feat: parallel block writes (#97)

* feat: parallel block writes

When using the `putMany` datastore method, write blocks in parallel
up to a configurable limit.

In local testing this almost doubles the throughput of this module
for multi-block writes.

* chore: use parallel for gets and deletes too

package.json

@@ -43,6 +43,7 @@
     "interface-datastore": "^5.1.1",
     "it-glob": "0.0.13",
     "it-map": "^1.0.5",
+    "it-parallel-batch": "^1.0.9",
     "mkdirp": "^1.0.4"
   },
   "devDependencies": {

src/index.js

@@ -12,6 +12,7 @@ const {
   Adapter, Key, Errors
 } = require('interface-datastore')
 const map = require('it-map')
+const parallel = require('it-parallel-batch')
 
 const noop = () => {}
 const fsAccess = promisify(fs.access || noop)
@@ -25,6 +26,11 @@ const fsUnlink = promisify(fs.unlink || noop)
  * @typedef {import('interface-datastore').KeyQuery} KeyQuery
  */
 
+/**
+ * @template TEntry
+ * @typedef {import('interface-store').AwaitIterable<TEntry>} AwaitIterable
+ */
+
 /**
  * Write a file atomically
  *
@@ -62,7 +68,7 @@ async function writeFile (path, contents) {
 class FsDatastore extends Adapter {
   /**
    * @param {string} location
-   * @param {{ createIfMissing?: boolean; errorIfExists?: boolean; extension?: string; } | undefined} [opts]
+   * @param {{ createIfMissing?: boolean, errorIfExists?: boolean, extension?: string, putManyConcurrency?: number } | undefined} [opts]
    */
   constructor (location, opts) {
     super()
@@ -71,7 +77,10 @@ class FsDatastore extends Adapter {
     this.opts = Object.assign({}, {
       createIfMissing: true,
       errorIfExists: false,
-      extension: '.data'
+      extension: '.data',
+      deleteManyConcurrency: 50,
+      getManyConcurrency: 50,
+      putManyConcurrency: 50
     }, opts)
   }
 
@@ -175,6 +184,23 @@ class FsDatastore extends Adapter {
     }
   }
 
+  /**
+   * @param {AwaitIterable<Pair>} source
+   * @returns {AsyncIterable<Pair>}
+   */
+  async * putMany (source) {
+    yield * parallel(
+      map(source, ({ key, value }) => {
+        return async () => {
+          await this.put(key, value)
+
+          return { key, value }
+        }
+      }),
+      this.opts.putManyConcurrency
+    )
+  }
+
   /**
    * Read from the file system without extension.
    *
@@ -215,6 +241,38 @@ class FsDatastore extends Adapter {
     return data
   }
 
+  /**
+   * @param {AwaitIterable<Key>} source
+   * @returns {AsyncIterable<Uint8Array>}
+   */
+  async * getMany (source) {
+    yield * parallel(
+      map(source, key => {
+        return async () => {
+          return this.get(key)
+        }
+      }),
+      this.opts.getManyConcurrency
+    )
+  }
+
+  /**
+   * @param {AwaitIterable<Key>} source
+   * @returns {AsyncIterable<Key>}
+   */
+  async * deleteMany (source) {
+    yield * parallel(
+      map(source, key => {
+        return async () => {
+          await this.delete(key)
+
+          return key
+        }
+      }),
+      this.opts.deleteManyConcurrency
+    )
+  }
+
   /**
    * Check for the existence of the given key.
    *
@@ -223,6 +281,7 @@ class FsDatastore extends Adapter {
    */
   async has (key) {
     const parts = this._encode(key)
+
     try {
       await fsAccess(parts.file)
     } catch (err) {