Class: Atmos::Metadata

Inherits:
AttributeHashBase show all
Defined in:
lib/atmos/attributes.rb

Overview

Metadata

In all cases, metadata refers to key/value pairs, and is represented as a ruby Hash attached to an Atmos::Object object.

Standard Metadata

In Atmos, metadata with no modifier (e.g. listable or system) refers to metadata on an object that is not indexed. In other words, objects cannot be referenced by the metadata information. The only way to get this metadata information is to already have the object the metadata is attached to.

Defaults

By default, when you create an object, there is no metadata. So:

obj.metadata => {}

Adding

Add metadata in key/value pairs as you would to a hash. Keys and values must be ruby Strings.

obj.metadata[key] = value
obj.metadata.store(key, value)
obj.metadata.merge!({key => value})

Modifying

Modify metadata as you would a hash. Keys and values must be ruby Strings.

obj.metadata[pre-existing-key] = new-value
obj.metadata.store(pre-existing-key, new-value)
obj.metadata.merge!({pre-existing-key => new-value})

Deleting

Delete metadata as you would a hash. Keys must be ruby Strings.

obj.metadata.delete(key)
obj.metadata.clear

Listable Metadata

Listable metadata means atmos indexes the object by the key in the key/value metadata pair. The keys of listable metadata are also known as listable tags. Currently, an Atmos server can handle about 10k listable tags easily, so use judiciously with very large datasets.

Defaults

By default, when you create an object, there is no listable metadata. So:

obj.listable_metadata => {}

Adding

Add metadata in key/value pairs as you would to a hash. Keys and values must be ruby Strings.

obj.listable_metadata[key] = value
obj.listable_metadata.store(key, value)
obj.listable_metadata.merge!({key => value})

Modifying

Modify metadata as you would a hash. Keys and values must be ruby Strings.

obj.listable_metadata[pre-existing-key] = new-value
obj.listable_metadata.store(pre-existing-key, new-value)
obj.listable_metadata.merge!({pre-existing-key => new-value})

Deleting

Delete metadata as you would a hash. Keys must be ruby Strings.

obj.listable_metadata.delete(key)
obj.listable_metadata.clear

System Metadata

System metadata is a standard group of information maintained by Atmos for each object, such as atime, mtime, type, policyname.

System metadata is not modifiable.

Constant Summary collapse

LISTABLE = 
1
NON_LISTABLE = 
2
SYSTEM = 
3

Instance Attribute Summary

Attributes inherited from AttributeHashBase

#last_reload_at

Instance Method Summary collapse

Methods inherited from AttributeHashBase

#clear_with_atmos, #default_with_atmos=, #delete_with_atmos, #header_name, #header_value, #merge_with_atmos, #merge_with_atmos!, #replace_with_atmos, #store, #to_canonicalized_header, #to_header

Constructor Details

#initialize(obj, type) ⇒ Metadata

This constructor is only meant for internal use. To get the metadata on an object:

obj.metadata => Hash
obj.listable_metadata => Hash
obj.system_metadata => Hash

Raises:



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# File 'lib/atmos/attributes.rb', line 422

def initialize(obj, type)
   raise Atmos::Exceptions::ArgumentException, "The 'obj' parameter cannot be nil." if (obj.nil?)
   raise Atmos::Exceptions::ArgumentException, "The 'obj' parameter must have an id." if (obj.aoid.nil?)
   raise Atmos::Exceptions::ArgumentException, "The 'type' parameter must be one of Atmos::Metadata::LISTABLE Atmos::Metadata::NON_LISTABLE Atmos::Metadata::SYSTEM." if (![SYSTEM, LISTABLE, NON_LISTABLE].include?(type))

   super()
   
   @obj = obj
   @type = type
   
   @header = (@type == LISTABLE) ? 'x-emc-listable-meta' : 'x-emc-meta'
   @reload_action = (@type == SYSTEM) ? :list_system_metadata : :list_metadata
   @set_action = (@type == LISTABLE) ? :set_listable_metadata : :set_metadata

   reload(@reload_action, @obj.aoid)
end

Instance Method Details

#[]=(key, value) ⇒ Object

Adds the specified metadata to the object unless the object is representing system metadata.

System metadata cannot be modified, so an Atmos::Exceptions::NotImplementedException is thrown.

The change is made on the Atmos server immediately.

Raises:



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# File 'lib/atmos/attributes.rb', line 448

def []=(key,value)
   raise Atmos::Exceptions::NotImplementedException, "System metadata cannot be modified." if (@type == SYSTEM)
   raise Atmos::Exceptions::ArgumentException, "The 'value' parameter must be of type String'." if (!value.nil? && !value.kind_of?(String))
   response = @obj.request.do(@set_action, :id => @obj.aoid, @header => "#{key}=#{value}")
   reload(@reload_action, @obj.aoid)
end

#clear ⇒ Object

Deletes all metadata from the object unless the object is representing system metadata.

System metadata cannot be modified, so an Atmos::Exceptions::NotImplementedException is thrown.

The change is made on the Atmos server immediately.

Raises:



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# File 'lib/atmos/attributes.rb', line 464

def clear
   raise Atmos::Exceptions::NotImplementedException, "System metadata cannot be modified." if (@type == SYSTEM)
   reload(@reload_action, @obj.aoid)         
   response = @obj.request.do(:delete_metadata, :id => @obj.aoid, 'x-emc-tags' => self.keys.join(','))
   self.clear_without_atmos
   reload(@reload_action, @obj.aoid)         
end

#delete(key) ⇒ Object

Deletes the specified metadata from the object unless the object is representing system metadata. System metadata cannot be modified, so an Atmos::Exceptions::NotImplementedException is thrown.

The deleted is executed on the Atmos server immediately.

Required:

*<tt>key</tt> -

Raises:



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# File 'lib/atmos/attributes.rb', line 483

def delete(key)
   raise Atmos::Exceptions::NotImplementedException, "System metadata cannot be modified." if (@type == SYSTEM)
   response = @obj.request.do(:delete_metadata, :id => @obj.aoid, 'x-emc-tags' => key)
   self.delete_without_atmos(key)
   reload(@reload_action, @obj.aoid)         
end

#listable? ⇒ Boolean

Returns true if this Metadata object is representing listable metadata.

Returns:

  • (Boolean) 


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# File 'lib/atmos/attributes.rb', line 494

def listable?
   @type == LISTABLE
end

#non_listable? ⇒ Boolean

Returns true if this Metadata object is representing non-listable metadata.

Returns:

  • (Boolean) 


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# File 'lib/atmos/attributes.rb', line 502

def non_listable?
   @type == NON_LISTABLE
end

#system? ⇒ Boolean

Returns true if this Metadata object is representing system metadata.

Returns:

  • (Boolean) 


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# File 'lib/atmos/attributes.rb', line 510

def system?
   @type == SYSTEM
end