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Re: Configuration approach recommendations


Jon, do you mean that get_node_processes() returns output without
'service:' and 'process:' prefixes? Actually controller expects that plugin
returns structure in format {service1: [process1, process2 ..., processN],
service2: [...], ...}, so there is no need to specify what is what here.

2013/5/28 Jon Maron <jmaron@xxxxxxxxxxxxxxx>

> Thank you!
> Minor note:
> - there seems to be an  inconsistency between config and
> get_node_processes:  one promotes the idea of referencing services as
> "service:<service name>", the other as simply "<service name>".  From the
> discussion of the Config object it appears the intent was to be consistent
> (i.e. always use "service:<service name>"
> On May 27, 2013, at 6:05 AM, Dmitry Mescheryakov <
> dmescheryakov@xxxxxxxxxxxx> wrote:
> Jon, I've corrected the following docs:
> https://wiki.openstack.org/wiki/Savanna/PluggableProvisioning/PluginAPI
> https://wiki.openstack.org/wiki/Savanna/Templates
> 2013/5/25 Sergey Lukjanov <slukjanov@xxxxxxxxxxxx>
>> Hi Jon,
>> Sure, I think we'll update all affected blueprints on Monday - Tuesday.
>> Sincerely yours,
>> Sergey Lukjanov
>> Software Engineer
>> Mirantis Inc.
>> GTalk: me@xxxxxxxxxxx
>> Skype: lukjanovsv
>> On May 24, 2013, at 17:52, Jon Maron <jmaron@xxxxxxxxxxxxxxx> wrote:
>> On May 24, 2013, at 5:32 AM, Dmitry Mescheryakov <
>> dmescheryakov@xxxxxxxxxxxx> wrote:
>> Jon, after a discussion we decided to postpone the idea with adding
>> process to config classification. We still think that it might be a
>> valuable feature, but we also don't have time to implement it in Vanilla
>> Hadoop plugin. Taking that into account seems like we are pretty aligned.
>> Here is the summary of proposed changes:
>> Redefine get_node_processes() in the following way:
>>     Returns all supported services and node processes for a given Hadoop
>> version. Each node process belongs to a single service and that
>> relationship is reflected in the returned dict object. See example for
>> details.
>>     Returns: dictionary having entries (service -> list of processes)
>>     Example return value: {"mapreduce": ["tasktracker", "jobtracker"],
>> "hdfs": ["datanode", "namenode"]}
>> Redefine 'config' object in the following way:
>> config:
>>     name
>>     description
>>     type
>>     default_value
>>     is_optional
>>    * applicable_target*
>> *    scope*
>> *
>> *
>> Where
>>     applicable_target = <service name> | “general”
>>     scope = “node” | “cluster”
>>     <service name> = “service:mapreduce” | “service:hdfs” | …
>> Do you agree?
>> Yes - this aligns with our thinking :)
>> Just so we have a complete picture:  these modifications should affect
>> the structure of the node group and cluster templates - the configuration
>> should also reflect this service based approach.  Would you mind updating
>> the templates wiki so we can see the nature of the modifications and make
>> sure we're aligned there as well?
>> Thanks!
>> Thanks,
>> Dmitry
>> 2013/5/23 Jon Maron <jmaron@xxxxxxxxxxxxxxx>
>>> We like this suggestion - it provides service mappings for properties
>>> and allows the controller to make the appropriate groupings.  But are still
>>> concerned about the focus on component based editing and the resultant
>>> templates.
>>> First and foremost - we discussed this approach with our internal Hadoop
>>> developers.  They indicate that there is no current resource (documentation
>>> etc) that really details the mapping of configuration properties to their
>>> associated components/processes.  This sort of mapping could ultimately be
>>> provided, but it would it be a fairly significant effort and is not
>>> currently planned.
>>> In addition, Let me illustrate a fundamental problem with component
>>> based editing:
>>> The following is a possible node group template created via component
>>> based UI panels (in this case, a panel that showed the properties available
>>> for a name node, followed by a UI that showed the properties available for
>>> a secondary name node):
>>> {
>>>        id: "aee4-strf-o14s-fd34",
>>>        flavor: "4",
>>>        image: "ah91-aij1-u78x-iunm",
>>>        name: ”HDFS master”
>>>         description: “a template for big nodes ...”,
>>>        plugin: “apache-hadoop”,
>>>        hadoop_version: “1.1.1”
>>>        node_processes: [“name node”, “secondary name node”]
>>>        node_configs:
>>>            {
>>>                ”name node”:
>>>                    {
>>>                        fs.checkpoint.dir: /hadoop/hdfs/*one*
>>>                        fs.checkpoint.period: *21600*,
>>>                        ...
>>>                    }
>>>                ”secondary name node”:
>>>                    {
>>>                        fs.checkpoint.dir: /hadoop/hdfs/*two*
>>>                        fs.checkpoint.period: *28600*,
>>>                        ...
>>>                    }
>>>                ”OS settings”:
>>>                    {
>>>                          …
>>>                    }
>>>            }
>>>    }
>>> In this instance, the user was presented with the option of configuring
>>> the node group via a series of component based UIs and created this node
>>> group template.  The properties you see above are actually associated to
>>> the service and will end up in the same configuration file on each given
>>> node within the node group.  So how do we, as a plugin, decide which
>>> property value wins?  The somewhat artificial attempt to provide properties
>>> on a component basis can potentially lead to these sort of issues in
>>> multiple instances.
>>> We think it would be much better to align the templates with the way
>>> properties are configured in a hadoop - on a cluster or node group basis,
>>> not on a per component basis.  This does not mean that the UI can not
>>> present the data in a way that is more palatable to the user - you can do
>>> some paging and filtering to make the UI more usable.  But ultimately, the
>>> entries the user makes should be aligned with the way properties are
>>> persisted in Hadoop to avoid issues like the one above and to present the
>>> user with a more "Hadoop-like" interface.
>>> I've posted some simple mock ups that show how you could present the
>>> user with property editing facilities that are aligned with services while
>>> allowing for an understanding of the components those properties affect.
>>>  They are posted here:
>>> https://wiki.openstack.org/wiki/File:Node_Group_Editor.png
>>> https://wiki.openstack.org/wiki/File:Service_Configuration_Editor.png
>>> Ultimately, I think we can work to achieving the UI and plugin
>>> requirements:
>>> - UI:  provide an manageable interface for configuration setting.  As
>>> long as you have an appropriate amount of metadata concerning the
>>> configuration properties, you should be able to create a usable interface,
>>> grouping the properties in a logical and usable fashion.
>>> - Plugin:  the properties are associated to associated to a particular
>>> service or to a GENERAL grouping, and are scoped to the node group or to
>>> the cluster.
>>> Note that the scope (group or cluster) is dependent on where it was
>>> specified by the user.  All properties can be supported at both levels
>>> (cluster and node), so there is no need to have a "scope" attribute in the
>>> config object.  Rather, the association of a property to a cluster object
>>> or node group indicates its scope.
>>> On May 23, 2013, at 6:47 AM, Dmitry Mescheryakov <
>>> dmescheryakov@xxxxxxxxxxxx> wrote:
>>> Jon,
>>> We discussed that and we agree to implement this approach in current
>>> phase. Regarding your modification proposals:
>>> 1) We want to keep applicable_target as a single-value field. How about
>>> if we instead redefine plugin.get_node_processes() in the following way:
>>> get_node_processes()
>>>     Returns all supported services and node processes for a given Hadoop
>>> version. Each node process belongs to a single service and that
>>> relationship is reflected in the returned dict object. See example for
>>> details.
>>>     Returns: dictionary having entries (service -> list of processes)
>>>     Example return value: {"mapreduce": ["tasktracker", "jobtracker"],
>>> "hdfs": ["datanode", "namenode"]}
>>> In that case if plugin just specifies that
>>> applicable_target="process:jobtracker", it will be enough for controller to
>>> identify the process/service config belongs to. If plugin specifies
>>> applicable_target="service:mapreduce", the controller will understand that
>>> this is a service general parameter and which processes are affected.
>>> 2) It is plugin which returns list of supported configs in get_configs()
>>> call. The 'scope' field in the 'config' object indicates to the controller,
>>> where the config needs to be presented to user: either on cluster level, or
>>> on node group level. Right?
>>> Thanks,
>>> Dmitry
>>> 2013/5/22 Jon Maron <jmaron@xxxxxxxxxxxxxxx>
>>>> On May 22, 2013, at 9:52 AM, Dmitry Mescheryakov <
>>>> dmescheryakov@xxxxxxxxxxxx> wrote:
>>>> *
>>>> Hello Jon,
>>>> We considered using services instead of processes and found that they
>>>> also have disadvantage. The problem with the services approach is in the
>>>> UI. Consider the following example:
>>>> User configures node group to run MapReduce workers, i.e. TaskTrackers
>>>> processes. It does not matter if he creates a Node Group Template, or edits
>>>> Node Group during cluster creation, since the UI will be similar in both
>>>> cases. Since properties are categorized by services, user is asked to fill
>>>> in all the parameters for that service (MapReduce) including those for
>>>> JobTracker like “JobTracker heap size”, etc. As a result user has to dig
>>>> through many irrelevant options during configuration, which is very bad. I
>>>> think we should not blindly copy files configuration even if users got used
>>>> to it. We are making a web console and we should use the advantages it
>>>> provides over editing files. I.e. if we can filter out irrelevant options
>>>> for user, then why not do it? That does not change configuration flow much,
>>>> but at the same time it is much more convenient for a user.
>>>> *
>>>> In the case above, it is true that we would return all service related
>>>> configuration properties.  However, we do specify the default values, and
>>>> we may be able to specify components as well for the purposes of enhancing
>>>> the UI.  The user would only have to modify the values for which the
>>>> default does not makes sense.  The bottom line is that the user is
>>>> presented with a single set of properties for a service because doing
>>>> otherwise introduces race conditions and uncertainty with respect to which
>>>> property value is actually used.  Let me illustrate again with the name
>>>> node and secondary name node which likely are both deployed on the same
>>>> instance.  In that case the property choices for each process/component are
>>>> obviously the same.  If a user decided to vary the values for the same
>>>> properties based on the two separate component property selection panels,
>>>> which property value are we expected to actually use?  Remember, Hadoop
>>>> does not configure components.  These values end up in node or service
>>>> based configuration files, so the selections from both the name node and
>>>> secondary name node ultimately end up in the same configuration file.
>>>>  Which value selection are expected to select?  Again, this is not a
>>>> contrived example.  More generally, component based configuration is simply
>>>> not a configuration scheme with which Hadoop users are familiar.  We are
>>>> lucky enough to have multiple developers of Hadoop working in the company,
>>>> and every single one we've spoken to has questioned the component based
>>>> configuration of Savanna.
>>>> *
>>>> As for Templates, our intention is to provide all users with ability to
>>>> create their own templates, both for Cluster and Node Group. In fact we see
>>>> no reason to reject a user have his own templates. We just _think_ that
>>>> users will prefer administrators or more experienced users to prepare
>>>> templates for them, because these people should be better at Hadoop cluster
>>>> tweaking.
>>>> Right now the main concern we have is timing. We already spent much
>>>> time designing phase 2 and I believe that our initial design evolved into
>>>> something much better. But we think that it is about time to freeze specs
>>>> we have for phase 2 and start implementing them. At the same time we can
>>>> have a background conversation on how we can improve the design in phase 3.
>>>> We believe that it will not be hard to change this part specifically.
>>>> The solution for the problem we see is to unify processes and services
>>>> categorization. Config object can have the following 2-dimensional
>>>> “coordinates”:
>>>>    - applicable_target = <process name> | <service name> | “general”
>>>>    - scope = “node” | “cluster”
>>>> where
>>>> <process name> = “process:tasktracker” | “process:jobtracker” |
>>>> “process:datanode” | …
>>>> <service name> = “service:mapreduce” | “service:hdfs” | …
>>>> Here is a table example parameters for various combinations of
>>>> target/scope:
>>>> Cluster
>>>> Node
>>>> Process
>>>> Don’t use this combination, use Service/Cluster instead
>>>> JobTracker heap size, mapred.tasktracker.map.tasks.maximum
>>>> Service
>>>> dfs.replication, mapred.output.compression.type
>>>> ?
>>>> General
>>>> user SSL key for cluster machines
>>>> OS parameters like ulimits
>>>> Again, as I said we propose to do this only after we complete Pluggable
>>>> Provisioning Mechanism and make sure it is working. Right now we suggest to
>>>> implement our old proposal with with processes, just to avoid further
>>>> changes in design in this phase.
>>>> *
>>>> This approach is acceptable with some modification:
>>>> 1)  applicable target should be modified to a list of targets, allowing
>>>> for the specification of service/component or general, e.g
>>>> applicable_targets = ["service:mapreduce", "process:job tracker"]
>>>> or
>>>> applicable_targets = ["general"]
>>>> 2)  The scope attribute is probably unnecessary since the scope is
>>>> implied by where the user_input is specified (It's not required for the
>>>> returned config objects).  When attached to a node_group, the scope is
>>>> "node".  When attached to the cluster object directly, the scope is
>>>> "cluster".
>>>> Also, I don't think this can wait till the next phase and I don't think
>>>> it affects your development much for the following reasons:
>>>> - the current form of the config and user_input objects remains
>>>> unchanged.  We are just changing some of the values
>>>> - for the time being we can try to return the associated process as
>>>> part of the applicable targets list so that you can at least provide a hint
>>>> on the service configuration page (and I don't believe the UIs work has
>>>> begun anyhow)
>>>> But from our perspective this will greatly enhance our capability of
>>>> implementing the plugin since the bottom line is that we need to associate
>>>> properties to services/node.  Attempting the artificial grouping of the
>>>> properties per component/process complicates our ability to property
>>>> structure the configuration of the Hadoop cluster.
>>>> *
>>>> Thanks,
>>>> Dmitry
>>>> *
>>>> 2013/5/22 Jon Maron <jmaron@xxxxxxxxxxxxxxx>
>>>>> We still have some concerns regarding the current configuration
>>>>> approach.  I'd like to highlight two major issues:
>>>>> 1)  Component level configuration - Configuring at the component level
>>>>> is contrary to the Hadoop configuration approach which is structured around
>>>>> host level configuration (as opposed to component level).  Trying to
>>>>> configure at the component level runs contrary to that configuration
>>>>> philosophy and would likely be questioned by Hadoop users.  In addition,
>>>>> this approach can be rather error prone.  For example, consider a
>>>>> deployment in which the name node and secondary name node are hosted on the
>>>>> same server (a not uncommon approach).  Both components obviously share a
>>>>> great deal of configuration properties.  If a user is leveraging the UI and
>>>>> is configuring these items at the component level he/she will:
>>>>> - repeat the configuration for each component, a process that may be
>>>>> rather frustrating
>>>>> - will have no idea which of the settings will actually be leveraged
>>>>> since there is essentially a race condition here - the properties
>>>>> potentially end up in the same configuration file on the given node group,
>>>>> so which of the properties actually win?
>>>>> 2)  There doesn't appear to be a facility for making changes that span
>>>>> node groups.  The cluster templates are essentially immutable - they are
>>>>> created by an admin and are not seen as modifiable via the UI by users (at
>>>>> least as far as we can tell).  The other configuration alternative
>>>>> currently is to configure the specific node groups.  So, for example, how
>>>>> do I approach the task of modifying 3 HDFS properties across all 10 node
>>>>> groups I've defined?  It seems that with the current approach I will have
>>>>> to repeatedly make the same modifications to each node group in turn?
>>>>> We believe both of these issues can be remedied by modifying the
>>>>> configuration approach to be more service centric rather than component
>>>>> centric.  While the cluster template still provides for global, immutable
>>>>> settings, allowing users to configure at the service level will allow for
>>>>> global changes across node groups.  We still want to address the node group
>>>>> level configuration (host level overrides), so perhaps the config structure
>>>>> could be redesigned as follows:
>>>>> *config*
>>>>> Describes a single config parameter.
>>>>> name
>>>>> description
>>>>>  type
>>>>> Type could be string, integer, enum, array of [int, string]
>>>>> default_value
>>>>>  is_optional
>>>>> * service - a service name or "GENERAL"*
>>>>> *
>>>>> *
>>>>> To be clear about what the service attribute values mean:
>>>>> *service name* - this property value is a service-based property that
>>>>> is valid at to be applied to the service across a cluster or to a specific
>>>>> node group (i.e. the property can be applied to all instances of the
>>>>> service across the cluster or to a specific set of hosts in a node group).
>>>>>  The scope is determined by where the user selected the property value (the
>>>>> node group interface or the cluster interface) and specified in the
>>>>> user_input "scope" attribute (see below)
>>>>> *"GENERAL"* - this property value is not specific to a hadoop
>>>>> service.  It can be specified at the cluster or node group level as well.
>>>>> * *
>>>>> In the UI, the interfaces can provide the setting of all values.  The
>>>>> UI can categorize the properties based on service etc to present to the
>>>>> user.  If the user is in a node group configuration panel, the
>>>>> configuration settings will be scoped to the node group.  If they are in a
>>>>> cluster template or the like, the property value should be scoped to the
>>>>> entire cluster.
>>>>> The user_input object remains unchanged.  User input values assigned
>>>>> to the cluster_configs attribute of the Cluster object are cluster scope
>>>>> properties (GENERAL or service based).  User input values associated to the
>>>>> embedded node groups (node_configs attribute within a particular node_group
>>>>> in node_groups list  of the cluster object) are associated to the specific
>>>>> node group (GENERAL or service based).
>>>>> Again, we feel that this aligns the interface much more closely with
>>>>> the way users interact with Hadoop.  The attempt to align configuration
>>>>> with specific service components is somewhat contrived and introduces an
>>>>> impedance mismatch that users will probably reject.
>>>>> --
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