Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
Hi,thanks, you are right, I have solved this
problem,but I want to know how to judge a grass
commond(called in my javaProgram) is successfully
exected?
check this:
if (ps.exitValue() != 0) {
??
exit values:
0 == success
1 == failure
other = failure
Hamish
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Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
2009/9/23 Sören Gebbert soerengebb...@gmx.de
Hello maven,
i guess the problem is located in your GrassMain.java line 200:
if (ps.exitValue() != 0) {
System.exit(ps.exitValue());
}
AFAIK, the tomcat server uses a container to run the several servlet
threads
inside.
If you call from any servlet thread the System.exit() command, the server
will
be shutdown.
Java doc of System.exit():
Hi,thanks, you are right, I have solved this problem,but I want to know how
to judge a grass commond(called in my javaProgram) is successfully exected?
Terminates the currently running Java Virtual Machine.
Best regards
Soeren
Am Sunday 20 September 2009 05:21:29 schrieb maven apache:
Hi,
In my application ,I provide a interface which can called by users to
execute some geo process through the web,for example,user send a map,and
a
width to the server ,then the server can do a buffer operation using the
grass(the server make the grass commond) according to the parameter from
client .
But I found that if user give a invalide parameter, then the grass
commond
maybe error, I can get the error message in the log, but my web server
(tomcat)shut down itself.
Any one have encountered the same suitation?
Annex is my java class to set up the grass environment. I hope some can
check it and identify it if any problem exist.
The GrassMain is the main class to set up the environment,the GrassThread
is to get the output result , the GrassThreadError is to get the error
message if so.
Thanks!
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Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
2009/9/23 Sören Gebbert soerengebb...@gmx.de
Hello maven,
i guess the problem is located in your GrassMain.java line 200:
if (ps.exitValue() != 0) {
System.exit(ps.exitValue());
}
AFAIK, the tomcat server uses a container to run the several servlet
threads
inside.
If you call from any servlet thread the System.exit() command, the server
will
be shutdown.
Java doc of System.exit():
Terminates the currently running Java Virtual Machine.
Thanks, you are right! ^_^
I have solved this problem,however I want to know how to judge whether the
grass commond(which I call in my program)is executed successfully?
Best regards
Soeren
Am Sunday 20 September 2009 05:21:29 schrieb maven apache:
Hi,
In my application ,I provide a interface which can called by users to
execute some geo process through the web,for example,user send a map,and
a
width to the server ,then the server can do a buffer operation using the
grass(the server make the grass commond) according to the parameter from
client .
But I found that if user give a invalide parameter, then the grass
commond
maybe error, I can get the error message in the log, but my web server
(tomcat)shut down itself.
Any one have encountered the same suitation?
Annex is my java class to set up the grass environment. I hope some can
check it and identify it if any problem exist.
The GrassMain is the main class to set up the environment,the GrassThread
is to get the output result , the GrassThreadError is to get the error
message if so.
Thanks!
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Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
Hello maven,
i guess the problem is located in your GrassMain.java line 200:
if (ps.exitValue() != 0) {
System.exit(ps.exitValue());
}
AFAIK, the tomcat server uses a container to run the several servlet threads
inside.
If you call from any servlet thread the System.exit() command, the server will
be shutdown.
Java doc of System.exit():
Terminates the currently running Java Virtual Machine.
Best regards
Soeren
Am Sunday 20 September 2009 05:21:29 schrieb maven apache:
Hi,
In my application ,I provide a interface which can called by users to
execute some geo process through the web,for example,user send a map,and a
width to the server ,then the server can do a buffer operation using the
grass(the server make the grass commond) according to the parameter from
client .
But I found that if user give a invalide parameter, then the grass commond
maybe error, I can get the error message in the log, but my web server
(tomcat)shut down itself.
Any one have encountered the same suitation?
Annex is my java class to set up the grass environment. I hope some can
check it and identify it if any problem exist.
The GrassMain is the main class to set up the environment,the GrassThread
is to get the output result , the GrassThreadError is to get the error
message if so.
Thanks!
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Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
Hi, Am Sunday 20 September 2009 14:18:58 schrieb Glynn Clements: maven apache wrote: In my application ,I provide a interface which can called by users to execute some geo process through the web,for example,user send a map,and a width to the server ,then the server can do a buffer operation using the grass(the server make the grass commond) according to the parameter from client . But I found that if user give a invalide parameter, then the grass commond maybe error, I can get the error message in the log, but my web server (tomcat)shut down itself. Any one have encountered the same suitation? The GRASS libraries typically handle errors by terminating the calling process via exit(). This eliminates the need for the caller to handle errors; either the function succeeds or the process is terminated. This approach is perfectly adequate for the intended use of the GRASS libraries, i.e. short-lived, non-interactive commands. OTOH, it's quite unsuitable for persistent processes, as any error will terminate the process. But persistent processes aren't the intended use of the GRASS libraries, and that isn't going to change. The problems with persistent processes aren't limited to error handling either. Many static variables are initialised upon first use and cannot be changed thereafter. If you want to use GRASS from within a web application, either run GRASS commands or fork() a new child process for each request. Finally, although you can override the fatal error handler with G_set_error_routine(), the supplied handler mustn't return, and you cannot safely use any GRASS functions once a fatal error has been detected, as the data structures used by the libraries will be in an undefined state. Well, thats exactly the problem that i face with grass trying to run several operations within on process using the vtkGRASSBridge. Is there any chance to implement a conterpart to G_init() like G_uninit() to compute several tasks in one process (not multithreaded). Is there really no way to reset the static variables to initial state? Best regards Soeren ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
Sören Gebbert wrote: Finally, although you can override the fatal error handler with G_set_error_routine(), the supplied handler mustn't return, and you cannot safely use any GRASS functions once a fatal error has been detected, as the data structures used by the libraries will be in an undefined state. Well, thats exactly the problem that i face with grass trying to run several operations within on process using the vtkGRASSBridge. Is there any chance to implement a conterpart to G_init() like G_uninit() to compute several tasks in one process (not multithreaded). Is there really no way to reset the static variables to initial state? The variables are littered throughout the various source files of the various libraries, and initialisation upon first use is a common idiom in GRASS. You would need to identify all of the relevant variables, make them non-static, and add a function to reset them. You would need a separate reset function for each library. And you would need to keep track of any new variables which were added (don't rely upon developers co-operating; I've had trouble implementing no static data policies even on projects which were generally well-organised). Oh; and some of the libraries which GRASS uses may have their own static data, so you would have to figure out how to reset those libraries. For lib/gis and and lib/raster, searching for struct state (in 7.0) will find many of them. Beyond that, searching the output from nm for symbols of type B, D, b and d will show static variables (some of which never change, but aren't in the rodata segment because adding the const qualifier introduces compatibility issues). -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
maven apache wrote: Thanks Glynn Clements: I noticed that you have mentioned Grass library more than one times? I think I did not use them? I just have three java class the handle the grass commond,and the real call of grass is through the Runtime.exec() method ,it do open a new process. In which case, I have no idea why Tomcat is terminating. -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
maven apache wrote: In my application ,I provide a interface which can called by users to execute some geo process through the web,for example,user send a map,and a width to the server ,then the server can do a buffer operation using the grass(the server make the grass commond) according to the parameter from client . But I found that if user give a invalide parameter, then the grass commond maybe error, I can get the error message in the log, but my web server (tomcat)shut down itself. Any one have encountered the same suitation? The GRASS libraries typically handle errors by terminating the calling process via exit(). This eliminates the need for the caller to handle errors; either the function succeeds or the process is terminated. This approach is perfectly adequate for the intended use of the GRASS libraries, i.e. short-lived, non-interactive commands. OTOH, it's quite unsuitable for persistent processes, as any error will terminate the process. But persistent processes aren't the intended use of the GRASS libraries, and that isn't going to change. The problems with persistent processes aren't limited to error handling either. Many static variables are initialised upon first use and cannot be changed thereafter. If you want to use GRASS from within a web application, either run GRASS commands or fork() a new child process for each request. Finally, although you can override the fatal error handler with G_set_error_routine(), the supplied handler mustn't return, and you cannot safely use any GRASS functions once a fatal error has been detected, as the data structures used by the libraries will be in an undefined state. -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] The tomcat shut down when encounter some error grass commond
-- Forwarded message -- From: maven apache apachemav...@gmail.com Date: 2009/9/20 Subject: Re: [GRASS-user] The tomcat shut down when encounter some error grass commond To: Glynn Clements gl...@gclements.plus.com Thanks for your reply! I am not exactly sure your meaning. What is short-lived process and what is persisitent process? Did you mean that if a process takes long time,then a error can terminate this thread? and the web server is in the same thread,so it is shut down? If so ,does it mean that I should open a new thread for each grass commond? 2009/9/20 Glynn Clements gl...@gclements.plus.com maven apache wrote: In my application ,I provide a interface which can called by users to execute some geo process through the web,for example,user send a map,and a width to the server ,then the server can do a buffer operation using the grass(the server make the grass commond) according to the parameter from client . But I found that if user give a invalide parameter, then the grass commond maybe error, I can get the error message in the log, but my web server (tomcat)shut down itself. Any one have encountered the same suitation? The GRASS libraries typically handle errors by terminating the calling process via exit(). This eliminates the need for the caller to handle errors; either the function succeeds or the process is terminated. This approach is perfectly adequate for the intended use of the GRASS libraries, i.e. short-lived, non-interactive commands. OTOH, it's quite unsuitable for persistent processes, as any error will terminate the process. But persistent processes aren't the intended use of the GRASS libraries, and that isn't going to change. The problems with persistent processes aren't limited to error handling either. Many static variables are initialised upon first use and cannot be changed thereafter. If you want to use GRASS from within a web application, either run GRASS commands or fork() a new child process for each request. Finally, although you can override the fatal error handler with G_set_error_routine(), the supplied handler mustn't return, and you cannot safely use any GRASS functions once a fatal error has been detected, as the data structures used by the libraries will be in an undefined state. -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
maven apache wrote: I am not exactly sure your meaning. What is short-lived process and what is persisitent process? By short-lived non-interactive command, I'm talking about a typical GRASS command: it reads parameters from the command line, performs some processing, then exits. If there are any errors, then it just exits, often without performing any significant processing. By persistent process I'm talking about something like a daemon or a GUI application, which performs multiple operations, and keeps performing operations until it is specifically instructed to terminate. Did you mean that if a process takes long time,then a error can terminate this thread? It doesn't matter how long it takes; any error will normally terminate the process. For a simple command, this isn't a problem; if the library function didn't terminate the process, the main program would terminate itself once the error was reported. But for a persistent process which performs multiple operations, an error would normally result in it aborting the current operation then proceding to the next operation. This isn't possible if you're using the GRASS libraries, as they don't generally permit the process to continue after an error has occurred. and the web server is in the same thread,so it is shut down? If so ,does it mean that I should open a new thread for each grass commond? This is about processes, not threads. AFAIK, Tomcat behaves as a server, receiving requests from Apache and passing them to Java modules for processing. If you use Tomcat to run a module which uses GRASS library functions, if the GRASS library function signals an error, it will call exit() which will terminate the current process, i.e. it will terminate Tomcat. If you want to avoid this, you need to process each request in a separate *process*; a separate thread doesn't help, as exit() terminates the process, not just a thread. AFAICT, Java doesn't have an equivalent of fork() (which doesn't exist on Windows); the normal mechanism for creating processes is with Runtime.exec(). I have no idea whether this is even permitted from within Tomcat, or whether there are any complications involved. -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
Re: [GRASS-user] The tomcat shut down when encounter some error grass commond
Thanks Glynn Clements: I noticed that you have mentioned Grass library more than one times? I think I did not use them? I just have three java class the handle the grass commond,and the real call of grass is through the Runtime.exec() method ,it do open a new process. 2009/9/21 Glynn Clements gl...@gclements.plus.com maven apache wrote: I am not exactly sure your meaning. What is short-lived process and what is persisitent process? By short-lived non-interactive command, I'm talking about a typical GRASS command: it reads parameters from the command line, performs some processing, then exits. If there are any errors, then it just exits, often without performing any significant processing. By persistent process I'm talking about something like a daemon or a GUI application, which performs multiple operations, and keeps performing operations until it is specifically instructed to terminate. Did you mean that if a process takes long time,then a error can terminate this thread? It doesn't matter how long it takes; any error will normally terminate the process. For a simple command, this isn't a problem; if the library function didn't terminate the process, the main program would terminate itself once the error was reported. But for a persistent process which performs multiple operations, an error would normally result in it aborting the current operation then proceding to the next operation. This isn't possible if you're using the GRASS libraries, as they don't generally permit the process to continue after an error has occurred. and the web server is in the same thread,so it is shut down? If so ,does it mean that I should open a new thread for each grass commond? This is about processes, not threads. AFAIK, Tomcat behaves as a server, receiving requests from Apache and passing them to Java modules for processing. If you use Tomcat to run a module which uses GRASS library functions, if the GRASS library function signals an error, it will call exit() which will terminate the current process, i.e. it will terminate Tomcat. If you want to avoid this, you need to process each request in a separate *process*; a separate thread doesn't help, as exit() terminates the process, not just a thread. AFAICT, Java doesn't have an equivalent of fork() (which doesn't exist on Windows); the normal mechanism for creating processes is with Runtime.exec(). I have no idea whether this is even permitted from within Tomcat, or whether there are any complications involved. -- Glynn Clements gl...@gclements.plus.com ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
[GRASS-user] The tomcat shut down when encounter some error grass commond
Hi, In my application ,I provide a interface which can called by users to execute some geo process through the web,for example,user send a map,and a width to the server ,then the server can do a buffer operation using the grass(the server make the grass commond) according to the parameter from client . But I found that if user give a invalide parameter, then the grass commond maybe error, I can get the error message in the log, but my web server (tomcat)shut down itself. Any one have encountered the same suitation? Annex is my java class to set up the grass environment. I hope some can check it and identify it if any problem exist. The GrassMain is the main class to set up the environment,the GrassThread is to get the output result , the GrassThreadError is to get the error message if so. Thanks! GrassThreadError.java Description: Binary data GrassMain.java Description: Binary data GrassThread.java Description: Binary data ___ grass-user mailing list grass-user@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/grass-user
