Found in bi-hourly testing.
Symptom: all tests using "ImageMagick" started and continued failing since 2005-10-27 12:00, typically test #1,2,3,7,9.

Found that one conversion failed in the "ImageMagick" queue around 10-27 11:35 am in SS on ss-5 in Nebula, and since then the queue got stuck.

Please see the attached ss log and polyglot log. Job 200490041 was the last successful ImageMagick conversion, while 200490043 failed.

Might be related with POL-148, but not the same, as this only locks up the queue, SS continued working with other queues.

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More details:

In successful conversion, the sequences are:
[Tue Oct 27 11:03:22 2015] [rabbitm] [200490041]: Consuming job-200490041, http://141.142.227.81:8184/file/world.bmp->tiff via ImageMagick
[Tue Oct 27 11:03:22 2015] [rabbitm] [200490041]: API call, http://localhost:8182/software/ImageMagick/convert/tiff/http%3A%2F%2F141.142.227.81%3A8184%2Ffile%2Fworld.bmp
[Tue Oct 27 11:03:22 2015] [restlet] [11907]: Setting session to session-11907, result will be at ^{[[94mhttp://141.142.208.117:8182/file/11907_world.tiff}[[0m
[Tue Oct 27 11:03:22 2015] [restlet] [11907]: Downloading ^{[[94mhttp://141.142.227.81:8184/file/world.bmp}[[0m (21.5 KB) ...
.
[Tue Oct 27 11:03:22 2015] [sserver] [11907]: Executing, scripts/sh/ImageMagick_convert.sh /home/polyglot/polyglot/tmp/SoftwareServer/Cache/11907_world.bmp /home/polyglot/polyglot/tmp/SoftwareServer/Cache/11907_world.tiff /home/polyglot/polyglot/tmp/SoftwareServer/Temp/11907_1445961802808_ ....
[Tue Oct 27 11:03:23 2015] [sserver] [11907]: Killing, scripts/sh/ImageMagick_convert.sh /home/polyglot/polyglot/tmp/SoftwareServer/Cache/11907_world.bmp /home/polyglot/polyglot/tmp/SoftwareServer/Cache/11907_world.tiff /home/polyglot/polyglot/tmp/SoftwareServer/Temp/11907_1445961802808_ ...
[Tue Oct 27 11:03:23 2015] [restlet] [11907]: Execution complete, result at ^{[[94m/home/polyglot/polyglot/tmp/SoftwareServer/Cache/11907_world.tiff}[[0m (0 B)
[Tue Oct 27 11:03:23 2015] [restlet] [11907]: Copied result to public folder
[Tue Oct 27 11:03:24 2015] [rabbitm] [200490041]: API call complete, result at http://141.142.208.117:8182/file/11907_world.tiff
[Tue Oct 27 11:03:24 2015] [rabbitm] [200490041]: Checking in result with Polyglot, http://141.142.227.81:8184/checkin/200490041/http%3A%2F%2F141.142.208.117%3A8182%2Ffile%2F11907_world.tiff
[Tue Oct 27 11:03:25 2015] [rabbitm] [200490041]: Checkin acknowledged!

The failed conversion got stuck after the log "Setting session to..." and did not have "Downloading...":
[Tue Oct 27 11:07:58 2015] [rabbitm] [200490043]: Consuming job-200490043, http://141.142.227.81:8184/file/photo1scale.bmp->tiff via ImageMagick
[Tue Oct 27 11:07:58 2015] [rabbitm] [200490043]: API call, http://localhost:8182/software/ImageMagick/convert/tiff/http%3A%2F%2F141.142.227.81%3A8184%2Ffile%2Fphoto1scale.bmp
[Tue Oct 27 11:07:58 2015] [restlet] [11908]: Setting session to session-11908, result will be at ^{[[94mhttp://141.142.208.117:8182/file/11908_photo1scale.tiff}[[0m