Add wip rfc for zebra-client/cli design

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Deirdre Connolly 2020-10-14 16:31:54 -04:00 committed by Deirdre Connolly
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- Feature Name: (`zebra-client`)
- Start Date: (fill me in with today's date, 2020-10-15)
- Design PR: [ZcashFoundation/zebra#0000](https://github.com/ZcashFoundation/zebra/pull/0000)
- Zebra Issue: [ZcashFoundation/zebra#0000](https://github.com/ZcashFoundation/zebra/issues/0000)
# Summary
[summary]: #summary
Handling blockchain scanning in subtasks via a zebra-client component in zebrad, and
a wallet component in zebra-cli to query that component for wallet balances and to construct
transactions and send them out via zebrad.
# Motivation
[motivation]: #motivation
We want to send money via Zebra efficiently and securely.
# Definitions
[definitions]: #definitions
# Guide-level explanation
[guide-level-explanation]: #guide-level-explanation
<!-- Explain the proposal as if it was already included in the project and you were teaching it to another Zebra programmer. That generally means: -->
<!-- - Introducing new named concepts. -->
<!-- - Explaining the feature largely in terms of examples. -->
<!-- - Explaining how Zebra programmers should *think* about the feature, and how it should impact the way they use Zebra. It should explain the impact as concretely as possible. -->
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zebra-client
- client component
- (does: key access, blockchain scanning)
- (has a whole separate sled DB for userss txs, keys, etc)
- (keeps track of where its scanned to)
- (can be executed in its own tokio subtask to isolate from timing)
- (has access to notifs from zebra-state about new blocks etc)
- (lives as a subtask of zebrad)
- zebra-cli talks to this subcomponent which is in a running zebrad
- (the scanning executes independently (but in the same process) of the normal node operation)
- (zebra-client, in side zebrad, runs in its own separate task, in case it crashes, its not noticeable)
zebra-cli
- (can use servo/bincode + servo/ipc-channel to communicate with zebrad)
- (separate processes)
# Reference-level explanation
[reference-level-explanation]: #reference-level-explanation
<!-- This is the technical portion of the RFC. Explain the design in sufficient detail that: -->
<!-- - Its interaction with other features is clear. -->
<!-- - It is reasonably clear how the feature would be implemented, tested, monitored, and maintained. -->
<!-- - Corner cases are dissected by example. -->
<!-- The section should return to the examples given in the previous section, and explain more fully how the detailed proposal makes those examples work. -->
## Module Structure
<!-- Describe the crate and modules that will implement the feature.-->
zebra-client ( currently and empty stub) zebra-cli (does not exist yet)
zebra-rfc? (exists as an empty stub, we way have zebra-cli communicate with
zebra-client inside zebrad via an RPC method any/or a private IPC layer)
## Test Plan
<!-- Explain how the feature will be tested, including: -->
<!-- * tests for consensus-critical functionality -->
<!-- * existing test vectors, if available -->
<!-- * Zcash blockchain block test vectors (specify the network upgrade, feature, or block height and network) -->
<!-- * property testing or fuzzing -->
<!-- The tests should cover: -->
<!-- * positive cases: make sure the feature accepts valid inputs -->
<!-- * using block test vectors for each network upgrade provides some coverage of valid inputs -->
<!-- * negative cases: make sure the feature rejects invalid inputs -->
<!-- * make sure there is a test case for each error condition in the code -->
<!-- * if there are lots of potential errors, prioritise: -->
<!-- * consensus-critical errors -->
<!-- * security-critical errors, and -->
<!-- * likely errors -->
<!-- * edge cases: make sure that boundary conditions are correctly handled -->
# Drawbacks
[drawbacks]: #drawbacks
<!-- Why should we *not* do this?-->
Supporting a wallet assumes risk.
# Rationale and alternatives
[rationale-and-alternatives]: #rationale-and-alternatives
<!-- - What makes this design a good design? -->
<!-- - Is this design a good basis for later designs or implementations? -->
<!-- - What other designs have been considered and what is the rationale for not choosing them? -->
> What is the impact of not doing this?
We can't send money with zebra alone.
# Prior art
[prior-art]: #prior-art
<!-- Discuss prior art, both the good and the bad, in relation to this proposal. -->
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<!-- - For community proposals: Is this done by some other community and what were their experiences with it? -->
<!-- - For other teams: What lessons can we learn from what other communities have done here? -->
<!-- - Papers: Are there any published papers or great posts that discuss this? If you have some relevant papers to refer to, this can serve as a more detailed theoretical background. -->
<!-- This section is intended to encourage you as an author to think about the lessons from other projects, to provide readers of your RFC with a fuller picture. -->
<!-- If there is no prior art, that is fine - your ideas are interesting to us whether they are brand new or if they are an adaptation from other projects. -->
<!-- Note that while precedent set by other projects is some motivation, it does not on its own motivate an RFC. -->
<!-- Please also take into consideration that Zebra sometimes intentionally diverges from common Zcash features and designs -->.
# Unresolved questions
[unresolved-questions]: #unresolved-questions
<!-- - What parts of the design do you expect to resolve through the RFC process before this gets merged? -->
<!-- - What parts of the design do you expect to resolve through the implementation of this feature before stabilization? -->
<!-- - What related issues do you consider out of scope for this RFC that could be addressed in the future independently of the solution that comes out of this RFC? -->
# Future possibilities
[future-possibilities]: #future-possibilities
<!-- Think about what the natural extension and evolution of your proposal would -->
<!-- be and how it would affect Zebra and Zcash as a whole. Try to use this -->
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<!-- interactions with the project and cryptocurrency ecosystem in your proposal. -->
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<!-- and of the relevant sub-team. -->
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<!-- RFC you are writing but otherwise related. -->
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<!-- you may simply state that you cannot think of anything. -->
<!-- Note that having something written down in the future-possibilities section -->
<!-- is not a reason to accept the current or a future RFC; such notes should be -->
<!-- in the section on motivation or rationale in this or subsequent RFCs. -->
<!-- The section merely provides additional information. -->