From 331f0a6a0cc755823ee5437386a25c690fe1c1a9 Mon Sep 17 00:00:00 2001
From: Vincent Weevers <mail@vincentweevers.nl>
Date: Mon, 31 Oct 2022 00:18:06 +0100
Subject: [PATCH] Support measuring the cost of hooks and events

Ref https://github.com/Level/abstract-level/pull/45
---
 benchmarks/batch-put.js |  2 +-
 lib/meta.js             |  2 ++
 lib/run.js              | 50 ++++++++++++++++++++++++++++++++++++++++-
 3 files changed, 52 insertions(+), 2 deletions(-)

diff --git a/benchmarks/batch-put.js b/benchmarks/batch-put.js
index 6306e97..658468f 100644
--- a/benchmarks/batch-put.js
+++ b/benchmarks/batch-put.js
@@ -48,7 +48,7 @@ exports.run = function (factory, stream, options) {
     function report () {
       console.log(
         'Wrote', options.n, 'entries in',
-        Math.floor((Date.now() - startTime) / 1e3) + 's,',
+        ((Date.now() - startTime) / 1e3).toFixed(2) + 's,',
         (Math.floor((totalBytes / 1048576) * 100) / 100) + 'MB'
       )
 
diff --git a/lib/meta.js b/lib/meta.js
index a84390c..f66ec67 100644
--- a/lib/meta.js
+++ b/lib/meta.js
@@ -103,6 +103,8 @@ function id (meta, peers, invert, opts) {
         }
       } else if (path.length > 2) {
         parts.push(`${path.slice(2).join('.')}.${k}=${v}`)
+      } else if (path.length === 2 && path[0] === 'options' && (path[1] === 'events' || path[1] === 'hooks')) {
+        parts.push(`${path[1]}.${k}=${v}`)
       } else if (typeof v === 'boolean') {
         parts.push(v ? k : `!${k}`)
       } else if (typeof v === 'number') {
diff --git a/lib/run.js b/lib/run.js
index 204ca62..ae5633d 100644
--- a/lib/run.js
+++ b/lib/run.js
@@ -87,6 +87,50 @@ module.exports = function (benchmark, targetId, options) {
 
   mkdirp.sync(path.dirname(csvFile))
 
+  const addHooksAndEvents = (db) => {
+    // Test the cost of adding X amount of hook functions
+    // E.g. level-bench run batch-put ../memory-level --hooks [ --prewrite=1 ]
+    // TODO: docs
+    if (options.hooks) {
+      for (const name of ['prewrite']) {
+        const count = parseInt(options.hooks[name] || 0, 10)
+
+        if (!Number.isInteger(count) || count < 0) {
+          throw new RangeError(`The "hooks.${name}" option must be >= 0`)
+        }
+
+        if (count > 0 && (!db.hooks || !db.hooks[name])) {
+          throw new Error(`Database does not support ${name} hook`)
+        }
+
+        for (let i = 0; i < count; i++) {
+          db.hooks[name].add(function () {})
+        }
+      }
+    }
+
+    // Test the cost of adding X amount of event listeners
+    // E.g. level-bench run batch-put ../memory-level --events [ --write=1 ]
+    // TODO: docs
+    if (options.events) {
+      for (const name of ['write', 'batch', 'put', 'del']) {
+        const count = parseInt(options.events[name] || 0, 10)
+
+        if (!Number.isInteger(count) || count < 0) {
+          throw new RangeError(`The "events.${name}" option must be >= 0`)
+        }
+
+        if (count > 0 && (!db.supports.events || !db.supports.events[name])) {
+          throw new Error(`Database does not support ${name} event`)
+        }
+
+        for (let i = 0; i < count; i++) {
+          db.on(name, function () {})
+        }
+      }
+    }
+  }
+
   let factory
 
   if (name === 'rave-level') {
@@ -103,6 +147,7 @@ module.exports = function (benchmark, targetId, options) {
         leader.getMany(['x'], function (err) {
           if (err) throw err
           const follower = target(loc)
+          addHooksAndEvents(follower)
           follower.open((err) => cb(err, follower))
         })
       })
@@ -113,6 +158,7 @@ module.exports = function (benchmark, targetId, options) {
 
     factory = (cb) => {
       const db = dbFactory(options.location)
+      addHooksAndEvents(db)
       db.open((err) => cb(err, db))
     }
   }
@@ -131,7 +177,9 @@ module.exports = function (benchmark, targetId, options) {
       class: undefined,
 
       db: options.db,
-      benchmark: options.benchmark
+      benchmark: options.benchmark,
+      hooks: options.hooks || undefined,
+      events: options.events || undefined
     }
   })