4. Feeds

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4.1 Adding Feeds

Feeds are added to Olive via the Add New Feed dialog, which is invoked by pressing 'C-a'.

  .-[ Add New Feed ]-----------------------------------------.
  |                                                          |
  | Location: [                                            ] |
  |                                                          |
  | Nickname: [                ]                             |
  |                                                          |
  |           [ ] Flag this feed                             |
  |                                                          |
  |           [ ] Force-poll this feed                       |
  |                                                          |
  |                                        < OK > < Cancel > |
  |                                                          |
  '----------------------------------------------------------'

Fill out the form and select OK to attempt to store the feed. It will be tested for network availablility, and if Olive can fetch the feed, it will be added. If the feed cannot be found or fetched, an error will be displayed and it will not be added to the feed list.

The Location field holds the URL of the feed.

Nickname is a short (16-character maximum) display name which will be used in the List Pane.

Toggling "Flag this feed" causes the feed to be flagged, as described in Section 2.4.

4.1.1 Enabling Force-poll

The "Force-poll this feed" option enables an on-demand override of normal feed polling procedure. It causes TTL checks to be skipped and treats a 304 Not Modified as a 200 OK, causing a fetch of the feed regardless of elapsed time or the actual modification status of that feed. This should only be used when there is a problem getting a feed which you know has changed, but which is not updating for whatever reason.

4.2 Editing Feeds

To change information about a feed, first invoke the Edit Feeds dialog by pressing 'C-e'. You will be presented with a list of feeds and their current statuses, ordered alphabetically by feed nickname.

  .-[ Edit Feeds ]-------------.
  |                            |
  |  Feed              Status  |
  |                            |
  |  ATC               f--   # |
  |  BBC News          ---   # |
  |  bda               f--   # |
  |  code4lib          --d   # |
  |  Dru               f--   # |
  |  Groklaw           ---   # |
  |  Kate              fp-   # |
  |  LtU               ---   | |
  |  OBSD Security     ---   | |
  |  Olive             -p-   | |
  |                            |
  |                    < OK >  |
  |                            |
  '----------------------------'

The three statuses are:

Flagged, indicated by an 'f' in the first status column.
Force-polled, indicated by a 'p' in the second status column.
Dormant, indicated by a 'd' in the third status column.

It is possible for a single feed to have multiple statuses set. Statuses not set display a hyphen.

Use the arrow keys to move through the list and select a feed with Enter. This will bring up the edit dialog for that feed.

  .-[ Edit BBC News ]----------------------------------------.
  |                                                          |
  | Location: [http://newsrss.bbc.co.uk/rss/newsonline_wor$] |
  |                                                          |
  | Nickname: [BBC News       ]                              |
  |                                                          |
  |           [ ] Flag this feed                             |
  |                                                          |
  |           [ ] Force-poll this feed                       |
  |                                                          |
  |           [ ] Feed is dormant                            |
  |                                                          |
  |                                        < OK > < Cancel > |
  |                                                          |
  '----------------------------------------------------------'

Everything here works just as above, except for the addition of the last checkbox. Feeds are tested for network accessibility before changes are applied.

4.2.1 Dormant Feeds

Dormant feeds are never polled, even if they are also marked as being force-polled. If Olive sets a feed dormant due to errors, you can come here to unset that flag. The dormant flag will not be unset if Olive cannot fetch the feed.

4.3 Removing Feeds

To change information about a feed, first invoke the Remove Feeds dialog by pressing 'C-r'. You will be presented with a list of feeds and their current statuses, ordered alphabetically by feed nickname.

  .-[ Remove Feeds ]---------------.
  |                                |
  |  Sel Feed              Status  |
  |                                |
  |  [ ] ATC               f--   # |
  |  [ ] BBC News          ---   # |
  |  [ ] bda               f--   # |
  |  [ ] code4lib          --d   # |
  |  [ ] Dru               f--   # |
  |  [ ] Groklaw           ---   # |
  |  [ ] Kate              fp-   # |
  |  [ ] LtU               ---   | |
  |  [ ] OBSD Security     ---   | |
  |  [ ] Olive             -p-   | |
  |                                |
  |                        < OK >  |
  |                                |
  '--------------------------------'

Simply go through the list, using Enter to select feeds for deletion, then select 'OK' to remove those feeds. Their stories will be removed from the story database, their feed and cache files will be deleted from disk, and their information will be purged from Olive's feed list.

4.4 Polling Feeds

Feeds are polled (checked for updates) every time the period specified in the Poll Wait option elapses. You can request an early poll with the 'p' key. Feeds which are marked as forced can be fetched on demand via the 'P' key.

Here is the proceedure Olive follows for polling non-forced feeds.

Each feed's last-checked time is subtracted from the current time and the difference is compared to that feed's TTL (time-to-live) value.
If the time difference is less than the TTL, no further action is taken for that feed.
If the time difference is greater than or equal to the TTL, the feed is polled.
A polled feed is first pinged, to check its status.
If the ping (not a literal ICMP ping, but a HTTP HEAD request) comes back as a 304 Not Modified, no further action is taken for that feed.
If the ping indicates success, the feed is fetched and processed.
If the ping comes back as 403 Forbidden or 410 Gone, the feed will be marked dormant and you will be notified of this via a dialog box.
If the ping indicates some other error condition, information is logged to the error log and the TTL is modified (first dropped, then incrementally lengthened on successive errors).
If a feed has 5 successive failures, it will be marked dormant and you will be notified of this via a dialog box.

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$Id: feeds.html 419 2006-02-03 19:33:50Z mdxi $