| 1 | .. $Id: overview.rst 624 2011-08-21 20:15:37Z jemian $ |
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| 2 | |
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| 3 | RRD database changes |
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| 4 | ------------------------------------------------------------------ |
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| 5 | |
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| 6 | * Each EPICS PV goes into its own RRD database. |
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| 7 | This simplifies the addition of PVs into the logging system. |
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| 8 | * 10x finer time granularity now than before. |
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| 9 | Data are being averaged into minimum 30-second bins. |
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| 10 | (Data can always be updated to system at 1 Hz, if available.) |
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| 11 | |
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| 12 | Default WWW page |
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| 13 | ------------------------------------------------------------------ |
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| 14 | |
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| 15 | The default WWW page is now PHP. This allows for greater |
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| 16 | flexibility in designing new interfaces. The default |
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| 17 | interface shows a gallery of available PNG plots with |
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| 18 | data logged from the last week. Each plot is linked to |
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| 19 | a full description of logged data (6 plots for last: |
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| 20 | hour, day, week, month, year, and decade). |
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| 21 | |
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| 22 | Codebase |
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| 23 | ------------------------------------------------------------------ |
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| 24 | |
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| 25 | Python has been used to implement the support code, calling ``rrdtool`` |
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| 26 | through the rrdtool Python support module. |
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| 27 | The main WWW page is rendered in PHP. |
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| 28 | |
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| 29 | Configuration details |
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| 30 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
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| 31 | |
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| 32 | Two XML files are used for configuration: |
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| 33 | * ``pvlist.xml`` |
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| 34 | describes each of the EPICS Process Variables to be logged |
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| 35 | * ``properties.xml`` |
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| 36 | describes various other configuration and implementation |
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| 37 | details for the support code. |
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| 38 | |
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| 39 | RRD database creation |
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| 40 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
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| 41 | |
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| 42 | Each PV has its own RRD database, created by :mod:`rrdCreate`. |
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| 43 | |
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| 44 | CGI script operation |
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| 45 | ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ |
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| 46 | |
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| 47 | A web page request will cause ``rrdcgi`` to generate |
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| 48 | the www page content (text and plots) on demand. |
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| 49 | It may be necessary to force the |
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| 50 | page to refresh the local browser cache in order for some of the |
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| 51 | longer-term plots to be rebuilt. Usually, ``<shift>-"Refresh"`` |
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| 52 | or similar will get this done. |
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| 53 | |
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| 54 | |
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| 55 | Dependencies |
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| 56 | ------------------------------------------------------------------ |
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| 57 | |
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| 58 | :note: TODO: verify |
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| 59 | |
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| 60 | Several different software tools are necessary to provide |
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| 61 | this support: |
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| 62 | * Python |
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| 63 | |
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| 64 | * librrdtool |
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| 65 | * CaChannel |
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| 66 | * xml.etree.ElementTree |
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| 67 | |
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| 68 | * PHP |
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| 69 | |
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| 70 | * rrdtool support |
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| 71 | |
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| 72 | * WWW server |
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| 73 | |
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| 74 | * rrdtool support |
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| 75 | |
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