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 the Automation Engine.
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://127.0.0.1:33776)
$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://127.0.0.1:33776)
| --- 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://127.0.0.1:33776)
| | --- 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)
etc.
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...
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:
{"MiqAeServiceServiceTemplateProvisionTask":["source","destination","miq_request"],
"MiqAeServiceServiceTemplateProvisionRequest":["miq_request","miq_request_tasks","requester","source"],
"MiqAeServiceServiceTemplate":["service_resources"],
"MiqAeServiceServiceResource":["resource","service_template"],
"MiqAeServiceMiqProvisionRequest":["miq_request","miq_request_tasks","miq_provisions"],
"MiqAeServiceManageIQ_Providers_Redhat_InfraManager_Provision":["ALL"],
"MiqAeServiceManageIQ_Providers_Redhat_InfraManager_Vm":["ems_cluster","ems_folder","resource_pool"],
"MiqAeServiceManageIQ_Providers_Openstack_CloudManager_Vm":["key_pairs","security_groups","tenant","flavor"],
"MiqAeServiceHardware":["ALL"],
"MiqAeServiceUser":["current_group"],
"MiqAeServiceGuestDevice":["hardware","lan","network"]}
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.
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:
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.
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)
Sometimes we want to know that the attribute is present, even if its value is nil, but at other times we only wish to know
about attributes with valid values (this also gives us a more concise dump output). In this case we can define an optional instance attribute of data type Boolean, called print_nil_values, and give it a value of false, as follows:
The resulting output dump will leave out any keys or attributes that have nil values.
In a suitable namespace, create an ObjectWalker class, and an instance and method each of name object_walker, as follows:
Edit the schema of the ObjectWalker class to add the attributes and an execute field to run the method, as follows:
Now edit the instance schema to add suitable attribute values, as follows:
We get an object_walker dump by simply calling the object_walker instance from anywhere 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:
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:
We can even call object_walker in-line from another automation method, using $evm.instantiate, as follows:
$evm.instantiate('/Discovery/ObjectWalker/object_walker')
Although we could inspect the lines printed by object_walker by following automation.log, the preferred way to read the output is to copy object_walker_reader.rb from the repository to the CloudForms/ManageIQ appliance. This 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
./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
...
./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
...
~/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://127.0.0.1:45024)
$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://127.0.0.1:45024)
| --- attributes follow ---
| $evm.root['ae_provider_category'] = infrastructure (type: String)
./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
6c6
< object_walker: $evm.current_object = /Bit63/Discovery/ObjectWalker/default (type: DRb::DRbObject, URI: druby://127.0.0.1:51860)
---
> object_walker: $evm.current_object = /Bit63/Discovery/ObjectWalker/default (type: DRb::DRbObject, URI: druby://127.0.0.1:54749)
10c10
< object_walker: $evm.root = /Bit63/Service/Provisioning/StateMachines/ServiceProvision_Template/CatalogItemInitialization (type: DRb::DRbObject, URI: druby://127.0.0.1:51860)
---
> object_walker: $evm.root = /Bit63/Service/Provisioning/StateMachines/ServiceProvision_Template/CatalogItemInitialization (type: DRb::DRbObject, URI: druby://127.0.0.1:54749)
12c12
< object_walker: $evm.root['ae_state'] = pre1 (type: String)
---
> object_walker: $evm.root['ae_state'] = pre3 (type: String)
14c14
< 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)
...