Minimiser les redémarrages du service des notifications du chef?

Question

Actuellement, ma recette avec des attributs qui comptent est structuré comme ceci:

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"

En faisant cela, nous nous assurons que le démarrage initial du service dispose des fichiers de configuration, pendant chaque exécution, le service est en cours d'exécution pour le deuxième bloc d'exécution, et si un fichier de configuration change, nous redémarrons le service pour récupérer les modifications. .

Cependant, si un chef de chef se produit lorsque l'état initial du service est arrêté (par exemple sur la première exécution ou si quelque chose de mauvais est arrivé), et que les fichiers de configuration ont changé (notamment sur la première exécution, mais possible pour les autres Exécution), le premier bloc exécuté fera que le service commence par les fichiers de configuration corrects déjà en place, puis à la fin de la course, le service redémarrera inutilement. (Supposons bien sûr que les ressources après le début initial ne provoquent pas de redémarrage du service)

Changer l'action cible des notifications ne semble pas fonctionner (car les notifications immédiates se produiront toujours immédiatement, les notifications retardées se produisent toujours) et, outre ne serait pas correcte.

Aussi, nous ne pouvons pas vous abonner le 2e exécuté au début du service car si c'est déjà en cours d'exécution, nous ne serrerons pas de ne pas l'exécuter.

Il est très difficile, mais y a-t-il un meilleur modèle qui pourrait être suivi pour minimiser les redémarrages d'un service pour la course initiale? Ou un mécanisme pour annuler les notifications retardées lorsqu'une action particulière est prise?

Answer 1

J'ai utilisé un fichier de drapeau pour y parvenir.

Comme ci-dessous "APT-GET UPDATE" n'est pas exécuté une fois.

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

Answer 2

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.

Answer 3

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)

Answer 4

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].