BSIP Draft: Versioning BitShares and Block Producer Publishing Version

bsip-versioning-bitshares-and-witness-publishing-version.md

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+    BSIP:       <NUMBER>
+    Title:      Create versioning for the Bitshares Blockchain
+    Authors:    Fabian Schuh <https://github.com/xeroc>
+    Status:     Draft
+    Type:       Protocol
+    Created:    2018-10-11
+    Discussion: https://github.com/bitshares/bitshares-core/issues/1173
+    Worker:     <Id of worker proposal>
+
+# Abstract
+
+In BitShares witnesses serve as a neutral third party. They are validating
+signatures and timestamping transactions by including them in blocks. One
+elected witness is signing the block and applying it to the database, hence
+changing the state of the database.
+
+Due to consensus requirements, all witnesses need to agree on the set of rules,
+i.e., the protocol.  Currently there is no way to tell whether a witness-node
+has an outdated version running or not.
+
+To solve this problem this BSIP introduces a way to store the version of the witness
+on the blockchain. Furthermore a versioning scheme, which is currently
+not part of the BitShares code, will be introduced to represent the version.
+
+# Motivation
+
+In case of a protocol upgrade a witness running an old version of the BitShares
+code will be unable to validate a transaction, which was introduced with the
+new upgrade. The transaction won't be applied to the blockchain. If the majority
+of the block producers agreed on a version different from the one used locally, the
+local blockchain will get stuck with no meaningful reason provided.
+
+The goal is to provide means to the node operators to identify that the
+blockchain protocol has advanced. This could be achieved by monitoring the
+blockchain and notifying the nodes when a outdated version is detected.
+
+# Specifications
+
+## Witness Object
+
+The `witness_object` is added a `running_version` variable. It shows the
+current running version of a particular witness.
+
+With every signed block it will be checked that, the `running_version` hasn't
+changed. If `running_version != current_version`, `running_version` is replaced
+by `current_version`. Also `current_version` is included in to the current
+block, so everyone can see that it has upgraded its code.
+
+## Versioning
+
+The used versioning scheme is `Major.Minor.Patch`.
+- Major: consensus changes
+- Minor: changes not impacting consensus
+- Patch: hotfix
+
+For the pupose of this BSIP a `version` class is used. It contains the three
+numbers of the version and the `hardfork_time`, which shows when the hardfork
+occured.
+
+For clarification all occurences of `HARDFORK_XXX_TIME` are changed to
+`HARDFORK_XXX_VERSION`.  To not change the old behaviour in the code, operator
+overloads for adding/subtracting time offsets for: 
+- `uint_32`
+- `fc::microseconds`
+- `fc::time_point_sec`
+were added to the `version` class. 
+
+When the version of the witness changes, it is included in to the block.
+Also the `witness_object.running_version` is modified in this case.
+
+# Discussion
+
+To be found in the forum - see link above.
+
+# Summary for Shareholders
+
+This BSIP introduces a way to publish the running version of a witness to the
+blockchain. It greatly reduces the risk of having an outdated version running
+on a witness node.
+
+# Copyright
+
+This document is placed in the public domain.