Class: Puppet::Context Private

Inherits:
Object show all
Defined in:
lib/puppet/context.rb

Overview

This class is part of a private API. You should avoid using this class if possible, as it may be removed or be changed in the future.

Puppet::Context is a system for tracking services and contextual information that puppet needs to be able to run. Values are “bound” in a context when it is created and cannot be changed; however a child context can be created, using #override, that provides a different value.

When binding a Proc, the proc is called when the value is looked up, and the result is memoized for subsequent lookups. This provides a lazy mechanism that can be used to delay expensive production of values until they are needed.

API:

  • private

Defined Under Namespace

Classes: DuplicateRollbackMarkError, StackUnderflow, TrustedInformation, UndefinedBindingError, UnknownRollbackMarkError

Instance Method Summary collapse

Constructor Details

#initialize(initial_bindings) ⇒ Context

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Returns a new instance of Context.

API:

  • private



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# File 'lib/puppet/context.rb', line 21

def initialize(initial_bindings)
  @table = initial_bindings
  @description = "root"
  @id = 0
  @rollbacks = {}
  @stack = [[0, nil, nil]]
end

Instance Method Details

#lookup(name, &block) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

API:

  • private



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# File 'lib/puppet/context.rb', line 47

def lookup(name, &block)
  if @table.include?(name)
    value = @table[name]
    value.is_a?(Proc) ? (@table[name] = value.call) : value
  elsif block
    block.call
  else
    raise UndefinedBindingError, "no '#{name}' in #{@table.inspect} at top of #{@stack.inspect}"
  end
end

#mark(name) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Mark a place on the context stack to later return to with #rollback.

Parameters:

  • The identifier for the mark

API:

  • private



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# File 'lib/puppet/context.rb', line 74

def mark(name)
  if @rollbacks[name].nil?
    @rollbacks[name] = @stack[-1][0]
  else
    raise DuplicateRollbackMarkError, "Mark for '#{name}' already exists"
  end
end

#override(bindings, description = "", &block) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

API:

  • private



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# File 'lib/puppet/context.rb', line 59

def override(bindings, description = "", &block)
  mark_point = "override over #{@stack[-1][0]}"
  mark(mark_point)
  push(bindings, description)

  yield
ensure
  rollback(mark_point)
end

#pop ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

API:

  • private



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# File 'lib/puppet/context.rb', line 38

def pop
  if @stack[-1][0] == 0
    raise(StackUnderflow, "Attempted to pop, but already at root of the context stack.")
  else
    (_, @table, @description) = @stack.pop
  end
end

#push(overrides, description = "") ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

API:

  • private



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# File 'lib/puppet/context.rb', line 30

def push(overrides, description = "")
  @id += 1
  @stack.push([@id, @table, @description])
  @table = @table.merge(overrides || {})
  @description = description
end

#rollback(name) ⇒ Object

This method is part of a private API. You should avoid using this method if possible, as it may be removed or be changed in the future.

Roll back to a mark set by #mark.

Rollbacks can only reach a mark accessible via #pop. If the mark is not on the current context stack the behavior of rollback is undefined.

Parameters:

  • The identifier for the mark

API:

  • private



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# File 'lib/puppet/context.rb', line 90

def rollback(name)
  if @rollbacks[name].nil?
    raise UnknownRollbackMarkError, "Unknown mark '#{name}'"
  end

  while @stack[-1][0] != @rollbacks[name]
    pop
  end

  @rollbacks.delete(name)
end