Clarity Event logging (AssetMaps, etc)

[jcnelson]

An important feature required by both exchanges and block explorers is the ability to see how much of each asset was moved by a given transaction (STX or otherwise). We track this with AssetMaps, but we don't expose any public interface for consuming them. We should provide an option to log all (txid, tx-fee-paid, asset-name, asset-recipient, asset-quantity) records to a dedicated sqlite database, which can be used to service these kinds of queries. We could also expose this information via the RPC interface.

Logging assets is effectively an optimization for operators who need to issue lots of random transaction queries. For low-volume use-cases (like personal nodes), the same information can be obtained by simply replaying the epoch data containing the transaction from the state indicated by the previous epoch's state root. The user would do so with a modified Clarity VM instance whose datastore was programmed to query data maps and variables from the blockchain state at that point in time.

[jcnelson]

In the same vein, make it so the Stacks node emits events through a local socket (e.g. a unix domain socket or whatever), and make it so smart contracts can emit particular events when they run, so receivers can be notified when things happen.

[jcnelson]

To be clear, I do not believe that this feature should be used to procure a publicly-accessible dataset without also making the act of logging the data as expensive as storing it in a data map. Otherwise, the act of curating a public dataset of log data is the act of giving enterprising app developers free hosting for data their smart contract "stores" via this facility.

[blockstack-devops]

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