krishvishal commented on code in PR #2546:
URL: https://github.com/apache/iggy/pull/2546#discussion_r2678799753
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core/common/src/types/consensus/header.rs:
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@@ -389,3 +397,200 @@ impl ConsensusHeader for ReplyHeader {
self.size
}
}
+
+/// StartViewChange message header.
+///
+/// Sent by a replica when it suspects the primary has failed.
+/// This is a header-only message with no body.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)]
+pub struct StartViewChangeHeader {
+ pub checksum: u128,
+ pub checksum_padding: u128,
+ pub checksum_body: u128,
+ pub checksum_body_padding: u128,
+ pub nonce_reserved: u128,
+ pub cluster: u128,
+ pub size: u32,
+ pub epoch: u32,
+ pub view: u32,
+ pub release: u32,
+ pub protocol: u16,
+ pub command: Command2,
+ pub replica: u8,
+ pub reserved_frame: [u8; 12],
+
+ pub reserved: [u8; 128],
+}
+
+unsafe impl Pod for StartViewChangeHeader {}
+unsafe impl Zeroable for StartViewChangeHeader {}
+
+impl ConsensusHeader for StartViewChangeHeader {
+ const COMMAND: Command2 = Command2::StartViewChange;
+
+ fn validate(&self) -> Result<(), ConsensusError> {
+ if self.command != Command2::StartViewChange {
+ return Err(ConsensusError::InvalidCommand {
+ expected: Command2::StartViewChange,
+ found: self.command,
+ });
+ }
+
+ if self.release != 0 {
+ return Err(ConsensusError::InvalidField("release !=
0".to_string()));
+ }
+ Ok(())
+ }
+
+ fn size(&self) -> u32 {
+ self.size
+ }
+}
+
+/// DoViewChange message header.
+///
+/// Sent by replicas to the primary candidate after collecting a quorum of
+/// StartViewChange messages.
+#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[repr(C)]
+pub struct DoViewChangeHeader {
+ pub checksum: u128,
+ pub checksum_padding: u128,
+ pub checksum_body: u128,
+ pub checksum_body_padding: u128,
+ pub nonce_reserved: u128,
+ pub cluster: u128,
+ pub size: u32,
+ pub epoch: u32,
+ pub view: u32,
+ pub release: u32,
+ pub protocol: u16,
+ pub command: Command2,
+ pub replica: u8,
+ pub reserved_frame: [u8; 12],
+
+ /// The highest op-number in this replica's log.
+ /// Used to select the most complete log when log_view values are equal.
+ pub op: u64,
+
+ /// The replica's commit number (highest committed op).
+ /// The new primary sets its commit to max(commit) across all DVCs.
+ pub commit: u64,
+
+ /// The view number when this replica's status was last normal.
+ /// This is the key field for log selection: the replica with the
+ /// highest log_view has the most authoritative log.
+ pub log_view: u32,
Review Comment:
From my understanding of VSR-revisited paper, `log_view` is essential for
correctness of consensus. Its called `v'` in the paper. Its used for correct
log selection during view changes. The paper states: "selects as the new log
the one contained in the message with the largest `v'`". Without it, we cannot
correctly determine which replica's log is authoritative, which can lead to
loss of committed operations.
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