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Improved LAN tree construction

This commit is contained in:
Tony Garnock-Jones 2019-06-20 23:09:55 +01:00
parent 286bf7ecc1
commit 864c54f53b
1 changed files with 86 additions and 30 deletions
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116
packages/server/src/disco.js
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@ -24,6 +24,7 @@ const M = activate require("@syndicate-lang/driver-mdns");
const P = activate require("./internal_protocol");
const S = activate require("@syndicate-lang/driver-streams-node");
const Federation = activate require("./federation");
const { TimeLaterThan } = activate require("@syndicate-lang/driver-timer");
import {
Set, Map,
@ -115,20 +116,24 @@ spawn named 'uplinkSelection' {
field this.gatewayIp = null;
on asserted M.DefaultGateway(_, $gatewayIp) this.gatewayIp = gatewayIp;
function orderByNodeId(peers) {
return peers.toList().sortBy(Peer._nodeId);
}
during OverlayNode($localId) {
during Federation.ManagementScope($managementScope) {
during P.Envelope(managementScope, Overlay($overlayId, $rootAddr)) {
// For each overlay:
//
// Collect all peers.
// Partition them into two sets: those on our actual gateway, and those not.
// For each set, pick the best element, measured by smallness of nodeId.
// If there's a best gateway peer, choose that.
// Otherwise, if there's a best non-gateway peer, choose that.
//
// Now, if we have chosen a peer, and that peer is not ourselves, use it;
// Otherwise, fall back to a direct connection to the root.
// We constantly maintain a notion of the best uplink to establish.
// Simultaneously, we try to maintain a stable connection to some upstream peer.
// To figure out the best uplink:
// Collect all peers into two sets:
// 1. Those on our current gateway IP whose _nodeId is not equal to ours.
// 2. Those not on the gateway IP whose _nodeId is strictly less than ours.
// If there are any nodes in set 1, select the node with the smallest _nodeId.
// Otherwise, if there are any nodes in set 2, sort by _nodeId and select the middle one.
// Otherwise, select the root.
field this.peers = Set();
on asserted $p(Peer(overlayId,_,_,_)) this.peers = this.peers.add(p);
@ -137,19 +142,21 @@ spawn named 'uplinkSelection' {
field this.bestAddr = null;
field this.bestPeer = null;
dataflow {
const gwPeers = orderByNodeId(this.peers.filter(
(p) => (Peer._ip(p) === this.gatewayIp) && (Peer._nodeId(p) !== localId)));
const others = orderByNodeId(this.peers.filter(
(p) => (Peer._ip(p) !== this.gatewayIp) && (Peer._nodeId(p) < localId)));
let best = null;
const better = (a) => {
if (!best) return true;
if (Peer._ip(a) === this.gatewayIp) {
if (Peer._ip(best) !== this.gatewayIp) return true;
return (Peer._nodeId(a) < Peer._nodeId(best));
} else {
if (Peer._ip(best) === this.gatewayIp) return false;
return (Peer._nodeId(a) < Peer._nodeId(best));
}
};
this.peers.forEach((p) => { if (better(p)) best = p; });
if (best && (Peer._nodeId(best) !== localId)) {
if (!gwPeers.isEmpty()) {
best = gwPeers.first();
} else if (!others.isEmpty()) {
best = others.get(others.size >> 1);
} else {
// Use the root
}
if (best) {
this.bestAddr = Peer._addr(best);
this.bestPeer = OverlayNode(Peer._nodeId(best));
} else {
@ -159,17 +166,66 @@ spawn named 'uplinkSelection' {
}
dataflow if (this.bestAddr) {
debug('Selected uplink peer for overlay', overlayId, 'is', this.bestPeer.toString(), 'at', this.bestAddr.toString());
debug('Current best uplink peer for overlay', overlayId,
'is', this.bestPeer.toString(),
'at', this.bestAddr.toString());
}
assert P.Proposal(managementScope, Federation.Uplink(overlayId, this.bestAddr, overlayId))
when (this.bestAddr);
//---------------------------------------------------------------------------
const loopbackAddr = C.Loopback(overlayId);
during C.ServerConnected(loopbackAddr) {
assert C.ToServer(loopbackAddr, OverlayLink(OverlayNode(localId), this.bestPeer))
when (this.bestAddr);
}
const futureTime = (deltaMs) => {
return (+(new Date())) + deltaMs;
};
const assertSelectedUplink = (link) => {
assert P.Proposal(managementScope, link);
};
const START = () => {
react {
// Wait for stability:
const timeout = futureTime(5000);
stop on asserted TimeLaterThan(timeout) CONNECT(null);
}
};
const CONNECT = (prevBestPeer) => {
// We've settled on something to try.
const peer = this.bestPeer;
const addr = this.bestAddr;
const link = Federation.Uplink(overlayId, addr, overlayId);
if (!prevBestPeer || !prevBestPeer.equals(peer)) {
debug('Selecting uplink', peer.toString(), 'for overlay', overlayId);
}
react {
assertSelectedUplink(link);
const timeout = futureTime(15000);
stop on asserted TimeLaterThan(timeout) CONNECT(peer);
stop on retracted peer CONNECT(null);
stop on asserted P.Envelope(managementScope, Federation.UplinkConnected(link)) {
MAINTAIN(peer, link);
}
}
};
const MAINTAIN = (peer, link) => {
// We're connected.
react {
assertSelectedUplink(link);
assert C.ToServer(C.Loopback(overlayId), OverlayLink(OverlayNode(localId), peer));
stop on retracted P.Envelope(managementScope, Federation.UplinkConnected(link)) {
CONNECT(peer);
}
if (OverlayRoot.isClassOf(peer)) {
// See if something better (more local) comes along every now and then.
const timeout = futureTime(5000);
stop on asserted TimeLaterThan(timeout) CONNECT(peer);
}
}
};
on start START();
}
}
}