public class NID extends SHA1Hash
A NID is a 20-byte SHA1 hash that uniquely identifies a node in the DHT keyspace. It serves as the primary key for routing table entries and is used extensively throughout the DHT system for node identification, distance calculations, and bucket placement.
Beyond the basic SHA1 hash functionality, this class tracks node health metrics including last seen time and failure count. This information is crucial for maintaining a healthy routing table by identifying and removing unreliable or unreachable nodes.
Key features:
- Extends SHA1Hash for efficient storage and comparison
- Tracks last seen time for node freshness assessment
- Maintains failure count to detect unreachable nodes
- Provides timeout detection after multiple consecutive failures
- Used extensively as map keys throughout the DHT system
Failure handling allows up to 5 consecutive timeouts before marking a node as problematic, providing resilience against temporary network issues while eventually removing persistently unreachable nodes.
HASH_LENGTH_data| Constructor and Description |
|---|
NID()Creates a new empty NID. |
NID(byte[] data)Creates a new NID with the specified data. |
| Modifier and Type | Method and Description |
|---|---|
long | lastSeen()Returns the timestamp when this node was last successfully seen. |
void | setLastSeen()Updates the last seen timestamp and resets failure count. |
boolean | timeout()Records a timeout and checks if the node should be considered problematic. |
calculateHash, equals, fromBase64, fromByteArray, getData, read, toBase64, toByteArray, toString, writeBytespublic NID()
Creates an NID with null data, typically used as a placeholder or for initialization purposes where the actual NID value will be set later.
public NID(byte[] data)
data - the 20-byte SHA1 hash data for this node identifier, or null for an empty NIDpublic long lastSeen()
public void setLastSeen()
This method should be called whenever successful communication with the node occurs. It updates the freshness metric and resets the failure counter, indicating the node is currently reachable.
public boolean timeout()
Increments the failure counter and returns whether the node has exceeded the maximum allowed consecutive failures. This helps identify nodes that are consistently unreachable and should be removed from the routing table.