Device Recovery

Before using your new Clean it is important to learn about Device Recovery as it is the second most important aspect to pyATS Clean.

The Methodology Behind Device Recovery

pyATS Clean provides a jack-of-all-trades for recovering devices that fail due to device malfunctions or if the clean process itself fails to execute (see below for details). Device Recovery can clear the line of a device from the terminal server and use a powercycler to restart the device. After restarting the device, Device Recovery will load the golden image and optionally apply a configuration onto the device.

The major advantage the device recovery feature provides is—you can recover a device and reset it back to a useable state regardless of the current state of the device.

How Device Recovery Works

Device Recovery is invoked after every stage and it will determine whether to continue or fail clean.

The following diagram explains, in detail, the flow of Device Recovery.

../../../_images/pyATS_clean_device_recovery_diagram.svg

How to Enable Device Recovery

Device Recovery requires that you have an Golden Image for each device which is guaranteed to boot and function correctly. This Golden Image can be kept on the device or on a tftp server which is accessible from the device. Once you have the Golden Image, follow the steps below.

  1. Add the required Terminal Server and/or Power Cycler information to the Testbed YAML

    The example below shows where to add the Terminal Server and the Power Cycler information.

    Note

    See Supported Power Cyclers for a list of available Power Cyclers and their respective arguments that can be used.

     1devices:
 2  PE1:
 3    peripherals:
 4      power_cycler:
 5        - type: dualcomm
 6          connect_type: snmp
 7          host: 127.0.0.1
 8          outlets: [22]
 9
10      terminal_server:
11        # <terminal server device>: <list of lines for the device>
12        # In this case, clearing line 22 would clear the line
13        # connected to 'PE1'
14        my-terminal-server: [22]
15
16  my-terminal-server:
17    # Fill out the rest of this device as normal
18    # such as connection info, credentials, etc

  2. Add the device_recovery section to the Clean YAML.

    Below you can find the Device Recovery schema.

     1Clean YAML - Device Recovery Schema
 2-----------------------------------
 3devices:
 4  <device>:
 5    device_recovery:
 6      break_count (int): How many attempts to break the booting process once
 7          either the console_activity_pattern or the grub_activity_pattern was
 8          matched.
 9
10      console_activity_pattern (str, optional): Used only for devices with
11          rommon boot mode. Once the pattern is matched, breaking of the
12          boot process begins.
13
14      console_breakboot_char (str, optional): Used in conjunction with
15          console_activity_pattern. This is the character(s) to send which should
16          break the rommon booting process.
17
18      grub_activity_pattern (str, optional): Used only for devices with
19          grub boot mode. Once the pattern is matched, breaking of the
20          boot process begins.
21
22      grub_breakboot_char (str, optional): Used in conjunction with
23          grub_activity_pattern. This is the character(s) to send which should
24          break the grub booting process.
25
26      timeout (int): Maximum time in seconds to recover the device.
27
28      recovery_password (str): Password to login to the device after the boot
29          process completes.
30
31      powercycler (bool, optional): Should Device Recovery powercycle
32          the device. Defaults to True.
33
34      powercycler_delay (int, optional): Powercycler delay between on and off in
35          seconds. Defaults to 30.
36
37      reconnect_delay (int, optional): Once device recovered, delay before
38          final reconnect in seconds. Defaults to 60.
39
40      clear_line (bool, optional): Should device recovery clear the lines.
41          Defaults to True.
42
43      post_recovery_configuration (str, optional): Configuration to apply after
44          booting. Defaults to None.
45
46      golden_image for NXOS
47      ---------------------
48      golden_image (dict, only if 'tftp_boot' from below is not defined):
49        kickstart (str, optional): Golden kickstart image. Defaults to None.
50        system (str, optional): Golden system image. Defaults to None.
51
52      golden_image for others
53      -----------------------
54      golden_image (list, only if 'tftp_boot' from below is not defined): Image
55         to boot.
56
57      tftp_boot (only if 'golden_image' from above is not defined):
58        image (list): Image to boot with.
59        ip_address (list): Management ip address to configure to reach to
60          the TFTP server.
61        subnet_mask (str): Management subnet mask.
62        gateway (str): Management gateway.
63        tftp_server (str): Tftp server is reachable with management interface.

    Below you can find a Device Recovery example.

     1Clean YAML - Device Recovery Example
 2------------------------------------
 3devices:
 4  PE1:
 5    device_recovery:
 6      grub_activity_pattern: '.*The highlighted entry will be executed automatically in.*'
 7      timeout: 600
 8      powercycler_delay: 5
 9      golden_image:
10        - 'GOLDEN IMAGE'

That’s it! Not as bad as it looked! Now pyATS Clean will handle cases where the device has malfunctioned or is otherwise unreachable.