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1 # Java VM settings for digilib
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2
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3 The Java virtual machine (Java-VM) only uses a fixed amount of memory for
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4 its operations. When an operation needs more memory than available it aborts
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5 with an error ("out of memory error").
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6
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7 digilib can need a lot of memory depending on the size and type of images.
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8 Since digilib runs as a servlet under Tomcat its in the same VM as the Tomcat
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9 server.
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10
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11 The amount of memory Tomcat (version 5.0) uses is configured by creating a
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12 "setenv.sh" script with a line
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13
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14 CATALINA_OPTS="-Xmx512m"
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15
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16 in Tomcat's `bin` directory (giving 512MB in this case).
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17
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18 You can check the amount of memory your digilib instance has available on the
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19 bottom of the web page `/server/dlConfig.jsp` in your digilib instance (e.g.
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20 [http://digilib.mpiwg-berlin.mpg.de/digitallibrary/server/dlConfig.jsp](http://digilib.mpiwg-berlin.mpg.de/digitallibrary/server/dlConfig.jsp)).
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21
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22 # Installing JAI ImageIO
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23
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24 In principle you should be able to install the
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25 [Java Advanced Imaging](http://java.sun.com/javase/technologies/desktop/media/jai/) JAI-ImageIO
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26 JAR file `jai_imageio.jar` (and native
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27 library files if available) in the `/WEB-INF/lib/` directory of the
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28 digilib web application as part of the default installation.
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29
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30 You can see if the Jai-ImageIO plugin is active by checking for the
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31 availability of the TIFF image format under "Supported image types" on the
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32 [`/server/dlConfig.jsp`](http://digilib.mpiwg-berlin.mpg.de/digitallibrary/server/dlConfig.jsp)
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33 status page.
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34
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35 But sometimes there are classloader issues. Newer versions of Tomcat refuse to load
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36 the libraries and I found that in some cases digilib stopped reading TIFF files
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37 after a period of running.
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38
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39 In these cases it helped to install the JAI files in Tomcats `lib/`
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40 directory or globally in the local Java JDK
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41 installation (i.e. in the Java's 'jre/lib/ext/' directory on linux).
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42
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43 # Sample setup
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44
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45 The current digilib setup at the MPIWG (as of December 2010):
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46
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47 * One frontend server running the lightweight web-multiplexer [pound](http://www.apsis.ch/pound/)
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48 on port 80 that distributes requests to three servers runnning digilib
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49 * the three servers run digilib under [Jetty](http://www.eclipse.org/jetty/) on port 8080 without Apache
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50
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51 * one server is the frontend server (Linux 32bit, Dual
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52 2.4GHz Xeon, 2GB RAM)
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53 * the other server is a separate, newer machine (Linux 64bit, Dual 1.8GHz
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54 Opteron, 2GB RAM)
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55 * the third server is a separate, newer machine (Linux 32bit, Dual 2.8GHz
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56 Xeon, 4GB RAM)
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57 * the digilib instances (digilib 2.0b1 as of 12.12.2011) run on Jetty 8.0.4 on Java
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58 1.6.0_26 with 1GB of [Java VM memory
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59 for digilib](#vm_settings) (-Xmx1024m) with JAI (1.1.3) and JAI-ImageIO (1.1) [installed in the Jetty/lib/ext](#installing_jai)(!)
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60 * both digilib servers access all image files over NFS (over GBit
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61 Ethernet) from a central file server (Solaris 10, Sun Fire 240, multiple RAIDs
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62 on Fibrechannel) |
