Property Filtering
Options may be passed to the roles() method (and implicitly in methods like
release_roles() and primary()) that affect the set of servers returned. These options
take the form of a Hash passed as the last parameter. Each of the key/value pairs in the
hash are evaluated in the sequence they are declared and if all are true for a specific
server then the server will be returned. The keys must always be symbols which have the
following meaning:
-
:filter, or:select: The value is either a property keyname or a lambda which is called with the server as parameter. The value must return true for the server to be included. -
:exclude: As above but the value must return false for the server to be included. -
Any other symbol is taken as a server property name whose value must equal the given value. A lambda will not be called if one is supplied!
Examples
server 'example1.com', roles: %w{web}, active: true
server 'example2.com', roles: %w{web}
server 'example3.com', roles: %w{app web}, active: true
server 'example4.com', roles: %w{app}, primary: true
server 'example5.com', roles: %w{db}, no_release: true, active: true
task :demo do
puts "All active release roles: 1,3"
release_roles(:all, filter: :active).each do |r|
puts "#{r.hostname}"
end
puts "All active roles: 1,3,5"
roles(:all, active: true).each do |r|
puts "#{r.hostname}"
end
puts "All web and db roles with selected names: 2,3"
roles(:web, :db, select: ->(s){ s.hostname =~ /[234]/}).each do |r|
puts "#{r.hostname}"
end
puts "All with no active property: 2,4"
roles(:all, active: nil).each do |r|
puts "#{r.hostname}"
end
puts "All except active: 2,4"
roles(:all, exclude: :active).each do |r|
puts "#{r.hostname}"
end
puts "All primary: 4"
roles(:all, select: :primary).each do |r|
puts "#{r.hostname}"
end
end
