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use hardlinks for empty bitmap tiles #107

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merged 8 commits into from
Jun 17, 2016
Merged

use hardlinks for empty bitmap tiles #107

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6bce004
let getJSONFeatures() always return an array
DerDakon Mar 13, 2016
ce5b1ed
use hardlinks to empty tile to save inodes and space
DerDakon Mar 13, 2016
ed35b72
do not mark vector and PNG tiles as executable
DerDakon Mar 13, 2016
b98e2e4
use getHeader() in one more place of BitmapTilerequest
DerDakon Mar 13, 2016
2251302
explicitely unlink tiles before overwriting them
DerDakon Mar 13, 2016
4b56c05
hardlink empty vector tiles to a common file
DerDakon Mar 14, 2016
1d9bb61
factor out BitmapTilerequest.renderCallback()
DerDakon Mar 15, 2016
5a1f60b
do not render a bitmap when the vector tile contains no features
DerDakon Mar 15, 2016
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104 changes: 56 additions & 48 deletions bitmaptilerequest.js
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Original file line number Diff line number Diff line change
Expand Up @@ -34,6 +34,51 @@ BitmapTilerequest = function(self)

BitmapTilerequest.prototype =
{
// save the rendered image to disk and send it to the client
renderCallback: function(err, image)
{
if (err)
self.tile.debug('Vectortile was empty.');
self.tile.saveBitmapData(image, function(err)
{
if (err)
{
self.response.writeHead(500, {'Content-Type': 'text/plain'});
self.response.end();
self.tile.debug('Empty bitmap tile was responded to the request.');
self.tile.debug('Finished request.');
return;
}

self.tile.getModifyTime(function(err, mtime)
{
var header = self.getHeader();

if (!err)
header['Last-Modified'] = mtime.toUTCString();

self.tile.trace('Responding bitmap data...');
var stream = image.createPNGStream();
self.response.writeHead(200, header);

// write PNG data stream
stream.on('data', function(data)
{
self.response.write(data);
});

// PNG data stream ended
stream.on('end', function()
{
self.response.end();
self.tile.debug('Bitmap tile was responded to the request.');
self.tile.debug('Finished request.');
return;
});
});
});
},

// serves a bitmap tile
getTile: function()
{
Expand Down Expand Up @@ -117,59 +162,23 @@ BitmapTilerequest.prototype =
self.abortRequest('Vectortile could not be created. Aborting.');
return;
}

self.tile.debug('Vector tile created successfully, saving vector tile...');
self.tile.saveVectorData(function(err)
{
if (err)
self.tile.warn('Vector tile could not be saved.');

self.tile.debug('Rendering bitmap tile with style '+self.tile.style);
self.tile.render(function(err, image)
if (self.data.features.length === 0)
{
if (err)
self.tile.debug('Vectortile was empty.');
self.tile.saveBitmapData(image, function(err)
{
if (err)
{
self.response.writeHead(500, {'Content-Type': 'text/plain'});
self.response.end();
self.tile.debug('Empty bitmap tile was responded to the request.');
self.tile.debug('Finished request.');
return;
}

self.tile.getModifyTime(function(err, mtime)
{
var header = {
'Content-Type': 'image/png',
'Cache-Control': 'public, max-age=3600'
};

if (!err)
header['Last-Modified'] = mtime.toUTCString();

self.tile.trace('Responding bitmap data...');
var stream = image.createPNGStream();
self.response.writeHead(200, header);

// write PNG data stream
stream.on('data', function(data)
{
self.response.write(data);
});

// PNG data stream ended
stream.on('end', function()
{
self.response.end();
self.tile.debug('Bitmap tile was responded to the request.');
self.tile.debug('Finished request.');
return;
});
});
});
});
self.tile.debug('Vector tile without features, serving empty PNG tile for style ' + self.tile.style);
renderCallback(false, null);
}
else
{
self.tile.debug('Rendering bitmap tile with style ' + self.tile.style);
self.tile.render(renderCallback);
}
});
});
}
Expand Down Expand Up @@ -206,8 +215,6 @@ BitmapTilerequest.prototype =

if (expired)
header['Cache-Control'] = 'max-age=0';
else
header['Cache-Control'] = 'public, max-age=3600';

self.tile.trace('Responding bitmap data...');
var stream = image.createPNGStream();
Expand Down Expand Up @@ -250,6 +257,7 @@ BitmapTilerequest.prototype =
{
return {
'Content-Type': 'image/png',
'Cache-Control': 'public, max-age=3600',
'Server': 'node-tileserver/0.3'
};
}
Expand Down
1 change: 1 addition & 0 deletions emptytile.json
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
{"features":[],"granularity":10}
74 changes: 42 additions & 32 deletions tile.js
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Original file line number Diff line number Diff line change
Expand Up @@ -140,7 +140,7 @@ Tile.prototype =
}

var filepath = configuration.vtiledir+'/'+this.z+'/'+this.x+'/';
var file = this.y+'.json';
var file = filepath + this.y + '.json';

this.debug('Creating path '+filepath+'...');
var self = this;
Expand All @@ -155,19 +155,37 @@ Tile.prototype =
});
}

self.debug('Created path. Saving vector tile at path: '+filepath+file);
fs.writeFile(filepath+file, JSON.stringify(self.data), {mode: 0777}, function(err)
if (self.data.features.length === 0)
{
self.debug('Created path. Linking empty vector tile to: ' + file);
fs.link('emptytile.json', file, function(err)
{
if (!err)
self.debug('Empty vector tile was stored.');
else
self.debug('Could not link empty vector file.');

return process.nextTick(function()
{
callback(true);
});
});
}

self.debug('Created path. Saving vector tile at path: ' + file);
fs.unlinkSync(file);
fs.writeFile(file, JSON.stringify(self.data), {mode: 0666}, function(err)
{
if (err)
{
self.error('Cannot save vector tile at path: '+filepath+file);
self.error('Cannot save vector tile at path: ' + file);
return process.nextTick(function()
{
callback(err);
});
}

self.debug('Saved vector tile at path: '+filepath+file);
self.debug('Saved vector tile at path: ' + file);
return process.nextTick(function()
{
callback(false);
Expand Down Expand Up @@ -428,15 +446,13 @@ Tile.prototype =
client.query(self.getDatabaseQuery(bbox_p), function(err, results)
{
var content = new Object();
content.features = new Array();

self.trace('All database queries finished, generating JSON data object.');
content.features = self.getJSONFeatures(results);

// catch tiles without data
if (!content.features)
if (content.features.length === 0)
{
content.features = new Array();
self.debug('Vector tile contains no data.');
}

Expand Down Expand Up @@ -491,8 +507,10 @@ Tile.prototype =
return;
}

self.debug('Saving bitmap tile at path: '+filepath+'/'+self.y+'.png');
var out = fs.createWriteStream(filepath+'/'+self.y+'.png', {mode: 0777});
var fname = filepath + '/' + self.y + '.png';
self.debug('Saving bitmap tile at path: ' + fname);
fs.unlinkSync(fname)
var out = fs.createWriteStream(fname, {mode: 0666});
var stream = image.createPNGStream();

// write PNG data stream
Expand Down Expand Up @@ -695,10 +713,11 @@ Tile.prototype =
// converts raw JSON features from database response to objects
getJSONFeatures: function(data)
{
var features = new Array();

if (typeof data == undefined || data == null)
return [];
return features;

var features = new Array();
for (var i=0; i<data.rows.length; i++)
{
// catch JSON parsing errors
Expand Down Expand Up @@ -774,40 +793,31 @@ Tile.prototype =
});
}

var fname = filepath + '/' + self.y + '.png';
fs.unlinkSync(fname);

// store empty tile if no image could be rendered
if (image == null)
{
self.debug('Bitmap tile empty.');

fs.readFile('emptytile.png', function(err, data)
fs.link('emptytile.png', fname, function(err)
{
if (err)
{
self.warn('Could not read empty bitmap tile.');
return process.nextTick(function()
{
callback(true);
});
}
if (!err)
self.debug('Empty bitmap tile was stored.');
else
self.debug('Could not link empty bitmap file.');

fs.writeFile(filepath+'/'+self.y+'.png', data, {mode: 0777}, function(err)
return process.nextTick(function()
{
if (!err)
self.debug('Empty bitmap tile was stored.');
else
self.debug('Could not save empty bitmap file.');

return process.nextTick(function()
{
callback(true);
});
callback(true);
});
});
}
else
{
self.trace('Saving bitmap data...');
var out = fs.createWriteStream(filepath+'/'+self.y+'.png', {mode: 0777});
var out = fs.createWriteStream(fname, {mode: 0666});
var stream = image.createPNGStream();

// write PNG data stream
Expand Down