charmhelpers.core.hookenv

Config A dictionary representation of the charm’s config.yaml, with some extra features:
Hooks A convenient handler for hook functions.
NoNetworkBinding
Serializable Wrapper, an object that can be serialized to yaml or json
UnregisteredHookError Raised when an undefined hook is called
action_fail Sets the action status to failed and sets the error message.
action_get Gets the value of an action parameter, or all key/value param pairs
action_name Get the name of the currently executing action.
action_set Sets the values to be returned after the action finishes
action_tag Get the tag for the currently executing action.
action_uuid Get the UUID of the currently executing action.
add_metric Add metric values.
application_name The name of the deployed application this unit belongs to.
application_version_set Charm authors may trigger this command from any hook to output what version of the application is running.
atexit Schedule a callback to run on successful hook completion.
atstart Schedule a callback to run before the main hook.
cached Cache return values for multiple executions of func + args
charm_dir Return the root directory of the current charm
charm_name Get the name of the current charm as is specified on metadata.yaml
close_port Close a service network port
close_ports Close a range of service network ports
config Get the juju charm configuration (scope==None) or individual key, (scope=str).
egress_subnets Retrieve the egress-subnets from a relation.
env_proxy_settings Get proxy settings from process environment variables.
execution_environment A convenient bundling of the current execution context
expected_peer_units Get a generator for units we expect to join peer relation based on goal-state.
expected_related_units Get a generator for units we expect to join relation based on goal-state.
flush Flushes any entries from function cache where the key is found in the function+args
goal_state Juju goal state values
has_juju_version Return True if the Juju version is at least the provided version
hook_name The name of the currently executing hook
in_relation_hook Determine whether we’re running in a relation hook
ingress_address Retrieve the ingress-address from a relation when available.
interface_to_relations Given an interface, return a list of relation names for the current charm that use that interface.
is_leader Does the current unit hold the juju leadership
is_relation_made Determine whether a relation is established by checking for presence of key(s).
iter_units_for_relation_name Iterate through all units in a relation
juju_version Full version string (eg.
leader_get Juju leader get value(s)
leader_set Juju leader set value(s)
local_unit Local unit ID
log Write a message to the juju log
metadata Get the current charm metadata.yaml contents as a python object
meter_info Get the meter status information, if running in the meter-status-changed hook.
meter_status Get the meter status, if running in the meter-status-changed hook.
model_name Name of the model that this unit is deployed in.
model_uuid UUID of the model that this unit is deployed in.
network_get Retrieve the network details for a relation endpoint
network_get_primary_address Deprecated since Juju 2.3; use network_get()
open_port Open a service network port
open_ports Opens a range of service network ports
opened_ports Get the opened ports
payload_register is used while a hook is running to let Juju know that a payload has been started.
payload_status_set is used to update the current status of a registered payload.
payload_unregister is used while a hook is running to let Juju know that a payload has been manually stopped.
peer_relation_id Get the peers relation id if a peers relation has been joined, else None.
principal_unit Returns the principal unit of this unit, otherwise None
related_units A list of related units
relation_clear Clears any relation data already set on relation r_id
relation_for_unit Get the json represenation of a unit’s relation
relation_get Get relation information
relation_id The relation ID for the current or a specified relation
relation_ids A list of relation_ids
relation_set Set relation information for the current unit
relation_to_interface Given the name of a relation, return the interface that relation uses.
relation_to_role_and_interface Given the name of a relation, return the role and the name of the interface that relation uses (where role is one of provides, requires, or peers).
relation_type The scope for the current relation hook
relation_types Get a list of relation types supported by this charm
relations Get a nested dictionary of relation data for all related units
relations_for_id Get relations of a specific relation ID
relations_of_type Get relations of a specific type
remote_service_name The remote service name for a given relation-id (or the current relation)
remote_unit The remote unit for the current relation hook
resource_get used to fetch the resource path of the given name.
role_and_interface_to_relations Given a role and interface name, return a list of relation names for the current charm that use that interface under that role (where role is one of provides, requires, or peers).
service_name

Deprecated since version 0.19.1.

status_get Retrieve the previously set juju workload state and message
status_set Set the workload state with a message
storage_get Get storage attributes
storage_list List the storage IDs for the unit
translate_exc
unit_doomed Determines if the unit is being removed from the model
unit_get Get the unit ID for the remote unit
unit_private_ip Get this unit’s private IP address
unit_public_ip Get this unit’s public IP address

Interactions with the Juju environment

class charmhelpers.core.hookenv.Config(*args, **kw)

Bases: dict

A dictionary representation of the charm’s config.yaml, with some extra features:

  • See which values in the dictionary have changed since the previous hook.
  • For values that have changed, see what the previous value was.
  • Store arbitrary data for use in a later hook.

NOTE: Do not instantiate this object directly - instead call hookenv.config(), which will return an instance of Config.

Example usage:

>>> # inside a hook
>>> from charmhelpers.core import hookenv
>>> config = hookenv.config()
>>> config['foo']
'bar'
>>> # store a new key/value for later use
>>> config['mykey'] = 'myval'


>>> # user runs `juju set mycharm foo=baz`
>>> # now we're inside subsequent config-changed hook
>>> config = hookenv.config()
>>> config['foo']
'baz'
>>> # test to see if this val has changed since last hook
>>> config.changed('foo')
True
>>> # what was the previous value?
>>> config.previous('foo')
'bar'
>>> # keys/values that we add are preserved across hooks
>>> config['mykey']
'myval'
CONFIG_FILE_NAME = '.juju-persistent-config'
changed(key)

Return True if the current value for this key is different from the previous value.

load_previous(path=None)

Load previous copy of config from disk.

In normal usage you don’t need to call this method directly - it is called automatically at object initialization.

Parameters:path – File path from which to load the previous config. If None, config is loaded from the default location. If path is specified, subsequent save() calls will write to the same path.
previous(key)

Return previous value for this key, or None if there is no previous value.

save()

Save this config to disk.

If the charm is using the Services Framework or :meth:’@hook <Hooks.hook>’ decorator, this is called automatically at the end of successful hook execution. Otherwise, it should be called directly by user code.

To disable automatic saves, set implicit_save=False on this instance.

class charmhelpers.core.hookenv.Hooks(config_save=None)

Bases: object

A convenient handler for hook functions.

Example:

hooks = Hooks()

# register a hook, taking its name from the function name
@hooks.hook()
def install():
    pass  # your code here

# register a hook, providing a custom hook name
@hooks.hook("config-changed")
def config_changed():
    pass  # your code here

if __name__ == "__main__":
    # execute a hook based on the name the program is called by
    hooks.execute(sys.argv)
execute(args)

Execute a registered hook based on args[0]

hook(*hook_names)

Decorator, registering them as hooks

register(name, function)

Register a hook

exception charmhelpers.core.hookenv.NoNetworkBinding

Bases: Exception

class charmhelpers.core.hookenv.Serializable(obj)

Bases: collections.UserDict

Wrapper, an object that can be serialized to yaml or json

json()

Serialize the object to json

yaml()

Serialize the object to yaml

exception charmhelpers.core.hookenv.UnregisteredHookError

Bases: Exception

Raised when an undefined hook is called

charmhelpers.core.hookenv.action_fail(message)

Sets the action status to failed and sets the error message.

The results set by action_set are preserved.

charmhelpers.core.hookenv.action_get(key=None)

Gets the value of an action parameter, or all key/value param pairs

charmhelpers.core.hookenv.action_name()

Get the name of the currently executing action.

charmhelpers.core.hookenv.action_set(values)

Sets the values to be returned after the action finishes

charmhelpers.core.hookenv.action_tag()

Get the tag for the currently executing action.

charmhelpers.core.hookenv.action_uuid()

Get the UUID of the currently executing action.

charmhelpers.core.hookenv.add_metric(*args, **kwargs)

Add metric values. Values may be expressed with keyword arguments. For metric names containing dashes, these may be expressed as one or more ‘key=value’ positional arguments. May only be called from the collect-metrics hook.

charmhelpers.core.hookenv.application_name()

The name of the deployed application this unit belongs to.

charmhelpers.core.hookenv.application_version_set(version)

Charm authors may trigger this command from any hook to output what version of the application is running. This could be a package version, for instance postgres version 9.5. It could also be a build number or version control revision identifier, for instance git sha 6fb7ba68.

charmhelpers.core.hookenv.atexit(callback, *args, **kwargs)

Schedule a callback to run on successful hook completion.

Callbacks are run in the reverse order that they were added.

charmhelpers.core.hookenv.atstart(callback, *args, **kwargs)

Schedule a callback to run before the main hook.

Callbacks are run in the order they were added.

This is useful for modules and classes to perform initialization and inject behavior. In particular:

  • Run common code before all of your hooks, such as logging the hook name or interesting relation data.
  • Defer object or module initialization that requires a hook context until we know there actually is a hook context, making testing easier.
  • Rather than requiring charm authors to include boilerplate to invoke your helper’s behavior, have it run automatically if your object is instantiated or module imported.

This is not at all useful after your hook framework as been launched.

charmhelpers.core.hookenv.cached(func)

Cache return values for multiple executions of func + args

For example:

@cached
def unit_get(attribute):
    pass

unit_get('test')

will cache the result of unit_get + ‘test’ for future calls.

charmhelpers.core.hookenv.charm_dir()

Return the root directory of the current charm

charmhelpers.core.hookenv.charm_name()

Get the name of the current charm as is specified on metadata.yaml

charmhelpers.core.hookenv.close_port(port, protocol='TCP')

Close a service network port

charmhelpers.core.hookenv.close_ports(start, end, protocol='TCP')

Close a range of service network ports

charmhelpers.core.hookenv.config(scope=None)

Get the juju charm configuration (scope==None) or individual key, (scope=str). The returned value is a Python data structure loaded as JSON from the Juju config command.

Parameters:scope (Optional[str]) – If set, return the value for the specified key.
Returns:Either the whole config as a Config, or a key from it.
Return type:Any
charmhelpers.core.hookenv.egress_subnets(rid=None, unit=None)

Retrieve the egress-subnets from a relation.

This function is to be used on the providing side of the relation, and provides the ranges of addresses that client connections may come from. The result is uninteresting on the consuming side of a relation (unit == local_unit()).

Returns a stable list of subnets in CIDR format. eg. [‘192.168.1.0/24’, ‘2001::F00F/128’]

If egress-subnets is not available, falls back to using the published ingress-address, or finally private-address.

Parameters:
  • rid – string relation id
  • unit – string unit name
Side effect:

calls relation_get

Returns:

list of subnets in CIDR format. eg. [‘192.168.1.0/24’, ‘2001::F00F/128’]

charmhelpers.core.hookenv.env_proxy_settings(selected_settings=None)

Get proxy settings from process environment variables.

Get charm proxy settings from environment variables that correspond to juju-http-proxy, juju-https-proxy and juju-no-proxy (available as of 2.4.2, see lp:1782236) in a format suitable for passing to an application that reacts to proxy settings passed as environment variables. Some applications support lowercase or uppercase notation (e.g. curl), some support only lowercase (e.g. wget), there are also subjectively rare cases of only uppercase notation support. no_proxy CIDR and wildcard support also varies between runtimes and applications as there is no enforced standard.

Some applications may connect to multiple destinations and expose config options that would affect only proxy settings for a specific destination these should be handled in charms in an application-specific manner.

Parameters:selected_settings (list) – format only a subset of possible settings
Return type:Option(None, dict[str, str])
charmhelpers.core.hookenv.execution_environment()

A convenient bundling of the current execution context

charmhelpers.core.hookenv.expected_peer_units()

Get a generator for units we expect to join peer relation based on goal-state.

The local unit is excluded from the result to make it easy to gauge completion of all peers joining the relation with existing hook tools.

Example usage: log(‘peer {} of {} joined peer relation’

.format(len(related_units()),
len(list(expected_peer_units()))))

This function will raise NotImplementedError if used with juju versions without goal-state support.

Returns:iterator
Return type:types.GeneratorType
Raises:NotImplementedError

Get a generator for units we expect to join relation based on goal-state.

Note that you can not use this function for the peer relation, take a look at expected_peer_units() for that.

This function will raise KeyError if you request information for a relation type for which juju goal-state does not have information. It will raise NotImplementedError if used with juju versions without goal-state support.

Example usage: log(‘participant {} of {} joined relation {}’

.format(len(related_units()),
len(list(expected_related_units())), relation_type()))
Parameters:reltype (str) – Relation type to list data for, default is to list data for the realtion type we are currently executing a hook for.
Returns:iterator
Return type:types.GeneratorType
Raises:KeyError, NotImplementedError
charmhelpers.core.hookenv.flush(key)

Flushes any entries from function cache where the key is found in the function+args

charmhelpers.core.hookenv.goal_state()

Juju goal state values

charmhelpers.core.hookenv.has_juju_version(minimum_version)

Return True if the Juju version is at least the provided version

charmhelpers.core.hookenv.hook_name()

The name of the currently executing hook

charmhelpers.core.hookenv.in_relation_hook()

Determine whether we’re running in a relation hook

charmhelpers.core.hookenv.ingress_address(rid=None, unit=None)

Retrieve the ingress-address from a relation when available. Otherwise, return the private-address.

When used on the consuming side of the relation (unit is a remote unit), the ingress-address is the IP address that this unit needs to use to reach the provided service on the remote unit.

When used on the providing side of the relation (unit == local_unit()), the ingress-address is the IP address that is advertised to remote units on this relation. Remote units need to use this address to reach the local provided service on this unit.

Note that charms may document some other method to use in preference to the ingress_address(), such as an address provided on a different relation attribute or a service discovery mechanism. This allows charms to redirect inbound connections to their peers or different applications such as load balancers.

Usage: addresses = [ingress_address(rid=u.rid, unit=u.unit)

for u in iter_units_for_relation_name(relation_name)]
Parameters:
  • rid – string relation id
  • unit – string unit name
Side effect:

calls relation_get

Returns:

string IP address

charmhelpers.core.hookenv.interface_to_relations(interface_name)

Given an interface, return a list of relation names for the current charm that use that interface.

Returns:A list of relation names.
charmhelpers.core.hookenv.is_leader()

Does the current unit hold the juju leadership

Uses juju to determine whether the current unit is the leader of its peers

charmhelpers.core.hookenv.is_relation_made(relation, keys='private-address')

Determine whether a relation is established by checking for presence of key(s). If a list of keys is provided, they must all be present for the relation to be identified as made

charmhelpers.core.hookenv.iter_units_for_relation_name(relation_name)

Iterate through all units in a relation

Generator that iterates through all the units in a relation and yields a named tuple with rid and unit field names.

Usage: data = [(u.rid, u.unit)

for u in iter_units_for_relation_name(relation_name)]
Parameters:relation_name – string relation name
Yield:Named Tuple with rid and unit field names
charmhelpers.core.hookenv.juju_version()

Full version string (eg. ‘1.23.3.1-trusty-amd64’)

charmhelpers.core.hookenv.leader_get(attribute=None)

Juju leader get value(s)

charmhelpers.core.hookenv.leader_set(settings=None, **kwargs)

Juju leader set value(s)

charmhelpers.core.hookenv.local_unit()

Local unit ID

charmhelpers.core.hookenv.log(message, level=None)

Write a message to the juju log

charmhelpers.core.hookenv.metadata()

Get the current charm metadata.yaml contents as a python object

charmhelpers.core.hookenv.meter_info()

Get the meter status information, if running in the meter-status-changed hook.

charmhelpers.core.hookenv.meter_status()

Get the meter status, if running in the meter-status-changed hook.

charmhelpers.core.hookenv.model_name()

Name of the model that this unit is deployed in.

charmhelpers.core.hookenv.model_uuid()

UUID of the model that this unit is deployed in.

charmhelpers.core.hookenv.network_get(endpoint, relation_id=None)

Retrieve the network details for a relation endpoint

Parameters:
  • endpoint – string. The name of a relation endpoint
  • relation_id – int. The ID of the relation for the current context.
Returns:

dict. The loaded YAML output of the network-get query.

Raise:

NotImplementedError if request not supported by the Juju version.

charmhelpers.core.hookenv.network_get_primary_address(binding)

Deprecated since Juju 2.3; use network_get()

Retrieve the primary network address for a named binding

Parameters:binding – string. The name of a relation of extra-binding
Returns:string. The primary IP address for the named binding
Raise:NotImplementedError if run on Juju < 2.0
charmhelpers.core.hookenv.open_port(port, protocol='TCP')

Open a service network port

charmhelpers.core.hookenv.open_ports(start, end, protocol='TCP')

Opens a range of service network ports

charmhelpers.core.hookenv.opened_ports()

Get the opened ports

Note that this will only show ports opened in a previous hook

Returns:Opened ports as a list of strings: ['8080/tcp', '8081-8083/tcp']
charmhelpers.core.hookenv.payload_register(ptype, klass, pid)

is used while a hook is running to let Juju know that a payload has been started.

charmhelpers.core.hookenv.payload_status_set(klass, pid, status)

is used to update the current status of a registered payload. The <class> and <id> provided must match a payload that has been previously registered with juju using payload-register. The <status> must be one of the follow: starting, started, stopping, stopped

charmhelpers.core.hookenv.payload_unregister(klass, pid)

is used while a hook is running to let Juju know that a payload has been manually stopped. The <class> and <id> provided must match a payload that has been previously registered with juju using payload-register.

charmhelpers.core.hookenv.peer_relation_id()

Get the peers relation id if a peers relation has been joined, else None.

charmhelpers.core.hookenv.principal_unit()

Returns the principal unit of this unit, otherwise None

charmhelpers.core.hookenv.related_units(relid=None)

A list of related units

charmhelpers.core.hookenv.relation_clear(r_id=None)

Clears any relation data already set on relation r_id

charmhelpers.core.hookenv.relation_for_unit(unit=None, rid=None)

Get the json represenation of a unit’s relation

charmhelpers.core.hookenv.relation_get(attribute=None, unit=None, rid=None)

Get relation information

charmhelpers.core.hookenv.relation_id(relation_name=None, service_or_unit=None)

The relation ID for the current or a specified relation

charmhelpers.core.hookenv.relation_ids(reltype=None)

A list of relation_ids

charmhelpers.core.hookenv.relation_set(relation_id=None, relation_settings=None, **kwargs)

Set relation information for the current unit

charmhelpers.core.hookenv.relation_to_interface(relation_name)

Given the name of a relation, return the interface that relation uses.

Returns:The interface name, or None.
charmhelpers.core.hookenv.relation_to_role_and_interface(relation_name)

Given the name of a relation, return the role and the name of the interface that relation uses (where role is one of provides, requires, or peers).

Returns:A tuple containing (role, interface), or (None, None).
charmhelpers.core.hookenv.relation_type()

The scope for the current relation hook

charmhelpers.core.hookenv.relation_types()

Get a list of relation types supported by this charm

charmhelpers.core.hookenv.relations()

Get a nested dictionary of relation data for all related units

charmhelpers.core.hookenv.relations_for_id(relid=None)

Get relations of a specific relation ID

charmhelpers.core.hookenv.relations_of_type(reltype=None)

Get relations of a specific type

charmhelpers.core.hookenv.remote_service_name(relid=None)

The remote service name for a given relation-id (or the current relation)

charmhelpers.core.hookenv.remote_unit()

The remote unit for the current relation hook

charmhelpers.core.hookenv.resource_get(name)

used to fetch the resource path of the given name.

<name> must match a name of defined resource in metadata.yaml

returns either a path or False if resource not available

charmhelpers.core.hookenv.role_and_interface_to_relations(role, interface_name)

Given a role and interface name, return a list of relation names for the current charm that use that interface under that role (where role is one of provides, requires, or peers).

Returns:A list of relation names.
charmhelpers.core.hookenv.service_name()

Deprecated since version 0.19.1: Alias for application_name().

charmhelpers.core.hookenv.status_get()

Retrieve the previously set juju workload state and message

If the status-get command is not found then assume this is juju < 1.23 and return ‘unknown’, “”

charmhelpers.core.hookenv.status_set(workload_state, message)

Set the workload state with a message

Use status-set to set the workload state with a message which is visible to the user via juju status. If the status-set command is not found then assume this is juju < 1.23 and juju-log the message unstead.

workload_state – valid juju workload state. message – status update message

charmhelpers.core.hookenv.storage_get(attribute=None, storage_id=None)

Get storage attributes

charmhelpers.core.hookenv.storage_list(storage_name=None)

List the storage IDs for the unit

charmhelpers.core.hookenv.translate_exc(from_exc, to_exc)
charmhelpers.core.hookenv.unit_doomed(unit=None)

Determines if the unit is being removed from the model

Requires Juju 2.4.1.

Parameters:unit – string unit name, defaults to local_unit
Side effect:calls goal_state
Side effect:calls local_unit
Side effect:calls has_juju_version
Returns:True if the unit is being removed, already gone, or never existed
charmhelpers.core.hookenv.unit_get(attribute)

Get the unit ID for the remote unit

charmhelpers.core.hookenv.unit_private_ip()

Get this unit’s private IP address

charmhelpers.core.hookenv.unit_public_ip()

Get this unit’s public IP address