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https://issues.apache.org/jira/browse/SAMZA-348?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14172783#comment-14172783
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Yan Fang commented on SAMZA-348:
--------------------------------
{quote}
We will certainly need a way to pipe config files into the ConfigStream.
{quote}
Another reason it is useful is that, if we allows the control.sh to pipe config
files, we will have an easier life in debugging a Samza job with the same
configuration:
1. start a samza job with initial configurations.
2. change configurations.
3. kill the samza job.
4. *dump the ConfigStream into a config file.*
5. start a new samza job with the same configuration.
Step 4 gives three advantages: 1) give an intuitive view of what is used in the
latest samza job 2) speed up the starting process because the AM does need to
read the whole ConfigStream again in step 5. 3) easily make changes in the
config file.
> Configure Samza jobs through a stream
> -------------------------------------
>
> Key: SAMZA-348
> URL: https://issues.apache.org/jira/browse/SAMZA-348
> Project: Samza
> Issue Type: Bug
> Affects Versions: 0.7.0
> Reporter: Chris Riccomini
> Labels: project
> Attachments: DESIGN-SAMZA-348-0.md, DESIGN-SAMZA-348-0.pdf,
> DESIGN-SAMZA-348-1.md, DESIGN-SAMZA-348-1.pdf
>
>
> Samza's existing config setup is problematic for a number of reasons:
> # It's completely immutable once a job starts. This prevents any dynamic
> reconfiguration and auto-scaling. It is debatable whether we want these
> feature or not, but our existing implementation actively prevents it. See
> SAMZA-334 for discussion.
> # We pass existing configuration through environment variables. YARN exports
> environment variables in a shell script, which limits the size to the varargs
> length on the machine. This is usually ~128KB. See SAMZA-333 and SAMZA-337
> for details.
> # User-defined configuration (the Config object) and programmatic
> configuration (checkpoints and TaskName:State mappings (see SAMZA-123)) are
> handled differently. It's debatable whether this makes sense.
> In SAMZA-123, [~jghoman] and I propose implementing a ConfigLog. This log
> would replace both the checkpoint topic and the existing config environment
> variables in SamzaContainer and Samza's YARN AM.
> I'd like to keep this ticket's scope limited to just the implementation of
> the ConfigLog, and not re-designing how Samza's config is used in the code
> (SAMZA-40). We should, however, discuss how this feature would affect dynamic
> reconfiguration/auto-scaling.
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