[Cppcms-users] cppdb::session connection pool makes asynchronous apps unstable

[CN <cn...@fa...>]

This program mounts both synchronous and asynchronous applications. Both
applications use cppdb::session. If the asynchronous application's
constructor includes connection pool (@pool_size=10) in cppdb::session
constructor's parameter, this program silently terminates immediately
after browser sends requests.

The deepest spot of the source I can trace trying to locate the problem
is exec() at line 465 in ~/booster/lib/aio/src/io_service.cpp:

			try {
				
				exec();
			}
			catch(...) {
				data_mutex_.lock();
				throw;
			}

I guess exec() must have thrown an uncaught exception and leads to
program termination.

What I have no clue is why singleton cppdb::session can make the system
unstable. If "@pool_size=10" is not included in cppdb::session's
constructor parameter, then the program seems to run properly.

This weird behavior happens only to asynchronous applications.

Any enlightenment will be much appreciated!

---This file should be able to compile and run:---
#include <cppcms/service.h>
#include <cppcms/rpc_json.h>
#include <cppdb/frontend.h>
#include <cppcms/applications_pool.h>
#include <cppcms/mount_point.h>
#include <cppcms/url_dispatcher.h>
#include <cppcms/url_mapper.h>
#include <cppcms/http_context.h>
#include <cppcms/session_interface.h>
#include <cppcms/service.h>
#include <cppcms/http_request.h>
#include <cppcms/http_response.h>
#include <fstream>
class sync : public cppcms::application
{
public:
	sync(cppcms::service &s) : cppcms::application(s){
		cppdb::session
		sess("postgresql:@pool_size=10;dbname=mydb;user=myname;password=mypassword");
		sess << "SET TIME ZONE 'UTC'" << cppdb::exec;
		dispatcher().assign(".*",&sync::show,this);
	}
private:
	void show(){
		std::ifstream myfile("/tmp/t.html");
		if(myfile.is_open()){
			std::string line;
			while(std::getline(myfile,line))
				response().out() << line;
			myfile.close();
		}
	}
};

class as : public cppcms::rpc::json_rpc_server
{
public:
	as(cppcms::service &s) : cppcms::rpc::json_rpc_server(s){
		//Next statement causes the program to terminate
		silently immediately after reqested:
		cppdb::session
		sess("postgresql:@pool_size=10;dbname=mydb;user=myname;password=mypassword");
		//Next statement does not cause problem:
		//cppdb::session
		sess("postgresql:dbname=mydb;user=myname;password=mypassword");
	} 
};

int main(int argc,char ** argv)
{
	cppcms::service s(argc,argv);
	s.applications_pool().mount(cppcms::applications_factory<sync>(),cppcms::mount_point("^/(?!as)(.*)",1));
	s.applications_pool().mount(new
	as(s),cppcms::mount_point("^/as/(.+)",1));
	s.run();
	return 0;
}

---file "/tmp/t.html":---
<html xmlns="http://www.w3.org/1999/xhtml">
<head>
	<title>My Title</title>
	<meta http-equiv="Content-Type" content="text/html;
	charset=utf-8" />
	<script type="text/javascript" src="json2.js"></script>
	<script type="text/javascript" src="jsonrpc.js"></script>
	<script type="text/javascript">
		rpc=new JsonRPC('/as',['any'],[]);
		rpc.any.on_result=function(r){ alert('ok'); }
		rpc.any.on_error=function(e){ alert('oops'); }
	</script>
</head>
<body>
my test.
</body>
</html>
---end of files---
Regards,
CN

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