Snapshots

From n² wiki

Nearby: Snapshot Job, Snapshot Collection

Snapshots files contain a snapshot of all the data contained in a store at a particular point in time.

The file is named in the format 200710101200.tar where the filename represents the date and time the snapshot was created.

The tar file can be extracted in the normal way, for example using WinZIP or the following unix command.

tar xvf 200710101200.tar

The tar file contain all content from the stores content box, all meta data from the stores meta box and some system data which can be used to restore the data into the store.

[edit] Content Box

Files contained in the stores content box are located in a directory called "contentbox". Individual files are named after the GUID used in the url assigned to the item when it was stored. For example, if you stored an image, myimage.jpg in you stores content box, you might access the file using the url http://api.talis.com/stores/yourstore/items/f550acf6-8a35-4afe-978f-4acb228d8962. So the image will be stored in the content box directory with the filename f550acf6-8a35-4afe-978f-4acb228d8962. As it is possible this directory would contain a large number of files, two levels of subdirectory are created using the first and second pairs of characters from the filename. So the two files f550acf6-8a35-4afe-978f-4acb228d8962 and 443315b7-dc97-4446-955c-cbc9a0403d16 would be contained in directories as shown below.

  /contentbox
    /44
      /33
        443315b7-dc97-4446-955c-cbc9a0403d16
    /f5
      /50
        f550acf6-8a35-4afe-978f-4acb228d8962

[edit] Meta Box

All the meta data from the store is located in a directory called "metabox". The directory contains a manifest file MANIFEST. This is an RDF file which describes the other files in this directory. An example of a MANIFEST is shown below.

<rdf:RDF
    xmlns:rdf="http://www.w3.org/1999/02/22-rdf-syntax-ns#"
    xmlns:bf="http://schemas.talis.com/2006/bigfoot/configuration#" > 
  <bf:Manifest rdf:about="http://api.talis.com/stores/yourstore/meta/manifest">
    <bf:manifestEntry>
      <bf:ManifestEntry rdf:about="http://api.talis.com/stores/yourstore/snapshots/metabox#entry1">
        <bf:file>meta</bf:file>
        <bf:graph rdf:resource="http://api.talis.com/stores/yourstore/meta"/>
      </bf:ManifestEntry>
    </bf:manifestEntry>
    <bf:manifestEntry>
      <bf:ManifestEntry rdf:about="http://api.talis.com/stores/yourstore/snapshots/metabox#entry2">
        <bf:file>dp1</bf:file>
        <bf:graph rdf:resource="http://api.talis.com/stores/yourstore/meta/graphs/dp1"/>
      </bf:ManifestEntry>
    </bf:manifestEntry>
  </bf:Manifest>
</rdf:RDF>

This manifest contains two entries - entry1 and entry2. entry1 states that the contents of the graph http://127.0.0.1:9898/stores/yourstore/meta is contained in the file meta. entry2 states that the contents of the graph http://127.0.0.1:9898/stores/yourstore/meta/graphs/dp1 is contained in the file dp1.

The files themselves contain the RDF from each graph in an N Triples format.

The contents of the metabox directory for the above manifest file would be as shown below.

  /metabox
    MANIFEST
    meta
    dp1

[edit] System Data

The system data needed to restore the snapshot into the store is contained in a file called "system". This file is not readable.

[edit] Complete Contents

Below is the complete contents from the snapshot file described in this document.

  /contentbox
    /44
      /33
        443315b7-dc97-4446-955c-cbc9a0403d16
    /f5
      /50
        f550acf6-8a35-4afe-978f-4acb228d8962
  /metabox
    MANIFEST
    meta
    dp1
  system