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Lowering the Space Object Footprint-The Binary Serialization Pattern
Summary: Lowering the Space Object Footprint - The Binary Serialization Pattern
OverviewBy default, when using the Java API with POJO or Entry based class, the space stores space object fields as is. No data compaction, or compression is done while the object is transported across the network or when stored within the space.
The binary serialization technique allows you to reduce the footprint associated with storing space object in memory in great manner. This means you will be able to store more space objects per memory unit. The basic idea of the binary serialization is simple: Total control on the format of the space object data while transported over the network and when stored within the space. This technique avoids the extra de-serialization involved when space object written to the space from a remote client (for non primitive fields such as user defined classes or collection field) and when replicated to a backup space(s) and the serialization involved when reading an object back from the space into the client process.
With the binary serialization pattern you should have all the fields used for matching and query as indexed fields , while all the rest (payload) stored into byte array field. Before writing the object to the space, the payload field should be packed into the byte array field and once the object is read from the space the payload fields should be unpacked. When the object is written to the space: When the object is read from the space: Using the binary serialization pattern can reduce the object footprint when stored within the space in drastic manner. As much as you will have more fields as part of the space object serialized using the binary serialization pattern , the memory footprint overhead will be smaller compared to regular space class. ExampleWith the attached example we have a space class with 37 fields.
The footprint overhead of a regular Space POJO class compared to a binary format Space POJO Class is 300%.
To run this example copy the example package zip into \GigaSpaces Root\examples\Advanced\DataGrid , extract the zip file and follow the instructions at the readme file. The Regular Space classOur example involves a space class that will be modified to follow the binary serialization pattern. The original class includes:
The original class would look like this: @SpaceClass(replicate=true) public class SimpleEntry { public SimpleEntry() { } private Integer _queryField; private Long _longFieldA1; ? @SpaceRouting @SpaceProperty(index=IndexType.BASIC) public Integer get_queryField() { return _queryField; } public void set_queryField(Integer field) { _queryField = field; } public Long get_longFieldA1() { return _longFieldA1; } public void set_longFieldA1(Long fieldA1) { _longFieldA1 = fieldA1; } The BinaryFormatEntry classThe modified class includes:
The modified class would look like this: @SpaceClass(includeProperties=IncludeProperties.EXPLICIT ,replicate=true) public class BinaryFormatEntry implements Externalizable { public BinaryFormatEntry(){} private Integer _queryField; private byte[] _binary; private Long _longFieldA1; ?. @SpaceRouting @SpaceProperty(index=IndexType.BASIC) public Integer get_queryField() { return _queryField; } public void set_queryField(Integer queryField) { _queryField = queryField; } @SpaceProperty public byte[] get_binary() { return _binary; } public void set_binary(byte[] _binary) { this._binary = _binary; } public Long get_longFieldA1() { return _longFieldA1; } public void set_longFieldA1(Long fieldA1) { _longFieldA1 = fieldA1; } ? public void pack() {} public void unpack() {} public void writeExternal(ObjectOutput out) {} public void readExternal(ObjectInput in) {} private long getnulls(){} {} private short checkNulls() {} The pack methodThe pack method serialize the object data. It is called before calling the space write operation. public void pack() { long nulls = 0; try{ ByteArrayOutputStream baos = new ByteArrayOutputStream(); nulls = getnulls(); PbsFormatter.writeLong(baos, nulls); if (_longFieldA1 != null) PbsFormatter.writeLong(baos, _longFieldA1); _binary = baos.toByteArray(); baos.close(); }catch (Exception e) { e.printStackTrace(); } } The unpack methodThis method de-serialize the object data by extracting the data from the byte array field and populating the fields with their corresponding values. Null values fields are non populated. This method is called after calling the space read operation. The PbsFormatter utility class is used to read the binary data and place it into the relevant field. public void unpack() { long nulls = 0; try{ int i = 0; ByteArrayInputStream bais = new ByteArrayInputStream(_binary); nulls = PbsFormatter.readLong(bais); if( (nulls & 1L << i) == 0 ) _longFieldA1 = PbsFormatter.readLong(bais); i++; ?. bais.close(); _binary = null; }catch (Exception e) { e.printStackTrace(); } } The writeExternal methodThe writeExternal method retrieves the object data and writes it into the output stream. public void writeExternal(ObjectOutput out) throws IOException { short nulls = 0; int i=0; nulls = checkNulls(); out.writeShort(nulls); if (_queryField != null) { out.writeInt(_queryField); } if (_binary != null) { out.write(_binary); } } The readExternal methodThe readExternal method essentially performs the opposite of the what the writeExternal method is doing. public void readExternal(ObjectInput in) throws IOException, ClassNotFoundException { short nulls; int i=0; nulls = in.readShort(); if( (nulls & 1L << i) == 0 ) _queryField = in.readInt(); i++; if( (nulls & 1L << i) == 0 ) { byte[] data = new byte[1000]; // ß Here you might need to create array with large enough size int len = in.read(data); _binary = new byte[len]; System.arraycopy(data, 0, _binary, 0, len); } } The checkNulls methodThis method goes through the query field and the byte array fields and place into a short data type field indication for the ones with null value using a bit map. private short checkNulls() { short nulls = 0; int i = 0; nulls = (short) ((_queryField == null) ? nulls | 1 << i : nulls); i++; nulls = (short) ((_binary == null) ? nulls | 1 << i : nulls); i++; return nulls; } The getnulls methodThis method goes through all class non indexed fields (the ones that their data is stored within the byte array) and place into a Long data type field indication for the ones with null value using a bit map. private long getnulls() { long nulls = 0; int i=0; nulls = ((_longFieldA1 == null) ? nulls | 1L << i : nulls ) ; i++; nulls = ((_longFieldB1 == null) ? nulls | 1L << i : nulls ) ; i++; ?. return nulls; } The Factory methodThe example using a factory method called generateBinaryFormatEntry to create the space object. Once it has been populated , its pack method is called. private BinaryFormatEntry generateBinaryFormatEntry(int id){ BinaryFormatEntry bfe = new BinaryFormatEntry(id, value1 , value2 ?) bfe.pack(); // the pack method is called implicitly as part of the factory method return bfe; } Writing and Reading the Object from the spaceThe following code snipped illustrates how the binary serialized object is written into the space and read from the space: BinaryFormatEntry testBFE = generateBinaryFormatEntry(500); _space.write(testBFE, null, Lease.FOREVER); BinaryFormatEntry templateBFE = new BinaryFormatEntry(); templateBFE._queryField = new Long(500); BinaryFormatEntry resBFE = (BinaryFormatEntry)_space.read(templateBFE, null, 0); resBFE.unpack(); ß this deserialize the binary data into the object fields |
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