Problems using Qt5 and Apache Thrift

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Problems using Qt5 and Apache Thrift

PAULUS, Raimund, TI-ABN
Problems using Qt5 and Apache Thrift

For several months i use Apache Thrift 0.11.0 on Cygwin 2.5.2 for data transfer between Windows boxes and my Linux host. On the Windows boxes a C++-application serves as a client. The user makes some input on an ascii-interface (created with libwed) and sometimes data must be transferred between the pc and the Linux host.

Here is the program sequence on the windows client:

//------------------------------------------------------------------------------
program starts
step 1: make the connection to the Linux server (Apache Thrift)
step 2: user interface (ASCII)
step 3: data transfer PC <-> Linux-Host (Apache Thrift)
step 4: user interface (ASCII)
step 5: data transfer PC <-> Linux-Host (Apache Thrift)
...
...
...
step n: close the connection to the host (Apache Thrift)
program ends
//------------------------------------------------------------------------------

This works flawlessly.

Now i want to implement the interface parts with Qt 5. Here is the new program sequence:

//------------------------------------------------------------------------------
program starts
step 1: make the connection to the Linux server (Apache Thrift)
step 2: initialize Qt interface (create widgets, buttons, ...)
step 3: user interface (Qt)
step 4: data transfer PC <-> Linux-Host (Apache Thrift)
step 5: user interface (Qt)
step 6: data transfer PC <-> Linux-Host (Apache Thrift)
...
...
...
step n-1: end Qt app
step n: close the connection to the host (Apache Thrift)
program ends
//------------------------------------------------------------------------------

During step 2 the connection to the linux server is broken. You can see it with the netstat command. First error message arises in step 4:

"TSocket::write_partial() send() <Host: my_host Port: 9090>Broken pipe"

On a Linux box the client program runs perfectly.

On the windows box the program works, if i initalize Qt before the connection to the server is made (step 2 before step 1). But that is not acceptable for me, because afterwards other widgets and buttons are created and i can not close and create the connection at each point.

For the tests I used the examples from the Apache Thrift Tutorial. The service on the linux box is created from CppServer.cpp. The client in the original is CppClient.cpp. But I modified it for Qt. Here is the source for CppClient.cpp. The connection is broken after line 66.


  1 #include <stdio.h>
  2 #include <iostream>
  3
  4 #include <QApplication>
  5 #include <QWidget>
  6 #include <QString>
  7 #include <QMessageBox>
  8 #include <QPushButton>
  9
 10 #include <thrift/protocol/TBinaryProtocol.h>
 11 #include <thrift/transport/TSocket.h>
 12 #include <thrift/transport/TTransportUtils.h>
 13 #include <thrift/stdcxx.h>
 14
 15 #include "../gen-cpp/Calculator.h"
 16
 17 using namespace std;
 18 using namespace apache::thrift;
 19 using namespace apache::thrift::protocol;
 20 using namespace apache::thrift::transport;
 21
 22 using namespace tutorial;
 23 using namespace shared;
 24
 25 // function for messagebox
 26 void MsgBox(const char *msg)
 27 {
 28   QMessageBox box;
 29   box.setIcon(QMessageBox::Information);
 30   box.setText("Server Return");
 31   box.setInformativeText(QString::fromStdString(msg));
 32   box.setStandardButtons(QMessageBox::Ok);
 33   box.exec();
 34 }
 35
 36 int main(int argc, char **argv) {
 37
 38   //-------------------------------------------------------
 39   // connect to host before initialising Qt
 40   //-------------------------------------------------------
 41 printf("Connect to host \"NAZV\"with port 9090\n");
 42
 43 //  stdcxx::shared_ptr<TTransport> socket(new TSocket("localhost", 9090));
 44   stdcxx::shared_ptr<TTransport> socket(new TSocket("NAZV", 9090));
 45   stdcxx::shared_ptr<TTransport> transport(new TBufferedTransport(socket));
 46   stdcxx::shared_ptr<TProtocol> protocol(new TBinaryProtocol(transport));
 47   CalculatorClient client(protocol);
 48
 49   try {
 50     transport->open();
 51
 52     //------------------------------------------------------
 53     // initialising Qt after connect to host
 54     //------------------------------------------------------
 55 printf("Stop 1; Press <Enter> to continue"); getchar();
 56
 57     QApplication app(argc, argv);
 58     QString txt;
 59
 60 printf("Stop 2; Press <Enter> to continue"); getchar();
 61
 62     QWidget *w = new QWidget();
 63
 64 printf("Stop 3; Press <Enter> to continue"); getchar();
 65
 66     QPushButton *b_end = new QPushButton("End", w);
 67
 68 printf("Stop 4; Press <Enter> to continue"); getchar();
 69
 70     QObject::connect(b_end, SIGNAL(clicked()), &app, SLOT(quit()));
 71
 72 printf("Stop 5; Press <Enter> to continue"); getchar();
 73
 74     w->show();
 75
 76 printf("Stop 6; Press <Enter> to continue"); getchar();
 77
 78
 79     client.ping();
 80     MsgBox("ping()");
 81
 82     txt.clear();
 83     txt.append("1 + 1 = ");
 84     txt.append(QString::number(client.add(1, 1)));
 85     MsgBox(txt.toStdString().c_str());
 86
 87     Work work;
 88     work.op = Operation::DIVIDE;
 89     work.num1 = 1;
 90     work.num2 = 0;
 91
 92     try {
 93       client.calculate(1, work);
 94       MsgBox("Whoa? We can divide by zero!");
 95     } catch (InvalidOperation& io) {
 96       txt.clear();
 97       txt.append("InvalidOperation: ");
 98       txt.append(io.why.c_str());
 99       MsgBox(txt.toStdString().c_str());
100     }
101
102     work.op = Operation::SUBTRACT;
103     work.num1 = 15;
104     work.num2 = 10;
105     int32_t diff = client.calculate(1, work);
106     txt.clear();
107     txt.append("15 - 10 = ");
108     txt.append(QString::number(diff));
109     MsgBox(txt.toStdString().c_str());
110
111
112     app.exec();
113
114     transport->close();
115   } catch (TException& tx) {
116     cout << "ERROR: " << tx.what();
117   }
118
119 }


The result is the same on Cygwin 3.1.4 and Apache Thrift 0.12.0.

I would be very grateful for your help

Raimund Paulus
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Re: Problems using Qt5 and Apache Thrift

Andrey Repin
Greetings, PAULUS, Raimund, TI-ABN!

> Problems using Qt5 and Apache Thrift

...snip...

> Now i want to implement the interface parts with Qt 5. Here is the new program sequence:

> //------------------------------------------------------------------------------
> program starts
> step 1: make the connection to the Linux server (Apache Thrift)
> step 2: initialize Qt interface (create widgets, buttons, ...)
> step 3: user interface (Qt)
> step 4: data transfer PC <-> Linux-Host (Apache Thrift)
> step 5: user interface (Qt)
> step 6: data transfer PC <-> Linux-Host (Apache Thrift)
> ...
> ...
> ...
> step n-1: end Qt app
> step n: close the connection to the host (Apache Thrift)
> program ends
> //------------------------------------------------------------------------------

> During step 2 the connection to the linux server is broken. You can see it
> with the netstat command. First error message arises in step 4:

> "TSocket::write_partial() send() <Host: my_host Port: 9090>Broken pipe"

I strongly suggest placing communication service in its own thread.
Then you could manage connection without having to worry about blocking
timeouts caused by GUI operations.
They will run asynchronously.

> On a Linux box the client program runs perfectly.

Only by coincidence, I suppose.

> On the windows box the program works, if i initalize Qt before the
> connection to the server is made (step 2 before step 1). But that is not
> acceptable for me, because afterwards other widgets and buttons are created
> and i can not close and create the connection at each point.

I suppose, the server dropping connection by timeout. But I'd urge you to
investigate this further.

> For the tests I used the examples from the Apache Thrift Tutorial.

Please include examples as text/plain attachments, if they are longer than a
few lines.


--
With best regards,
Andrey Repin
Wednesday, March 25, 2020 14:08:25

Sorry for my terrible english...

--
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Re: Problems using Qt5 and Apache Thrift

PAULUS, Raimund, TI-ABN
In reply to this post by PAULUS, Raimund, TI-ABN
Supplement to my first email: the ascii-interface is created with libcurses.

> -----Ursprüngliche Nachricht-----
> Von: Andrey Repin [mailto:[hidden email]]
> Gesendet: Mittwoch, 25. März 2020 12:13
> An: PAULUS, Raimund, TI-ABN; [hidden email]
> Betreff: Re: Problems using Qt5 and Apache Thrift
>
> Greetings, PAULUS, Raimund, TI-ABN!
>
> > Problems using Qt5 and Apache Thrift
>
> ...snip...
>
> > Now i want to implement the interface parts with Qt 5. Here is the new program
> sequence:
>
> > //------------------------------------------------------------------------------
> > program starts
> > step 1: make the connection to the Linux server (Apache Thrift)
> > step 2: initialize Qt interface (create widgets, buttons, ...)
> > step 3: user interface (Qt)
> > step 4: data transfer PC <-> Linux-Host (Apache Thrift)
> > step 5: user interface (Qt)
> > step 6: data transfer PC <-> Linux-Host (Apache Thrift)
> > ...
> > ...
> > ...
> > step n-1: end Qt app
> > step n: close the connection to the host (Apache Thrift)
> > program ends
> > //------------------------------------------------------------------------------
>
> > During step 2 the connection to the linux server is broken. You can see it
> > with the netstat command. First error message arises in step 4:
>
> > "TSocket::write_partial() send() <Host: my_host Port: 9090>Broken pipe"
>
> I strongly suggest placing communication service in its own thread.
> Then you could manage connection without having to worry about blocking
> timeouts caused by GUI operations.
> They will run asynchronously.
>
> > On a Linux box the client program runs perfectly.
>
> Only by coincidence, I suppose.
>
> > On the windows box the program works, if i initalize Qt before the
> > connection to the server is made (step 2 before step 1). But that is not
> > acceptable for me, because afterwards other widgets and buttons are created
> > and i can not close and create the connection at each point.
>
> I suppose, the server dropping connection by timeout. But I'd urge you to
> investigate this further.
>
> > For the tests I used the examples from the Apache Thrift Tutorial.
>
> Please include examples as text/plain attachments, if they are longer than a
> few lines.
>
>
> --
> With best regards,
> Andrey Repin
> Wednesday, March 25, 2020 14:08:25
>
> Sorry for my terrible english...

--
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Re: Problems using Qt5 and Apache Thrift

PAULUS, Raimund, TI-ABN
In reply to this post by PAULUS, Raimund, TI-ABN
Hello Andrey Repin

The sources and the documentation are her:

https://thrift.apache.org/tutorial/cpp

You must have libthrift installed.

Maybe using threads is a better programming style, but i don't know, if it solves the problem. I use connecting and disconnecting to the service like braces around the rest of the application. At some points the application transfers data to the service and expects an answer. It is a synchronous communication and i use it like RPC (remote procedure call). The client sends a request and the service has to respond. Without the response the client cannot continue. Every client has its own service.

Greetings

Ramund Paulus

> -----Ursprüngliche Nachricht-----
> Von: Andrey Repin [mailto:[hidden email]]
> Gesendet: Mittwoch, 25. März 2020 12:13
> An: PAULUS, Raimund, TI-ABN; [hidden email]
> Betreff: Re: Problems using Qt5 and Apache Thrift
>
> Greetings, PAULUS, Raimund, TI-ABN!
>
> > Problems using Qt5 and Apache Thrift
>
> ...snip...
>
> > Now i want to implement the interface parts with Qt 5. Here is the new program
> sequence:
>
> > //------------------------------------------------------------------------------
> > program starts
> > step 1: make the connection to the Linux server (Apache Thrift)
> > step 2: initialize Qt interface (create widgets, buttons, ...)
> > step 3: user interface (Qt)
> > step 4: data transfer PC <-> Linux-Host (Apache Thrift)
> > step 5: user interface (Qt)
> > step 6: data transfer PC <-> Linux-Host (Apache Thrift)
> > ...
> > ...
> > ...
> > step n-1: end Qt app
> > step n: close the connection to the host (Apache Thrift)
> > program ends
> > //------------------------------------------------------------------------------
>
> > During step 2 the connection to the linux server is broken. You can see it
> > with the netstat command. First error message arises in step 4:
>
> > "TSocket::write_partial() send() <Host: my_host Port: 9090>Broken pipe"
>
> I strongly suggest placing communication service in its own thread.
> Then you could manage connection without having to worry about blocking
> timeouts caused by GUI operations.
> They will run asynchronously.
>
> > On a Linux box the client program runs perfectly.
>
> Only by coincidence, I suppose.
>
> > On the windows box the program works, if i initalize Qt before the
> > connection to the server is made (step 2 before step 1). But that is not
> > acceptable for me, because afterwards other widgets and buttons are created
> > and i can not close and create the connection at each point.
>
> I suppose, the server dropping connection by timeout. But I'd urge you to
> investigate this further.
>
> > For the tests I used the examples from the Apache Thrift Tutorial.
>
> Please include examples as text/plain attachments, if they are longer than a
> few lines.
>
>
> --
> With best regards,
> Andrey Repin
> Wednesday, March 25, 2020 14:08:25
>
> Sorry for my terrible english...

--
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Re: Problems using Qt5 and Apache Thrift

PAULUS, Raimund, TI-ABN
In reply to this post by PAULUS, Raimund, TI-ABN
In the meantime i tested using a thread for the Thrift-connection to my service.
If the thread is started, messages are sent in a loop to the service and a sleep() is included so that i have enough time to check the connection via netstat command.
The result is the same as in my first attempt. The network connection is broken after line 27 (create the QPushButton) in main.cpp. The thread prints the error message:

"Thrift: Mon Mar 30 18:45:27 2020 TSocket::write_partial() send() <Host: 192.168.178.200 Port: 9090>Broken pipe"

Here are the sources:

main.cpp:

      1 #include <stdio.h>
      2
      3 #include <QApplication>
      4 #include <QWidget>
      5 #include <QPushButton>
      6 #include <QThread>
      7
      8 #include "thrift_clnt.hpp"
      9
     10 int main(int argc, char **argv) {
     11
     12   printf("Stop 1; Press <Enter> to continue"); getchar();
     13
     14   QApplication app(argc, argv);
     15
     16   QThread* thread = new QThread();
     17   ThriftClnt* thrift_cl = new ThriftClnt;
     18   thrift_cl->moveToThread(thread);
     19   QObject::connect(thread, SIGNAL(started()), thrift_cl, SLOT (process()));
     20   QObject::connect(thrift_cl, SIGNAL (finished()), thread, SLOT (quit()));
     21   QObject::connect(thrift_cl, SIGNAL (finished()), thrift_cl, SLOT (deleteLater()));
     22   QObject::connect(thread, SIGNAL (finished()), thread, SLOT (deleteLater()));
     23   thread->start();
     24
     25   printf("Stop 2; Press <Enter> to continue"); getchar();
     26
     27   QPushButton *b_end = new QPushButton("End");
     28
     29   printf("Stop 3; Press <Enter> to continue"); getchar();
     30
     31   QObject::connect(b_end, SIGNAL(clicked()), &app, SLOT(quit()));
     32
     33   printf("Stop 4; Press <Enter> to continue"); getchar();
     34
     35   b_end->show();
     36
     37   printf("Stop 6; Press <Enter> to continue"); getchar();
     38
     39   app.exec();
     40
     41   thread->wait();  // do not exit before the thread is completed!
     42
     43 }



thrift_clnt.hpp:

      1 #ifndef __THRIFT_CLNT_HPP
      2 #define __THRIFT_CLNT_HPP
      3
      4 #include <QObject>
      5
      6 class ThriftClnt : public QObject
      7 {
      8   Q_OBJECT
      9
     10 public:
     11   ThriftClnt();
     12   ~ThriftClnt();
     13
     14 public slots:
     15   void process();
     16
     17 signals:
     18   void finished();
     19   void error(QString err);
     20
     21 private:
     22   // add your variables here
     23 };
     24
     25 #endif // __THRIFT_CLNT_HPP



thrift_clnt.cpp:

      1 #include "thrift_clnt.hpp"
      2
      3 #include <thrift/protocol/TBinaryProtocol.h>
      4 #include <thrift/transport/TSocket.h>
      5 #include <thrift/transport/TTransportUtils.h>
      6 #include <thrift/stdcxx.h>
      7
      8 #include "../gen-cpp/Calculator.h"
      9
     10 using namespace std;
     11 using namespace apache::thrift;
     12 using namespace apache::thrift::protocol;
     13 using namespace apache::thrift::transport;
     14
     15 using namespace tutorial;
     16 using namespace shared;
     17
     18 ThriftClnt::ThriftClnt() {
     19 }
     20
     21 ThriftClnt::~ThriftClnt() {
     22 }
     23
     24 void ThriftClnt::process()
     25 {
     26
     27   stdcxx::shared_ptr<TTransport> socket(new TSocket("192.168.178.200", 9090));
     28 //  stdcxx::shared_ptr<TTransport> socket(new TSocket("localhost", 9090));
     29
     30   stdcxx::shared_ptr<TTransport> transport(new TBufferedTransport(socket));
     31   stdcxx::shared_ptr<TProtocol> protocol(new TBinaryProtocol(transport));
     32
     33   CalculatorClient client(protocol);
     34
     35   try {
     36     transport->open();
     37
     38     char txt[128];
     39     for(int i=1; 1<20; i++)
     40     {
     41       sprintf(txt, "%d + %d = %d", i, i, client.add(i, i));
     42       sleep(5);
     43     }
     44
     45   } catch (TException& tx) {
     46     printf("ERROR: %s\n", tx.what());
     47   }
     48
     49   emit finished();
     50 }
     51




QT-Thrift.pro:

      1 ######################################################################
      2 # Automatically generated by qmake (3.0) Mo. März 23 15:29:31 2020
      3 ######################################################################
      4
      5 QT += core gui widgets
      6
      7 TEMPLATE = app
      8 TARGET = QtClient
      9 INCLUDEPATH += .
     10 INCLUDEPATH += ../gen-cpp
     11
     12 linux: {
     13   TOOLS_DIR = /software/tools
     14 }
     15
     16 cygwin: {
     17   TOOLS_DIR = /cygdrive/e/Software/Cygwin/2_5_2-tools
     18 }
     19
     20 # directories for thrift
     21 TOOLS_INCL = $${TOOLS_DIR}/include
     22 TOOLS_LIB  = $${TOOLS_DIR}/lib
     23
     24 INCLUDEPATH += $${TOOLS_INCL}
     25
     26 LIBS += -L $${TOOLS_LIB} -lthrift
     27
     28 # Input
     29 HEADERS += thrift_clnt.hpp ../gen-cpp/Calculator.h
     30
     31 SOURCES += main.cpp thrift_clnt.cpp \
     32         ../gen-cpp/Calculator.cpp \
     33         ../gen-cpp/SharedService.cpp \
     34         ../gen-cpp/shared_constants.cpp \
     35         ../gen-cpp/shared_types.cpp \
     36         ../gen-cpp/tutorial_constants.cpp \
     37         ../gen-cpp/tutorial_types.cpp \


The modules in directory gen-cpp are built with the Thrift compiler in Linux. The Thrift libs are built in Cygwin after unpacking the tar ball thrift-0.11.0.tar.gz
with the commands:

>./bootstrap.sh
>export CXXFLAGS="-D_HAVE_SYS_TIME_H -DPTHREAD_MUTEX_RECURSIVE_NP=PTHREAD_MUTEX_RECURSIVE -O2 -std=gnu++11 -D_GNU_SOURCE"
>./configure --with-qt4=no --with-qt5=no --with-csharp=no --with-java=no \
  --with-erlang=no --with-nodejs=no --with-lua=no --with-python=no --with-perl=no \
  --with-php=no --with-php_extension=no --with-dart=no --with-ruby=no --with-haskell=no \
  --with-go=no --with-rs=no --with-cl=no --with-haxe=no --with-dotnetcore=no --with-d=no \
  --disable-tests --prefix=/cygdrive/e/Software/Cygwin/2_5_2-tools
> make
> make install


Greetings

Raimund Paulus


> -----Ursprüngliche Nachricht-----
> Von: Cygwin [mailto:[hidden email]] Im Auftrag von PAULUS,
> Raimund, TI-ABN
> Gesendet: Donnerstag, 26. März 2020 07:59
> An: '[hidden email]'
> Betreff: Re: Problems using Qt5 and Apache Thrift
>
> Hello Andrey Repin
>
> The sources and the documentation are her:
>
> https://thrift.apache.org/tutorial/cpp
>
> You must have libthrift installed.
>
> Maybe using threads is a better programming style, but i don't know, if it solves the
> problem. I use connecting and disconnecting to the service like braces around the
> rest of the application. At some points the application transfers data to the service
> and expects an answer. It is a synchronous communication and i use it like RPC
> (remote procedure call). The client sends a request and the service has to respond.
> Without the response the client cannot continue. Every client has its own service.
>
> Greetings
>
> Ramund Paulus
>
> > -----Ursprüngliche Nachricht-----
> > Von: Andrey Repin [mailto:[hidden email]]
> > Gesendet: Mittwoch, 25. März 2020 12:13
> > An: PAULUS, Raimund, TI-ABN; [hidden email]
> > Betreff: Re: Problems using Qt5 and Apache Thrift
> >
> > Greetings, PAULUS, Raimund, TI-ABN!
> >
> > > Problems using Qt5 and Apache Thrift
> >
> > ...snip...
> >
> > > Now i want to implement the interface parts with Qt 5. Here is the new program
> > sequence:
> >
> > > //------------------------------------------------------------------------------
> > > program starts
> > > step 1: make the connection to the Linux server (Apache Thrift)
> > > step 2: initialize Qt interface (create widgets, buttons, ...)
> > > step 3: user interface (Qt)
> > > step 4: data transfer PC <-> Linux-Host (Apache Thrift)
> > > step 5: user interface (Qt)
> > > step 6: data transfer PC <-> Linux-Host (Apache Thrift)
> > > ...
> > > ...
> > > ...
> > > step n-1: end Qt app
> > > step n: close the connection to the host (Apache Thrift)
> > > program ends
> > > //------------------------------------------------------------------------------
> >
> > > During step 2 the connection to the linux server is broken. You can see it
> > > with the netstat command. First error message arises in step 4:
> >
> > > "TSocket::write_partial() send() <Host: my_host Port: 9090>Broken pipe"
> >
> > I strongly suggest placing communication service in its own thread.
> > Then you could manage connection without having to worry about blocking
> > timeouts caused by GUI operations.
> > They will run asynchronously.
> >
> > > On a Linux box the client program runs perfectly.
> >
> > Only by coincidence, I suppose.
> >
> > > On the windows box the program works, if i initalize Qt before the
> > > connection to the server is made (step 2 before step 1). But that is not
> > > acceptable for me, because afterwards other widgets and buttons are created
> > > and i can not close and create the connection at each point.
> >
> > I suppose, the server dropping connection by timeout. But I'd urge you to
> > investigate this further.
> >
> > > For the tests I used the examples from the Apache Thrift Tutorial.
> >
> > Please include examples as text/plain attachments, if they are longer than a
> > few lines.
> >
> >
> > --
> > With best regards,
> > Andrey Repin
> > Wednesday, March 25, 2020 14:08:25
> >
> > Sorry for my terrible english...
>
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