mapnik / mapnik-support

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Can't use sqlite layer in multiple Mapnik instances #125

Open zdila opened 5 years ago

zdila commented 5 years ago

We create pool of 8 mapnik instances using nodejs. First gets created successfully but other 7 fail with this error:

Error creating or configuring Mapnik: [Error: Sqlite Plugin: 'database is locked' (shading/contours.sqlite.index)
Full sql was: 'BEGIN IMMEDIATE TRANSACTION'  encountered during parsing of layer 'Unnamed' in Layer]

Layer is defined like this:

  <Layer maximum-scale-denominator="200000">
    <StyleName>contours</StyleName>
    <Datasource>
      <Parameter name="type">sqlite</Parameter>
      <Parameter name="file">shading/contours.sqlite</Parameter>
      <Parameter name="table">(select geometry, height from contour) as foo</Parameter>
      <Parameter name="geometry_field">GEOMETRY</Parameter>
    </Datasource>
  </Layer>

Is there a way to fix it?