HDFS CSV File Writer Output Adapter

Contents

Introduction
Properties
Typechecking and Error Handling
Suspend and Resume Behavior
Related Topics

Introduction

The TIBCO StreamBase® CSV File Writer For Apache Hadoop Distributed File System (HDFS) is suitable for saving tuples to comma-separated value (CSV) format files.

There are a number of options that help you control how and when files are created, how big files can be, and how strings are saved in the file.

Tip

In the StreamBase application that contains the HDFS CSV File Writer adapter, if the output CSV file will be used by an application that requires a specific order of fields, and the fields in the stream's tuples do not match that order, you can use a Map operator to arrange the fields as needed.

Tip

If you write a CSV file containing timestamps and import it into Microsoft Excel, by default Excel does not display fractions of seconds. To display times with millisecond precision, in Excel assign timestamp columns a custom format that you define as hh:mm:ss.000.

Note

When using the HDFS core libraries on Windows, you may see a console message similar to Failed to locate the winutils binary in the hadoop binary path. The Apache Hadoop project acknowledges that this is an error to be fixed in a future Hadoop release. In the meantime, you can either ignore the error message as benign, or you can download, build, and install the winutils executable as discussed on numerous Internet resources.

Properties

This section describes the properties you can set for this adapter, using the various tabs of the Properties view in StreamBase Studio.

In the tables in this section, the Property column shows each property name as found in the one or more adapter properties tabs of the Properties view for this adapter.

Use the StreamSQL names of the adapter's properties when using this adapter in a StreamSQL program with the APPLY JAVA statement, or when specifying properties for a stream-to-CSV container connection (which uses this adapter's technology).

General Tab

Name: Use this field to specify or change the component's name, which must be unique in the application. The name must contain only alphabetic characters, numbers, and underscores, and no hyphens or other special characters. The first character must be alphabetic or an underscore.

Adapter: A read-only field that shows the formal name of the adapter.

Class: A field that shows the fully qualified class name that implements the functionality of this adapter. Use this class name when loading the adapter in StreamSQL programs with the APPLY JAVA statement. You can right-click this field and select Copy from the context menu to place the full class name in the system clipboard.

Start with application: If this field is set to Yes or to a module parameter that evaluates to true, an instance of this adapter starts as part of the containing StreamBase Server. If this field is set to No or to a module parameter that evaluates to false, the adapter is loaded with the server, but does not start until you send an sbadmin resume command, or until you start the component with StreamBase Manager. With this option set to No or false, the adapter does not start even if the application as a whole is suspended and later resumed. The recommended setting is selected by default.

Enable Error Output Port: Select this check box to add an Error Port to this component. In the EventFlow canvas, the Error Port shows as a red output port, always the last port for the component. See Using Error Ports and Error Streams to learn about Error Ports.

Description: Optionally enter text to briefly describe the component's purpose and function. In the EventFlow canvas, you can see the description by pressing Ctrl while the component's tooltip is displayed.

File Creation Tab

Property	Data Type	Default	Description	StreamSQL Property
File Name	string	none	Name of file to write to. If this adapter is configured with a maximum file size, then this filename is appended with the date and time when the maximum file size is reached. When using the Compress Data option described below, StreamBase recommends using the `.csv.gz` file name extension. The `.gz` extension is not added automatically.	FileName
User	string	none	The user if none is provided on the control input port	DefaultUser
Use Default Charset	check box	Selected	If selected, specifies whether the Java platform default character set is to be used. If cleared, a valid character set name must be specified for the Character Set property.	UseDefaultCharset
Character Set	string	None	The name of the character set encoding that the adapter is to use to read input or write output.	Charset
Include Header In File	check box	true (selected)	Specifies the Inclusion of an optional row at the top of each file with the name of each column.	IncludeHeaderInFile
If File Doesn't Exist	radio buttons	Create new file	Specifies the action to take if the specified CSV file does not exist when the adapter is started: Create new file or Fail.	IfFileDoesntExist
If File Exists	drop-down list	Append to existing file	Specifies the action to take if the specified CSV file already exists when the adapter is started: Append to existing file, Truncate existing file, or Fail.	IfFileExists
Open File During Initialization	check box	false (cleared)	When selected, the output file is created, or opened and truncated, even if the adapter is not configured to start with the application, or the container in which the adapter is running has not started. (StreamSQL parameter name: OpenOutputFileDuringInit)	OpenOutputFileDuringInit
Compress data	check box	false (cleared)	If selected, the adapter compresses its output in gzip format.	CompressData
Start control port	check box	false (cleared)	Select this check box to give this adapter instance a control port you can use to specify a new output file name. The schema for the control port must begin with a field of type string used to convey the name of the new file to open. When a tuple is enqueued to this port, the existing file, if any, is closed, and the new file is opened.	StartControlPort
Start event port	check box	false (cleared)	Select this check box to create an output port that emits an informational tuple each time a CSV file is opened or closed. The informational tuple schema has five fields: Type, string Object, string Action, string Status, int Info, string For a file open event, the event port tuple's `Type` field is set to "Open", while the `Object` field is set to the path name of the CSV file being opened. For a file close event, the event port tuple's `Type` field is set to "Close", while the `Object` field is set to the path name of the CSV file being closed. For both open and close operations, the `Status` field is set to 0 to indicate success or -1 to indicate failure. The `Info` field always contains a text message describing the event. For data events the event ports tuple `Type` field is set to "Write" or "Flush" depending on the operation which caused the status event. The `Data` field will contain the input data tuple. These status event only output when `Pass Through Data To Event Port` is enabled.	StartEventPort
Pass Through Data To Event Port	check box	false (cleared)	If enabled, when data tuples are passed in and a status event occurs the data tuple will be passed to the status event.	PassThroughDataToEventPort

Record Formatting Tab

Property	Data Type	Default	Description	StreamSQL Property
Field Delimiter	string	, (comma)	Specifies the character used to mark the end of one field and the beginning of another. Control characters can be entered as &#ddd; where `ddd` is the character's ASCII value.	FieldDelimiter
String Quote Character	string	" (double quote)	Specifies the character to use to quote strings when they contain the field delimiter.	StringQuoteCharacter
String Quote Option	drop-down list	Quote if necessary	Specifies when string fields are quoted in the CSV file: Quote if necessary, Always quote, or Never quote.	StringQuoteOption
Null Value Representation	string	"null"	Specifies the string to write when a field is null.	NullValueRepresentation
Timestamp Format	string	yyyy-MM-dd HH:mm:ss.SSSZ	Determines the format of all timestamp objects written to the csv output.	TimestampFormat
Add Timestamp	drop-down list	None	Optionally prepend or append a timestamp to each CSV row of output. The header name will be "Timestamp"	AddTimestamp
Capture Transform Strategy	radio button	FLATTEN	The strategy to use when transforming capture fields for this operator: FLATTEN or NEST.	CaptureTransformStrategy

Rolling and Flushing Tab

Property	Data Type	Default	Description	StreamSQL Property
Max File Size	int	0 (no rollover)	Maximum size, in bytes, of the file on disk. If the file reaches this limit, it is renamed with the current timestamp and new data is written to the current name specified in the File Name property.	MaxFileSize
Max Roll Seconds	int	0 (no rollover)	The maximum number of seconds before file names are rolled over as described in the previous row. The Roll Period and Max Roll Seconds properties are mutually exclusive.	MaxRollSecs
Roll Period	drop-down list	None	Select among None, Weekly, Daily, and Hourly to specify the time period for automatic file rollover. Weekly file rollover is performed at 12:00 AM every Monday. If the program starts after Monday, the rollover is performed the following Monday at 12:00 AM, and at subsequent Mondays thereafter. When rollover is performed, the current file is renamed by appending the previous week's Monday starting date, in the format `yyyyMMdd`. Daily file rollover is performed at 12:00 AM every day by default. If the program starts during the day, the rollover is performed at the next 12:00 AM by default, and subsequent midnights going forward. When rollover is performed, the current file is renamed by appending the current date in the format `yyyyMMdd`. The roll over time can also be modified using the roll hour/minute/second options Hourly rollover is performed every hour on the hour (1:00 AM, 2:00 AM, and so on). If the program starts after the hour (such as 1:20 PM), rollover starts at the next hour mark (such as 2:00 PM), and at subsequent hour marks. When rollover is performed, the current file is renamed by appending the timestamp in the format `yyyyMMddHHmm`.	RollPeriod
Roll Hour	int	0	Allows for selecting which hour (0-23) to perform the file roll when daily is selected as the roll period. Defaults to 0 meaning 12:00:00 AM	RollHour
Roll Minute	int	0	Allows for selecting which minute (0-59) to perform the file roll when daily is selected as the roll period. Defaults to 0 meaning 12:00:00 AM	RollMinute
Roll Second	int	0	Allows for selecting which second (0-59) to perform the file roll when daily is selected as the roll period. Defaults to 0 meaning 12:00:00 AM	RollSecond
Check for Roll at Startup	check box	false (cleared)	If selected, causes the adapter to roll the file at startup if, based on the file's last modification time, the configured roll period, and the current time, the file would have been rolled before the adapter was started.	CheckForRollAtStartup
Flush Interval	int	1	Specifies how often, in seconds, to force tuples to disk. Set this value to zero to flush immediately.	FlushInterval
Sync on flush	check box	false (cleared)	If selected, StreamBase syncs operating system buffers to the file system on flush, to make sure that all changes are written. Using this options incurs a significant performance penalty.	SyncOnFlush

Miscellaneous Tab

Property	Data Type	Default	Description	StreamSQL Property
Throttle Error Messages	check box	false (cleared)	Specifies showing any particular error message only once.	ThrottleErrorMessages
Log Level	drop-down list	INFO	Controls the level of verbosity the adapter uses to send notifications to the console. This setting can be higher than the containing application's log level. If set lower, the system log level will be used. Available values, in increasing order of verbosity, are: OFF, ERROR, WARN, INFO, DEBUG, TRACE, and ALL.	LogLevel

HDFS Tab

Property	Data Type	Description
Buffer Size (Bytes)	Int	The size of the buffer to be used. If empty, the default is used.
Replication	Short	The required block replication for the file. If empty, the server default is used, and only used during file creation.
Block Size (Bytes)	Long	The default data block size. If empty, the server default is used, and only used during file creation.
Configuration Files	String	The HDFS configuration files to use when connecting to the HDFS file system. For example, `core-defaults.xml` is the standard file to use.

Concurrency Tab

Use the Concurrency tab to specify parallel regions for this instance of this component, or multiplicity options, or both. The Concurrency tab settings are described in Concurrency Options, and dispatch styles are described in Dispatch Styles.

Caution

Concurrency settings are not suitable for every application, and using these settings requires a thorough analysis of your application. For details, see Execution Order and Concurrency, which includes important guidelines for using the concurrency options.

Typechecking and Error Handling

Typechecking fails in the following circumstances:

The File Name is null or a zero length string.
The Flush Interval is less than zero.
The Max File Size is less than zero.
More than one string quote character is specified.
More than one field delimiter is specified.
An illegal string quote option is specified.
The Max Roll Seconds value greater than zero and the Roll Period option selected is other than None.

Suspend and Resume Behavior

On suspend, this adapter stops processing tuples, flushes all tuples to disk, and closes the current CSV file.

On resumption, it reopens the current CSV file and begins processing tuples again.