netmap: add some sane limits to rep/cbf, fix #307

These are mostly some sanity checks, having unlimited replicas can be
problematic. Limiting the overall number of nodes is important wrt signature
collection, stack can't have more than 2048 elements.

Explain CBF a bit better at the same time.

Signed-off-by: Roman Khimov <[email protected]>

netmap/types.proto

@@ -97,7 +97,7 @@ message Selector {
 // selector set, the root bucket containing all possible nodes will be used by
 // default.
 message Replica {
-  // How many object replicas to put
+  // How many object replicas to put. Limited to 8.
   uint32 count = 1 [json_name = "count"];
 
   // Named selector bucket to put replicas
@@ -109,11 +109,13 @@ message Replica {
 // storage policy definition languages.
 message PlacementPolicy {
   // Rules to set number of object replicas and place each one into a named
-  // bucket
+  // bucket. Limited to 256 items.
   repeated Replica replicas = 1 [json_name = "replicas"];
 
-  // Container backup factor controls how deep NeoFS will search for nodes
-  // alternatives to include into container's nodes subset
+  // Container backup factor (CBF) controls how deep NeoFS will search for
+  // alternative nodes to include into container's nodes subset. In total,
+  // the number of container nodes is Selector (used by Replica) count
+  // times CBF. This number is limited to 64 per-Replica and 512 overall.
   uint32 container_backup_factor = 2 [json_name = "containerBackupFactor"];
 
   // Set of Selectors to form the container's nodes subset

proto-docs/netmap.md

@@ -480,8 +480,8 @@ storage policy definition languages.
 
 | Field | Type | Label | Description |
 | ----- | ---- | ----- | ----------- |
-| replicas | [Replica](#neo.fs.v2.netmap.Replica) | repeated | Rules to set number of object replicas and place each one into a named bucket |
-| container_backup_factor | [uint32](#uint32) |  | Container backup factor controls how deep NeoFS will search for nodes alternatives to include into container's nodes subset |
+| replicas | [Replica](#neo.fs.v2.netmap.Replica) | repeated | Rules to set number of object replicas and place each one into a named bucket. Limited to 256 items. |
+| container_backup_factor | [uint32](#uint32) |  | Container backup factor (CBF) controls how deep NeoFS will search for alternative nodes to include into container's nodes subset. In total, the number of container nodes is Selector (used by Replica) count times CBF. This number is limited to 64 per-Replica and 512 overall. |
 | selectors | [Selector](#neo.fs.v2.netmap.Selector) | repeated | Set of Selectors to form the container's nodes subset |
 | filters | [Filter](#neo.fs.v2.netmap.Filter) | repeated | List of named filters to reference in selectors |
 | subnet_id | [neo.fs.v2.refs.SubnetID](#neo.fs.v2.refs.SubnetID) |  | DEPRECATED. Was used for subnetwork ID to select nodes from, currently ignored. |
@@ -497,7 +497,7 @@ default.
 
 | Field | Type | Label | Description |
 | ----- | ---- | ----- | ----------- |
-| count | [uint32](#uint32) |  | How many object replicas to put |
+| count | [uint32](#uint32) |  | How many object replicas to put. Limited to 8. |
 | selector | [string](#string) |  | Named selector bucket to put replicas |