Caching the Uncacheable [Long Version]

Caching
The
Uncacheable
Leveraging
Your
CDN
To
Cache
Dynamic
Content
Hooman
Behesh+,
VP
Technology

Dynamic
Content
Is
Really
Interes<ng!

What
Is
Dynamic
Content?
• Stuff
that’s
not
sta+c!
• With
web
traffic,
generally
the
base
HTML
– Big
deal
because
it’s
blocking
– And
some+mes
a
large
object
à
longer
download

What
Is
Dynamic
Content?
• Stuff
that’s
not
sta+c!
• With
web
traffic,
generally
the
base
HTML
– Big
deal
because
it’s
blocking
– And
some+mes
a
large
object
à
longer
download
• Could
be
other
things
too
– AJAX
calls
– API
calls
• More…

Classically,
with
dynamic
content…
Caching

Dynamic
Content
Caching
Problems
• Serving
stale
pages
– Lack
of
good
invalida+on
framework

Dynamic
Content
Caching
Problems
• Serving
stale
pages
– Lack
of
good
invalida+on
framework
• Real-‐+me
visibility
– Real-‐+me
analy+cs/stats
– Real-‐+me
logging/tracking

CDNs
and
Dynamic
Content
• Generally,
handling
dynamic
content
has
been
a
maRer
of
transport
– Op+mize
from-‐origin
delivery
– “DSA”
(Dynamic
Site
Accelera+on)
– Middle
mile
op+miza+ons
– TCP
tweaks

Dynamic
Content,
Tradi<onally
CDN
Node
Client
Origin
Some
TCP
Tweaks

Dynamic
Content,
Tradi<onally
CDN
Node
CDN
Node
Client
Origin
Lots
of
TCP
Tweaks

Dynamic
Content,
Tradi<onally
• We
some+mes
do
micro
caching
of
HTML
– Short
TTL
for
HTML
content
via
Cache-‐Control
– Not
full
proof
• Ex:
news
stories
faux-‐pas!
• ESI
(Edge
Side
Includes)
– Par+al
caching
– Hard
and
onerous

Actually…
• Dynamic
content
is
more
cacheable
than
we
think
• Sta+c
for
shorter
periods
of
+me
• Unpredictable
invalida+on
– Standard
HTTP
caching
rules
aren’t
good
enough

A
Lot
BeLer!
CDN
Node
CDN
Node
Client
Origin

So
Many
Benefits!
• Performance
– Faster
+me
to
first
byte
– Faster
start
render
– Happy
users!
• Offload
– Less
work
for
our
servers
– Less
bandwidth
at
origin

Programma<c
Invalida<on
• Invalida+on
API
• Granular
– Specific
URL
– URL
groups
– All
– Etc…

Purge
• As
a
page
gets
published/updated,
a
purge
command
also
gets
published
• Must
be
Instant!
• Big
problem
with
classic
CDNs
– mul+-‐minute
purges!
– Ex:
News
story,
part
2

Instant?
• IS
NOT:
– 12
minutes!
– quick
acknowledgment!
• IS:
– <1sec
– predictable
and
determinis+c
behavior
– (has
to
also
include
propaga+on)

Power
of
the
Purge!
• Purge
dependencies
– Surrogate
Keys
– Using
tags/labels
to
purge
en+re
chunks
of
content
at
once

WordPress:
Before
CDN
Node
Cache

WordPress:
AVer
CDN
Node
HTTP/1.1 200 OK
Content-Type: text/html
Content-Length: 55,666
Cache-Control: Totally Long Time!

WordPress:
AVer
CDN
Node
PURGE

WordPress:
AVer
CDN
Node
(Has
to
be
instantaneous!)
PURGE

Before
CDN
Node
Origin
http://www.3rdparty.com/customer1.js
(Referer: www.customer1.com)

Before
CDN
Node
Origin

Before
CDN
Node
Origin
HTTP/1.1 200 OK
Cache-Control: max-age=60
Last-Modified: Wed, 24 Sep 2014 19:51:30 GMT
Content-Type: application/javascript
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache
Content-Length: 7835

Before
CDN
Node
Origin
HTTP/1.1 200 OK
Cache-Control: max-age=60
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache

Before
CDN
Node
Origin
(Ager
1
min)

Before
CDN
Node
Origin
(Ager
1
min)
http://www.3rdparty.com/customer1.js VALIDATION
If-Modified-Since: Wed, 24 Sep 2014
19:51:30 GMT

Before
CDN
Node
Origin
(Ager
1
min)
304 Not Modified

AVer
CDN
Node
Origin

AVer
CDN
Node
Origin
HTTP/1.1 200 OK
Cache-Control: max-age=60, s-maxage=2592000
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache

AVer
CDN
Node
Origin
HTTP/1.1 200 OK
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache

AVer
CDN
Node
Origin
(Ager
1
min)

This
happens
many
many
<mes!
(many
many
happy
visitors!)

AVer
CDN
Node
Origin
Customer1
changes
config
(Ager
1
min)

AVer
CDN
Node
Origin
PURGE
customer1.js
Customer1
changes
config
(Ager
1
min)

AVer
CDN
Node
Origin
(Ager
1
min)
HTTP/1.1 200 OK
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache

AVer
CDN
Node
Origin
HTTP/1.1 200 OK
Date: Thu, 25 Sep 2014 12:22:20 GMT
Server: Apache
(Ager
1
min)

More
than
just
Invalida<on…

The
Influence
of
Clouds
• The
CDN
is
an
extension
of
the
app
• No
longer
a
black
box
• Real-‐+me
integra+on
with
the
app
• Infrastructure
as
code
– Your
content
=>
You
need
control

Control
• Programmability
– Configura+on
API
– Invalida+on
API
– Instantaneous
and
real
+me

Caching
Control
• Granular
caching
– Dynamic
caching
– flexible
cache
keys
– etc
• Ex:
Geo-‐based
caching

Control
at
the
Edge
• Moving
app
logic
to
the
edge
• VCL
– Varnish
Configura+on
Language
– Script-‐like
configura+on
for
func+onality
at
the
edge

Visibility
• Real
+me
analy+cs
– Network
stats
– HTTP
stats
(status
codes
,
etc)
– Caching
stats
(hits,
misses,
etc)
– Stats
API
• Logging
– Real
+me
logs
– Streaming
to
various
log
des+na+ons

Example:
Beacon
Termina<on
at
the
Edge

Before
CDN
Node
Origin
Log
Analysis
http://collector.site.com/beacon.img?a=1&b=2&c=3

Before
CDN
Node
Origin
Log
Analysis
HTTP/1.1 200 OK
Pragma: no-cache
Expires: Wed, 19 Apr 2000 11:43:00 GMT
Cache-Control: no-cache, no-store
Last-Modified: Wed, 21 Jan 2004 19:51:30 GMT
Content-Type: image/gif
Date: Fri, 20 Jun 2014 12:22:20 GMT
Server: Apache
Content-Length: 35

AVer
CDN
Node
Origin

AVer
CDN
Node
Origin
HTTP/1.1 200 OK
Pragma: no-cache
Expires: Wed, 19 Apr 2000 11:43:00 GMT
Cache-Control: no-cache, no-store
Last-Modified: Wed, 21 Jan 2004 19:51:30 GMT
Content-Type: image/gif
Date: Fri, 20 Jun 2014 12:22:20 GMT
Server: Apache
Content-Length: 35

AVer
CDN
Node
Origin
HTTP/1.1 204 No Content
Date: Sat, 21 Jun 2014 23:21:12 GMT
Server: Awesome Server
Content-Length: 0

AVer
CDN
Node
Origin
Syslog
/
S3
/
FTP/etc

Example:
Edge-‐generated
Content

JSON
Data
Center
ID
CDN
Node
Origin
http://www.site.com/which_datacenter.js

JSON
Data
Center
ID
http://www.site.com/which_datacenter.js
CDN
Node
Origin
{ ‘datacenter’ : ‘SJC’ }

JSON
Geo
IP
http://www.site.com/geo_ip.js
CDN
Node
Origin
{
“city” : “New York”,
“state”: “New York”,
“country”: “United States”,
“ip”: “173.18.14.237”
}

More
Examples
• Caching
with
tracking
cookies:
– hRp://www.fastly.com/blog/how-‐to-‐cache-‐with-‐
tracking-‐cookies
• API
Caching:
– hRp://www.fastly.com/blog/api-‐caching-‐part-‐iii
(part
3,
with
links
to
previous
two
parts)
• Log
Streaming:
– hRp://www.fastly.com/blog/+ps-‐for-‐streaming-‐logs

Summary
• Dynamic
content
can
be
cached
– We
need
instant
purging
– We
need
real-‐+me
logs
and
stats
• Real-‐+me
integra+on
of
our
CDN
with
our
app
is
cool!
– Extensive/granular
API
to
control
the
CDN
– Control
and
visibility
at
the
edge
lets
us
be
really
crea+ve
• Never
use
“Totally Long Time!” in
a
Cache-Control
header!

Thank
you!
hooman@fastly.com

Caching the Uncacheable [Long Version]

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Caching the Uncacheable [Long Version]