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From "Konstantinos Karanasos (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (YARN-3409) Add constraint node labels
Date Wed, 30 Nov 2016 04:10:58 GMT

    [ https://issues.apache.org/jira/browse/YARN-3409?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15707465#comment-15707465

Konstantinos Karanasos commented on YARN-3409:

Hi guys, thank you for driving this, for the documentation, and for all the discussion. I
think it is a super-useful feature to have.
We also built a prototype over the summer with the end goal of supporting placement constraints
(of the form affinity/anti-affinity/cardinality, similar in spirit to YARN-1042), and had
to add some initial support for similar node labels along the way.
Please find some comments below.

# As was mentioned above in one of [~leftnoteasy]'s comments too, I also (strongly :)) suggest
to use these ConstraintNodeLabels in the context of YARN-1042 for supporting (anti-)affinity
constraints as well. I think it will greatly avoid duplicate effort and simplify the code.
# On a similar note, can these ContraintNodeLabels be added/removed dynamically? For example,
when a container starts its execution, it might contain some attributes (to be added -- I
know such attributes cannot be specified at the moment). Those attributes will then be added
to the node's labels, for the time the container is running. This can be useful for (anti-)affinity
constraints. For instance, a task can add the label "HBase-master", and then another resource
request can have a constraint of the form "don't put me at a node with an HBase-master label".
What do you think?
# A few people above mentioned that the naming of ContainerNodeLabels might not be ideal.
I think they look more like attributes (as in key-value pairs), so we might consider using
a name that denotes that (labels sound to me more like something that exists or not, but does
not have a value).
# I like that you don't take headroom into account when it comes to constraint label expressions.
# +1 for Option 1. It might also be that the implementation of ConstraintNodeLabels will be
easier at some places than that of NodeLabels/Partitions (e.g., given there is no need for
supporting headroom). In terms of logistics, +1 for the branch too. I think we should make
this an umbrella JIRA.
# Can you please give an example of a cluster-level constraint?
# bq. Constraints will be matched within the scope of a node partition.
Making sure I understand.. Why do we need this constraint? I think they are orthogonal, right?
Unless you mean that if the user specifies a constraint, it has to be taken into account too,
which I understand.
# Also adding one last thing we did in our prototype that I think is related to the locality
(node/rack/any) discussion above and might be useful to consider. We assumed that the ConstraintNodeLabels
are following the hierarchy of the cluster. That is, a rack was inheriting the ConstraintNodeLabels
of all its nodes. A detail here is that we considered only existential ConstraintNodeLabels
(as I mentioned above, without values), which avoids conflicts. In the more general case you
are describing, it is not clear what happens if a node of the rack has Java 6 and the other
Java 7 (not clear what should be the label of the rack). We will need to resolve conflicts
in those case. However, I think that design is quite powerful. Think that eventually we can
even define different logical classes of nodes and register them in the RM. For instance,
group nodes that belong to the same upgrade domain (being upgraded at the same time -- we
see this use case a lot in our clusters).

> Add constraint node labels
> --------------------------
>                 Key: YARN-3409
>                 URL: https://issues.apache.org/jira/browse/YARN-3409
>             Project: Hadoop YARN
>          Issue Type: Sub-task
>          Components: api, capacityscheduler, client
>            Reporter: Wangda Tan
>            Assignee: Naganarasimha G R
>         Attachments: Constraint-Node-Labels-Requirements-Design-doc_v1.pdf
> Specify only one label for each node (IAW, partition a cluster) is a way to determinate
how resources of a special set of nodes could be shared by a group of entities (like teams,
departments, etc.). Partitions of a cluster has following characteristics:
> - Cluster divided to several disjoint sub clusters.
> - ACL/priority can apply on partition (Only market team / marke team has priority to
use the partition).
> - Percentage of capacities can apply on partition (Market team has 40% minimum capacity
and Dev team has 60% of minimum capacity of the partition).
> Constraints are orthogonal to partition, they’re describing attributes of node’s
hardware/software just for affinity. Some example of constraints:
> - glibc version
> - JDK version
> - Type of CPU (x86_64/i686)
> - Type of OS (windows, linux, etc.)
> With this, application can be able to ask for resource has (glibc.version >= 2.20
&& JDK.version >= 8u20 && x86_64).

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