Make the minimum mapping block 1, not genesis

crates/sc-consensus-subspace/src/archiver.rs

@@ -73,6 +73,7 @@ use sp_runtime::traits::{
 use sp_runtime::Justifications;
 use std::error::Error;
 use std::future::Future;
+use std::num::NonZeroU32;
 use std::slice;
 use std::sync::atomic::{AtomicU16, Ordering};
 use std::sync::Arc;
@@ -365,8 +366,13 @@ pub struct ObjectMappingNotification {
 pub enum CreateObjectMappings {
     /// Start creating object mappings from this block number.
     ///
-    /// This can be lower than the latest archived block.
-    Block(BlockNumber),
+    /// This can be lower than the latest archived block, but must be greater than genesis.
+    ///
+    /// The genesis block doesn't have mappings, so starting mappings at genesis is pointless.
+    /// The archiver will fail if it can't get the data for this block, but snap sync doesn't store
+    /// the genesis data on disk.  So avoiding genesis also avoids this error.
+    /// <https://github.com/paritytech/polkadot-sdk/issues/5366>
+    Block(NonZeroU32),
 
     /// Create object mappings as archiving is happening.
     Yes,
@@ -377,11 +383,14 @@ pub enum CreateObjectMappings {
 }
 
 impl CreateObjectMappings {
+    /// The minimum mapping block number.
+    pub const MIN_BLOCK: CreateObjectMappings = CreateObjectMappings::Block(NonZeroU32::MIN);
+
     /// The fixed block number to start creating object mappings from.
     /// If there is no fixed block number, or mappings are disabled, returns None.
     fn block(&self) -> Option<BlockNumber> {
         match self {
-            CreateObjectMappings::Block(block) => Some(*block),
+            CreateObjectMappings::Block(block) => Some(block.get()),
             CreateObjectMappings::Yes => None,
             CreateObjectMappings::No => None,
         }

crates/subspace-malicious-operator/src/bin/subspace-malicious-operator.rs

@@ -200,7 +200,7 @@ fn main() -> Result<(), Error> {
                 base: consensus_chain_config,
                 // Domain node needs slots notifications for bundle production.
                 force_new_slot_notifications: true,
-                create_object_mappings: CreateObjectMappings::Block(0),
+                create_object_mappings: CreateObjectMappings::MIN_BLOCK,
                 subspace_networking: SubspaceNetworking::Create { config: dsn_config },
                 dsn_piece_getter: None,
                 sync: Default::default(),

crates/subspace-node/src/commands/run/consensus.rs

@@ -15,6 +15,7 @@ use sc_telemetry::TelemetryEndpoints;
 use std::collections::HashSet;
 use std::fmt;
 use std::net::{IpAddr, Ipv4Addr, Ipv6Addr, SocketAddr};
+use std::num::NonZeroU32;
 use std::path::PathBuf;
 use std::str::FromStr;
 use subspace_core_primitives::BlockNumber;
@@ -308,10 +309,17 @@ struct TimekeeperOptions {
 pub enum CreateObjectMappingConfig {
     /// Start creating object mappings from this block number.
     ///
-    /// This can be lower than the latest archived block.
-    Block(BlockNumber),
+    /// This can be lower than the latest archived block, but must be greater than genesis.
+    ///
+    /// The genesis block doesn't have mappings, so starting mappings at genesis is pointless.
+    /// The archiver will fail if it can't get the data for this block, and snap sync doesn't store
+    /// the genesis data on disk. So avoiding genesis also avoids this error.
+    /// <https://github.com/paritytech/polkadot-sdk/issues/5366>
+    Block(NonZeroU32),
 
     /// Create object mappings as archiving is happening.
+    /// This continues from the last archived segment, but mappings that were in the channel or RPC
+    /// segment when the node shut down can be lost.
     Yes,
 
     /// Don't create object mappings.
@@ -337,7 +345,7 @@ impl FromStr for CreateObjectMappingConfig {
             "no" => Ok(Self::No),
             "yes" => Ok(Self::Yes),
             block => block.parse().map(Self::Block).map_err(|_| {
-                "Unsupported create object mappings setting: use `yes`, `no` or a block number"
+                "Unsupported create object mappings setting: use `yes`, `no` or a non-zero block number"
                     .to_string()
             }),
         }
@@ -354,6 +362,12 @@ impl fmt::Display for CreateObjectMappingConfig {
     }
 }
 
+impl CreateObjectMappingConfig {
+    /// The minimum mapping block number.
+    pub const MIN_BLOCK: CreateObjectMappingConfig =
+        CreateObjectMappingConfig::Block(NonZeroU32::MIN);
+}
+
 /// Options for running a node
 #[derive(Debug, Parser)]
 pub(super) struct ConsensusChainOptions {
@@ -443,10 +457,10 @@ pub(super) struct ConsensusChainOptions {
 
     /// Create object mappings during archiving.
     ///
-    /// Can be set to `no` (default), `yes` (creates object mappings as archiving is happening) or
-    /// block number from which to continue creating object mappings.
+    /// Can be set to `no` (default), `yes` (creates object mappings as archiving is happening), or
+    /// a non-zero block number where the node starts creating object mappings.
     ///
-    /// --dev mode enables mappings from genesis automatically, unless the value is supplied
+    /// --dev mode enables mappings from the first block automatically, unless a value is supplied
     /// explicitly.
     /// Use `no` to disable mappings in --dev mode.
     #[arg(long)]
@@ -534,7 +548,7 @@ pub(super) fn create_consensus_chain_configuration(
             timekeeper_options.timekeeper = true;
 
             if create_object_mappings.is_none() {
-                create_object_mappings = Some(CreateObjectMappingConfig::Block(0));
+                create_object_mappings = Some(CreateObjectMappingConfig::MIN_BLOCK);
             }
 
             if sync.is_none() {