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update guid section

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Feng 2016-04-02 15:08:10 +08:00
parent 313f4568dd
commit 9ed5d4fb86
1 changed files with 10 additions and 17 deletions
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docs/source/design.rst
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@ -31,28 +31,22 @@ Design Philosophy
System Layers
-------------
1. Connection Layer:
1. Connection Layer
Handle TCP and WebSocket connections, encode/decode MQTT packets.
2. Session Layer:
2. Session Layer
Process MQTT PUBLISH/SUBSCRIBE Packets received from client, and deliver MQTT messages to client.
3. PubSub Layer:
3. PubSub Layer
Dispatch MQTT messages to subscribers in a node.
4. Routing(Distributed) Layer:
4. Routing(Distributed) Layer
Route MQTT messages between clustered nodes.
.. code::
-------------- ----------- ---------- ----------
Client --> | Connection | --> | Session | --> | PubSub | --> | Router |
-------------- ----------- ---------- ----------
----------------
Connection Layer
----------------
@ -132,13 +126,12 @@ PacketId and MessageId
The 16bits PacketId is defined by MQTT Protocol Specification, used by client/server to PUBLISH/PUBACK packets. A GUID(128bits globally unique Id) will be generated by the broker and assigned to a MQTT message.
Format of the globally unique message id:
Format of the globally unique message id::
+------------------------+----------------+------------+
| Timestamp | NodeID + PID | Sequence |
+------------------------+----------------+------------+
| <-------64bits-------> | <---48bits---> | <-16bits-> |
+------------------------+----------------+------------+
--------------------------------------------------------
| Timestamp | NodeID + PID | Sequence |
|<------- 64bits ------->|<--- 48bits --->|<- 16bits ->|
--------------------------------------------------------
1. Timestamp: erlang:system_time if Erlang >= R18, otherwise os:timestamp
2. NodeId: encode node() to 2 bytes integer