RSS Reader Input Adapter

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Introduction

The Spotfire Streaming RSS Reader is an embedded adapter that reads RSS data from any number of HTTP feeds. Utilizing the schema of RSS (versions 0.90, 0.91N, 0.91U, 0.92, 0.93, 0.94, 1.0 or 2.0.x) or Atom (versions 0.3 or 1.0), the adapter interprets this data and emits tuples containing the relevant information from the feeds. One tuple will be emitted for each entry of each feed.

The adapter will periodically access each feed (see the Poll Frequency property below) to see if there have been changes. New tuples will be emitted when entries have changed.

When a publish date is present for a given feed's entries or for the feed itself, this will be used to determine when updates are needed (that is, a new tuple will be emitted whenever the publish date of an entry changes). However because publish dates are optional values in most RSS and Atom feeds, it may not be possible to detect if a given entry has been modified after initial publication. In that case, no further update tuples will be emitted for that entry.

Properties

Property	Description
Enable control port?	Enable the control port to allow the user to add/remove/list rss feeds during runtime.
Enable status port?	Enable the status port to receive status information about what is happening in the adapter.
RSS Feed(s)	List of your RSS and Atom feeds. At least one feed is required.
Use Proxy	Use a proxy server to connect to the RSS feed.
Proxy Host	The proxy server host name or IP address.
Proxy Port	The proxy server TCP port number.
Poll Frequency	The time, in seconds, to wait before polling the RSS server again to see if there were updates to the feed. Required. Defaults to 5 (that is, poll every five seconds.)
Maximum String Size	The maximum size of string fields in the schema. Required. Defaults to 500.
Number Of Connection Retries	The maximum number of times the adapter should attempt to reconnect to a feed before giving up. To specify an unlimited number of retries, enter a value of -1. Optional. Defaults to 5. The adapter waits 30 seconds before each retry. Once the adapter has given up connecting to a feed, it will be removed from the list of feeds to watch. If the list becomes empty, the adapter will exit.
Show Title?	Show the titles of feed entries. Optional. Defaults to true.
Show Link?	Show the URL of feed entries. Optional. Defaults to true.
Show URI?	Show the HTTP web address for each of feed entries. Optional. Defaults to false.
Show Description?	Show the item synopsis of feed entries. (RSS ONLY.) Optional. Defaults to true.
Show Contents?	Show the item synopsis of feed entries. (Atom ONLY.) Optional. Defaults to false.
Show Author?	Show the e-mail addresses of the authors of feed entries. Optional. Defaults to false.
Show Categories?	Show the comma-separated list of tags used to categorize each individual entry. Optional. Defaults to false.
Show Published Date (As String)?	Show the dates that entries were published to the web, as a string. Optional. Defaults to true. Cannot be combined with Show Published Date (As Timestamp).
Show Published Date (As Timestamp)?	Show the dates that entries were published to the web, as a timestamp. Optional. Defaults to false. Cannot be combined with Show Published Date (As String).
Show RSS Feed?	Show the RSS feed that this item comes from.
Log Level	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 is used. Available values, in increasing order of verbosity, are: OFF, ERROR, WARN, INFO, DEBUG, TRACE.

Schema

The schema of the tuples emitted by the adapter have different fields depending on the selected properties:

Property	Field Name	Field Type
Show Title	title	string
Show Link	link	string
Show URI	uri	string
Show Description	description	string
Show Contents	contents	string
Show Author	authors	string
Show Categories	categories	string
Show Published Date (As String or As Timestamp)	publishedDate	string or timestamp
Show RSS Feed	rssFeed	string

Description of This Adapter's Ports

The RSS Reader adapter's ports are used as follows:

Control (input): Tuples enqueued on this port cause the adapter to perform actions on RSS Feeds. The schema for this port has the following fields:
- Command, string, the command to perform:
  1. Add - Add a RSS feed.
  2. Remove - Remove a RSS feed.
  3. List - List all the current RSS feeds.
- Feed, string, Required by the Add and Remove commands, the URL of the feed.
Status (output): The adapter emits tuples from this port when significant events occur, such as when an attempt to add/remove/list feeds. The schema for this port has the following fields:
- Type, string: returns one of the following values to convey the type of event:
  - User Input
  - System
  - Proxy
  - Feed
- Action, string: returns an action associated with the event Type:
  - Start
  - Stop
  - Read
  - Removed
  - Added
  - Failed
  - Error
  - Max Unsuccessful
  - Empty
  - List
  - Missing Fields
- Object, string: returns an event type-specific value, such as the name of the feed.
- Message, string: Returns a human-readable description of the event.
- Time, timestamp: Returns the time this event occurred.

Typechecking and Error Handling

Typechecking fails if there is not at least one correctly formatted HTTP RSS feed in RSS Feed(s) or if Period is less than or equal to zero.

Typechecking also fails if both Show Published Date (As String) and Show Published Date (As Timestamp) are checked.

At runtime, if a property (such as Show Contents or Show Author) was requested that is not available for a particular feed, a warning is issued saying that the corresponding tuple fields will be set to null. This can happen when the official specification for the RSS or Atom version of this feed does not include the requested property, when the property is optional and was simply not specified in this feed, or when the property was not properly formatted according to the feed version's specifications so that it could not be read.