Tecno Brain wrote:
Hi Andre,
These files can be huge (for a few of my clients). It can take more than an
hour for the entire file to be generated.
Then you also have to take into account that when the browser issues a request to the
server, it expects *some* answer within a maximum of about 5 minutes maximum. If it
doesn't get that, the browser will drop the connection and display a message like "the
server is not responding"...
I just didn't want to save them. I was expecting that if the file was too
big, the process would just be aborted. As it is now, my webapp keeps
working eventhough no browser is receiving the data.
I guess I will have to save them (In S3) an notify my client via e-mail
when the file is available.
I am not even sure that in such a case, having the file be generated by a webserver webapp
is the best design. It means that when the browser issues such a request, one of the
webserver's threads/children is busy with that request for a very extended period of time,
unable to do anything else. That looks like an ideal case for a Denial of Service e.g.
You may want to re-examine the whole principle of this thing.
In some restaurants, if you want some special dish that take a long time to prepare, you
have to order it in advance; you can't just walk in and order it from the menu.
I'll also ask Amazon about it.
Thank you,
-Jorge
On Thu, Jul 9, 2015 at 2:06 AM, André Warnier <a...@ice-sa.com> wrote:
Tecno Brain wrote:
I am running Tomcat 8.0.20 in Ubuntu with Java 1.8u45
This server runs in Amazon EC2 behind an ELB (load balancer), although the
cluster size is just one server.
My application allows to download some data in CSV format.
The CSV data is generated on the fly, and there is no way to known in
advance the size of the response. So, the data is an attachment.
response.setContentType("text/csv;charset=utf-8");
filename = "data.csv"
response.setHeader("Content-Disposition", "attachment; filename=\"" +
filename + ".csv\"");
The download starts immediately but after 100 MB the browser stopped
received data -my internet connection was not the best-, so I canceled the
download as it was not progressing anymore.
Nevertheless, my web app keeps generating the CSV data, unaware that the
connection has been dropped. I was expecting that my code would get an
IOException when writing to the servlet OutputStream (which was wrapped by
a BufferedOutputStream and wrapped by an OutputStreamWriter).
Is this a problem I can solve through the configuration of the NIO
connector ?
Or is this a problem of Amazon ELB that still consumes the stream even
though it can't be forwarded to the browser anymore?
Yes, that kind of thing. There may also be load-balancers, proxies,
gateways, etc. between Tomcat and the end-user browser.
As long as Tomcat itself is able to write to that connection, there is no
way for an application within Tomcat, to even find out that the ultimate
client has gone away.
I don't remember having this problem when working with Apache HTTP as the
load balancer. If I remember correctly, I would get an error indicating
that the client closed the connection.
Yes, in some cases, because then there was less buffering in-between.
Any pointers are appreciated.
If your generated files are really that big, I would suggest that the
Tomcat side writes them to disk to a temporary file, and then returns to
the client a short response, with a link where it can retrieve that file.
Then there could be a separate cleanup procedure, which cleans up such
temporary files when they are more than a certain age.
-Jorge
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