Github user nickwallen commented on the issue:
https://github.com/apache/metron/pull/740
This is a replay of an offline conversation....
> Sorry for the confusion on my part @ottobackwards . I know much of the
innards of Stellar is only documented in the code (if that), so let's level set
on that.
>
> A "StellarExecutor" is responsible for running Stellar code for the REPL.
The executor can maintain additional "Context" that provides resources for the
Stellar code that it is executing. Each of these resources in the "Context"
are called "Capabilities". For example, a Zookeeper Client is available as a
Capability called "ZOOKEEPER_CLIENT". There is also the "GLOBAL_CONFIG"
capability that exposes Metron's global configuration to Stellar code.
>
> These capabilities, like the GLOBAL_CONFIG, are exposed to Stellar code
in the same way when running either in the REPL or in a topology. A Stellar
function can be written that fails if the GLOBAL_CONFIG is not available. It
can also be written to use acceptable defaults, if a GLOBAL_CONFIG does not
exist.
>
> Previously the only way to create the GLOBAL_CONFIG in the REPL, was to
have a Zookeeper service running with the Metron config deployed and then
launch the REPL with `bin/stellar -z node1:2181". Without doing that there was
no GLOBAL_CONFIG. Any function that was written to expect a GLOBAL_CONFIG, was
not usable in the REPL, unless you launched and configured a Zk instance.
>
> This PR provides the ability to...
> (1) Create a GLOBAL_CONFIG manually in the REPL without the need for Zk
and
> (2) Modify a GLOBAL_CONFIG manually within a single session, without
modifying Zk.
>
> There really is no such thing as an "incompletely formed" GLOBAL_CONFIG.
The GLOBAL_CONFIG is just a key/value store. It contains whatever it contains.
But if there is a missing value in the GLOBAL_CONFIG that your function needs,
then this change only makes it far simpler to add that missing value to the
GLOBAL_CONFIG.
>
> And this is something you would need per your PR #690. If you expect to
run the REPL disconnected from a Metron cluster, then you need a way to create
a GLOBAL_CONFIG without a Zk instance.
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