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Viewing changes to hooks/charmhelpers/contrib/hahelpers/cluster.py

  • Committer: james.page at ubuntu
  • Date: 2015-08-10 16:38:33 UTC
  • Revision ID: james.page@ubuntu.com-20150810163833-lwvkk1s3iea5zd35
Tags: 15.07
[gnuoy] 15.07 Charm release

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hooks/charmhelpers/contrib/hahelpers/cluster.py
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    ERROR,
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    WARNING,
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    unit_get,
 
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    is_leader as juju_is_leader
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)
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from charmhelpers.core.decorators import (
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    retry_on_exception,
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    bool_from_string,
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)
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DC_RESOURCE_NAME = 'DC'
 
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class HAIncompleteConfig(Exception):
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    pass
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    pass
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class CRMDCNotFound(Exception):
 
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    pass
 
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def is_elected_leader(resource):
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    """
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    Returns True if the charm executing this is the elected cluster leader.
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    It relies on two mechanisms to determine leadership:
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        1. If the charm is part of a corosync cluster, call corosync to
 
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        1. If juju is sufficiently new and leadership election is supported,
 
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        the is_leader command will be used.
 
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        2. If the charm is part of a corosync cluster, call corosync to
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        determine leadership.
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        2. If the charm is not part of a corosync cluster, the leader is
 
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        3. If the charm is not part of a corosync cluster, the leader is
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        determined as being "the alive unit with the lowest unit numer". In
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        other words, the oldest surviving unit.
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    """
 
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    try:
 
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        return juju_is_leader()
 
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    except NotImplementedError:
 
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        log('Juju leadership election feature not enabled'
 
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            ', using fallback support',
 
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            level=WARNING)
 
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    if is_clustered():
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        if not is_crm_leader(resource):
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            log('Deferring action to CRM leader.', level=INFO)
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    return False
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@retry_on_exception(5, base_delay=2, exc_type=CRMResourceNotFound)
 
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def is_crm_dc():
 
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    """
 
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    Determine leadership by querying the pacemaker Designated Controller
 
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    """
 
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    cmd = ['crm', 'status']
 
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    try:
 
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        status = subprocess.check_output(cmd, stderr=subprocess.STDOUT)
 
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        if not isinstance(status, six.text_type):
 
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            status = six.text_type(status, "utf-8")
 
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    except subprocess.CalledProcessError as ex:
 
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        raise CRMDCNotFound(str(ex))
 
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    current_dc = ''
 
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    for line in status.split('\n'):
 
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        if line.startswith('Current DC'):
 
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            # Current DC: juju-lytrusty-machine-2 (168108163) - partition with quorum
 
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            current_dc = line.split(':')[1].split()[0]
 
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    if current_dc == get_unit_hostname():
 
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        return True
 
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    elif current_dc == 'NONE':
 
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        raise CRMDCNotFound('Current DC: NONE')
 
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    return False
 
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@retry_on_exception(5, base_delay=2,
 
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                    exc_type=(CRMResourceNotFound, CRMDCNotFound))
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def is_crm_leader(resource, retry=False):
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    """
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    Returns True if the charm calling this is the elected corosync leader,
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    We allow this operation to be retried to avoid the possibility of getting a
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    false negative. See LP #1396246 for more info.
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    """
 
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    if resource == DC_RESOURCE_NAME:
 
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        return is_crm_dc()
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    cmd = ['crm', 'resource', 'show', resource]
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    try:
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        status = subprocess.check_output(cmd, stderr=subprocess.STDOUT)