Poise-Service Cookbook
A Chef cookbook to provide a unified interface for services.
What is poise-service?
Poise-service is a tool for developers of "library cookbooks" to define a
service without forcing the end-user of the library to adhere to their choice of
service management framework. The poise_service
resource represents an
abstract service to be run, which can then be customized by node attributes and
the poise_service_options
resource. This is a technique called dependency
injection, and allows a
measure of decoupling between the library and application cookbooks.
Why would I use poise-service?
Poise-service is most useful for authors of library-style cookbooks, for example
the apache2
, mysql
, or application
cookbooks. When using other service
management options with Chef, the author of the library cookbook has to add
specific code for each service management framework they want to support, often
resulting in a cookbook only supporting the favorite framework of the author or
depending on distribution packages for their init scripts. The poise_service
resource allows library cookbook authors a way to write generic code for all
service management frameworks while still allowing users of that cookbook to
choose which service management framework best fits their needs.
How is this different from the built-in service resource?
Chef includes a service
resource which allows interacting with certain
service management frameworks such as SysV, Upstart, and systemd.
poise-service
goes further in that it actually generates the configuration
files needed for the requested service management framework, as well as offering
a dependency injection system for application cookbooks to customize which
framework is used.
What service management frameworks are supported?
Quick Start
To create a service user and a service to run Apache2:
poise_service_user 'www-data'
poise_service 'apache2' do
command '/usr/sbin/apache2 -f /etc/apache2/apache2.conf -DFOREGROUND'
stop_signal 'WINCH'
reload_signal 'USR1'
end
or for a hypothetical Rails web application:
poise_service_user 'myapp'
poise_service 'myapp-web' do
command 'bundle exec unicorn -p 8080'
user 'myapp'
directory '/srv/myapp'
environment RAILS_ENV: 'production'
end
Resources
poise_service
The poise_service
resource is the abstract definition of a service.
poise_service 'myapp' do
command 'myapp --serve'
environment RAILS_ENV: 'production'
end
Actions
-
:enable
– Create, enable and start the service. (default) -
:disable
– Stop, disable, and destroy the service. -
:start
– Start the service. -
:stop
– Stop the service. -
:restart
– Stop and then start the service. -
:reload
– Send the configured reload signal to the service.
Attributes
-
service_name
– Name of the service. (name attribute) -
command
– Command to run for the service. This command must stay in the foreground and not daemonize itself. (required) -
user
– User to run the service as. Seepoise_service_user
for any easy way to create service users. (default: root) -
directory
– Working directory for the service. (default: home directory for user, or / if not found) -
environment
– Environment variables for the service. -
stop_signal
– Signal to use to stop the service. Some systems will fall back to SIGKILL if this signal fails to stop the process. (default: TERM) -
reload_signal
– Signal to use to reload the service. (default: HUP) -
restart_on_update
– If true, the service will be restarted if the service definition or configuration changes. If'immediately'
, the notification will happen in immediate mode. (default: true)
Service Options
The poise-service
library offers an additional way to pass configuration
information to the final service called "options". Options are key/value pairs
that are passed down to the service provider and can be used to control how it
creates and manages the service. These can be set in the poise_service
resource using the options
method, in node attributes or via the
poise_service_options
resource. The options from all sources are merged
together in to a single hash.
When setting options in the resource you can either set them for all providers:
poise_service 'myapp' do
command 'myapp --serve'
options status_port: 8000
end
or for a single provider:
poise_service 'myapp' do
command 'myapp --serve'
options :systemd, after_target: 'network'
end
Setting via node attributes is generally how an end-user or application cookbook will set options to customize services in the library cookbooks they are using. You can set options for all services or for a single service, by service name or by resource name:
# Global, for all services.
override['poise-service']['options']['after_target'] = 'network'
# Single service.
override['poise-service']['myapp']['template'] = 'myapp.erb'
The poise_service_options
resource is also available to set node attributes
for a specific service in a DSL-friendly way:
poise_service_options 'myapp' do
template 'myapp.erb'
restart_on_update false
end
Unlike resource attributes, service options can be different for each provider. Not all providers support the same options so make sure to check the documentation for each provider to see what options are available.
poise_service_options
The poise_service_options
resource allows setting per-service options in a
DSL-friendly way. See the Service Options section for more
information about service options overall.
poise_service_options 'myapp' do
template 'myapp.erb'
restart_on_update false
end
Actions
-
:run
– Apply the service options. (default)
Attributes
-
resource
– Name of the service. (name attribute) -
for_provider
– Provider to set options for.
All other attribute keys will be used as options data.
poise_service_user
The poise_service_user
resource is an easy way to create service users. It is
not required to use poise_service
, it is only a helper.
poise_service_user 'myapp' do
home '/srv/myapp'
end
Actions
-
:create
– Create the user and group. (default) -
:remove
– Remove the user and group.
Attributes
-
user
– Name of the user. (name attribute) -
group
– Name of the group. Set tofalse
to disable group creation. (name attribute) -
uid
– UID of the user. (default: automatic) -
gid
– GID of the group. (default: automatic) -
home
– Home directory of the user. -
shell
– Shell of the user. (default: /bin/nologin if present or /bin/false)
Providers
sysvinit
The sysvinit
provider supports SystemV-style init systems on Debian-family and
RHEL-family platforms. It will create the /etc/init.d/<service_name>
script
and enable/disable the service using the platform-specific service resource.
poise_service 'myapp' do
provider :sysvinit
command 'myapp --serve'
end
By default a PID file will be created in /var/run/service_name.pid
. You can
use the pid_file
option detailed below to override this and rely on your
process creating a PID file in the given path.
Options
-
pid_file
– Path to PID file that the service command will create. -
pid_file_external
– If true, assume the service will create the PID file itself. (default: true ifpid_file
option is set) -
template
– Override the default script template. If you want to use a template in a different cookbook use'cookbook:template'
. -
command
– Override the service command. -
directory
– Override the service directory. -
environment
– Override the service environment variables. -
reload_signal
– Override the service reload signal. -
stop_signal
– Override the service stop signal. -
user
– Override the service user. -
never_start
– Never try to start the service. -
never_stop
– Never try to stop the service. -
never_restart
– Never try to restart the service. -
never_reload
– Never try to reload the service. -
script_path
– Override the path to the generated service script.
upstart
The upstart
provider supports Upstart. It will
create the /etc/init/service_name.conf
configuration.
poise_service 'myapp' do
provider :upstart
command 'myapp --serve'
end
As a wide variety of versions of Upstart are in use in various Linux
distributions, the provider does its best to identify which features are
available and provide shims as appropriate. Most of these should be invisible
however Upstart older than 1.10 does not support setting a reload signal
so
only SIGHUP can be used. You can set a reload_shim
option to enable an
internal implementaion of reloading to be used for signals other than SIGHUP,
however as this is implemented inside Chef code, running initctl reload
would
still result in SIGHUP being sent. For this reason, the feature is disabled by
default and will throw an error if a reload signal other than SIGHUP is used.
Options
-
reload_shim
– Enable the reload signal shim. See above for a warning about this feature. -
template
– Override the default configuration template. If you want to use a template in a different cookbook use'cookbook:template'
. -
command
– Override the service command. -
directory
– Override the service directory. -
environment
– Override the service environment variables. -
reload_signal
– Override the service reload signal. -
stop_signal
– Override the service stop signal. -
user
– Override the service user. -
never_start
– Never try to start the service. -
never_stop
– Never try to stop the service. -
never_restart
– Never try to restart the service. -
never_reload
– Never try to reload the service.
systemd
The systemd
provider supports systemd.
It will create the /etc/systemd/system/service_name.service
configuration.
poise_service 'myapp' do
provider :systemd
command 'myapp --serve'
end
Options
-
template
– Override the default configuration template. If you want to use a template in a different cookbook use'cookbook:template'
. -
command
– Override the service command. -
directory
– Override the service directory. -
environment
– Override the service environment variables. -
reload_signal
– Override the service reload signal. -
stop_signal
– Override the service stop signal. -
user
– Override the service user. -
never_start
– Never try to start the service. -
never_stop
– Never try to stop the service. -
never_restart
– Never try to restart the service. -
never_reload
– Never try to reload the service. -
auto_reload
– Runsystemctl daemon-reload
after changes to the unit file. (default: true) -
restart_mode
– Restart mode for the generated service unit. (default: on-failure)
inittab
The inittab
provider supports managing services via /etc/inittab
using
SystemV Init. This can provide basic
process supervision even on very old *nix machines.
poise_service 'myapp' do
provider :inittab
command 'myapp --serve'
end
NOTE: Inittab does not allow stopping services, and they are started as soon as they are enabled.
Options
-
never_start
– Never try to start the service. -
never_stop
– Never try to stop the service. -
never_restart
– Never try to restart the service. -
never_reload
– Never try to reload the service. -
pid_file
– Path to PID file that the service command will create. -
service_id
– Unique 1-4 character tag for the service. Defaults to an auto-generated hash based on the service name. If these collide, bad things happen. Don't do that.
dummy
The dummy
provider supports launching services directly from Chef itself.
This is for testing purposes only and is entirely unsuitable for use in
production. This is mostly useful when used alongside kitchen-docker.
poise_service 'myapp' do
provider :dummy
command 'myapp --serve'
end
The service information is written to /var/run
. The PID file is service_name.pid
,
the command output is service_name.out
, and the service parameters are in
service_name.json
.
Options
-
never_start
– Never try to start the service. -
never_stop
– Never try to stop the service. -
never_restart
– Never try to restart the service. -
never_reload
– Never try to reload the service. -
restart_delay
– Number of seconds to wait between stop and start when restarting. (default: 1)
ServiceMixin
For the common case of a resource (LWRP or plain Ruby) that roughly maps to
"some config files and a service" poise-service provides a mixin module,
PoiseService::ServiceMixin
. This mixin adds the standard service actions
(enable
, disable
, start
, stop
, restart
, and reload
) with basic
implementations that call those actions on a poise_service
resource for you.
You customize the service by defining a service_options
method on your
provider class:
def service_options(service)
# service is the PoiseService::Resource object instance.
service.command "/usr/sbin/#{new_resource.name} -f /etc/#{new_resource.name}/conf/httpd.conf -DFOREGROUND"
service.stop_signal 'WINCH'
service.reload_signal 'USR1'
end
You will generally want to override the enable
action to install things
related to the service like packages, users and configuration files:
def action_enable
notifying_block do
package 'apache2'
poise_service_user 'www-data'
template "/etc/#{new_resource.name}/conf/httpd.conf" do
# ...
end
end
# This super call will run the normal service enable,
# creating the service and starting it.
super
end
See the poise_service_test_mixin resource
and provider for
examples of using ServiceMixin
in an LWRP.
Sponsors
Development sponsored by Bloomberg.
The Poise test server infrastructure is sponsored by Rackspace.
License
Copyright 2015-2016, Noah Kantrowitz
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.