Data Movement and Integration
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Chapter 12. Using Advanced Falcon Features

Locating and Managing Entities

There are two methods you can use to locate entities in Falcon. You can use the Falcon web UI search functionality to find feed, process, or mirror entities that are defined for the cluster. To display a list of cluster entities, you use the Cluster icon. After locating an entity, you can perform actions on them or view information about them.

Available data sources can only be viewed from the Datasource field on the Create New Feed page.

Steps

  1. Type your query in the Search field, and press Enter.

    [Note]Note

    You can use Search to find feed, process, and mirror entities, but not cluster or data source entities. See Step 3 to locate cluster entities. Available data sources can only be viewed from the Datasource field on the Create New Feed page.

    You can filter the entity search based on names, types, or tags. By default, the first argument in your query is the Name filter. Wildcards are supported, such as asterisk (*). The search is interactive so you can refine your search by adding and removing tags to tune your result set.

    [Tip]Tip

    To see all feed, process, and mirror entities, search using an asterisk (*) for the entity name.

    Filter

    Description

    Name

    Can be entered as a subsequence of the entity name (feed, process, or mirror name). Not case sensitive. The characters entered must be in the same order as the original sequence in the entity name.

    For example:

    • "sample1" matches the entity named "SampleFeed1-2"

    • "mhs" matches the entity named "New-My-Hourly-Summary"

    Searching on the asterisk (*) character displays all feed, process, and mirror entities.

    Tag

    Keywords in metadata tags. Not case sensitive. Entities that are returned in search results have tags that match all of the tag keywords.

    Type

    Specifies the type of entity. Valid entity types are feed, process, and mirror. The Falcon search UI infers the filter type automatically. For example, to add a "process" filter type, enter process in the search field, and then choose type:process from the hints offered in the UI as shown in the previous screen capture.

  2. In the search results, you can do the following:

    • Display the actions you can perform on the entity by selecting the checkbox next to the entity name.

      You can schedule, resume, pause, edit, copy, delete, or download the entity definition XML for a feed, process, or mirror.

    • Display the instances and property details of the entity by clicking the entity name.

  3. Click the Clusters icon to view a list of cluster entities.

    Figure 12.1. Clusters icon


  4. In the search results, you can do the following:

    • Display the actions you can perform on the entity by selecting the check-box next to the cluster name.

      You can delete a cluster entity or download the entity definition XML.

      You can edit the cluster entity if your Falcon service is in safemode.

    • Display the properties of the cluster entity by clicking the cluster name.

Accessing File Properties from Ambari

You can set properties for files such as core-site.xml, oozie-site.xml, hive-site.xml, and so forth, from the Ambari UI.

You can access the properties by performing the following steps:

  1. Log in to Ambari at http://[cluster ip]:8080.

  2. Click Service and select the service that you want to modifiy.

    A page with details about the service displays.

  3. On the service details page, click Configs, then click Advanced, if available.

    An Advanced page is not available for all services.

  4. Click the section name for the Custom or Advanced properties to expand the section.

  5. To add a property to the list, scroll to the bottom of properties and click Add Property.

    The Add Property option is available only for some configuration files.

Enabling Transparent Data Encryption

Falcon provides transparent data encryption (TDE) for data at rest, such as databases. TDE encryption is supported in Falcon on HDFS, Hive, and snapshot mirroring jobs.

You can enable the TDE encryption property in the following ways:

  • Select the TDE Encryption option when creating a mirror in the Falcon web UI.

  • Add the property tdeEncryptionEnabled=true directly to the properties file extensions in a <workflow>.xml file.

  • Add <arg>skipChecksum</arg> and <arg>true</arg> to a <properties>.json file.

TDE encryption performs a checksum to determine if changes have been made to the data. If the checksum value is different, HDP performs a replication. The encryptions key can be different in the source and target clusters, which would result in a modified checksum value, so the checksum might indicate changes even if the data has not changed. If you skip the checksum, HDP compares individual blocks to see if replication is needed, which can increase the time to complete a mirror job.

Putting Falcon in Safe Mode

Safe mode (read-only mode) is useful when you want to prevent Falcon users from scheduling entities in the workflow engine, such as when upgrading Hadoop clusters or updating Falcon cluster entities. When in safe mode, users can only perform limited operations. For example, you cannot perform submit, schedule, edit, delete, or resume operations on entities. For further detail, see the Falcon Community Documentation.

You must be superuser or administrative (admin) user to set safe mode. A superuser is the user who owns the Falcon process or belongs to a group specified in the Falcon startup property falcon.security.authorization.superusergroup. An admin user is the user listed under the Falcon startup property falcon.security.authorization.admin.users, or they belong to a group listed under the startup property falcon.security.authorization.admin.groups.

If you want to modify a cluster entity, you must be in safe mode.

  1. Put the Falcon server in safe mode:

    /bin/falcon admin -setsafemode true

  2. Take the Falcon server out of safe mode:

    /bin/falcon admin -setsafemode false

Viewing Alerts in Falcon

Falcon provides alerting for a variety of events to let you monitor the health of your data pipelines. All events are logged to the metric.log file, which is installed by default in your $user/logs/ directory. You can view the events from the log or capture them using a custom interface.

Each event logged provides the following information:

  • Date: UTC date of action.

  • Action: Event name.

  • Dimensions: List of name/value pairs of various attributes for a given action.

  • Status: Result of the action. Can be FAILED or SUCCEEDED (when applicable).

  • Time-taken: Time in nanoseconds for a given action to complete.

For example, a new process-definition alert would log the following information:

2012-05-04 12:23:34,026 {Action:submit, Dimensions:{entityType=process}, Status: SUCCEEDED, Time-taken:97087000 ns}

Table 12.1. Available Falcon Event Alerts

Entity TypeActionReturns Success/Failure
ClusterNew cluster definitions submitted to FalconYes
ClusterCluster update eventsYes
ClusterCluster remove eventsYes
Feed New feed definition submitted to FalconYes
FeedFeed update eventsYes
FeedFeed suspend events Yes
FeedFeed resume eventsYes
FeedFeed remove eventsYes
FeedFeed instance deletion eventNo
FeedFeed instance deletion failure event (no retries)No
FeedFeed instance replication eventNo
FeedFeed instance replication failure eventNo
FeedFeed instance replication auto-retry eventNo
FeedFeed instance replication retry exhaust eventNo
FeedFeed instance late arrival eventNo
FeedFeed instance post cut-off arrival eventNo
ProcessNew process definition posted to FalconYes
ProcessProcess update eventsYes
ProcessProcess suspend eventsYes
ProcessProcess resume events Yes
ProcessProcess remove events Yes
ProcessProcess instance kill eventsYes
ProcessProcess instance re-run eventsYes
ProcessProcess instance generation eventsNo
ProcessProcess instance failure eventsNo
ProcessProcess instance auto-retry eventsNo
ProcessProcess instance retry exhaust eventsNo
ProcessProcess re-run due to late feed eventNo
N/ATransaction rollback failed eventNo

Late Data Handling

Late data handling in Falcon defines how long data can be delayed and how that late data is handled. For example, a late arrival cut-off of hours(6) in the feed entity means that data for the specified hour can delay as much as 6 hours later. The late data specification in the process entity defines how this late data is handled and the late data policy in the process entity defines how frequently Falcon checks for late data.

The supported policies for late data handling are:

  • backoff: Take the maximum late cut-off and check every specified time.

  • exp-backoff (default): Recommended. Take the maximum cut-off date and check on an exponentially determined time.

  • final:Take the maximum late cut-off and check once.

The policy, along with delay, defines the interval at which a late data check is done. The late input specification for each input defines the workflow that should run when late data is detected for that input.

To handle late data, you need to modify the feed and process entities.

  1. Specify the cut-off time in your feed entity.

    For example, to set a cut-off of 4 hours:

    <late-arrival cut-off="hours(4)”/>
  2. Specify a check for late data in all your process entities that reference that feed entity.

    For example, to check each hour until the cut-off time with a specified policy of backoff and a delay of 1 hour:

    <late-process policy="exp-backoff" delay="hours(1)”>
       <late-input input="input" workflow-path="/apps/clickstream/late" />
    </late-process>

Setting a Retention Policy

You can set retention policies on a per-cluster basis. You must specify the amount of time to retain data before deletion. You set a retention policy in the feed entity.

Falcon kicks off the retention policy on the basis of the time value you specify:

  • Less than 24 hours: Falcon kicks off the retention policy every 6 hours.

  • More than 24 hours: Falcon kicks off the retention policy every 24 hours.

  • When a feed is scheduled: Falcon kicks off the retention policy immediately.

[Note]Note

When a feed is successfully scheduled, Falcon triggers the retention policy immediately regardless of the current timestamp or state of the cluster.

To set a retention policy, add the following lines to your feed entity for each cluster that the feed belongs to:

<clusters>
        <cluster name="corp" type="source">
            <validity start="2012-01-30T00:00Z" end="2013-03-31T23:59Z"
                      timezone="UTC" />
            <retention limit="$unitOfTime($n)" action="delete" /> <!--Retention policy.  --> 
        </cluster>
 </clusters>

Where limit can be minutes, hours, days, or months and then a specified numeric value. Falcon then retains data spanning from the current moment back to the time specified in the attribute. Any data beyond the limit (past or future) is erased.

Setting a Retry Policy

You can set retry policies on a per-process basis. The policies determine how workflow failures are handled. Depending on the delay and number of attempts, the workflow is retried after specified intervals. The retry policy is set on the process entity.

To set a retry policy, add the following lines to your process entity:

<retry policy=[retry policy] delay=[retry delay]attempts=[attempts]/>
<retry policy="$policy" delay="minutes($n)" attempts="$n"/>

For example:

<process name ="[sample-process]">
...
     <retry policy="periodic" delay="minutes(10)" attempts="3"/>
...
</process>

In this example, the workflow is retried after 10 minutes, 20 minutes, and 30 minutes.

Enabling Email Notifications

You can enable email notifications in feed entities and process entities. When email notifications are enabled, an email is sent to the specified email address when the scheduled feed or process instance completes. Email notifications can be specified in feed or process entities.

You can set email notifications in feed and process entities from the web UI. This can be done when initially creating an entity, or you can edit an existing entity to add or modify email notifications.

Setting Email Notifications from the CLI

To set email notifications, add the following to the feed or process entity:

<process name="<process_name>
     ...
     <notification type="email" to="jdoe@example.com, sjones@company.com"/>
     ...
</process>

Where type specifies the type of notification. Currently, only the email notification type is supported. The to attribute specifies where the notification is to be sent. In the case of email notifications, specify the email address where you want notifications sent for the to attribute. Multiple recipients can be specified as a comma-separated list of email addresses as shown in the previous example. The <notification> tag must be placed before the <ACL> tag.

If you are using email notification in a Hive or HDFS disaster recovery configuration, you must add the following properties to the Falcon server-side extensions file:

  • jobNotificationType=email

  • jobNotificationReceivers=<address-of-email-receiver>

    The email addresses are entered as a comma-separated list.

Falcon email notifications require SMTP server configurations to be defined in the Falcon startup.properties file that is located in the FALCON_HOME/conf directory. After setting the values, restart the Falcon service.

Falcon does not check for multiple versions of properties in the properties file. If multiple versions of a property exist, Falcon uses the last one in the file.

Configure the following startup properties for email notifications:

Table 12.2. Email Notification Startup Properties

Property

Description

Default Values

falcon.email.smtp.host

Name of the host where the SMTP server can be found.

localhost

falcon.email.smtp.port

The SMTP server host port to connect to.

25

falcon.email.from.address

The "From:" address used for all notification emails.

falcon@localhost

falcon.email.smtp.auth

Indicates whether user sending the email is authenticated. Boolean value (true | false)

false

falcon.email.smtp.user

If authentication is enabled, this property specifies the username that is used to log in.

none

falcon.email.smtp.password

If authentication is enabled, the username's password that is used to authenticate the user.

none

monitoring.plugins

Ensure that the email notification plugin is listed for this property to enable email notifications.

For example:

org.apache.falcon.plugin.EmailNotificationPlugin, 
org.apache.falcon.plugin.DefaultMonitoringPlugin

none


Understanding Dependencies in Falcon

Cross-entity dependencies in Falcon are important because a dependency cannot be removed until all the dependents are first removed. For example, if Falcon manages two clusters, one in Oregon and one in Virginia, and the Oregon cluster is going to be taken down, you must first resolve the Virginia cluster dependencies as one Dataset (Dataset 3) has a cross-entity dependency and depends on Email Ingest (Process 1).

Figure 12.2. Entity dependencies in Falcon


To remove the Oregon cluster, you must resolve this dependency. Before you can remove the Oregon Hadoop cluster, you must remove not only Process 1, Datasets 1 and 2 but also modify the Dataset 3 entity to remove its dependence on Process 1.

As Falcon manages more clusters, viewing these dependencies becomes more crucial. For further information about dependencies and cross-entity validations, see the Falcon Community Documentation

Viewing Dependencies

The Falcon web UI provides dependency viewing for clusters, datasets, and processes that shows lineage in a graphical format. You can view the relationships between dependencies as a graph to determine requirements for removal.

You can access the dependencies graph from the entity lists.

To view cluster dependencies:

  1. Click the Clusters icon.

  2. In the list that displays, click on the name of a cluster.

To view feed or process entities, or mirror jobs:

  1. Enter a term in the Search field.

  2. In the search results, click on the name of an entity or mirror job.

Figure 12.3. Graph view of dependencies