Consensus Engine API #4

aludvik · 2018-03-15T17:07:38Z

Signed-off-by: Adam Ludvik [email protected]

Signed-off-by: Adam Ludvik <[email protected]>

dcmiddle · 2018-03-15T20:44:22Z

text/0000-consensus-api.md

+[summary]: #summary
+
+This RFC describes a new Consensus API for supporting both the existing
+_Nakamoto-style_ consensus algorithms as _elected leader_ algorithms such as


typo?
:s/as/as well as

dcmiddle · 2018-03-15T20:45:40Z

text/0000-consensus-api.md

+
+This RFC describes a new Consensus API for supporting both the existing
+_Nakamoto-style_ consensus algorithms as _elected leader_ algorithms such as
+rBFT.


PBFT is the general case. rBFT is probably the first PBFT-like consensus we'll add.

dcmiddle · 2018-03-15T20:52:10Z

text/0000-consensus-api.md

+
+These observations led to the creation of the _Consensus Engine_ abstraction,
+which can be used to implement any consensus algorithm that is either an
+_elected leader_ algorithm or a _Nakamoto-style_ algorithm.


The hyperledger architecture paper on consensus breaks these methods into lottery (PoET, POW, etc) and voting (PBFT, RBFT, RAFT, etc) based elections. The use of elected leader could be misunderstood. (see https://www.hyperledger.org/wp-content/uploads/2017/08/Hyperledger_Arch_WG_Paper_1_Consensus.pdf)

Signed-off-by: Adam Ludvik <[email protected]>

This is to be consistent with the Hyperledger Language Signed-off-by: Adam Ludvik <[email protected]>

aludvik · 2018-03-21T16:02:05Z

Pushed some commits to address @dcmiddle comments

dcmiddle · 2018-04-06T16:26:39Z

text/0000-consensus-api.md

+
+The Consensus Engine interface and implementations of the interface should be
+reusable in other applications. Specifically, the interface should support
+non-blockchain applications.


This is too vague for me. Can you give an example of why and what non-blockchain app needs this?

For example, it would be nice if we can re-use consensus engines to implement a distributed oracle.

dcmiddle · 2018-04-06T16:52:04Z

text/0000-consensus-api.md

+
+| Method | Description |
+| --- | --- |
+| GetSetting(setting) -> data | Read the current value of the setting. Supports R4. |


Is this a convenience method wrapping GetState(address) or does it imply settings outside of global state?

dcmiddle · 2018-04-06T16:54:29Z

text/0000-consensus-api.md

+| Method | Description |
+| --- | --- |
+| OnMessageReceived(message) | Called when a new consensus message is received |
+| OnNewBlockReceived(block) | Called when a new block is received and validated |


Does "and validated" imply that validator will validate transactions before consensus considers whether the block is valid or has precedence?

That was what the original design called for. The API was changed to include a CheckBlocks() method which signals to the validator that it should "check that the block can be committed" which allows the validator to send blocks to consensus before they are validated. At this time however, blocks are still validated prior to sending them to consensus. The alternative requires two new feautres: 1. the ability to process all consensus-specific transactions separately from regular transactions and 2. the ability to read, write, and verify state sub-trees.

dcmiddle · 2018-04-06T16:54:51Z

text/0000-consensus-api.md

+| Method | Description |
+| --- | --- |
+| OnMessageReceived(message) | Called when a new consensus message is received |
+| OnNewBlockReceived(block) | Called when a new block is received and validated |


Do you envision sending the entire block or just the block header?

In the end, everything but batches are sent.

dcmiddle · 2018-04-06T16:55:14Z

text/0000-consensus-api.md

+| --- | --- |
+| GetSetting(setting) -> data | Read the current value of the setting. Supports R4. |
+| GetState(address) -> data | This is needed to read values from arbitrary addresses used by consensus (eg., validator registry). Supports R5. |
+| GetBlock(block_id) -> block | Retrieve consensus-related information about a block. |


Will this return the entire block or just the block header?

In the end, everything but batches are sent.

dcmiddle · 2018-04-06T17:01:08Z

text/0000-consensus-api.md

+The Block Publisher handles the creation of blocks. It is directed by the
+Consensus Engine on when to do this. When a block is finalized, it is forwarded
+to the Block Validator.
+


Block Store and Block Cache from the diagram are not defined here. No need for unnecessary work if the definitions remain the same as here: https://sawtooth.hyperledger.org/docs/core/releases/latest/architecture/journal.html.

These are not very relevant to the discussion and are superseded by the block manager.

Signed-off-by: Adam Ludvik <[email protected]>

kulkarniamol · 2018-05-13T22:57:15Z

text/0000-consensus-api.md

+| --- | --- |
+| Startup() | Startup and synchronize with any peers if necessary. |
+| Shutdown() | Shutdown and notify peers if necessary. |
+


How does one register a consensus engine with the validator?

This is more detail than I think belongs in the RFC and I will include it in the documentation.

vaporos · 2018-09-18T02:26:49Z

This RFC should be updated to match the implementation prior to FCP.

Signed-off-by: Adam Ludvik <[email protected]>

danintel

2 comments
1 apparent error (read vs. read/write)

danintel · 2018-09-21T21:54:22Z

text/0000-consensus-api.md

+  of the fork-resolution logic.
+
+Examples of _lottery_ consensus algorithms include Proof-of-Work (PoW)
+and Proof-of-Elapsed-Time (PoET).


Just a suggestion--I would add "Also known as Nakamoto-style consensus"

danintel · 2018-09-21T21:54:42Z

text/0000-consensus-api.md

+  coordinate consensus.
+
+Examples of _voting_ algorithms include PBFT, rBFT, Tendermint, and
+Raft.


Just a suggestion--I would add "Also known as classical consensus"

danintel · 2018-09-21T21:57:56Z

text/0000-consensus-api.md

+**R5 - Read/Write Access to Global State**
+
+PoET depends on tracking authorized block publishers in global state and
+therefore requires read access to a PoET specific namespace.


Where does the "Write" (from "Read/Write Access") come in here. I think you mean "read/write" access on line 128.

This should just say Read

kirkwood · 2018-09-23T18:03:38Z

text/0000-consensus-api.md

+This design borrows some ideas from the [Tendermint ABCI][tendermint] and the
+[Parity Consensus Engine][parity] interface.
+
+[tendermint]: https://tendermint.readthedocs.io/en/master/app-development.html#abci-design)


Dead link; https://tendermint.com/docs/spec/abci/ maybe?

This is not intended to be part of the API. Signed-off-by: Adam Ludvik <[email protected]>

Signed-off-by: Adam Ludvik <[email protected]>

aludvik · 2018-10-03T16:06:01Z

@danintel @kirkwood addressed your comments.

Signed-off-by: Adam Ludvik <[email protected]>

dcmiddle · 2018-10-17T12:56:59Z

I move that this RFC enter Final Comment Period with a disposition to merge.

dcmiddle · 2018-10-25T13:16:08Z

Checkboxes for core team:

Consensus Engine API

2614f17

Signed-off-by: Adam Ludvik <[email protected]>

dcmiddle reviewed Mar 15, 2018

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askmish self-requested a review March 17, 2018 06:27

Adam Ludvik added 2 commits March 21, 2018 10:57

Fix typo

89591e8

Signed-off-by: Adam Ludvik <[email protected]>

Update consensus language to use voting/lottery

18de26a

This is to be consistent with the Hyperledger Language Signed-off-by: Adam Ludvik <[email protected]>

dcmiddle reviewed Apr 6, 2018

View reviewed changes

Fix typos

500b368

Signed-off-by: Adam Ludvik <[email protected]>

kulkarniamol reviewed May 13, 2018

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Reflect API changes during implementation

7355af7

Signed-off-by: Adam Ludvik <[email protected]>

aludvik requested review from dcmiddle and vaporos September 21, 2018 21:07

danintel suggested changes Sep 21, 2018

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kirkwood reviewed Sep 23, 2018

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Adam Ludvik added 2 commits October 3, 2018 09:03

Remove Write typo from API

0a47adb

This is not intended to be part of the API. Signed-off-by: Adam Ludvik <[email protected]>

Fix dead tendermint link

28a737c

Signed-off-by: Adam Ludvik <[email protected]>

danintel approved these changes Oct 3, 2018

View reviewed changes

Add alternative names for consensus types

7feec96

Signed-off-by: Adam Ludvik <[email protected]>

dcmiddle approved these changes Oct 16, 2018

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dcmiddle requested review from agunde406 and jsmitchell October 16, 2018 14:36

dcmiddle requested review from peterschwarz and TomBarnes October 16, 2018 14:36

dcmiddle assigned aludvik Oct 16, 2018

jsmitchell approved these changes Oct 16, 2018

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agunde406 approved these changes Oct 16, 2018

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peterschwarz approved these changes Oct 16, 2018

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TomBarnes approved these changes Oct 16, 2018

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aludvik merged commit 7822584 into hyperledger-archives:master Nov 2, 2018

hyperledger-archives deleted a comment from Sidaretta May 16, 2019

hyperledger-archives deleted a comment from rberg2 May 16, 2019

hyperledger-archives deleted a comment from Sidaretta May 16, 2019

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Consensus Engine API #4

Consensus Engine API #4

aludvik commented Mar 15, 2018

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Consensus Engine API #4

Consensus Engine API #4

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vaporos commented Sep 18, 2018

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aludvik commented Oct 3, 2018

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