The Zope Component Architecture is a very powerful tool which is widely used in Plone and the Plone community. For stock users of Plone it can seem like an encumbrance, slowing the site down and complicating development without any advantages. However, even basic applications built with Plone can benefit from some ZCA tricks that are not as widely known as they should be. This talk will demonstrate simple uses of the component architecture which, along with a typical Plone stack, allow developers to deliver very performance Plone sites while simultaneously freeing the developer from the normal optimisation worries.

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Matthew Wilkes
Jarn

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High Performance made easy
Some tips and tricks that defy conventional wisdom

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About
me
Matthew Wilkes
Former Bristolian
living in Berlin
Working at Jarn
Plone 4 FWT
member

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Old wives’ tales

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Performance ‘is’…
… never waking an object
… avoiding adapter lookups
… heavily optimising your python code

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What’s really important
•Planning
• What will be the profile of reads/writes be?
•Agility
• Defer optimisation as late as you can

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What’s really important
•Cacheability
• Can the design be made more cacheable?
•Analysis
• Real world numbers, not just profiling code

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Know your users
Find out expected usage
patterns
Are accesses distributed evenly
or are there some content
hotspots?
Are you using the right
technologies for the load?

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Heard it on the grapevine!
FACT: The catalogue is fast
MYTH: “You should never wake objects”

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BURN HIM

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No, really. Look.
What if we want some basic
information from some
specific objects?
Waking them is faster for up to
about 50 objects 0
40
80
120
160
200
0 10 20 30 40 50 60 70 80 90
Single attribute, known location
Traversal Catalogue

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No, really. Look.
Or we might want to show a
folder listing
Catalogue is faster for much
smaller object sets
0
20
40
60
80
100
0 10 20 30 40 50 60 70 80 90
5 attributes, known location
Traversal Catalogue

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I should forget the catalog?
NO! Remember agility.
Not catalogue specific, make more decisions based
on real numbers.
Until you’ve written your code you don’t know if you
should use the catalog or not.

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Become a catalogue agnostic

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(be indifferent to brains)
Photo: Kevin Dooley

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What does that mean?
Catalogue brains are very different to real objects
We can’t call methods
The same data is exposed differently
ZCA is designed to allow us to be implementation
agnostic

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Tip: Register an adapter!
Your content has an interface anyway, right?
Register an adapter from ICatalogBrain to it
Implement data from the catalogue directly
Use a custom __getattr__ to allow fallback

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Tip: Register an adapter!
Your code doesn’t know if it is dealing with a brain
or a real object – your catalogue fiddling is deferred
Reduces the amount of stuff you need to keep in
your head

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Real numbers
Use Apache CustomLog or HAProxy logs to get
request times
Good: If you’re iterating with a customer run it there
Better: Soft-launch with a subset of users and run
there!

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Varnish HTTP Cache
HTTP caching is the
single most powerful
trick we have
Improves read
performance by 2-3
orders of magnitude
Leaves the instances
free for writes

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Anonymous users
Easiest to cache for - Varnish + plone.app.caching
Almost everything can be kept in the cache
Need to balance longer TTLs with difficulty of
getting PURGE right.

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Authenticated users
Only images, JS and CSS cacheable at first glance
Pages refer to the username and some things are
role dependent.
No way to solve this problem in the general case

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Page composition
But we don’t care about the
general case
We know the site we’re making
Use ESIs to separate content
that varies between users from
the common things

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If we didn’t plan out what parts of each page are
cacheable it might be impossible to split it out
efficiently.
Keep the blocks that are user-specific small, few and
separate.
Make those sections send cache-control: private
The main page should send cache-control: public

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Easy to hack into existing sites if you’re in a pickle
Can bring authenticated accesses up to the same
speed as cached anonymous users
Tip: Use ESI

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Any template code backed by a Python class will do.
Custom __call__ method that checks for a header
turning on ESI and if it is being rendered directly
Return an ESI tag or the full content
Makes it easy to enable/disable if needed
Tip: Make use of views

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Change is good

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Often the big changes in terms of performance are
small changes to the client
Should a page have 5 items or 20?
Can we simplify the workflow?
Both cut down the number of page loads needed

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Any questions?