add small merkle tree cache

Author: mafintosh

lib/merkle-tree.js

@@ -1,11 +1,13 @@
 const flat = require('flat-tree')
 const crypto = require('hypercore-crypto')
 const c = require('compact-encoding')
+const Xache = require('xache')
 const b4a = require('b4a')
 const caps = require('./caps')
 
 const BLANK_HASH = b4a.alloc(32)
 const OLD_TREE = b4a.from([5, 2, 87, 2, 0, 0, 40, 7, 66, 76, 65, 75, 69, 50, 98])
+const TREE_CACHE = 128 // speeds up linear scans by A LOT
 
 class NodeQueue {
   constructor (nodes, extra = null) {
@@ -140,6 +142,7 @@ class MerkleTreeBatch {
         : this.ancestors
 
       this.tree.truncated = true
+      this.tree.cache = new Xache({ maxSize: this.tree.cache.maxSize })
       truncateMap(this.tree.unflushed, this.ancestors)
       if (this.tree.flushing !== null) truncateMap(this.tree.flushing, this.ancestors)
     }
@@ -350,6 +353,7 @@ module.exports = class MerkleTree {
 
     this.storage = storage
     this.unflushed = new Map()
+    this.cache = new Xache({ maxSize: TREE_CACHE })
     this.flushing = null
     this.truncated = false
     this.truncateTo = 0
@@ -403,6 +407,9 @@ module.exports = class MerkleTree {
   }
 
   get (index, error = true) {
+    const c = this.cache.get(index)
+    if (c) return c
+
     let node = this.unflushed.get(index)
 
     if (this.flushing !== null && node === undefined) {
@@ -422,7 +429,7 @@ module.exports = class MerkleTree {
       return Promise.resolve(node)
     }
 
-    return getStoredNode(this.storage, index, error)
+    return getStoredNode(this.storage, index, this.cache, error)
   }
 
   async flush () {
@@ -495,6 +502,7 @@ module.exports = class MerkleTree {
   }
 
   clear () {
+    this.cache = new Xache({ maxSize: this.cache.maxSize })
     this.truncated = true
     this.truncateTo = 0
     this.roots = []
@@ -754,7 +762,7 @@ module.exports = class MerkleTree {
 
     const roots = []
     for (const index of flat.fullRoots(2 * length)) {
-      roots.push(await getStoredNode(storage, index, true))
+      roots.push(await getStoredNode(storage, index, null, true))
     }
 
     return new MerkleTree(storage, roots, opts.fork || 0, opts.signature || null)
@@ -1085,7 +1093,7 @@ function blankNode (index) {
 
 // Storage methods
 
-function getStoredNode (storage, index, error) {
+function getStoredNode (storage, index, cache, error) {
   return new Promise((resolve, reject) => {
     storage.read(40 * index, 40, (err, data) => {
       if (err) {
@@ -1103,7 +1111,9 @@ function getStoredNode (storage, index, error) {
         return
       }
 
-      resolve({ index, size, hash })
+      const node = { index, size, hash }
+      if (cache !== null) cache.set(index, node)
+      resolve(node)
     })
   })
 }
@@ -1122,7 +1132,7 @@ async function autoLength (storage) {
   if (!nodes) return 0
   const ite = flat.iterator(nodes - 1)
   let index = nodes - 1
-  while (await getStoredNode(storage, ite.parent(), false)) index = ite.index
+  while (await getStoredNode(storage, ite.parent(), null, false)) index = ite.index
   return flat.rightSpan(index) / 2 + 1
 }
 

package.json

@@ -48,7 +48,7 @@
     "safety-catch": "^1.0.1",
     "sodium-universal": "^3.0.4",
     "streamx": "^2.12.4",
-    "xache": "^1.0.0"
+    "xache": "^1.1.0"
   },
   "devDependencies": {
     "brittle": "^2.0.0",