Pass ApplicationExecutionResult to IPersistencePlugin

[RavenXce]

Can we add pass execution_results to the IPersistencePlugins as well here?

neo/neo/Ledger/Blockchain.cs

Line 505 in 77ae335

List<ApplicationExecutionResult> execution_results = new List<ApplicationExecutionResult>();

neo/neo/Ledger/Blockchain.cs

Line 608 in 77ae335

plugin.OnPersist(snapshot);

We want to persist the notifications that happened, and don't want to use the async version in IActorRefs as we need guaranteed writes (we want to abort persist if our plugin fails).

Alternatively, having a blocking version of the Actor plugins would work too.

[vncoelho]

@RavenXce, this is an useful thing, it would be nice to have this notification tool inside neo-cli as @localhuman suggested #352.

Now, considering this OnPersist plugin it will probably be easier and simpler.

EDIT:
@RavenXce, however, the abort part does not look so easy to revert and implement.
Is there really plenty of cases in which the plugin will fail?
Maybe you can handle this inside the plugin, you cache the notifications (namely execution_results) and perform your strategy.

[RavenXce]

@vncoelho since OnPersist is blocking and called just before Commit, simply throwing when an unrecoverable error occurs (such as persistent failure to connect to a remote db) within the plugin should crash the whole app, aborting persisting of the block. An external supervisor can reboot the node if required.

[vncoelho]

I got, it, the external supervisor reboot is the part I thought to be more complex, anyway...

But why a notification plugin should avoid a block to persist if all verification's passed until that moment, would not it be a selective Block filter plugin? aehuaheuaea

[erikzhang]

Because it may be that something went wrong, and we don't want to miss this block and resynchronize.