
  ``java_package`` specifies in what Java package name your generated
  classes should live. If you don't specify this explicitly, it simply
  matches the package name given by the package declaration, but these
  names usually aren't appropriate Java package names (since they
  usually don't start with a domain name). The ``java_outer_classname``
  option defines the class name which should contain all of the classes
  in this file. If you don't give a ``java_outer_classname explicitly``,
  it will be generated by converting the file name to camel case. For
  example, "my\_proto.proto" would, by default, use "MyProto" as the
  outer class name.
| In this case this file is not generated, because
  ``java_multiple_files`` option is true, so for each message we
  generate a different class.

For further clarifications see
`here <https://developers.google.com/protocol-buffers/docs/javatutorial>`__

Notes
-----

For gRPC interface you need that neo4jmanager service is already
deployed, so if this is not the case, please follow the instructions at
this
`link <https://github.com/netgroup-polito/verigraph/blob/a3c008a971a8b16552a20bf2484ebf8717735dd6/README.md>`__.

In this version there are some modified files compared to the original
`Verigraph project <https://github.com/netgroup-polito/verigraph>`__

**it.polito.escape.verify.service.NodeService:**

At line 213 we modified the path, because this service is intended to
run not only in container, as Tomcat, so we added other possibility that
files is placed in src/main/webapp/json/ folder.

**it.polito.escape.verify.service.VerificationService:**

In the original case it searches for python files in "webapps" folder,
that is present if the service is deployed in a container, but absent
otherwise. So we added another string that will be used in the case the
service doesn't run in Tomcat.

**it.polito.escape.verify.databese.DatabaseClass:**

Like before we added the possibility that files are not in "webapps"
folder, so is modified in order to run in any environment. Modification
in method loadDataBase() and persistDatabase().

| Pay attention that Python is needed for the project. If it is not
  already present on your computer, please `download
  it <https://www.python.org/download/releases/2.7.3/>`__.
| It works fine with Python 2.7.3, or in general Python 2.

| If you have downloaded a Python version for 64-bit architecture please
  copy the files in "service/z3\_64" and paste in "service/build" and
  substitute them,
| because this project works with Python for 32-bit architecture.

Python and Z3 must support the same architetcure.

Moreover you need the following dependencies installed on your python
distribution:

- "requests" python package ->
http://docs.python-requests.org/en/master/

- "jsonschema" python package -> https://pypi.python.org/pypi/jsonschema

| HINT - to install a package you can raise the following command (Bash
  on Linux or DOS shell on Windows): python -m pip install jsonschema
  python -m pip install requests
| Pay attention that it is possible that you have to modify the PATH
  environment variable because is necessary to address the python
  folder, used for verification phase.

Remember to read the
`README.rtf <https://gitlab.com/serena.spinoso/DP2.2017.SpecialProject2.gRPC/tree/master>`__
and to follow the instructions in order to deploy the Verigraph service.

| In the latest version of Maven there is the possibility that the
  downloaded files are incompatible with Java Version of the project
  (1.8).
| In this case you have to modify the file ``hk2-parent-2.4.0-b31.pom``
  under your local Maven repository (e.g.
  'C:\\Users\\Standard.m2\\repository')
| and in the path ``\org\glassfish\hk2\hk2-parent\2.4.0-b31`` find the
  file and modify at line 1098 (in section ``profile``) the ``jdk``
  version to ``[1.8,)`` .

| Admittedly, the version that is supported by the downloaded files from
  Maven Dependencies is incompatible with jdk of the project.
| So modify the file ``gson-2.3.pom`` in Maven repository, under
  ``com\google\code\gson\gson\2.3`` directory, in particular line 91,
  from ``[1.8,`` to ``[1.8,)``.

This project was also tested on Linux Ubuntu 15.10.