Wubot::Guide::GettingStarted - monitoring and reacting to a feed
This recipe downloads worldwide earthquake data from the USGS RSS feed. The feed contains an item for each earthquake 5.0 and greater. The recipe below filters out earthquakes that are less than 6.0, and sends a console and growl notification for each. Earthquakes of 7 or greater get a colorized growl notification. Earthquakes of 8 or greater get a sticky growl notification. The filtered feed is then stored in a SQLite database and fed back out again to your favorite RSS reader.
Start by defining an RSS monitor config.
The RSS plugin config files live here:
Start by creating a file named usgs-m5.yaml in that directory. Here is an example of a minimalist RSS monitor config:
--- delay: 15m url: http://earthquake.usgs.gov/eqcenter/catalogs/7day-M5.xml
The 'delay' param tells wubot-monitor how frequently to run the check, and the 'url' tag is the URL of the RSS/Atom feed. For more info on the RSS monitor, see Wubot::Plugin::RSS.
After creating this config file, run wubot-monitor. It will find the new config file and will schedule an immediate check of the RSS feed. For each entry in the feed, it will send a message (a data structure) containing the RSS feed data that will, by default, get serialized and stored in the queue to go to the reactor process. The message will look something like this:
- body: ~ config.delay: 300 config.url: http://earthquake.usgs.gov/eqcenter/catalogs/7day-M5.xml key: RSS-usgs-m5 lastupdate: 1311212434 link: http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc00051ms.php plugin: Wubot::Plugin::RSS subject: 'M 6.0, Solomon Islands' title: 'M 6.0, Solomon Islands'
Notice that the original config params are available in the message under config.*. The 'key' is unique for every monitor instance, it contains the plugin directory and filename joined with a dash. The full plugin name is available in 'plugin'. The 'lastupdate' field contains the time the message was generated. These are standard message fields which will be set in every message by wubot-monitor. The 'subject' field is an optional field that the notification plugins make use of. If the message has a subject, that subject will be sent in a notification.
Other fields in the message are initially set by the message plugins and vary from plugin to plugin. For the RSS plugin, the custom fields available in this feed are 'body', 'link', and 'title'. The body has no content in this example.
After the monitor runs and successfully delivers it's messages to the reactor queue, it will write a cache file here:
The cache file contains a list of the subjects that have previously been seen, so that the next time the monitor runs (15 minutes later per the 'delay' config param), it will only send any new items that show up in the feed. If you remove the cache file and restart wubot-monitor, it will schedule another immediate check and will re-send all the data from the feed.
Now that the messages have been delivered to the reactor queue, you need a reactor config to determine what action to take when the message arrives.
The reactor is configured with a series of rules. For a list of the properties of a rule, have a peak at Wubot::Guide::Rules. For an overview of the available reactor plugins, see Wubot::Guide::ReactorPlugins.
Let's start with the individual rules and work up to the full rule tree.
The first thing we need is a rule that captures the magnitude of the earthquake. The title of the feed contains the magnitude, e.g.:
M 6.0, Solomon Islands
The following rule will use the CaptureData plugin to capture the number from the 'title' field of the RSS message and store it in a new field called 'size':
- name: size plugin: CaptureData config: source_field: title regexp: '^M ([\d\.]+),' target_field: size
After this rule runs, the message will have a new field named 'size'.
- body: ~ config.delay: 300 config.url: http://earthquake.usgs.gov/eqcenter/catalogs/7day-M5.xml key: RSS-usgs-m5 lastupdate: 1311212434 link: http://earthquake.usgs.gov/earthquakes/recenteqsww/Quakes/usc00051ms.php plugin: Wubot::Plugin::RSS size: 6.0 subject: 'M 6.0, Solomon Islands' title: 'M 6.0, Solomon Islands'
The next step is to ignore earthquakes in the 5.x range. According to the USGS, there are an average of 1319 earthquakes in this range every year. That will add up to a lot of notifications. We're just watching for the bigger ones here, so we need to select those that are less than 6, and then set the magical 'last_rule' rule, which prevents any further rules from running. This is the equivalent of routing the message out /dev/null.
- name: suppress less than 6.0 condition: size < 6 last_rule: 1
There are only an average of 134 earthquakes in the 6 to 7 range, so we'll let those through so we'll get notification for earthquakes in that range. But there are only an average of 16 earthquakes per year that are over 7.0. We want to make the notifications for these events to stand out. This is pretty similar to the previous rule, but we'll set the 'sticky' and 'yellow' properties on the rule.
- name: sticky greater than 7.0 condition: size >= 7 plugin: SetField config: set: sticky: 1 color: yellow
To enable the notifications, see Wubot::Guide::Notifications.
After enabling the notifications, go to images.google.com and find a .png file that you would like to use for this feed (try searching for usgs). Save the file as:
Note that this matches the filename that was created in ~/wubot/config/plugins/RSS.
So now let's put it all together. The reactor config lives here:
Here are the final contents of the reactor config, including some notifications rules discussed in Wubot::Guide::Notifications.
Warning: if you are not familiar with YAML, it is extremely sensitive to whitespace!
--- rules: - name: earthquakes condition: key matches ^RSS-usgs-m5 rules: - name: size plugin: CaptureData config: source_field: title regexp: '^M ([\d\.]+),' target_field: size - name: suppress less than 6.0 condition: size < 6 last_rule: 1 - name: sticky greater than 7.0 condition: size >= 7 plugin: SetField config: set: sticky: 1 color: yellow - name: notifications condition: subject is true rules: - name: console plugin: Console - name: growl color plugin: HashLookup config: source_field: color target_field: growl_priority lookup: red: 2 yellow: 1 orange: 1 grey: 0 bold black: 0 green: -1 magenta: -2 purple: -2 blue: -2 cyan: -2 - name: growl icon plugin: Icon config: image:dir: /Users/your_id/.icons - name: growl notify plugin: Growl
Starting the Reactor
To start the reactor, simply run: wubot-reactor
For more information on the wubot webui, please see the document Wubot::Guide::WebUI.
The Web UI reads the data out of the rss SQLite database, so before we can use the Web UI, we need to go back to the reactor and add some rules to store the message.
- name: rss sqlite condition: key matches ^RSS AND mailbox is true plugin: SQLite config: file: /home/myuserid/wubot/sqlite/rss.sql tablename: feeds
The SQLite plugin will look at the schema to determine which message fields you are interested in, and will then attempt to insert a new row into the database. If SQLite throws and error that the table does not exist, the SQLite reactor will catch the error and use the schema above to create the table and then insert the message again. Also you can add a new column to the schema at any time (a restart of wubot may be required to read the new schema from the config). When the SQLite plugin goes to insert the data, it will catch the error that the column does not exist, and will then attempt to alter the table and add the row. Note that it will not change the type on a column that has already been created in the table, or remove a column that was previously added. For more information, see Wubot::SQLite.
You could easily add a rule in the reactor to select the RSS-usgs-m5 key and then add a 'mailbox' field. But this is a good opportunity to point out that you can also define a reaction that will run directly in the wubot-monitor process. When you do this, the monitor will process the rules before ever storing the message to the reactor queue. The advantage here is that the rule is defined close to the monitoring config, so you can edit all the custom config specific to that feed in one place. Start with the monitor config we used earlier:
--- delay: 15m url: http://earthquake.usgs.gov/eqcenter/catalogs/7day-M5.xml
And add a 'react' section to define your rules. We'll use the 'SetField' plugin to manually set the mailbox for this feed:
--- delay: 15m url: http://earthquake.usgs.gov/eqcenter/catalogs/7day-M5.xml react: - name: set mailbox plugin: SetField config: field: mailbox value: earthquake
If you already ran the wubot-monitor after defining the RSS monitor but before adding this rule, then the monitor has already pulled all the items from the RSS feed and cached them. So when you add this rule to the reactor, your database will not even get created until the first new entry shows up in the feed. You could remove the monitor cache file (see above in the monitor section) and restart the monitor, and it will send all the items back through the feed again. Thus your database will contain all the items that are currently available in the feed.
The monitor config is a great place to define simple reactions for a monitor, e.g. adding or modifying fields on the message. But there are some limitations to be aware of. First, you can only define reactions that are specific to a single instance of a monitor. If you have a rule that you wanted to apply to all RSS feeds, then you would have to duplicate that rule in every file in the RSS directory. So reactions that cross across many plugins (e.g. the notifications) should always be defined in the reactor. Second, not all reactor plugins work in the wubot-monitor process. For example, the 'State' and 'Command' plugins will not work properly or fully in the wubot-monitor process. Third, the reason that the monitor and the reactor are separate processes is by design. This ensures that the monitors can continually gather data on schedule and won't get hung up waiting for a reaction to occur.
See the Wubot::Guide::WebUI document for more information on starting up the web ui. Once the process is started up, point your RSS reader here, and enjoy your filtered feed: