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Net::ZooIt High level recipes for Apache ZooKeeper

DESCRIPTION

Net::ZooIt provides high level recipes for working with ZooKeeper in Perl, like locks, leader election or queues.

Net::ZooKeeper Handles

Net::ZooIt methods always take a Net::ZooKeeper handle object as a parameter and delegate their creation to the user. Rationale: enterprises often have customised ways to create those handles, Net::ZooIt aims to be instantly usable without such customisation.

Automatic Cleanup

Net::ZooIt constructors return a Net::ZooIt object, which automatically clean up their znodes when they go out of scope at the end of the enclosing block. If you want to clean up earlier, call

  $zooit_obj->DESTROY;

Implication: if you call Net::ZooIt constructors in void context, the created object goes out of scope immediately, and your znodes are deleted. Net::ZooIt logs a ZOOIT_ERR message in this case.

Error Handling

Net::ZooIt constructors return nothing in case of errors during creation.

Once you hold a lock or other resource, you're not notified of connection loss errors. If you need to take special action, check your Net::ZooKeeper handle.

If you give up Net::ZooIt resources during connection loss, your znodes cannot be cleaned up immediately, they will enter a garbage collection queue and Net::ZooIt will clean them up once connection is resumed.

Logging

Net::ZooIt logs to STDERR. Log messages are prefixed with Zulu military time, PID and the level of the current message: ZOOIT_DIE ZOOIT_ERR ZOOIT_WARN ZOOIT_INFO ZOOIT_DEBUG.

If Net::ZooIt throws an exception, it prints a ZOOIT_DIE level message before dying. This allows seeing the original error message even if an eval {} block swallows it.

To capture Net::ZooIt log messages to a file instead of STDERR, redirect STDERR to a new file handle in the normal Perl manner:

open(OLDERR, '>&', fileno(STDERR)) or die("unable to dup STDERR: $!");
open(STDERR, '>', $log_file) or die("unable to redirect STDERR: $!");

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