Github user vidaha commented on the pull request:
https://github.com/apache/spark/pull/1899#issuecomment-51949860
Hi Josh,
IMHO, it's best not to require a Spark cluster name and the security group
to be the same. While you can reuse an existing security group to launch
another cluster, you can't launch more than one cluster with the same security
group. Perhaps a company wants to have an internal-applications or dev
security group and reuse that for launch multiple Spark clusters. In addition,
AWS has a strict limit of 100 on the number of security groups on a VPC, and
since two security groups are required (one of the masters and one for the
workers), this means, that only 50 Spark cluster can be launched on a VPC.
While that might seem like a reasonable limit, I can easily see companies
having a use case to exceed that.
Do you mind illustrating the problem about name conflicts? If I understand
what you are saying, you are mentioned this scenario:
% ./spark-ec2 ⦠âsecurity-group my-security-group launch my-cluster-name
And then later, you also run:
% ./spark-ec2 ⦠launch my-security-group
This works fine - I tested it - there will be two clusters with the same
security group, but different names. These are some error cases that I thought
might offer and tested for manually and they worked out fine:
- Can you then run ./spark-ec2 ⦠âdelete-groups destroy
my-security-group and delete the security group when another cluster is using
that security group?
I tried this, and amazon has the correct controls to prevent deleting a
security group still in use by another cluster.
- Can you forget to include the security group override on a launched
cluster and create problems?
I tried this as well, and since the get_existing_cluster code was modified
to use the name rather than the security group to identify the instance, this
works right. You canât run:
% ./spark-ec2 ⦠launch my-cluster-name
if there is already a cluster with my-cluster-name launched.
Are there some other possible conflicts that you can think of? If you can
write out the commands to illustrate the use cases you are thinking of - I can
run them and see what happens.
-Vida
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