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Implement routing table computation & sketch routing #2
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cache-nez
commented
Nov 27, 2020
id/mod.go
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| } | ||
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| func BaseAndLenFromPlayers(numPlayers int) (base byte, len int) { | ||
| return 16, 3 |
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A dummy implementation. This method is where the id space computation happens, the first actual implementation will probably be one for hashed ids.
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Different approaches to this computation to be explored in a separate PR.
cache-nez
commented
Nov 27, 2020
routing/handshake.go
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| func (h Handshake) Serialize(ctx serde.Context) ([]byte, error) { | ||
| format := hsFormats.Get(ctx.GetFormat()) | ||
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| data, err := format.Encode(ctx, h) | ||
| if err != nil { | ||
| return nil, xerrors.Errorf("encode: %v", err) | ||
| } | ||
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| return data, nil | ||
| } | ||
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| // - implements router.HandshakeFactory | ||
| type HandshakeFactory struct { | ||
| addrFac mino.AddressFactory | ||
| } | ||
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| // NewHandshakeFactory creates a new factory. | ||
| func NewHandshakeFactory(addrFac mino.AddressFactory) HandshakeFactory { | ||
| return HandshakeFactory{ | ||
| addrFac: addrFac, | ||
| } | ||
| } | ||
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| // Deserialize implements serde.Factory. It populates the handshake if | ||
| // appropriate, otherwise it returns an error. | ||
| func (fac HandshakeFactory) Deserialize(ctx serde.Context, data []byte) (serde.Message, error) { | ||
| return fac.HandshakeOf(ctx, data) | ||
| } | ||
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| // HandshakeOf implements router.HandshakeFactory. It populates the handshake if | ||
| // appropriate, otherwise it returns an error. | ||
| func (fac HandshakeFactory) HandshakeOf(ctx serde.Context, data []byte) (router.Handshake, error) { | ||
| format := hsFormats.Get(ctx.GetFormat()) | ||
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| ctx = serde.WithFactory(ctx, types.AddrKey{}, fac.addrFac) | ||
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| msg, err := format.Decode(ctx, data) | ||
| if err != nil { | ||
| return nil, xerrors.Errorf("decode: %v", err) | ||
| } | ||
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| hs, ok := msg.(Handshake) | ||
| if !ok { | ||
| return nil, xerrors.Errorf("invalid handshake '%T'", msg) | ||
| } | ||
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| return hs, nil | ||
| } |
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All methods are exactly the same as in dela's tree.Handshake, just the handshake content is different.
cache-nez
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…of a handshake. * Define a handshake, whose content will be used to initialize a routing table on non-orchestrator nodes * Implement serialization and deserialization of a handshake. This is similar to dela's implementation, and the content is changed to represent our handshake's content.
This commit introduces the following changes: * defines a Router (implementing dela's router.Router). It contains no routing information. Its methods GenerateTableFrom(handshake) and New(players, thisAddress) call NewTable(addresses, thisId), which constructs the routing table from the addresses of other participating nodes and the id of the current node. * implements NewTable. This function traverses shuffled addresses and if the prefix of the given address does not appear in the routing table yet, this address becomes the next hope for this prefix. * sketches the routing. In this prototype, RoutingTable.Forward simply chooses the next hop from the routing table (it assumes the next hop is always in the table). OnFailure does nothing.
…sed routing implementation
A node can receive multiple handshakes and we shouldn't recompute the routing table on each handshake. To keep the first computed routing table: * Change all router's methods to have a pointer receiver * Store the routing table in the router when it's first computed * If a routing table is already computed when a node receives a handshake, do not recompute the table
…uting table. When the node, booting the protocol, calls `Router:New` to create a routing table, the node's address is not included in the set of players' addresses, passed to the method. However, the node *is* a player and should be included in the routing. This is enough to make all other players aware of this node, because the same array of addresses, where the booting node is now included, is passed in a handshake to any new node.
the destination address is not equal to this node's address. This is a hack to accommodate for minogrpc's design, where the only way to reach the client side of the orchestrator is routing a message to nil from the server side of the orchestrator.
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cache-nez
commented
Jan 8, 2021
| // OnFailure implements router.RoutingTable. It changes the next hop for a | ||
| // given destination because the provided next hop is not available. | ||
| func (t RoutingTable) OnFailure(to mino.Address) error { | ||
| // TODO: keep redundancy in the routing table, use the alternative hop |
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To be implemented in a separate PR.
gnarula
suggested changes
Jan 11, 2021
gnarula
suggested changes
Jan 11, 2021
| func (t RoutingTable) OnFailure(to mino.Address) error { | ||
| // TODO: keep redundancy in the routing table, use the alternative hop | ||
| // and mark this node as unreachable | ||
| return nil |
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Suggested change
| return nil | |
| return xerrors.Errorf("TODO") |
| } | ||
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| func randomShuffle(addresses []mino.Address) { | ||
| rand.Seed(time.Now().UnixNano()) |
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Perhaps this can be moved to init() so that the Seed is initialised only once
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This PR introduces the following changes:
defines a
Router(implementing dela'srouter.Router). Its methodsGenerateTableFrom(handshake)andNew(players, thisAddress)callNewTable, which constructs the routing table from the addresses of other participating nodes and the id of the current node. Once a routing table is computed, it is stored in the router and returned in all future calls toGenerateTableFrom(however,Newconstructs a new routing table).implements
NewTable. This function traverses shuffled addresses and if the prefix of the given address does not appear in the routing table yet, this address becomes the next hope for this prefix.implements non-resilient routing.
Forwardsimply chooses the next hop from the routing table (since all nodes are known in advance, it's guaranteed to have a next hop per destination), with one important exception: the orchestrator's client side, which is the destination of players' messages, is not participating in a protocol. The only way to reach it is to send the messages to the orchestrator's server side and route them tonilto reach the client side. Therefore, the id of the client and the server side of the orchestrator is the same and the only case the message is routed tonilis when it's routed to this node's id but not this node's address.