network_protocol.md 4.5 KB
Network Protocol
The protocol checks that Events properly broadcast through the
network before adding Events to the Model.
The read_confirms inside each Event indicate how many times the
Event has been read from other nodes in the network.
The protocol classifies the Events by their state:
Unread: read_confirms < MAX_CONFIRMS
Read: read_confirms >= MAX_CONFIRMS
Inv
Inventory vectors notify other nodes about objects they have or data which is being requested.
| Description | Data Type | Comments |
|---|---|---|
| invs | Vec<[u8; 32]> |
Inventory items |
Receiving an Inv message
Allows a node to advertise its knowledge of one or more objects. It can
be received unsolicited or in reply to getevents.
An Inv message is a confirmation from a node in the network that the
Event has been read.
Confirmation for an Event does not exist in the UnreadEvents list.
Instead, the protocol sends a GetData message to request the missing
Event.
The protocol updates the Event in the UnreadEvents list by
increasing the read_confirms by one.
The updated Event state changes to read when the read_confirms exceed
MAX_CONFIRMS. Then, the UnreadEvents list removes the Event and
adds it to the Model.
The protocol rebroadcasts the received Inv to the network.
Sending an Inv message
Upon receiving an Event with unread status from the network, the
protocol sends back an Inv message to confirm that the Event has
been read.
GetData
| Description | Data Type | Comments |
|---|---|---|
| events | Vec<EventId> |
A list of EventIds |
Receiving a GetData message
The protocol searches in both Model and UnreadEvents for the
requested Events in GetData message.
UnreadEvents
| Description | Data Type | Comments |
|---|---|---|
| Messages | HashMap<EventId, Event> |
Hold all the Events that have broadcasted to other nodes but haven't confirmed yet |
Add new Event to UnreadEvents
To add an Event to UnreadEvents, the protocol first must check the
validity of Event.
The Event is not valid in the network if it's either too far in the
future or in the past.
Updating UnreadEvents list
The protocol continuously broadcasts unread Events to the network,
after a certain period of time (SEND_UNREAD_EVENTS_INTERVAL),
until the state of Event updates to read.
SyncEvent
| Description | Data Type | Comments |
|---|---|---|
| Leaves | Vec<EventId> |
Hash of Events |
Synchronization
To achieve complete synchronization between nodes, the protocol sends a
SyncEvent message every 2 seconds to other nodes in the network.
The SyncEvent contains the hashes of Events set in the leaves of
Model's tree.
On receiving SyncEvent message, the leaves in SyncEvent should
match the leaves in the Model's tree; otherwise, the protocol sends
Events which are the children of Events in SyncEvent.
Seen
This prevents receiving duplicate objects. The list contains only 2^16 ids.
| Description | Data Type | Comments |
|---|---|---|
| Ids | Vec<ObjectId> |
Contains objects ids |
Receiving a new Event
The new received Event with unread status is added to the
UnreadEvents buffer after increasing the read_confirms by one.
The Event with read status is added to the Model.
The protocol broadcasts the received Event to the network, again.
This ensures all nodes in the network get the Event.
Sending an Event
A new created Event has unread status with read_confirms equal to 0.
The protocol broadcasts the Event to the network after adding it to
the UnreadEvents.
Add new Event to Model
For the Event to be successfully added to the Model, the protocol
checks if the previous Event's hash inside the Event exists in the
Model.
In case the previous Event check fails, the protocol
sends a GetData message requesting the previous Event.