Attribute Persistence

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All attributes except for normal attributes are reset at the beginning of a Chef Infra Client run. Attributes set via chef-client -j with a JSON file have normal precedence and are persisted between Chef Infra Client runs. Chef Infra Client rebuilds these attributes using automatic attributes collected by Ohai at the beginning of each Chef Infra Client run, and then uses default and override attributes that are specified in cookbooks, roles, environments, and Policyfiles. All attributes are then merged and applied to the node according to attribute precedence. The attributes that were applied to the node are saved to the Chef Infra Server as part of the node object at the conclusion of each Chef Infra Client run.

Limiting Attribute Persistence

Some organizations find it helpful to control attribute data stored to the Chef Infra Server in order to limit the disk and CPU resources used when processing unused attributes. For example, your organization may find the data from the Ohai Package plugin useful when writing cookbooks, but you don’t see the need in saving ~100k of package information for each Chef Infra Client run. By limiting the data that is saved to the Chef Infra Server, it will still be available on the node within cookbooks, but won’t be saved to the Chef Infra Server where it is available in searches.

Attribute Blocklist

Attributes that should not be saved by a node may be blocklisted in the client.rb file. The blocklist is a Hash of keys that specify each attribute to be filtered out.

Attributes are blocklisted by attribute type, with each attribute type being blocklisted independently. Each attribute type—automatic, default, normal, and override—may define blocklists by using the following settings in the client.rb file:

Blocklisting Ohai (automatic) Attributes

The recommended practice is to use blocked_automatic_attributes to block attributes populated by Ohai’s system information gathering. Ohai gathers a large number of attributes that can consume a signicant amount of storage space on the Chef Infra Server. Many of these attributes may be considered highly valuable, while others could be blocklisted without any impact to data available in search. Normal, default, and override attributes are typically much more important attributes used within cookbooks and are more likely to cause issues if they are blocklisted incorrectly.

For example, automatic attribute data similar to:

{
  "filesystem" => {
    "/dev/disk0s2" => {
      "size" => "10mb"
    },
    "map - autohome" => {
      "size" => "10mb"
    }
  },
  "network" => {
    "interfaces" => {
      "eth0" => {...},
      "eth1" => {...},
    }
  }
}

To blocklist the filesystem attributes and allow the other attributes to be saved, update the client.rb file:

blocked_automatic_attributes ['filesystem']

When a blocklist is defined, any attribute of that type that is not specified in that attribute blocklist will be saved. So based on the previous blocklist for automatic attributes, the filesystem and map - autohome attributes will not be saved, but the network attributes will.

For attributes that contain slashes (/) within the attribute value, such as the filesystem attribute '/dev/diskos2', use an array. For

example:

blocked_automatic_attributes [['filesystem', '/dev/diskos2']]

Attribute Allowlist

Attributes that should be saved by a node may be allowlisted in the client.rb file. The allowlist is a hash of keys that specifies each attribute to be saved.

Attributes are allowlisted by attribute type, with each attribute type being allowlisted independently. Each attribute type—automatic, default, normal, and override—may define allowlists by using the following settings in the client.rb file:

Allowlisting Ohai (automatic) Attributes

The recommended practice is to use allowed_automatic_attributes to allow specific attributes populated by Ohai’s system information gathering. Ohai gathers a large number of attributes that can consume a signicant amount of storage space on the Chef Infra Server. Many of these attributes may be considered highly valuable, while others could be skipped without any impact to data available in search. Normal, default, and override attributes are typically much more important attributes used within cookbooks and are more likely to cause issues if they are ommited from an allowlist incorrectly.

For example, automatic attribute data similar to:

{
  "filesystem" => {
    "/dev/disk0s2" => {
      "size" => "10mb"
    },
    "map - autohome" => {
      "size" => "10mb"
    }
  },
  "network" => {
    "interfaces" => {
      "eth0" => {...},
      "eth1" => {...},
    }
  }
}

To allowlist the network attributes and prevent the other attributes from being saved, update the client.rb file:

allowed_automatic_attributes ['network/interfaces/']

When a allowlist is defined, any attribute of that type that is not specified in that attribute allowlist will not be saved. So based on the previous allowlist for automatic attributes, the filesystem and map - autohome attributes will not be saved, but the network attributes will.

Leave the value empty to prevent all attributes of that attribute type from being saved:

allowed_automatic_attributes []

For attributes that contain slashes (/) within the attribute value, such as the filesystem attribute '/dev/diskos2', use an array. For example:

allowed_automatic_attributes [['filesystem', '/dev/diskos2']]