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from charmhelpers.core.hookenv import relation_id as current_relation_id
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from charmhelpers.core.hookenv import (
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This helper provides functions to support use of a peer relation
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for basic key/value storage, with the added benefit that all storage
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can be replicated across peer units.
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To use this, the "peer_echo()" method has to be called form the peer
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relation's relation-changed hook:
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@hooks.hook("cluster-relation-changed") # Adapt the to your peer relation name
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def cluster_relation_changed():
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Once this is done, you can use peer storage from anywhere:
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@hooks.hook("some-hook")
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# You can store and retrieve key/values this way:
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if is_relation_made("cluster"): # from charmhelpers.core.hookenv
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# There are peers available so we can work with peer storage
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peer_store("mykey", "myvalue")
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value = peer_retrieve("mykey")
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print "No peers joind the relation, cannot share key/values :("
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def peer_retrieve(key, relation_name='cluster'):
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"""Retrieve a named key from peer relation `relation_name`."""
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cluster_rels = relation_ids(relation_name)
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if len(cluster_rels) > 0:
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cluster_rid = cluster_rels[0]
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return relation_get(attribute=key, rid=cluster_rid,
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raise ValueError('Unable to detect'
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'peer relation {}'.format(relation_name))
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def peer_retrieve_by_prefix(prefix, relation_name='cluster', delimiter='_',
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inc_list=None, exc_list=None):
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""" Retrieve k/v pairs given a prefix and filter using {inc,exc}_list """
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inc_list = inc_list if inc_list else []
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exc_list = exc_list if exc_list else []
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peerdb_settings = peer_retrieve('-', relation_name=relation_name)
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for k, v in peerdb_settings.items():
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full_prefix = prefix + delimiter
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if k.startswith(full_prefix):
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new_key = k.replace(full_prefix, '')
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if new_key in exc_list:
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if new_key in inc_list or len(inc_list) == 0:
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def peer_store(key, value, relation_name='cluster'):
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"""Store the key/value pair on the named peer relation `relation_name`."""
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cluster_rels = relation_ids(relation_name)
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if len(cluster_rels) > 0:
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cluster_rid = cluster_rels[0]
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relation_set(relation_id=cluster_rid,
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relation_settings={key: value})
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raise ValueError('Unable to detect '
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'peer relation {}'.format(relation_name))
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def peer_echo(includes=None):
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"""Echo filtered attributes back onto the same relation for storage.
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This is a requirement to use the peerstorage module - it needs to be called
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from the peer relation's changed hook.
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rdata = relation_get()
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echo_data = rdata.copy()
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for ex in ['private-address', 'public-address']:
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for attribute, value in rdata.iteritems():
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for include in includes:
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if include in attribute:
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echo_data[attribute] = value
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if len(echo_data) > 0:
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relation_set(relation_settings=echo_data)
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def peer_store_and_set(relation_id=None, peer_relation_name='cluster',
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peer_store_fatal=False, relation_settings=None,
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delimiter='_', **kwargs):
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"""Store passed-in arguments both in argument relation and in peer storage.
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It functions like doing relation_set() and peer_store() at the same time,
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@param relation_id: the id of the relation to store the data on. Defaults
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to the current relation.
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@param peer_store_fatal: Set to True, the function will raise an exception
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should the peer sotrage not be avialable."""
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relation_settings = relation_settings if relation_settings else {}
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relation_set(relation_id=relation_id,
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relation_settings=relation_settings,
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if is_relation_made(peer_relation_name):
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for key, value in dict(kwargs.items() +
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relation_settings.items()).iteritems():
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key_prefix = relation_id or current_relation_id()
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peer_store(key_prefix + delimiter + key,
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relation_name=peer_relation_name)
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raise ValueError('Unable to detect '
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'peer relation {}'.format(peer_relation_name))
added
removed
hooks/charmhelpers/contrib/peerstorage/__init__.py
