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annotate xml/ru/docs/njs/preload_objects.xml @ 2984:cc475ba7d406

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Added Preload Objects article in njs.
author Yaroslav Zhuravlev <yar@nginx.com>
date Thu, 01 Jun 2023 17:12:18 +0100
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children 48f245493600
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2984
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1 <?xml version="1.0"?>
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2
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3 <!--
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4 Copyright (C) Nginx, Inc.
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5 -->
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6
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7 <!DOCTYPE article SYSTEM "../../../../dtd/article.dtd">
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8
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9 <article name="Предзагруженные объекты"
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10 link="/ru/docs/njs/preload_objects.html"
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11 lang="ru"
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12 rev="1"
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13 toc="no">
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14
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15 <section id="summary">
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16
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17 <para>
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18 Для каждого входящего запроса в njs создаётся отдельная виртуальная машина.
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19 Это позволяет прогнозировать предсказуемое поглощение памяти
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20 или осуществить изоляцию запросов.
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21 </para>
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22
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23 <para>
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24 Однако у такого подхода есть недостатки.
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25 Поскольку все запросы являются изолированными, то
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26 если обработчику запроса необходимо получить доступ к данным,
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27 ему нужно сначала их прочитать самому.
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28 Это неэффективно, особенно если объём данных большой.
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29 </para>
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30
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31 <para>
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32 Это ограничение можно обойти
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33 при помощи разделяемого предзагруженного объекта.
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34 Такие объекты создаются неизменяемыми и не имеют цепочки прототипов:
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35 у них нет возможности
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36 изменить значения или добавить/удалить свойства в объектах/массивах.
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37 </para>
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38
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39 </section>
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40
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41
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42 <section id="working_with_preload_objects"
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43 name="Работа с предзагруженными объектами">
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44
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45 <para>
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46 Примеры работы с предзагруженными объектами в njs:
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47
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48 <list type="bullet">
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49
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50 <listitem>
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51 доступ к свойствам по имени:
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52 <programlisting>
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53 preloaded_object.prop_name
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54 preloaded_object[prop_name]
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55 </programlisting>
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56 </listitem>
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57
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58 <listitem>
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59 перечисление свойств:
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60 <programlisting>
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61 for (i in preloaded_object_name) {
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62 ...
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63 }
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64 </programlisting>
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65 </listitem>
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66
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67 <listitem>
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68 применение встроенных методов, не изменяющих состояние,
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69 при помощи <literal>call()</literal>:
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70 <programlisting>
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71 Array.prototype.filter.call(preloaded_object_name, ...)
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72 </programlisting>
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73 </listitem>
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74
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75 </list>
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76 </para>
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77
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78 </section>
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79
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80 </article>