/**
* Determines whether to remove, forward or to do nothing with the value that is associated with
* the given valueId.
*/
private Operation getOperation(Contact node, Contact existing, KUID valueId) {
// To avoid redundant STORE forward, a node only transfers a value
// if it is the closest to the key or if its ID is closer than any
// other ID (except the new closest one of course)
// TODO: maybe relax this a little bit: what if we're not the closest
// and the closest is stale?
int k = KademliaSettings.REPLICATION_PARAMETER.getValue();
RouteTable routeTable = context.getRouteTable();
List<Contact> nodes =
org.limewire.collection.CollectionUtils.toList(
routeTable.select(valueId, k, SelectMode.ALL));
Contact closest = nodes.get(0);
Contact furthest = nodes.get(nodes.size() - 1);
if (LOG.isDebugEnabled()) {
LOG.debug(
MessageFormat.format(
"node: {0}, existing: {1}, close nodes: {2}", node, existing, nodes));
}
// StringBuilder sb = new StringBuilder();
// sb.append("ME: "+context.getLocalNode()+"\n");
// sb.append("Them: "+node).append("\n");
// sb.append("RT nearest: " + closest).append("\n");
// sb.append("RT furthest: " + furthest).append("\n");
// sb.append(CollectionUtils.toString(nodes)).append("\n");
// We store forward if:
// #1 We're the nearest Node of the k-closest Nodes to
// the given valueId
//
// #2 We're the second nearest of the k-closest Nodes to
// the given valueId AND the other Node is the nearest.
// In other words it changed its instance ID 'cause it
// was offline for a short period of time or whatsoever.
// (see also pre-condition(s) from where we're calling
// this method)
//
// The first condition applies if the Node is new
// and we're the closest Node. The second condition
// applies if the Node has changed it's instanceId.
// That means we're the second closest and since
// the other Node has changed its instanceId we must
// re-send the values
if (context.isLocalNode(closest)
|| (node.equals(closest) && nodes.size() > 1 && context.isLocalNode(nodes.get(1)))) {
KUID nodeId = node.getNodeID();
KUID furthestId = furthest.getNodeID();
// #3 The other Node must be equal to the furthest Node
// or better
if (nodeId.equals(furthestId) || nodeId.isNearerTo(valueId, furthestId)) {
// sb.append("CONDITION B (FORWARD)").append("\n");
// sb.append("Local (from): " + context.getLocalNode()).append("\n");
// sb.append("Remote (to): " + node).append("\n");
// sb.append(CollectionUtils.toString(nodes)).append("\n");
// System.out.println(sb.toString());
if (LOG.isTraceEnabled()) {
LOG.trace(
"Node " + node + " is now close enough to a value and we are responsible for xfer");
}
return Operation.FORWARD;
}
// We remove a value if:
// #1 The value is stored at k Nodes
// (i.e. the total number of Nodes in the DHT
// is equal or greater than k. If the DHT has
// less than k Nodes then there's no reason to
// remove a value)
//
// #2 This Node is the furthest of the k-closest Nodes
//
// #3 The new Node isn't in our RouteTable yet. That means
// adding it will push this Node out of the club of the
// k-closest Nodes and makes it the (k+1)-closest Node.
//
// #4 The new Node is nearer to the given valueId then
// the furthest away Node (we).
} else if (nodes.size() >= k
&& context.isLocalNode(furthest)
&& (existing == null || existing.isDead())) {
KUID nodeId = node.getNodeID();
KUID furthestId = furthest.getNodeID();
if (nodeId.isNearerTo(valueId, furthestId)) {
// sb.append("CONDITION C").append("\n");
// sb.append("ME:").append(context.getLocalNode()).append("\n");
// sb.append("VALUE:").append(valueId).append("\n");
// sb.append("NODE:").append(node).append("\n");
// sb.append(CollectionUtils.toString(nodes)).append("\n");
// System.out.println(sb.toString());
return Operation.DELETE;
}
}
return Operation.NOTHING;
}
/**
* Adds the given <code>Contact</code> or updates it if it's already in our <code>RouteTable
* </code>
*/
private synchronized void addLiveContactInfo(Contact node, DHTMessage message) {
RouteTable routeTable = context.getRouteTable();
// If the Node is going to shutdown then don't bother
// further than this.
if (node.isShutdown()) {
if (LOG.isInfoEnabled()) {
LOG.info(node + " is going to shut down");
}
synchronized (routeTable) {
// Make sure there's an existing Contact in the RouteTable.
// Otherwise don't bother!
Contact existing = routeTable.get(node.getNodeID());
if (node.equals(existing)) {
// Update the new Contact in the RouteTable and
// mark it as shutdown
// mark the existing contact as shutdown if its alive or
// it will not be removed.
if (existing.isAlive()) existing.shutdown(true);
routeTable.add(node);
node.shutdown(true);
}
}
return;
}
// Ignore firewalled Nodes
if (node.isFirewalled()) {
if (LOG.isInfoEnabled()) {
LOG.info(node + " is firewalled");
}
return;
}
if (ContactUtils.isPrivateAddress(node)) {
if (LOG.isInfoEnabled()) {
LOG.info(node + " has a private address");
}
return;
}
KUID nodeId = node.getNodeID();
if (context.isLocalNodeID(nodeId)) {
// This is expected if there's a Node ID collision
assert (message instanceof PingResponse)
: "Expected a PingResponse but got a "
+ message.getClass()
+ " from "
+ message.getContact();
if (LOG.isInfoEnabled()) {
LOG.info("Looks like our NodeID collides with " + node);
}
return;
}
if (StoreSettings.STORE_FORWARD_ENABLED.getValue()) {
// Only do store forward if it is a new node in our routing table
// (we are (re)connecting to the network) or a node that is reconnecting
Contact existing = routeTable.get(nodeId);
if (existing == null
|| existing.isDead()
|| existing.getInstanceID() != node.getInstanceID()) {
// Store forward only if we're bootstrapped
if (context.isBootstrapped()) {
int k = KademliaSettings.REPLICATION_PARAMETER.getValue();
// we select the 2*k closest nodes in order to also check those values
// where the local node is part of the k closest to the value but not part
// of the k closest to the new joining node.
Collection<Contact> nodes = routeTable.select(nodeId, 2 * k, SelectMode.ALL);
// Are we one of the K nearest Nodes to the contact?
if (containsNodeID(nodes, context.getLocalNodeID())) {
if (LOG.isTraceEnabled()) {
LOG.trace(
"Node "
+ node
+ " is new or has changed his instanceID, will check for store forward!");
}
forwardOrRemoveValues(node, existing, message);
}
}
}
}
// Add the Node to our RouteTable or if it's
// already there update its timeStamp and whatsoever
routeTable.add(node);
}