doc/historic/2003/pycon/pb/pb-slides.py

   1 #! /usr/bin/python
   2
   3 from slides import Lecture, NumSlide, Slide, Bullet, SubBullet, PRE, URL
   4
   5 class Raw:
   6     def __init__(self, title, html):
   7         self.title = title
   8         self.html = html
   9     def toHTML(self):
  10         return self.html
  11
  12 class HTML(Raw):
  13     def __init__(self, html):
  14         self.html = html
  15
  16 server_lore = """<div class="py-listing">
  17 <pre><span class="py-src-keyword">class</span> <span class="py-src-identifier">ServerObject</span><span class="py-src-op">(</span><span class="py-src-parameter">pb</span><span class="py-src-op">.</span><span class="py-src-parameter">Referenceable</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline"></span>
  18 <span class="py-src-indent">    </span><span class="py-src-keyword">def</span> <span class="py-src-identifier">remote_add</span><span class="py-src-op">(</span><span class="py-src-parameter">self</span><span class="py-src-op">,</span> <span class="py-src-parameter">one</span><span class="py-src-op">,</span> <span class="py-src-parameter">two</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline">
  19 </span><span class="py-src-indent">        </span><span class="py-src-variable">answer</span> <span class="py-src-op">=</span> <span class="py-src-variable">one</span> <span class="py-src-op">+</span> <span class="py-src-variable">two</span><span class="py-src-newline">
  20 </span>        <span class="py-src-keyword">print</span> <span class="py-src-string">&quot;returning result:&quot;</span><span class="py-src-op">,</span> <span class="py-src-variable">answer</span><span class="py-src-newline">
  21 </span>        <span class="py-src-keyword">return</span> <span class="py-src-variable">answer</span><span class="py-src-endmarker"></span></pre>
  22 <div class="py-caption">Server Code</div>
  23 </div>
  24 """
  25
  26 client_lore = """<div class="py-listing"><pre>
  27 <span class="py-src-nl"></span>    <span class="py-src-dedent"></span><span class="py-src-keyword">def</span> <span class="py-src-identifier">got_RemoteReference</span><span class="py-src-op">(</span><span class="py-src-parameter">remoteref</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline">
  28 </span>        <span class="py-src-keyword">print</span> <span class="py-src-string">&quot;asking it to add&quot;</span><span class="py-src-newline">
  29 </span>        <span class="py-src-variable">deferred</span> <span class="py-src-op">=</span> <span class="py-src-variable">remoteref</span><span class="py-src-op">.</span><span class="py-src-variable">callRemote</span><span class="py-src-op">(</span><span class="py-src-string">&quot;add&quot;</span><span class="py-src-op">,</span> <span class="py-src-number">1</span><span class="py-src-op">,</span> <span class="py-src-number">2</span><span class="py-src-op">)</span><span class="py-src-newline">
  30 </span>        <span class="py-src-variable">deferred</span><span class="py-src-op">.</span><span class="py-src-variable">addCallbacks</span><span class="py-src-op">(</span><span class="py-src-variable">add_done</span><span class="py-src-op">,</span> <span class="py-src-variable">err</span><span class="py-src-op">)</span><span class="py-src-newline">
  31 </span>        <span class="py-src-comment"># this Deferred fires when the method call is complete
  32 </span>    <span class="py-src-dedent"></span><span class="py-src-keyword">def</span> <span class="py-src-identifier">add_done</span><span class="py-src-op">(</span><span class="py-src-parameter">result</span><span class="py-src-op">)</span><span class="py-src-op">:</span><span class="py-src-newline">
  33 </span><span class="py-src-indent">        </span><span class="py-src-keyword">print</span> <span class="py-src-string">&quot;addition complete, result is&quot;</span><span class="py-src-op">,</span> <span class="py-src-variable">result</span><span class="py-src-newline">
  34 </span><span class="py-src-endmarker"></span></pre><div class="py-caption">Client Code</div></div>
  35 """
  36
  37
  38 # title graphic: PB peanut butter jar, "Twist(ed)" on lid
  39 lecture = Lecture(
  40     "Perspective Broker: Translucent RPC in Twisted",
  41     # intro
  42     Raw("Title", """
  43     <h1>Perspective Broker: Translucent RPC in Twisted</h1>
  44     <h2>PyCon 2003</h2>
  45     <h2>Brian Warner &lt; warner @ lothar . com &gt; </h2>
  46     """),
  47
  48     Slide("Introduction",
  49           Bullet("Overview/definition of RPC"),
  50           Bullet("What is Perspective Broker?"),
  51           Bullet("How do I use it?"),
  52           Bullet("Security Issues"),
  53           Bullet("Future Directions"),
  54           ),
  55
  56     Slide("Remote Procedure Calls",
  57           Bullet("Action at a distance: separate processes, safely telling each other what to do",
  58                  SubBullet("Separate memory spaces"),
  59                  SubBullet("Usually on different machines"),
  60                  ),
  61           Bullet("Frequently called RMI these days: Remote Method Invocation"),
  62           Bullet("Three basic parts: Addressing, Serialization, Waiting"),
  63           ),
  64
  65     Slide("Addressing",
  66           Bullet("What program are you talking to?",
  67                  SubBullet("hostname, port number"),
  68                  SubBullet("Some systems use other namespaces: sunrpc")
  69                  ),
  70           Bullet("Which object in that program?"),
  71           Bullet("Which method do you want to run?"),
  72           Bullet("Related issues",
  73                  SubBullet("How do you know what the arguments are?"),
  74                  SubBullet("(do you care?)"),
  75                  SubBullet("How do you know what methods are available?"),
  76                  SubBullet("(do you care?)"),
  77                  ),
  78           ),
  79
  80     Slide("Serialization",
  81           Bullet("What happens to the arguments you send in?"),
  82           Bullet("What happens to the results that are returned?",
  83                  SubBullet("Representation differences: endianness, word length"),
  84                  SubBullet("Dealing with user-defined types"),
  85                  ),
  86           Bullet("How to deal with references"),
  87           ),
  88     Slide("The Waiting (is the hardest part)",
  89           Bullet("Asynchronous: results come later, or not at all"),
  90           Bullet("Need to do other work while waiting"),
  91           ),
  92
  93     Slide("Whither Translucence?",
  94           Bullet("Not 'Transparent': don't pretend remote objects are really local",
  95                  SubBullet("CORBA (in C) does this, makes remote calls look like local calls"),
  96                  SubBullet("makes it hard to deal with the async nature of RPC"),
  97                  ),
  98           Bullet("Not 'Opaque': make it easy to deal with the differences",
  99                  SubBullet("Including extra failure modes, delayed results"),
 100                  ),
 101
 102           Bullet("Exceptions and Deferreds to the rescue")),
 103
 104     Slide("Other RPC protocols",
 105           Bullet("HTML"),
 106           Bullet("XML-RPC"),
 107           Bullet("CORBA"),
 108           Bullet("when you control both ends of the wire, use PB"),
 109           ),
 110
 111     Raw("Where does PB fit?",
 112         """<h2>PB sits on top of <span class=\"py-src-identifier\">twisted.internet</span></h2>
 113         <img src=\"twisted-overview.png\" />
 114         """),
 115
 116     Slide("pb.RemoteReference",
 117           Bullet(HTML("<span class=\"py-src-identifier\">pb.Referenceable</span>: Object which can be accessed by remote systems."),
 118                  SubBullet(HTML("Defines methods like <span class=\"py-src-identifier\">remote_foo</span> and <span class=\"py-src-identifier\">remote_bar</span> which can be invoked remotely.")),
 119                  SubBullet(HTML("Methods without the <span class=\"py-src-identifier\">remote_</span> prefix are local-only.")),
 120                  ),
 121           Bullet(HTML("<span class=\"py-src-identifier\">pb.RemoteReference</span>: Used by distant program to invoke methods."),
 122                  SubBullet(HTML("Offers <span class=\"py-src-identifier\">.callRemote()</span> to trigger remote method on a corresponding <span class=\"py-src-identifier\">pb.Referenceable</span>.")),
 123                  ),
 124           ),
 125
 126     Raw("Sample code",
 127         "<h2>Sample Code</h2>" + server_lore + client_lore),
 128     #Slide("Simple Demo"),
 129     # "better demo: manhole, or reactor running in another thread"
 130
 131     #build up from callRemote?
 132     Slide("What happens to those arguments?",
 133           Bullet("Basic structures should travel transparently",
 134                  SubBullet("Actually quite difficult in some languages"),
 135                  ),
 136           Bullet("Object graph should remain the same",
 137                  SubBullet("Serialization context"),
 138                  SubBullet("(same issues as Pickle)")),
 139           Bullet("Instances of user-defined classes require more care",
 140                  SubBullet("User-controlled unjellying"),)
 141           ),
 142
 143     #serialization (skip banana)
 144     Slide("40% More Sandwich Puns Than The Leading Brand",
 145           Bullet("twisted.spread: python package holding other modules"),
 146           Bullet("PB: remote method invocation"),
 147           Bullet("Jelly: mid-level object serialization"),
 148           Bullet("Banana: low-level serialization of s-expressions"),
 149           Bullet("Taster: security context, decides what may be received"),
 150           Bullet("Marmalade: like Jelly, but involves XML, so it's bitter"),
 151           Bullet("better than the competition",
 152                  SubBullet("CORBA: few or no sandwich puns"),
 153                  SubBullet("XML-RPC: barely pronounceable"),
 154                  ),
 155           ),
 156
 157     Slide("Jellying objects",
 158           Bullet("'Jellying' vs 'Unjellying'"),
 159           Bullet("Immutable objects are copied whole"),
 160           Bullet("Mutable objects get reference IDs to insure shared references remain shared",
 161                  SubBullet("(within the same Jellying context)")),
 162           ),
 163
 164     Slide("Jellying instances",
 165           Bullet(HTML("User classes inherit from one of the <span class=\"py-src-identifier\">pb.flavor</span> classes")),
 166           Bullet(HTML("<span class=\"py-src-identifier\">pb.Referenceable</span>: methods can be called remotely")),
 167           Bullet(HTML("<span class=\"py-src-identifier\">pb.Copyable</span>: contents are selectively copied")),
 168           Bullet(HTML("<span class=\"py-src-identifier\">pb.Cacheable</span>: contents are copied and kept up to date")),
 169           Bullet(HTML("Classes define <span class=\"py-src-identifier\">.getStateToCopy</span> and other methods to restrict exported state")),
 170           ),
 171
 172     Slide("pb.Copyable example",
 173           PRE("""class SenderPond(FrogPond, pb.Copyable):
 174     def getStateToCopy(self):
 175         d = self.__dict__.copy()
 176         d['frogsAndToads'] = d['numFrogs'] + d['numToads']
 177         del d['numFrogs']
 178         del d['numToads']
 179         return d
 180
 181 class ReceiverPond(pb.RemoteCopy):
 182     def setCopyableState(self, state):
 183         self.__dict__ = state
 184         self.localCount = 12
 185     def count(self):
 186         return self.frogsAndToads
 187
 188 pb.setUnjellyableForClass(SenderPond, ReceiverPond)
 189 """)),
 190
 191     Slide("Secure Unjellying",
 192           Bullet("Pickle has security problems",
 193                  SubBullet("Pickle will import any module the sender requests."),
 194                  SubBullet(HTML("2.3 gave up, removed safety checks like <span class=\"py-src-identifier\">__safe_for_unpickling__</span> .")),
 195                  ),
 196           Bullet("Jelly attempts to be safe in the face of hostile clients",
 197                  SubBullet("All classes rejected by default"),
 198                  SubBullet(HTML("<span class=\"py-src-identifier\">registerUnjellyable()</span> used to accept safe ones")),
 199                  SubBullet(HTML("Registered classes define <span class=\"py-src-identifier\">.setCopyableState</span> and others to process remote state")),
 200                  ),
 201           Bullet("Must mark (by subclassing) to transmit"),
 202           ),
 203
 204     Slide("Transformation of references in transit",
 205           Bullet("All referenced objects get turned into their counterparts as they go over the wire"),
 206           Bullet("References are followed recursively",
 207                  SubBullet("Sending a reference to a tree of objects will cause the whole thing to be transferred"),
 208                  SubBullet("(subject to security restrictions)"),
 209                  ),
 210           Bullet(HTML("<span class=\"py-src-identifier\">pb.flavors</span> get reference ids"),
 211                  SubBullet("They are recognized when they return, transformed into the original reference"),
 212                  SubBullet("Reference ids are scoped to the connection"),
 213                  SubBullet("One side-effect: no 'third party' references"),
 214                  ),
 215           ),
 216
 217     Slide("Perspectives: pb.cred and the Identity/Service model",
 218           Bullet("A layer to provide common authentication services to Twisted applications"),
 219           Bullet(HTML("<span class=\"py-src-identifier\">Identity</span>: named user accounts with passwords")),
 220           Bullet(HTML("<span class=\"py-src-identifier\">Service</span>: something a user can request access to")),
 221           Bullet(HTML("<span class=\"py-src-identifier\">Perspective</span>: user accessing a service")),
 222           Bullet(HTML("<span class=\"py-src-identifier\">pb.Perspective</span>: first object, a <span class=\"py-src-identifier\">pb.Referenceable</span> used to access everything else")),
 223           ),
 224     #picture would help
 225
 226     Slide("Future directions",
 227           Bullet("Other language bindings: Java, elisp, Haskell, Scheme, JavaScript, OCaml"),
 228           # donovan is doing the JavaScript port
 229           Bullet("Other transports: UDP, Airhook"),
 230           Bullet("Componentization"),
 231           Bullet("Performance improvements: C extension for Jelly"),
 232           Bullet("Refactor addressing model: PB URLs"),
 233           ),
 234
 235     Slide("Questions", Bullet("???")),
 236
 237     )
 238
 239 lecture.renderHTML("slides", "slide-%02d.html", css="stylesheet.css")
 240