Merge pull request #100 from danielquinn/issue/98

Issue/98

docs/changelog.rst

@@ -3,6 +3,10 @@ Changelog
 
 * 0.2.0
 
+  * `#98`_: Added optional environment variables for ImageMagick so that it
+    doesn't explode when handling Very Large Documents or when it's just
+    running on a low-memory system.  Thanks to `Florian Harr`_ for his help on
+    this one.
   * Added support for guessing the date from the file name along with the
     correspondent, title, and tags.  Thanks to `Tikitu de Jager`_ for his pull
     request that I took forever to merge and to `Pit`_ for his efforts on the
@@ -97,6 +101,7 @@ Changelog
 .. _zedster: https://github.com/zedster
 .. _Martin Honermeyer: https://github.com/djmaze
 .. _Tim White: https://github.com/timwhite
+.. _Florian Harr: https://github.com/evils
 
 .. _#20: https://github.com/danielquinn/paperless/issues/20
 .. _#44: https://github.com/danielquinn/paperless/issues/44
@@ -111,3 +116,4 @@ Changelog
 .. _#68: https://github.com/danielquinn/paperless/issues/68
 .. _#71: https://github.com/danielquinn/paperless/issues/71
 .. _#94: https://github.com/danielquinn/paperless/issues/71
+.. _#98: https://github.com/danielquinn/paperless/issues/71

docs/troubleshooting.rst

@@ -3,17 +3,47 @@
 Troubleshooting
 ===============
 
-.. _troubleshooting_ocr_language_files_missing:
+.. _troubleshooting-languagemissing:
 
 Consumer warns ``OCR for XX failed``
 ------------------------------------
 
-If you find the OCR accuracy to be too low, and/or the document consumer warns that ``OCR for
-XX failed, but we're going to stick with what we've got since FORGIVING_OCR is enabled``, then you
-might need to install the `Tesseract language files
-<http://packages.ubuntu.com/search?keywords=tesseract-ocr>`_ marching your documents languages.
+If you find the OCR accuracy to be too low, and/or the document consumer warns
+that ``OCR for XX failed, but we're going to stick with what we've got since
+FORGIVING_OCR is enabled``, then you might need to install the
+`Tesseract language files <http://packages.ubuntu.com/search?keywords=tesseract-ocr>`_
+marching your documents languages.
 
-As an example, if you are running Paperless from the Vagrant setup provided (or from any Ubuntu or Debian
-box), and your documents are written in Spanish you may need to run::
+As an example, if you are running Paperless from the Vagrant setup provided
+(or from any Ubuntu or Debian box), and your documents are written in Spanish
+you may need to run::
 
     apt-get install -y tesseract-ocr-spa
+
+
+.. _troubleshooting-convertpixelcache:
+
+Consumer dies with ``convert: unable to extent pixel cache``
+------------------------------------------------------------
+
+During the consumption process, Paperless invokes ImageMagick's ``convert``
+program to translate the source document into something that the OCR engine can
+understand and this can burn a Very Large amount of memory if the original
+document is rather long.  Similarly, if your system doesn't have a lot of
+memory to begin with (ie. a Rasberry Pi), then this can happen for even
+medium-sized documents.
+
+The solution is to tell ImageMagick *not* to Use All The RAM, as is its
+default, and instead tell it to used a fixed amount.  ``convert`` will then
+break up the job into hundreds of individual files and use them to slowly
+compile the finished image.  Simply set ``PAPERLESS_CONVERT_MEMORY_LIMIT`` in
+``/etc/paperless.conf`` to something like ``32000000`` and you'll limit
+``convert`` to 32MB.  Fiddle with this value as you like.
+
+**HOWEVER**: Simply setting this value may not be enough on system where
+``/tmp`` is mounted as tmpfs, as this is where ``convert`` will write its
+temporary files.  In these cases (most Systemd machines), you need to tell
+ImageMagick to use a different space for its scratch work.  You do this by
+setting ``PAPERLESS_CONVERT_TMPDIR`` in ``/etc/paperless.conf`` to somewhere
+that's actually on a physical disk (and writable by the user running
+Paperless), like ``/var/tmp/paperless`` or ``/home/my_user/tmp`` in a pinch.

paperless.conf.example

@@ -32,7 +32,32 @@ PAPERLESS_PASSPHRASE="secret"
 # have a shared secret here.
 PAPERLESS_SHARED_SECRET=""
 
+#
+# The following values use sensible defaults for modern systems, but if you're
+# running Paperless on a low-resource machine (like a Rasberry Pi), modifying
+# some of these values may be necessary.
+#
+
 # By default, Paperless will attempt to use all available CPU cores to process
 # a document, but if you would like to limit that, you can set this value to
 # an integer:
 #PAPERLESS_OCR_THREADS=1
+
+# On smaller systems, or even in the case of Very Large Documents, the consumer
+# may explode, complaining about how it's "unable to extent pixel cache".  In
+# such cases, try setting this to a reasonably low value, like 32000000.  The
+# default is to use whatever is necessary to do everything without writing to
+# disk, and units are in megabytes.
+#
+# For more information on how to use this value, you should probably search
+# the web for "MAGICK_MEMORY_LIMIT".
+#PAPERLESS_CONVERT_MEMORY_LIMIT=0
+
+# Similar to the memory limit, if you've got a small system and your OS mounts
+# /tmp as tmpfs, you should set this to a path that's on a physical disk, like
+# /home/your_user/tmp or something.  ImageMagick will use this as scratch space
+# when crunching through very large documents.
+#
+# For more information on how to use this value, you should probably search
+# the web for "MAGICK_TMPDIR".
+#PAPERLESS_CONVERT_TMPDIR=/var/tmp/paperless

src/documents/consumer.py

@@ -129,10 +129,13 @@ class Consumer(object):
 
         # Convert PDF to multiple PNMs
         pnm = os.path.join(tempdir, "convert-%04d.pnm")
-        subprocess.Popen((
-            self.CONVERT, "-density", "300", "-depth", "8",
-            "-type", "grayscale", doc, pnm
-        )).wait()
+        run_convert(
+            self.CONVERT,
+            "-density", "300",
+            "-depth", "8",
+            "-type", "grayscale",
+            doc, pnm,
+        )
 
         # Get a list of converted images
         pnms = []
@@ -159,13 +162,12 @@ class Consumer(object):
 
         self.log("info", "Generating the thumbnail")
 
-        subprocess.Popen((
+        run_convert(
             self.CONVERT,
             "-scale", "500x5000",
             "-alpha", "remove",
-            doc,
-            os.path.join(tempdir, "convert-%04d.png")
-        )).wait()
+            doc, os.path.join(tempdir, "convert-%04d.png")
+        )
 
         return os.path.join(tempdir, "convert-0000.png")
 
@@ -334,6 +336,16 @@ def image_to_string(args):
 
 def run_unpaper(args):
     unpaper, pnm = args
-    subprocess.Popen((
-        unpaper, pnm, pnm.replace(".pnm", ".unpaper.pnm")
-    )).wait()
+    subprocess.Popen(
+        (unpaper, pnm, pnm.replace(".pnm", ".unpaper.pnm"))).wait()
+
+
+def run_convert(*args):
+
+    environment = {}
+    if settings.CONVERT_MEMORY_LIMIT:
+        environment["MAGICK_MEMORY_LIMIT"] = settings.CONVERT_MEMORY_LIMIT
+    if settings.CONVERT_TMPDIR:
+        environment["MAGICK_TMPDIR"] = settings.CONVERT_TMPDIR
+
+    subprocess.Popen(args, env=environment).wait()

src/paperless/settings.py

@@ -189,6 +189,8 @@ GNUPG_HOME = os.getenv("HOME", "/tmp")
 
 # Convert is part of the ImageMagick package
 CONVERT_BINARY = os.getenv("PAPERLESS_CONVERT_BINARY")
+CONVERT_TMPDIR = os.getenv("PAPERLESS_CONVERT_TMPDIR")
+CONVERT_MEMORY_LIMIT = os.getenv("PAPERLESS_CONVERT_MEMORY_LIMIT")
 
 # Unpaper
 UNPAPER_BINARY = os.getenv("PAPERLESS_UNPAPER_BINARY", "unpaper")
@@ -226,7 +228,7 @@ PASSPHRASE = os.getenv("PAPERLESS_PASSPHRASE")
 SHARED_SECRET = os.getenv("PAPERLESS_SHARED_SECRET", "")
 
 #
-# TODO: Remove after 1.2
+# TODO: Remove after 0.2
 #
 # This logic is here to address issue #44, wherein we were using inconsistent
 # constant names vs. environment variables.  If you're using Paperless for the