91 lines
2.7 KiB
Markdown
91 lines
2.7 KiB
Markdown
# Overview
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This interface handles the communication with the hacluster subordinate
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charm using the `ha` interface protocol.
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# Usage
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## Requires
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The interface layer will set the following reactive states, as appropriate:
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* `{relation_name}.connected` The relation is established and ready for
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the local charm to configure the hacluster subordinate charm. The
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configuration of the resources to managed for the hacluster charm
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can be managed via one of the following methods:
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* `manage_resources` method
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* `bind_on` method
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Configuration of the managed resources within the hacluster can be
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managed by passing `common.CRM` object definitions to the
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`manage_resources` method.
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* `{relation_name}.available` The hacluster is up and ready.
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For example:
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```python
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from charms.reactive import when, when_not
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from charms.reactive import set_state, remove_state
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from relations.hacluster.common import CRM
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@when('ha.connected')
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def cluster_connected(hacluster):
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resources = CRM()
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resources.primitive('res_vip', 'ocf:IPAddr2',
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params='ip=10.0.3.100 nic=eth0',
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op='monitor interval="10s"')
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resources.clone('cl_res_vip', 'res_vip')
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hacluster.bind_on(iface='eth0', mcastport=4430)
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hacluster.manage_resources(resources)
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```
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Additionally, for more code clarity a custom object implements the interface
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defined in common.ResourceDescriptor can be used to simplify the code for
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reuse.
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For example:
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```python
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import ipaddress
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from relation.hacluster.common import CRM
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from relation.hacluster.common import ResourceDescriptor
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class VirtualIP(ResourceDescriptor):
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def __init__(self, vip, nic='eth0'):
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self.vip = vip
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self.nic = 'eth0'
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def configure_resource(self, crm):
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ipaddr = ipaddress.ip_address(self.vip)
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if isinstance(ipaddr, ipaddress.IPv4Address):
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res_type = 'ocf:heartbeat:IPAddr2'
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res_parms = 'ip={ip} nic={nic}'.format(ip=self.vip,
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nic=self.nic)
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else:
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res_type = 'ocf:heartbeat:IPv6addr'
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res_params = 'ipv6addr={ip} nic={nic}'.format(ip=self.vip,
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nic=self.nic)
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crm.primitive('res_vip', res_type, params=res_params,
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op='monitor interval="10s"')
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crm.clone('cl_res_vip', 'res_vip')
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```
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Once the VirtualIP class above has been defined in charm code, it can make
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the code a bit cleaner. The example above can thusly be written as:
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```python
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@when('ha.connected')
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def cluster_connected(hacluster):
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resources = CRM()
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resources.add(VirtualIP('192.168.100.1'))
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hacluster.bind_on(iface='eth0', mcastport=4430)
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hacluster.manage_resources(resources)
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```
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