Minimizar los reinicios del servicio de las notificaciones del chef?
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26-12-2019 - |
Pregunta
Actualmente mi receta con atributos que importan están estructurados de esta manera:
service 'myservice' do
action :nothing
supports :status => true, :start => true, :stop => true, :restart => true
end
package 'packagename' do
...
end
template 'configfile1'
notifies :restart, 'service[myservice]'
end
...
template 'configfileN'
notifies :restart, 'service[myservice]'
end
execute "a command from package which generates and enables the init script" do
notifies :start, 'service[myservice]', :immediately
end
execute "a command that should run once every time, that requires service to be running"
Al hacer esto, nos aseguramos de que el inicio inicial del servicio tenga los archivos de configuración, durante cada ejecución, el servicio se está ejecutando para el segundo bloque de ejecución, y si algún archivo de configuración cambia, reiniciamos el servicio para recoger los cambios. .
Sin embargo, si se produce un chef ejecutado cuando se detiene el estado inicial del servicio, (como la primera ejecución o si sucedió algo malo), y los archivos de configuración han cambiado (especialmente en la primera ejecución, pero posible para otros RUNS), el primer bloque de ejecución hará que el servicio comience con los archivos de configuración correctos que ya están en su lugar, luego al final de la ejecución, el servicio se reiniciará innecesariamente. (Asumir, por supuesto, los recursos después del inicio inicial no causan un reinicio del servicio)
Cambiar la acción objetivo de las notificaciones no parece funcionar (ya que las notificaciones inmediatas seguirán ocurriendo de inmediato, las notificaciones retrasadas aún sucedieron), y además no serían correctas.
Además, no podemos suscribir el 2º Ejecuto al inicio del servicio, ya que si ya está funcionando, terminaríamos no lo ejecutamos.
Es muy exigente, pero ¿hay un mejor patrón que pueda seguirse para minimizar los reinicios de un servicio para la ejecución inicial? ¿O un mecanismo para cancelar notificaciones retrasadas cuando se toma una acción en particular?
Solución
Usé un archivo de bandera para lograr esto.
Como a continuación "Apt-Get Actuald" no se ejecuta una vez.
cookbook_file '/etc/apt/sources.list.d/maven.list' do
source "repo_files/ubuntu_maven.list"
cookbook "fluig-files"
mode 0644
notifies :run, "execute[should_update_repo]", :immediately
end
cookbook_file '/etc/apt/sources.list.d/couchbase.list' do
source "repo_files/ubuntu_couchbase.list"
cookbook "fluig-files"
mode 0644
notifies :run, "execute[should_update_repo]", :immediately
end
execute "apt-key couchbase" do
command "apt-key adv --keyserver keyserver.ubuntu.com --recv-keys A3FAA648D9223EDA"
action :run
not_if "apt-key list | grep couchbase"
notifies :run, "execute[should_update_repo]", :immediately
end
execute "should_update_repo" do
command "touch /tmp/should_update_repo"
action :nothing
end
# Update system
execute "apt-get update" do
command "rm -rf /tmp/should_update_repo && apt-get update"
action :run
only_if "test -f /tmp/should_update_repo"
end
Otros consejos
Chef is designed to express configuration policy (system state), which is a slightly different thing than expressing a sequence of tasks to perform.
Fortunately since the DSL is ruby-based, resources can be redefined at runtime.
template "configfile1" do
notifies :create, "ruby_block[restart_service1]", :immediately
end
template "configfile2" do
notifies :create, "ruby_block[restart_service1]", :immediately
end
service "service1" do
action [:enable, :start]
end
ruby_block "restart_service1" do
block do
r = resources(:service => "service1")
a = Array.new(r.action)
a << :restart unless a.include?(:restart)
a.delete(:start) if a.include?(:restart)
r.action(a)
end
action :nothing
end
This will rewrite the service resource to have "action [:enable, :restart]" instead of "action [:enable, :start]", if any of the template resources change state this run. So the ordering stays the same, and you only get one call through the service resource, instead of potentially three.
I am not sure, if will solve your problems with restarting the service too many times, but this structure seems more logical to me.
#Prepare everything to start the service
package 'packagename' do
...
end
template 'configfile1'
notifies :restart, 'service[myservice]'
end
...
template 'configfileN'
notifies :restart, 'service[myservice]'
end
execute "a command from package which generates and enables the init script" do
notifies :restart, 'service[myservice]'
end
#Start the service
service 'myservice' do
action :start
supports :status => true, :start => true, :stop => true, :restart => true
end
#At this point service is surely running
execute "a command that should run once every time, that requires service to be running"
Every resource that changes the configuration file(s), should notify the service to restart.
I guess Chef is clever enough not to restart the service it just started. (I didn't pay attention to that before, but it seems to me that I would have, if there were unnecessary restarts)
Chef will only execute an action per resource, regardless of the number of times it's notified. It is, however, specific to each action. So if you send it a action :restart
and also a action :start
notification, then both will be executed in the order in which Chef encountered them. So what you are seeing with your code example is the initial :start
notification from the execute block, followed by the template :restart
notifications.
You should be able to avoid this by restructuring your recipe a bit and using subscribes
if I'm following correctly.
package 'packagename' do
...
end
execute "a command from package which generates and enables the init script" do
not_if File.exists?('/etc/init.d/myservice_script')
end
template 'configfile1'
notifies :restart, 'service[myservice]'
end
...
template 'configfileN'
notifies :restart, 'service[myservice]'
end
service 'myservice' do
supports :status => true, :start => true, :stop => true, :restart => true
subscribes :run, 'execute[a command from package which generates and enables the init script]', :immediately
action :start
end
execute "a command that should run once every time, that requires service to be running"
First, we move the service
resource to the bottom of the recipe so that it is only called once all other resources have been evaluated. Then we change the execute
resource to subscribe to the :start
action of the service[myservice]
resource so that it will only ever execute this command when the :start
action is called. We also add a bit of idempotency in there to make sure it doesn't just re-create the init script every run.
Finally, we add in all the templates with the normal notifications for service[myservice]
.