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Executing Event Scripts in an Event Policy

Event scripts are Extensible Stylesheet Transformation (XSLT) or Stylesheet Language Alternative Syntax (SLAX) scripts that you write and that are run when triggered by an event policy. Event scripts can perform any function available through Junos XML or Junos XML protocol remote procedure calls (RPCs). Additionally, you can pass to an event script a set of arguments that you define.

A script can change the device configuration, build and run an operational mode command, receive the command output, inspect the output, and determine the next appropriate action. This process can be repeated until the source of the problem is determined. The script can then report the source of the problem to you on the CLI.

You can configure an event policy that causes event scripts to be run and the output of those scripts to be uploaded to a specified location for analysis.

[edit]
user@host# set event-options policy policy-name events ?
Possible completions:
  <event>
  [                    Open a set of values
  acct_accounting_ferror
  acct_accounting_fopen_error
  ...

Some of the system log messages that you can reference in an event policy are not listed in the output of the set event-options policy policy-name events ? command. For information about referencing these system log messages in your event policies, see Using Nonstandard System Log Messages to Trigger Event Policies.

In addition, you can reference internally generated events, which are discussed in Generating Internal Events to Trigger Event Policies.

In the event-script statement, you can specify a script to be executed on receipt of an event. The eventd process runs the scripts in the order in which they appear in the configuration. The scripts that you reference in the event-script statement must be located in the /var/db/scripts/event directory on the device’s hard drive or the /config/scripts/event/ directory on the flash drive. Furthermore, the event scripts must be enabled at the [edit event-options event-script file] hierarchy level. For more information, see Storing and Enabling Scripts.

You can include arguments to the script as name/value pairs. You can include variables in the argument values to allow data from the triggering event to be automatically included in the argument. The eventd process replaces each variable with values contained in the event that triggers the policy. You can use variables of the following forms:

• {$$.attribute-name}—The double dollar sign ($$) notation represents the event that is triggering a policy. When combined with an attribute name, the variable is replaced by the value of the attribute name in the triggering event. For example, {$$.interface-name} stands for the value of the interface-name attribute in the triggering event.
• {$event.attribute-name}—The {$event.attribute-name} notation represents the most recent event that matches the specified event. The variable is replaced by the value of the attribute name of the most recent event that matches event. For example, when you include an argument called interface and define the value as {$COSD_CHAS_SCHED_MAP_INVALID.interface-name}, the {$COSD_CHAS_SCHED_MAP_INVALID.interface-name} variable is replaced by the interface-name attribute of the most recent COSD_CHAS_SCHED_MAP_INVALID event cached by the eventd process.

Name:        COSD_CHASSIS_SCHEDULER_MAP_INVALID
Message:     Chassis scheduler map incorrectly applied to interface <interface-name>: <error-message>
...

Possible completions:
 count                Count occurrences
 display              Show additional kinds of information
 except               Show only text that does not match a pattern
 find                 Search for first occurrence of pattern
 hold                 Hold text without exiting the --More-- prompt
 last                 Display end of output only
 match                Show only text that matches a pattern
 no-more              Don't paginate output
 request              Make system-level requests
 resolve              Resolve IP addresses
 save                 Save output text to file
 trim                 Trim specified number of columns from start of line

For more information about using the pipe symbol, see the CLI User Guide.

[edit event-options policy policy-name]
user@host# set attributes-match event ?

[edit event-options policy p1]
user@host# set attributes-match cosd_chassis_scheduler_map_invalid?
Possible completions:
  <from-event-attribute>  First attribute to compare
  cosd_chassis_scheduler_map_invalid.error-message
  cosd_chassis_scheduler_map_invalid.interface-name

In this set command, there is no space between the event name and the question mark (?).

[edit event-options policy policy-name]
user@host# set attributes-match ?
Possible completions:
  <from-event-attribute>  First attribute to compare
  acct_accounting_ferror
  acct_accounting_fopen_error
  ...

By default, the command output format is text. To change this, include the output-format xml statement.

In the optional output-filename statement, assign the name of the file to which to write script output for the specified script.

The filename format is hostname_filename_YYYYMMDD_HHMMSS_index-number.

For each uploaded file, a hostname and timestamp are automatically added to the filename to ensure that the uploaded files have unique filenames. If a policy is triggered multiple times in a 1-second period, an index number is added to ensure the filenames are unique. The index number range is 001 through 999.

• r1_ifl-events_20060623_132333
• r1_ifl-events_20060623_132333_001
• r1_ifl-events_20060623_132333_002

In the optional destination statement, include the destination name that you configured at the [edit event-options destinations] hierarchy level. For more information, see Example: Defining Destinations for File Archiving by Event Policies.

For the output-filename and destination statements, there are four configuration scenarios:

• You can omit the output-filename and destination statements. This option makes sense when the event script has no output. For example, the event script might execute only request commands, which have no output.
• You can include the destination statement in the configuration. You omit the output-filename statement in the configuration and specify an output filename in the event script instead. The script output is sent to the destination specified in the configuration. If you do not include the destination statement in the configuration, the script output is not uploaded.

  In this scenario, the event policy extracts the filename from the event script. The event script writes the output filename as STDOUT. The XML syntax to use in the event script is:

  <output>
      <event-script-output-filename>filename</event-script-output-filename>
  </output>
  

  The <event-script-output-filename> element must be the first child tag within the <output> parent tag.

  On a device named device2, configure an event script action with a destination host, and omit the output-filename statement. Define the destination host as ftp://user@device1//tmp.

  In the script1.xsl event script, write the following output to STDOUT:

  <event-script-output-filename>/var/cmd.txt</event-script-output-filename>

  Configure the policy1 event policy as follows:

  [edit event-options]policy policy1 {then {event-script script1.xsl { destination host;}}}destinations {host {archive-sites {"ftp://user@device1//tmp" password "$9$xkJNbYg4ZDH.oJ.fQnpuSyl";   ## SECRET-DATA***}}}

  In this example, the /var/cmd.txt file resides on device device2. The event policy uses the File Transfer Protocol (FTP) to upload this file to the /tmp directory on device device1.

  The event policy reads the output filename /var/cmd.txt from STDOUT. Then the event policy uploads the /var/cmd.txt file to the configured destination, which is the /tmp directory on device device1. The event policy renames the /var/cmd.txt file as device2_cmd.txt_YYYYMMDD_HHMMSS_range.

• You can include the output-filename and destination statements. If you include the output-filename statement in the configuration, you must also include the destination statement in the configuration. In this case, the script output is redirected to the output filename specified in the configuration and is sent to the destination specified in the configuration.
• You can include the output-filename and destination statements, and also specify an output filename directly within the event script. If you do this, the output filename specified in the configuration overrides the output filename specified in the event script.