Module datarush.library
Package com.pervasive.datarush.operators.io

Class WriteSink

  • All Implemented Interfaces:
    LogicalOperator, RecordSinkOperator, SinkOperator<RecordPort>
    public final class WriteSink
extends ExecutableOperator
implements RecordSinkOperator
    Writes a stream of records to a data sink. The sink accepts a sequence of bytes which represent formatted records, identical in logical structure. The mapping between physical and logical structure is encapsulated in a format descriptor which must be provided.

    This operator is low-level, providing a generalized model for reading files in a distributed fashion. Typically, WriteSink is not directly used in a graph, instead being indirectly used though a composite operator such as one derived from AbstractWriter providing a more appropriate interface to the end user.

    Parallelized writes are supported by creating multiple output sinks from the original target, called fragments, each representing the portion of data on one partition. In the case of a write to as file system, this would result in a directory of files. To write in parallel, the target must support the concept of fragmenting. If a target does not, the write is forced to be non-parallel.

    A port is provided which signals completion of the writer. This can be used to express a dependency between operators based on the target having been successfully written.

    The writer makes a best-effort attempt to validate the target before execution, but cannot always guarantee correctness, depending on the nature of the target. This is done to try to prevent misconfigured graphs from executing where the writer may not execute until a late phase when a failure may result in the loss of a significant amount of work being lost.

    • Constructor Detail

      • WriteSink

        public WriteSink()
        Writes an empty target with default settings. Both the target and format must be set before execution or an error will be raised.
        See Also:
        setTarget(ByteSink), setFormat(DataFormat)

      • WriteSink

        public WriteSink​(boolean includeDoneSignal)
        Writes an empty target with default settings. Both the target and format must be set before execution or an error will be raised.
        See Also:
        setTarget(ByteSink), setFormat(DataFormat)

      • WriteSink

        public WriteSink​(ByteSink target,
                 DataFormat format)
        Reads the specified target using the given format. Default options are used.
        Parameters:
        target - the target to write
        format - the target data format

    • Method Detail

      • getIncludeDoneSignal

        public boolean getIncludeDoneSignal()
        Gets the property value for the include done signal setting.
        Returns:
        true if enabled; false by default

      • getFormat

        public DataFormat getFormat()
        Gets the data format for the configured target.
        Returns:
        the data format

      • setFormat

        public void setFormat​(DataFormat format)
        Sets the data format for the configured target.
        Parameters:
        format - the target data format

      • getTarget

        public ByteSink getTarget()
        Gets the target sink for the reader.
        Returns:
        the write target

      • setTarget

        public void setTarget​(ByteSink target)
        Sets the target sink for the reader.
        Parameters:
        target - the target to write

      • getFormatOptions

        public FormattingOptions getFormatOptions()
        Gets the formatting options used by the writer.
        Returns:
        the format options

      • setFormatOptions

        public void setFormatOptions​(FormattingOptions options)
        Sets the formatting options used by the writer.
        Parameters:
        options - the format options to use
        See Also:
        DataFormat.DataFormatter

      • getMode

        public WriteMode getMode()
        Gets how existing files should be handled by the writer.
        Returns:
        the configured behavior with respect to target files

      • setMode

        public void setMode​(WriteMode mode)
        Sets how the writer should handle an existing target.
        Parameters:
        mode - the behavior to use for existing files

      • getWriteSingleSink

        public boolean getWriteSingleSink()
        Indicates whether the writer produces a single output file.
        Returns:
        true if the writer should write a single output, false otherwise.

      • setWriteSingleSink

        public void setWriteSingleSink​(boolean enabled)
        Set whether the writer should produce a single output file or multiple ones. By default, an output file will be produced for each partition, if the target sink supports this.
        Parameters:
        enabled - indicates whether a single output file should be written

      • getWriteOnClient

        public boolean getWriteOnClient()
        Indicates whether the writer should write a file on the client. This also disables the parallelism on the sink.
        Returns:
        true if the writer should a file on the client, false otherwise.

      • setWriteOnClient

        public void setWriteOnClient​(boolean writeOnClient)
        Set whether the writer should write a file on the local client. This has the effect of disabling the parallelism on the sink.
        Parameters:
        writeOnClient - indicates whether the writer should write a file on the client.

      • isIgnoreSortOrder

        public boolean isIgnoreSortOrder()
        If set to true, the writer will write in any order. If false, the writer will preserve the current sorted state of the input.
        Returns:
        whether to ignore sort order.

      • setIgnoreSortOrder

        public void setIgnoreSortOrder​(boolean ignoreSortOrder)
        If set to true, the writer will write in any order. If false, the writer will preserve the current sorted state of the input.
        Parameters:
        ignoreSortOrder - whether to ignore sort order.

      • computeMetadata

        protected void computeMetadata​(StreamingMetadataContext ctx)
        Description copied from class: StreamingOperator
        Implementations must adhere to the following contracts

        General

        Regardless of input ports/output port types, all implementations must do the following:

        1. Validation. Validation of configuration should always be performed first.
        2. Declare parallelizability.. Implementations must declare parallelizability by calling StreamingMetadataContext.parallelize(ParallelismStrategy).

        Input record ports

        Implementations with input record ports must declare the following:
        1. Required data ordering:
          2. Implementations that have data ordering requirements must declare them by calling RecordPort#setRequiredDataOrdering, otherwise data may arrive in any order.
        2. Required data distribution (only applies to parallelizable operators):
          3. Implementations that have data distribution requirements must declare them by calling RecordPort#setRequiredDataDistribution, otherwise data will arrive in an unspecified partial distribution.
        Note that if the upstream operator's output distribution/ordering is compatible with those required, we avoid a re-sort/re-distribution which is generally a very large savings from a performance standpoint. In addition, some operators may chose to query the upstream output distribution/ordering by calling RecordPort#getSourceDataDistribution and RecordPort#getSourceDataOrdering. These should be viewed as a hints to help chose a more efficient algorithm. In such cases, though, operators must still declare data ordering and data distribution requirements; otherwise there is no guarantee that data will arrive sorted/distributed as required.

        Output record ports

        Implementations with output record ports must declare the following:
        1. Type: Implementations must declare their output type by calling RecordPort#setType.
        Implementations with output record ports may declare the following:
        1. Output data ordering: Implementations that can make guarantees as to their output ordering may do so by calling RecordPort#setOutputDataOrdering
        2. Output data distribution (only applies to parallelizable operators): Implementations that can make guarantees as to their output distribution may do so by calling RecordPort#setOutputDataDistribution
        Note that both of these properties are optional; if unspecified, performance may suffer since the framework may unnecessarily re-sort/re-distributed the data.

        Input model ports

        In general, there is nothing special to declare for input model ports. Models are implicitly duplicated to all partitions when going from non-parallel to parallel operators. The case of a model going from a parallel to a non-parallel node is a special case of a "model reducer" operator. In the case of a model reducer, the downstream operator, must declare the following:
        1. Merge handler: Model reducers must declare a merge handler by calling AbstractModelPort#setMergeHandler.
        Note that MergeModel is a convenient, re-usable model reducer, parameterized with a merge-handler.

        Output model ports

        SimpleModelPort's have no associated metadata and therefore there is never any output metadata to declare. PMMLPort's, on the other hand, do have associated metadata. For all PMMLPorts, implementations must declare the following:
        1. pmmlModelSpec: Implementations must declare the PMML model spec by calling PMMLPort.setPMMLModelSpec.
        Specified by:
        computeMetadata in class StreamingOperator
        Parameters:
        ctx - the context

      • execute

        protected void execute​(ExecutionContext ctx)
        Description copied from class: ExecutableOperator
        Executes the operator. Implementations should adhere to the following contracts:
        1. Following execution, all input ports must be at end-of-data.
        2. Following execution, all output ports must be at end-of-data.
        Specified by:
        execute in class ExecutableOperator
        Parameters:
        ctx - context in which to lookup physical ports bound to logical ports

      • cloneForExecution

        protected ExecutableOperator cloneForExecution()
        Description copied from class: ExecutableOperator
        Performs a deep copy of the operator for execution. The default implementation is implemented in terms of JSON serialization: we perform a JSON serialization followed by a JSON deserialization. As a best-practice, operator implementations should not override this method. If they must override, though, then they must guarantee that cloneForExecution copies any instance variables that are modified by execute.
        Overrides:
        cloneForExecution in class ExecutableOperator
        Returns:
        a deep copy of this operator