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Diffstat (limited to 'contrail-kubernetes/hooks/charmhelpers/core/services/base.py')
| -rw-r--r-- | contrail-kubernetes/hooks/charmhelpers/core/services/base.py | 351 |
1 files changed, 351 insertions, 0 deletions
diff --git a/contrail-kubernetes/hooks/charmhelpers/core/services/base.py b/contrail-kubernetes/hooks/charmhelpers/core/services/base.py new file mode 100644 index 0000000..ca9dc99 --- /dev/null +++ b/contrail-kubernetes/hooks/charmhelpers/core/services/base.py @@ -0,0 +1,351 @@ +# Copyright 2014-2015 Canonical Limited. +# +# Licensed under the Apache License, Version 2.0 (the "License"); +# you may not use this file except in compliance with the License. +# You may obtain a copy of the License at +# +# http://www.apache.org/licenses/LICENSE-2.0 +# +# Unless required by applicable law or agreed to in writing, software +# distributed under the License is distributed on an "AS IS" BASIS, +# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. +# See the License for the specific language governing permissions and +# limitations under the License. + +import os +import json +from inspect import getargspec +from collections import Iterable, OrderedDict + +from charmhelpers.core import host +from charmhelpers.core import hookenv + + +__all__ = ['ServiceManager', 'ManagerCallback', + 'PortManagerCallback', 'open_ports', 'close_ports', 'manage_ports', + 'service_restart', 'service_stop'] + + +class ServiceManager(object): + def __init__(self, services=None): + """ + Register a list of services, given their definitions. + + Service definitions are dicts in the following formats (all keys except + 'service' are optional):: + + { + "service": <service name>, + "required_data": <list of required data contexts>, + "provided_data": <list of provided data contexts>, + "data_ready": <one or more callbacks>, + "data_lost": <one or more callbacks>, + "start": <one or more callbacks>, + "stop": <one or more callbacks>, + "ports": <list of ports to manage>, + } + + The 'required_data' list should contain dicts of required data (or + dependency managers that act like dicts and know how to collect the data). + Only when all items in the 'required_data' list are populated are the list + of 'data_ready' and 'start' callbacks executed. See `is_ready()` for more + information. + + The 'provided_data' list should contain relation data providers, most likely + a subclass of :class:`charmhelpers.core.services.helpers.RelationContext`, + that will indicate a set of data to set on a given relation. + + The 'data_ready' value should be either a single callback, or a list of + callbacks, to be called when all items in 'required_data' pass `is_ready()`. + Each callback will be called with the service name as the only parameter. + After all of the 'data_ready' callbacks are called, the 'start' callbacks + are fired. + + The 'data_lost' value should be either a single callback, or a list of + callbacks, to be called when a 'required_data' item no longer passes + `is_ready()`. Each callback will be called with the service name as the + only parameter. After all of the 'data_lost' callbacks are called, + the 'stop' callbacks are fired. + + The 'start' value should be either a single callback, or a list of + callbacks, to be called when starting the service, after the 'data_ready' + callbacks are complete. Each callback will be called with the service + name as the only parameter. This defaults to + `[host.service_start, services.open_ports]`. + + The 'stop' value should be either a single callback, or a list of + callbacks, to be called when stopping the service. If the service is + being stopped because it no longer has all of its 'required_data', this + will be called after all of the 'data_lost' callbacks are complete. + Each callback will be called with the service name as the only parameter. + This defaults to `[services.close_ports, host.service_stop]`. + + The 'ports' value should be a list of ports to manage. The default + 'start' handler will open the ports after the service is started, + and the default 'stop' handler will close the ports prior to stopping + the service. + + + Examples: + + The following registers an Upstart service called bingod that depends on + a mongodb relation and which runs a custom `db_migrate` function prior to + restarting the service, and a Runit service called spadesd:: + + manager = services.ServiceManager([ + { + 'service': 'bingod', + 'ports': [80, 443], + 'required_data': [MongoRelation(), config(), {'my': 'data'}], + 'data_ready': [ + services.template(source='bingod.conf'), + services.template(source='bingod.ini', + target='/etc/bingod.ini', + owner='bingo', perms=0400), + ], + }, + { + 'service': 'spadesd', + 'data_ready': services.template(source='spadesd_run.j2', + target='/etc/sv/spadesd/run', + perms=0555), + 'start': runit_start, + 'stop': runit_stop, + }, + ]) + manager.manage() + """ + self._ready_file = os.path.join(hookenv.charm_dir(), 'READY-SERVICES.json') + self._ready = None + self.services = OrderedDict() + for service in services or []: + service_name = service['service'] + self.services[service_name] = service + + def manage(self): + """ + Handle the current hook by doing The Right Thing with the registered services. + """ + hookenv._run_atstart() + try: + hook_name = hookenv.hook_name() + if hook_name == 'stop': + self.stop_services() + else: + self.reconfigure_services() + self.provide_data() + except SystemExit as x: + if x.code is None or x.code == 0: + hookenv._run_atexit() + hookenv._run_atexit() + + def provide_data(self): + """ + Set the relation data for each provider in the ``provided_data`` list. + + A provider must have a `name` attribute, which indicates which relation + to set data on, and a `provide_data()` method, which returns a dict of + data to set. + + The `provide_data()` method can optionally accept two parameters: + + * ``remote_service`` The name of the remote service that the data will + be provided to. The `provide_data()` method will be called once + for each connected service (not unit). This allows the method to + tailor its data to the given service. + * ``service_ready`` Whether or not the service definition had all of + its requirements met, and thus the ``data_ready`` callbacks run. + + Note that the ``provided_data`` methods are now called **after** the + ``data_ready`` callbacks are run. This gives the ``data_ready`` callbacks + a chance to generate any data necessary for the providing to the remote + services. + """ + for service_name, service in self.services.items(): + service_ready = self.is_ready(service_name) + for provider in service.get('provided_data', []): + for relid in hookenv.relation_ids(provider.name): + units = hookenv.related_units(relid) + if not units: + continue + remote_service = units[0].split('/')[0] + argspec = getargspec(provider.provide_data) + if len(argspec.args) > 1: + data = provider.provide_data(remote_service, service_ready) + else: + data = provider.provide_data() + if data: + hookenv.relation_set(relid, data) + + def reconfigure_services(self, *service_names): + """ + Update all files for one or more registered services, and, + if ready, optionally restart them. + + If no service names are given, reconfigures all registered services. + """ + for service_name in service_names or self.services.keys(): + if self.is_ready(service_name): + self.fire_event('data_ready', service_name) + self.fire_event('start', service_name, default=[ + service_restart, + manage_ports]) + self.save_ready(service_name) + else: + if self.was_ready(service_name): + self.fire_event('data_lost', service_name) + self.fire_event('stop', service_name, default=[ + manage_ports, + service_stop]) + self.save_lost(service_name) + + def stop_services(self, *service_names): + """ + Stop one or more registered services, by name. + + If no service names are given, stops all registered services. + """ + for service_name in service_names or self.services.keys(): + self.fire_event('stop', service_name, default=[ + manage_ports, + service_stop]) + + def get_service(self, service_name): + """ + Given the name of a registered service, return its service definition. + """ + service = self.services.get(service_name) + if not service: + raise KeyError('Service not registered: %s' % service_name) + return service + + def fire_event(self, event_name, service_name, default=None): + """ + Fire a data_ready, data_lost, start, or stop event on a given service. + """ + service = self.get_service(service_name) + callbacks = service.get(event_name, default) + if not callbacks: + return + if not isinstance(callbacks, Iterable): + callbacks = [callbacks] + for callback in callbacks: + if isinstance(callback, ManagerCallback): + callback(self, service_name, event_name) + else: + callback(service_name) + + def is_ready(self, service_name): + """ + Determine if a registered service is ready, by checking its 'required_data'. + + A 'required_data' item can be any mapping type, and is considered ready + if `bool(item)` evaluates as True. + """ + service = self.get_service(service_name) + reqs = service.get('required_data', []) + return all(bool(req) for req in reqs) + + def _load_ready_file(self): + if self._ready is not None: + return + if os.path.exists(self._ready_file): + with open(self._ready_file) as fp: + self._ready = set(json.load(fp)) + else: + self._ready = set() + + def _save_ready_file(self): + if self._ready is None: + return + with open(self._ready_file, 'w') as fp: + json.dump(list(self._ready), fp) + + def save_ready(self, service_name): + """ + Save an indicator that the given service is now data_ready. + """ + self._load_ready_file() + self._ready.add(service_name) + self._save_ready_file() + + def save_lost(self, service_name): + """ + Save an indicator that the given service is no longer data_ready. + """ + self._load_ready_file() + self._ready.discard(service_name) + self._save_ready_file() + + def was_ready(self, service_name): + """ + Determine if the given service was previously data_ready. + """ + self._load_ready_file() + return service_name in self._ready + + +class ManagerCallback(object): + """ + Special case of a callback that takes the `ServiceManager` instance + in addition to the service name. + + Subclasses should implement `__call__` which should accept three parameters: + + * `manager` The `ServiceManager` instance + * `service_name` The name of the service it's being triggered for + * `event_name` The name of the event that this callback is handling + """ + def __call__(self, manager, service_name, event_name): + raise NotImplementedError() + + +class PortManagerCallback(ManagerCallback): + """ + Callback class that will open or close ports, for use as either + a start or stop action. + """ + def __call__(self, manager, service_name, event_name): + service = manager.get_service(service_name) + new_ports = service.get('ports', []) + port_file = os.path.join(hookenv.charm_dir(), '.{}.ports'.format(service_name)) + if os.path.exists(port_file): + with open(port_file) as fp: + old_ports = fp.read().split(',') + for old_port in old_ports: + if bool(old_port): + old_port = int(old_port) + if old_port not in new_ports: + hookenv.close_port(old_port) + with open(port_file, 'w') as fp: + fp.write(','.join(str(port) for port in new_ports)) + for port in new_ports: + if event_name == 'start': + hookenv.open_port(port) + elif event_name == 'stop': + hookenv.close_port(port) + + +def service_stop(service_name): + """ + Wrapper around host.service_stop to prevent spurious "unknown service" + messages in the logs. + """ + if host.service_running(service_name): + host.service_stop(service_name) + + +def service_restart(service_name): + """ + Wrapper around host.service_restart to prevent spurious "unknown service" + messages in the logs. + """ + if host.service_available(service_name): + if host.service_running(service_name): + host.service_restart(service_name) + else: + host.service_start(service_name) + + +# Convenience aliases +open_ports = close_ports = manage_ports = PortManagerCallback() |