Walk and Dump CloudForms objects
Clone or download
Fetching latest commit…
Cannot retrieve the latest commit at this time.
Type Name Latest commit message Commit time
Failed to load latest commit information.



One of the challenges when starting out writing CloudForms or ManageIQ automation scripts, is knowing where the objects and attributes are under $evm.root that we may need to access. For example, depending on the automation action, we may have an $evm.root['vm'] object, or we may not.

This script is an attempt to demystify the object structure that is available at any point in an Automation workflow.

Calling the script from any point will walk the object hierarchy from $evm.root downwards, printing objects and attributes as it goes, i.e.

Object Walker 1.8 Starting
     --- walk_association_policy details ---
     walk_association_policy = whitelist
     walk_association_whitelist = { 'MiqAeServiceMiqProvisionRequest': ['miq_request','miq_request_tasks','miq_provisions','requester','resource','source','vm_template'], 'MiqAeServiceManageIQ_Providers_Redhat_InfraManager_Provision': ['source','destination','miq_provision_request','miq_request','miq_request_task','vm','vm_template','tenant'], 'MiqAeServiceManageIQ_Providers_Redhat_InfraManager_Vm': ['ems_cluster','ems_folder','resource_pool','service','ext_management_system','storage','hardware','operating_system'], 'MiqAeServiceHardware': ['nics','guest_devices','ports','vm'], 'MiqAeServiceUser': ['current_group'], 'MiqAeServiceGuestDevice': ['hardware','lan','network'] }
     --- $evm.current_* details ---
     $evm.current_namespace = Bit63/Stuff   (type: String)
     $evm.current_class = ObjectWalker   (type: String)
     $evm.current_instance = object_walker   (type: String)
     $evm.current_method = object_walker   (type: String)
     $evm.current_message = create   (type: String)
     $evm.current_object = /Bit63/Stuff/ObjectWalker/object_walker   (type: DRb::DRbObject, URI: druby://
     $evm.current_object.current_field_name = execute   (type: String)
     $evm.current_object.current_field_type = method   (type: String)
     --- automation instance hierarchy ---
     /ManageIQ/System/Process/AUTOMATION  ($evm.root)
     |    /ManageIQ/infrastructure/VM/Lifecycle/Provisioning
     |    |    /ManageIQ/Infrastructure/VM/Provisioning/Profile/EvmGroup-super_administrator
     |    |    /Bit63/Infrastructure/VM/Provisioning/StateMachines/VMProvision_vm/template  ($evm.parent)
     |    |    |    /ManageIQ/Infrastructure/VM/Provisioning/StateMachines/Methods/CustomizeRequest
     |    |    |    /ManageIQ/Infrastructure/VM/Provisioning/Placement/default
     |    |    |    /Bit63/Stuff/ObjectWalker/object_walker  ($evm.object)
     --- walking $evm.root ---
     $evm.root = /ManageIQ/System/Process/AUTOMATION   (type: DRb::DRbObject, URI: druby://
     |    --- attributes follow ---
     |    $evm.root['ae_next_state'] =    (type: String)
     |    $evm.root['ae_provider_category'] = infrastructure   (type: String)
     |    $evm.root['ae_result'] = ok   (type: String)
     |    $evm.root['ae_state'] = WalkObjects   (type: String)
     |    $evm.root['ae_state_retries'] = 0   (type: Fixnum)
     |    $evm.root['ae_state_started'] = 2016-08-01 09:55:59 UTC   (type: String)
     |    $evm.root['ae_state_step'] = main   (type: String)
     |    $evm.root['ae_status_state'] = on_exit   (type: String)
     |    $evm.root['miq_group'] => #<MiqAeMethodService::MiqAeServiceMiqGroup:0x0000000c6728c8>   (type: DRb::DRbObject, URI: druby://
     |    |    --- attributes follow ---
     |    |    $evm.root['miq_group'].created_on = 2016-05-25 08:09:35 UTC   (type: ActiveSupport::TimeWithZone)
     |    |    $evm.root['miq_group'].description = EvmGroup-super_administrator   (type: String)
     |    |    $evm.root['miq_group'].filters = nil
     |    |    $evm.root['miq_group'].group_type = system   (type: String)
     |    |    $evm.root['miq_group'].id = 2   (type: Fixnum)
     |    |    $evm.root['miq_group'].sequence = 1   (type: Fixnum)
     |    |    $evm.root['miq_group'].settings = nil
     |    |    $evm.root['miq_group'].tenant_id = 1   (type: Fixnum)
     |    |    $evm.root['miq_group'].updated_on = 2016-05-25 08:09:35 UTC   (type: ActiveSupport::TimeWithZone)
     |    |    --- end of attributes ---
     |    |    --- virtual columns follow ---
     |    |    $evm.root['miq_group'].allocated_memory = 1073741824   (type: Fixnum)
     |    |    $evm.root['miq_group'].allocated_storage = 42949672960   (type: Fixnum)
     |    |    $evm.root['miq_group'].allocated_vcpu = 1   (type: Fixnum)


Several of the objects in the Automate model have circular references to themselves either directly or indirectly through other associations. To prevent the same object being printed multiple times the script records where it's been, and prints:

    |    (object type: MiqAeServiceManageIQ_Providers_Openstack_CloudManager_Vm, object ID: 23)
    |    |    Object MiqAeServiceManageIQ_Providers_Openstack_CloudManager_Vm with ID 23 has already been printed...

Configuration Instance - NEW!

object_walker 2.0 comes with a new configuration instance containing the configuration attributes. The configuration instance must be called /Discovery/ObjectWalker/configuration.


For backwards compatibility and for invoking object_walker via $evm.instantiate or from an instance relationship, the object_walker instance still remains, however this no longer contains the configuration attributes.


print_evm_object can be used to toggle whether or not to walk the object structure of the $evm.object (i.e current) object. If object_walker has been invoked from $evm.instantiate or from a relationship then $evm.object will be object_walker itself. If object_walker has been invoked from an embedded method then $evm.object is the calling method's instance.


print_evm_parent can be used to toggle whether or not to walk the object structure of the $evm.parent object. If object_walker has been invoked from $evm.instantiate or from a relationship then $evm.parent will be the calling instance.


Many attributes that get printed have a value of 'nil', i.e.

     |    |    $evm.root['user'].userid = admin   (type: String)
     |    |    --- end of attributes ---
     |    |    --- virtual columns follow ---
     |    |    $evm.root['user'].allocated_memory = 0   (type: Fixnum)
     |    |    $evm.root['user'].allocated_storage = 0   (type: Fixnum)
     |    |    $evm.root['user'].allocated_vcpu = 0   (type: Fixnum)
     |    |    $evm.root['user'].custom_1 = nil
     |    |    $evm.root['user'].custom_2 = nil
     |    |    $evm.root['user'].custom_3 = nil
     |    |    $evm.root['user'].custom_4 = nil
     |    |    $evm.root['user'].custom_5 = nil
     |    |    $evm.root['user'].custom_6 = nil
     |    |    $evm.root['user'].custom_7 = nil
     |    |    $evm.root['user'].custom_8 = nil
     |    |    $evm.root['user'].custom_9 = nil
     |    |    $evm.root['user'].ldap_group = EvmGroup-super_administrator   (type: String)
     |    |    $evm.root['user'].miq_group_description = EvmGroup-super_administrator   (type: String)

print_nil_values can be used to toggle whether or not to include keys that have a nil value in the output dump. There are often many, and including them will usually increase verbosity, but it is sometimes useful to know that a key/attribute exists, even if it currently has no assigned value.


Many of the objects that we can walk through are in fact Rails Active Record Associations (object representations of database records), and we often don't want to print all of them. The script uses a walk_association_policy, variable to help decide which associations to traverse; it should have the value of either "whitelist" or "blacklist". This variable defaults to "whitelist" unless overridden by an instance schema attribute called walk_association_policy (read as $evm.object['walk_association_policy']).


If walk_association_policy = whitelist, then object_walker will only traverse associations of objects that are explicitly mentioned in the walk_association_whitelist JSON-like hash (either defined in the instance schema, or in a service dialog). The string "ALL" can be used to walk all associations of an object type. A typical whitelist hash is as follows:


The hash enables us to carefully control what is traversed and printed. If object_walker finds an association that isn't in the hash, it will print a line similar to:

$evm.root['user'].current_tenant (type: Association)
*** not walking: 'current_tenant' isn't in the walk_association_whitelist hash for MiqAeServiceUser ***

If we decide to explore and dump this current_tenant association, we edit the hash to add its name to the list associated with the object type. In the example whitelist hash above, we would add to the list defined by the MiqAeServiceUser key, for example:

"MiqAeServiceUser":["current_group", "current_tenant"],


if walk_association_policy = blacklist, then object_walker will traverse all associations of all objects, except those that are explicitly mentioned in the walk_association_blacklist hash. This enables us to run a more exploratory dump, at the cost of a much more verbose output. The format of the blacklist is the same as the whitelist, and the string "ALL" can be used to avoid walking any associations of an object type.

Note: the object_associations file in the repository lists all associations of all MiqAeService objects, and can be used as a reference. The sample_whitelists file contains examples of typical whitelists that could be used for various investigations.

Defining the Hashes in the configuration Instance Schema

The walk_association_whitelist and walk_association_blacklist hash definitions are JSON-like hashes, but either single or double quotes can be used, and the quotes don't need to be escaped by backslashes. We define the walk_association_policy, walk_association_whitelist and walk_association_blacklist as attributes of data type String in the class and instance schema.

The following sceenshot is an example of typical schema attribute definitions:

Screenshot 01

Defining the Hashes in a Service Dialog

When exploring the object model, we frequently update the walk_association_whitelist or walk_association_blacklist schema attributes as new associations are being explored.

To avoid having to edit the instance attributes in such circumstances, a service dialog can be created containing a text area box element named walk_association_whitelist or walk_association_blacklist. Any valid JSON-like whitelist hash entered into this dialog field will be used as a run-time override of the walk_association_whitelist or walk_association_blacklist defined in the instance schema. The object_walker instance can then be called from a button, configured to display the dialog.

Screenshot 07


There are two ways of installing object_walker.

Importing the datastore via git

If you have the Git Repositories Owner server role enabled on an appliance you can git import object_walker straight into the automate datastore. Use the URL https://github.com/pemcg/object_walker

Screenshot 09

This will import a domain called Investigative_Debugging containing the Discovery namespace, and its class, instance and method. The class schema contains a sample general-purpose whitelist.

Importing the domain from a zip file

Copy the investigative_debugging.zip datastore export to your local system, and import it from the Automate -> Import / Export menu. This will import the Investigative_Debugging domain.

Upgrading to 2.0

The schema of the ObjectWalker class has changed. If any customisations have been made to an object_walker v1.x instance (such as an updated whitelist) these should be saved, and the old ObjectWalker class and associated object_walker v1.x instance and method should be deleted. Once object_walker v2.0 has been installed the previous modifications can be re-applied to a copy of the new configuration instance.

Invoking object_walker

There are three ways of invoking object_walker.

As an Embedded Method - NEW!

object_walker can be callable as an embedded method with CloudForms 4.6 / ManageIQ Gaprindashvili . The calling method should embed the /Discovery/ObjectWalker/object_walker "library" method, and invoke it using:


For example:

Screenshot 08

Calling object_walker in this way gives the most accurate view of the $evm object structure in relation to the calling method.

From an Instance Relationship

An object_walker dump can be obtained by simply calling the /Discovery/ObjectWalker/object_walker instance from a relationship in any instance in the automation namespace.

For example if we wish to examine the $evm.root object structure part-way through a VM provisioning workflow, we could add a call to object_walker from a state in the VM Provision State Machine, as follows:

Screenshot 07

If we simply wished to examine the object structure related to a VM object, we could call object_walker from a button on a VM in the WebUI, as follows:

Screenshot 08

From $evm.instantiate

object_walker can be called in-line from another automation method, using $evm.instantiate, as follows:


Reading the Output

Although we could inspect the lines printed by object_walker by following automation.log, the preferred way to read the output is to install object_walker_reader.rb from the repository to the CloudForms/ManageIQ appliance.

This can be done either using RPM as follows:

rpm -ivh https://github.com/pemcg/object_walker/raw/master/object_walker_reader-<version>.noarch.rpm

...or by copying the object_walker_reader-<version>.tar.gz to /root on an appliance and unpacking it.

object_walker_reader.rb formats the output, and gives us several options for selecting various object_walker dumps.


Use object_walker_reader to extract the latest (no arguments), or a selected object_walker dump from automation.log or other renamed or saved log file.

Usage: object_walker_reader.rb [options]
    -l, --list                       list object_walker dumps in the file
    -f, --file filename              Full file path to automation.log (if not /var/www/miq/vmdb/log/automtion.log)
    -t, --timestamp timestamp        Date/time of the object_walker dump to be listed (hint: copy from -l output)
    -d, --diff timestamp1,timestamp2 Date/time of two object_walker dumps to be compared using 'diff'
    -h, --help                       Displays Help                    Displays Help


Listing object_walker dumps using the '-l' switch
 ./object_walker_reader.rb -l
 Found object_walker dump at 2014-09-17T13:28:42.052043
 Found object_walker dump at 2014-09-17T13:34:52.649359
 Found object_walker dump at 2014-09-17T15:06:29.250086
 Found object_walker dump at 2014-09-17T15:22:46.034628
 Found object_walker dump at 2014-09-18T07:56:08.201025
Listing dumps in a non-default (i.e. copied from another system) log file using the '-f' switch
 ./object_walker_reader.rb -l -f /Documents/CloudForms/cf30-automation-log
 Found object_walker dump at 2014-09-18T09:52:28.797868
 Found object_walker dump at 2014-09-18T09:53:31.455892
 Found object_walker dump at 2014-09-18T10:05:39.040744
 Found object_walker dump at 2014-09-18T12:00:59.142460
Dumping a particular object_walker output by timestamp using the '-t' switch
~/object_walker_reader.rb -t 2016-08-02T09:17:06.722068
Object Walker 1.8 Starting
     *** detected 'print_nil_values = false' so attributes with nil values will not be printed ***
     --- walk_association_policy details ---
     walk_association_policy = whitelist
     walk_association_whitelist = {"MiqAeServiceUser": ["current_group", "current_tenant"]}
     --- $evm.current_* details ---
     $evm.current_namespace = Bit63/stuff   (type: String)
     $evm.current_class = objectwalker   (type: String)
     $evm.current_instance = object_walker   (type: String)
     $evm.current_method = object_walker   (type: String)
     $evm.current_message = create   (type: String)
     $evm.current_object = /Bit63/stuff/objectwalker/object_walker   (type: DRb::DRbObject, URI: druby://
     $evm.current_object.current_field_name = execute   (type: String)
     $evm.current_object.current_field_type = method   (type: String)
     --- automation instance hierarchy ---
     /ManageIQ/SYSTEM/PROCESS/Request  ($evm.root)
     |    /ManageIQ/System/Request/call_instance  ($evm.parent)
     |    |    /Bit63/stuff/objectwalker/object_walker  ($evm.object)
     --- walking $evm.root ---
     $evm.root = /ManageIQ/SYSTEM/PROCESS/Request   (type: DRb::DRbObject, URI: druby://
     |    --- attributes follow ---
     |    $evm.root['ae_provider_category'] = infrastructure   (type: String)
Comparing the output from two object_walker dumps using the '-d' switch
 ./object_walker_reader.rb -d 2015-05-11T14:41:58.031661,2015-05-11T14:42:08.186930
 Getting diff comparison from dumps at 2015-05-11T14:41:58.031661 and 2015-05-11T14:42:08.186930
 <      object_walker:   $evm.current_object = /Bit63/Discovery/ObjectWalker/default   (type: DRb::DRbObject, URI: druby://
 >      object_walker:   $evm.current_object = /Bit63/Discovery/ObjectWalker/default   (type: DRb::DRbObject, URI: druby://
 <      object_walker:   $evm.root = /Bit63/Service/Provisioning/StateMachines/ServiceProvision_Template/CatalogItemInitialization   (type: DRb::DRbObject, URI: druby://
 >      object_walker:   $evm.root = /Bit63/Service/Provisioning/StateMachines/ServiceProvision_Template/CatalogItemInitialization   (type: DRb::DRbObject, URI: druby://
 <      object_walker:   $evm.root['ae_state'] = pre1   (type: String)
 >      object_walker:   $evm.root['ae_state'] = pre3   (type: String)
 <      object_walker:   $evm.root['ae_state_started'] = 2015-05-11 14:41:56 UTC   (type: String)
 >      object_walker:   $evm.root['ae_state_started'] = 2015-05-11 14:42:07 UTC   (type: String)