How to handle TerminateSessionException sendfile?

[Henry Laxen]

Dear Snappers,

I've been using Snap for a few years now, and every few days I get an email like this:

snip

...

177.192.105.60 - - [20/May/2017:21:25:42 -0400] "GET /static/favicon.ico HTTP/1.1" 200 3638 "http://maztravel.com/haskell/mySqlToCouchDB.html" "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/58.0.3029.110 Safari/537.36"

------------------------------------------------------------------------

A web handler threw an exception. Details:

sendfile: resource vanished (Connection reset by peer)

[20/May/2017:16:28:56 -0400] Exception leaked to httpSession during phase 'user handler': 

During processing of request from 86.143.35.116:58136

request:

"GET /us/houses/reno/images/large/reno_n_bath1.jpg HTTP/1.1

connection: Keep-Alive

host: www.maztravel.com

accept-encoding: gzip, deflate

user-agent: Mozilla/5.0 (Windows NT 10.0; WOW64; Trident/7.0; rv:11.0) like Gecko

accept-language: en-GB

accept: image/png, image/svg+xml, image/jxr, image/*;q=0.8, */*;q=0.5

sn=\"www.maztravel.com\" c=86.143.35.116:58136 s=65.111.168.75:80 ctx=/ clen=n/a"

A web handler threw an exception. Details:

TerminateSessionException sendfile: resource vanished (Connection reset by peer)

[20/May/2017:18:06:32 -0400] Exception leaked to httpSession during phase 'sending-response': 

During processing of request from 172.56.20.36:42168

request:

"GET /maz/images/large/peso10a.jpg HTTP/1.1

user-agent: com.google.GoogleMobile/27.0.0 iPhone/10.2 hw/iPhone8_1

accept-encoding: gzip, deflate

connection: keep-alive

accept-language: en-us

accept: */*

host: www.maztravel.com

sn=\"www.maztravel.com\" c=172.56.20.36:42168 s=65.111.168.75:80 ctx=/ clen=n/a"

A web handler threw an exception. Details:

sendfile: resource vanished (Broken pipe)

[20/May/2017:18:06:32 -0400] Exception leaked to httpSession during phase 'user handler': 

During processing of request from 172.56.20.36:42168

request:

"GET /maz/images/large/peso10a.jpg HTTP/1.1

user-agent: com.google.GoogleMobile/27.0.0 iPhone/10.2 hw/iPhone8_1

accept-encoding: gzip, deflate

connection: keep-alive

accept-language: en-us

accept: */*

host: www.maztravel.com

sn=\"www.maztravel.com\" c=172.56.20.36:42168 s=65.111.168.75:80 ctx=/ clen=n/a"

A web handler threw an exception. Details:

TerminateSessionException sendfile: resource vanished (Broken pipe)

which has made me resort to a shell wrapper around my snap server (called nlh):

while [ 1 ]; do
    ./nlh -p 80
    tail -20 log/access.log >access.txt
    tail -20 log/error.log  >error.txt
    cat access.txt divider.txt error.txt | mail -s "NLH crash" nadine.and.henry@pobox.com
done

So my question is how can I catch this exception in my code so

that it doesn't escape to the top level.  The files above are

static files being served by the following lines in the depths

of the nlh code:

import           Snap.Util.FileServe
...


myServeFile  :: MonadSnap m => FilePath -> m ()
myServeFile fp = do
  setReferer -- just sets the Referer header
  when isVideo $ extendTimeout (5 * 60)
----------------------------
  serveFileAs mimeType fp -- from Snap.Util.FileServe
----------------------------
  where
    mimeType = fileType myMimeTypes (takeFileName fp)
    isVideo = B8.take (length ("video" :: String)) mimeType ==  "video"

Any pointers would be appreicated.

Best wishes,

Henry Laxen

[Gregory Collins]

You can wrap your snap monad action in the exception functions from Control.Exception.Lifted. You can also replace the toplevel exception handler via setErrorHandler.

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Gregory Collins <gr...@gregorycollins.net>