Callback

Callbacks allow users to run some command when a particular event occurs. These callbacks are typically used for notification purposes.

The following callback events are supported:

afmFilesetExpired afmFilesetUnexpired nodeJoin nodeLeave quorumReached quorumLoss quorumNodeJoin quorumNodeLeave clusterManagerTakeover afmHomeConnected afmHomeDisconnected afmManualResyncComplete

afmPrepopEnd afmRecoveryStart afmRecoveryEnd deadlockDetected deadlockOverload diskFailure filesetLimitExceeded lowDiskSpace mmProtocolTraceFileChange noDiskSpace preMount preUnmount

mount unmount preShutdown preStartup sendRequestToNodes shutdown snapshotCreated softQuotaExceeded startup tiebreakerCheck usageUnderSoftQuota

The following PixStor variables are available to use as callback parameters:

blockLimit blockQuota blockUsage clusterManager clusterName diskName downNodes eventName

eventNode filesLimit filesQuota filesUsage filesetName filesetSize fsName homeServer

myNode nodeNames prepopCompletedReads prepopData quorumNodes quotaID quotaOwnerName quotaType

reason requestType snapshotID snapshotName storagePool upNodes userName waiterLength

If you want to use PixStor variables (as listed above) with a Python function callback, they can be passed with the ‘parms’ keyword as normal, e.g.

>>> def logger(msg):
...    ...
>>>
>>> Callback(command=logger, parm=['%eventNode'])

Or they can be specified as part of the function definition, in which case they don’t need to be passed seperately, e.g.

>>> def logger(eventNode):
...    ...
>>>
>>> Callback(command=logger)

Warning

Callback scripts and functions are run as root.

Description

class arcapix.fs.gpfs.callback.Callback(callbackId, command=None, event=None, **kwargs)

A callback is an executable that is triggered by some event

Parameters:

• callbackId – An identifier for the callback
• command – Path to an executable, or some Python callable, that the callback should run.
• event – An event or list of events that should trigger the callback
• parms – List of parameters to be passed to the command. These can include GPFS variables.
• node – A node or list of nodes on which the callback should be installed (default=all)

Note

A callback executable should be installed on all nodes on which the callback could be triggered, and its path should be fully qualified.

id

Returns the callback identifier

Synonym for callbackId

Return type:str

name

Returns the callback identifier

Synonym for callbackId

Return type:str

callbackId

Returns the callback identifier

Return type:str

command

Returns the path to the callback script or the Python callable

Return type:str Return type:callable

script

Resturns the script that the callback runs.

If the callback is Python callable-based the ArcaPix callback driver script will be returned

Return type:str

function

Resturns the function that the callback runs.

If the callback is script-based a wrapper function that calls the script will be returned

Return type:callable

events

Returns a list of events that trigger the callback

Return type:list of str

nodes

Returns a list of nodes that the callback is installed on

Return type:list of str

parms

Returns a list of command parameters

Doesn’t include implicit parms from callable-based callbacks

Return type:list of str

priority

Returns the priority of the callback

Default:-1 (if priority isn’t set) Return type:float

sync

Returns whether the callback is (a)sync

Return type:bool

timeout

Returns the timeout (delay) in seconds

Return type:int

onError

Action to take if callback command fails.

Can be one of [continue, quorumLoss, shutdown].

Default:‘continue’ Return type:str

validate()

Tries to pre-catch issues before they are sent to GPFS.

This is faster, and less destructive than relying on GPFS to catch errors. This can make debugging easier.

create()

Install the callback on GPFS

delete()

Deletes the callback from GPFS

add(**kwargs)

Add extra events or nodes to the callback

Parameters:

• events – list of events (names) which should trigger the callback
• nodes – list of nodes (names) on which the callback should run

remove(**kwargs)

Remove events or nodes from the callback

Parameters:

• events – list of events (names) which should no longer trigger the callback
• nodes – list of nodes (names) on which the callback should no longer run

change(**kwargs)

Change one of the callback’s parameters

Parameters:

• nodes – list of nodes (names) on which the callback should run
• events – list of events (names) that should trigger the callback
• parms – list of parameters that should be passed to the callback script
• sync (bool) – Specifies whether GPFS will wait for the user program to complete (default=False)
• timeout – If sync=True, timeout is how long GPFS will wait for the user program to complete (in seconds)
• onerror – Action to take if callback command fails. One of: ‘continue’, ‘quorumLoss’, ‘shutdown’. (default=’continue’)
• priority (float) – Determines the order in which callbacks run. Smallest runs first. (default=lowest priority)

Examples

Create a new callback

>>> from arcapix.fs.gpfs import Callback
>>>
>>> # Instantiate a callback object
... mycallback = Callback("test1", "/tmp/myscript.sh", "startup")
>>>
>>> # Install on cluster
... mycallback.create()
>>>

Create a new callback on a node

>>> from arcapix.fs.gpfs import Node
>>>
>>> # Instantiate a node
... local = Node("localhost")
>>>
>>> # Create shutdown callback
... local.onShutdown.new("/home/auser/callbacks/notify.sh", callbackId="local_sd", params=["%eventNode"])
>>>

Create a shutdown log for all nodes on a cluster

>>> from arcapix.fs.gpfs import Cluster
>>> from time import strftime, localtime
>>>
>>> # Define a logging function
... def logger(eventNode):
...    with open("/tmp/shutdown.log", 'a') as log
...       out = "{0} shutdown as {1}\n".format(eventNode, strftime("%H:%M:%S, %a %d %b %Y", localtime()))
...       log.write(out)
...    return out
>>>
>>> # Create shutdown callback
... Cluster().onShutdown.new(logger)
>>>