Github user cestella commented on the issue:
https://github.com/apache/metron/pull/717
Ok, I think maybe a better explanation is in order then. Currently, when
you start a topology, you can specify certain properties of the topology via
the CLI. These are things like the spout parallelism, number of executors,
etc. Originally these were added to the CLI because they were the things that
you needed to adjust to scale a given parser. What this PR is about is giving
you the alternative to specify these topological or structural properties in
the parser config in zookeeper. This enables the admin to specify a config
setup for a given instance of a parser in zookeeper without having to specify
the CLI options.
Now, it bears mentioning that this is also backwards compatible. For these
configuration options mentioned in this PR's description, the order of
precedence is:
* CLI
* Zookeeper
which is to say that properties specified in the CLI will be honored first.
In a post-777 world, you would still have these CLI parameters for the
basic topological properties (likely) and the config is still stored in
zookeeper, so there really should be no conflict between this and what's going
on in 777, I think.
Now, as to the 'how', well, when starting the parser, in the CLI code, we
pull the zookeeper config and figure out the parameters to
`ParserTopologyBuilder.build(...)` which gets invoked to construct the parser
topology, like it did prior to this PR.
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