docs: add reactor sections (#6510)

2026-09-19 06:31:57 +00:00 · 2021-10-22 18:14:43 +02:00
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+---
+order: 3
+---
+
+# Implementation
+
+## Blocksync Reactor
+
+- coordinates the pool for syncing
+- coordinates the store for persistence
+- coordinates the playing of blocks towards the app using a sm.BlockExecutor
+- handles switching between fastsync and consensus
+- it is a p2p.BaseReactor
+- starts the pool.Start() and its poolRoutine()
+- registers all the concrete types and interfaces for serialisation
+
+### poolRoutine
+
+- listens to these channels:
+    - pool requests blocks from a specific peer by posting to requestsCh, block reactor then sends
+    a &bcBlockRequestMessage for a specific height
+    - pool signals timeout of a specific peer by posting to timeoutsCh
+    - switchToConsensusTicker to periodically try and switch to consensus
+    - trySyncTicker to periodically check if we have fallen behind and then catch-up sync
+        - if there aren't any new blocks available on the pool it skips syncing
+- tries to sync the app by taking downloaded blocks from the pool, gives them to the app and stores
+  them on disk
+- implements Receive which is called by the switch/peer
+    - calls AddBlock on the pool when it receives a new block from a peer
+
+## Block Pool
+
+- responsible for downloading blocks from peers
+- makeRequestersRoutine()
+    - removes timeout peers
+    - starts new requesters by calling makeNextRequester()
+- requestRoutine():
+    - picks a peer and sends the request, then blocks until:
+        - pool is stopped by listening to pool.Quit
+        - requester is stopped by listening to Quit
+        - request is redone
+        - we receive a block
+            - gotBlockCh is strange
+
+## Go Routines in Blocksync Reactor
+
+![Go Routines Diagram](img/bc-reactor-routines.png)