stream: add global Stream.defaultHighwaterMark

doc/api/stream.md

@@ -25,6 +25,16 @@ const stream = require('stream');
 The `stream` module is useful for creating new types of stream instances. It is
 usually not necessary to use the `stream` module to consume streams.
 
+### Class property: `Stream.defaultHighWaterMark`
+<!-- YAML
+added: v0.11.3
+-->
+
+* {integer} **Default:** `16 * 1024`
+
+This is the size (in bytes) for the default high water mark for
+readable and writable streams. This value may be modified.
+
 ## Organization of this document
 
 This document contains two primary sections and a third section for notes. The

lib/internal/streams/legacy.js

@@ -2,8 +2,16 @@
 
 const {
   ArrayIsArray,
+  ObjectDefineProperty,
   ObjectSetPrototypeOf,
+  NumberIsInteger,
 } = primordials;
+const {
+  codes: {
+    ERR_INVALID_ARG_TYPE,
+    ERR_INVALID_ARG_VALUE,
+  }
+} = require('internal/errors');
 
 const EE = require('events');
 
@@ -111,4 +119,40 @@ function prependListener(emitter, event, fn) {
     emitter._events[event] = [fn, emitter._events[event]];
 }
 
+let defaultHighWaterMark = 16 * 1024;
+ObjectDefineProperty(Stream, 'defaultHighWaterMark', {
+  get() {
+    return defaultHighWaterMark;
+  },
+  set(value) {
+    if (!NumberIsInteger(value)) {
+      throw ERR_INVALID_ARG_TYPE('value', 'Integer', value);
+    }
+
+    if (value < 1) {
+      throw ERR_INVALID_ARG_VALUE('value', value);
+    }
+
+    defaultHighWaterMark = value;
+  }
+});
+
+let defaultObjectModeHighWaterMark = 16;
+ObjectDefineProperty(Stream, 'defaultObjectModeHighWaterMark', {
+  get() {
+    return defaultObjectModeHighWaterMark;
+  },
+  set(value) {
+    if (!NumberIsInteger(value)) {
+      throw ERR_INVALID_ARG_TYPE('value', 'Integer', value);
+    }
+
+    if (value < 1) {
+      throw ERR_INVALID_ARG_VALUE('value', value);
+    }
+
+    defaultObjectModeHighWaterMark = value;
+  }
+});
+
 module.exports = { Stream, prependListener };

lib/internal/streams/state.js

@@ -6,14 +6,16 @@ const {
 } = primordials;
 
 const { ERR_INVALID_ARG_VALUE } = require('internal/errors').codes;
+const { Stream } = require('internal/streams/legacy');
 
 function highWaterMarkFrom(options, isDuplex, duplexKey) {
   return options.highWaterMark != null ? options.highWaterMark :
     isDuplex ? options[duplexKey] : null;
 }
 
 function getDefaultHighWaterMark(objectMode) {
-  return objectMode ? 16 : 16 * 1024;
+  return objectMode ? Stream.defaultObjectModeHighWaterMark :
+    Stream.defaultHighWaterMark;
 }
 
 function getHighWaterMark(state, options, duplexKey, isDuplex) {