Revert LRU removal (#199)

* Revert "Remove db-diskdown LRU (#198)"

This reverts commit 219f12a65b.

* Re-add LRU for db-diskdown

* Re-add depth check

packages/db-diskdown/package.json

@@ -32,6 +32,7 @@
     "@polkadot/util": "^0.28.17",
     "@types/mkdirp": "^0.5.2",
     "abstract-leveldown": "^5.0.0",
+    "lru_map": "^0.3.3",
     "mkdirp": "^0.5.1"
   },
   "devDependencies": {

packages/db-diskdown/src/index.ts

@@ -5,11 +5,13 @@
 import { DiskStore } from './types';
 
 import { AbstractLevelDOWN } from 'abstract-leveldown';
+import { LRUMap } from 'lru_map';
 import isUndefined from '@polkadot/util/is/undefined';
 import logger from '@polkadot/util/logger';
 
 import Combined from './store/Combined';
 
+const LRU_SIZE = 16384;
 const KEY_LENGTH = 32;
 
 const l = logger('disk/scatter');
@@ -18,11 +20,13 @@ const noop = () =>
 
 class DiskDown extends AbstractLevelDOWN {
   _disk: DiskStore;
+  _store: LRUMap<string, Buffer>;
 
   constructor (location: string) {
     super(location);
 
     this._disk = new Combined(location);
+    this._store = new LRUMap(LRU_SIZE);
   }
 
   compact (progress: (message: string) => void): void {
@@ -69,6 +73,7 @@ class DiskDown extends AbstractLevelDOWN {
   _del (key: Buffer, options: any, callback: Function) {
     l.debug(() => ['_del', key]);
 
+    this._store.delete(key.toString());
     this._disk.delete(key);
 
     process.nextTick(callback);
@@ -77,7 +82,7 @@ class DiskDown extends AbstractLevelDOWN {
   _get (key: Buffer, options: any, callback: Function) {
     l.debug(() => ['_get', key.toString('hex')]);
 
-    const value = this._disk.get(key);
+    const value = this._store.get(key.toString()) || this._disk.get(key);
 
     if (isUndefined(value)) {
       process.nextTick(callback, new Error('NotFound'));
@@ -90,6 +95,7 @@ class DiskDown extends AbstractLevelDOWN {
   _put (key: Buffer, value: Buffer, options: any, callback: Function) {
     l.debug(() => ['_put', key.toString('hex'), value]);
 
+    this._store.set(key.toString(), value);
     this._disk.set(key, value);
 
     process.nextTick(callback);

packages/db-diskdown/src/store/Combined.ts

@@ -101,14 +101,14 @@ export default class Combined implements DiskStore {
     const newStat = fs.lstatSync(newFile);
     const oldStat = fs.lstatSync(this._file);
     const percentage = 100 * (newStat.size / oldStat.size);
-    const sizeMb = newStat.size / (1024 * 1024);
+    const sizeMB = newStat.size / (1024 * 1024);
     const elapsed = (Date.now() - start) / 1000;
 
     fs.unlinkSync(this._file);
     // fs.renameSync(this._file, `${this._file}.old`);
     fs.renameSync(newFile, this._file);
 
-    l.log(`compacted in ${elapsed.toFixed(2)}s, ${(count / 1000).toFixed(2)}k keys, ${sizeMb.toFixed(2)}MB (${percentage.toFixed(2)}%)`);
+    l.log(`compacted in ${elapsed.toFixed(2)}s, ${(count / 1000).toFixed(2)}k keys, ${sizeMB.toFixed(2)}MB (${percentage.toFixed(2)}%)`);
   }
 
   delete (key: Buffer): void {