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Description
Don’t miss out! Join us at our upcoming event: KubeCon + CloudNativeCon North America 2021 in Los Angeles, CA from October 12-15. Learn more at https://kubecon.io The conference features presentations from developers and end users of Kubernetes, Prometheus, Envoy, and all of the other CNCF-hosted projects.
CoreDNS Deep Dive: Building Custom Plugins - Yong Tang, Ivanti
CoreDNS is a cloud-native DNS server with a focus on service discovery. While best known as the default cluster DNS for Kubernetes, CoreDNS is very flexible and extensible for any new features thanks to its plugin-based architecture: new functionalities can be easily added as plugins with Golang. In this session, we will take a detailed look at the plugin system of CoreDNS. We will walk through the complete code of a demo plugin from the scratch to showcase the simplicity and ease of convenience of CoreDNS plugins. We also provide updates and future roadmap of CoreDNS and the community event in this session.
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As
many
of
you
know,
codiness
is
a
flexible
dna
server
reading
go,
it
was
developed
and
started
in
2016.
at
the
beginning.
It
was
really
a
fork
of
a
caddy
xct
server.
Over
the
years.
The
relationship
between
coding
and
center
caddy
has
been
gradually
decoupled,
although
even
as
of
now,
you
can
still
find
some
more
traces
of
paddy
reference,
including
as
codebase.
A
Unlike
some
other
dns
servers
coding,
s
has
a
focus
on
service
discovery.
It
is
a
plugin
based,
which
means
it
can
be
easily
extended
for
new
functionalities.
If
you
have
a
new
feature,
you
want
to
add,
and
it's
not
available
in
default
plugins,
then
you
can
write
on
your
own
if
you
know
how
to
write
in
go.
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In
2020,
we
also
released
a
version
of
1.8.0
to
1.8.3.
1.8.0
was
released
on
october.
The
most
important
change
is
that
we
internalize
academy.
As
I
mentioned,
the
coordinates
was
actually
a
fork
at
the
beginning
of
cad
atp
server.
Over
the
years,
caddy
has
been
migrated
from
version
1
to
version
2..
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If
you're
looking
for
help,
including
us,
there
are
several
places
you
can
find,
the
github
is
the
most
active
one.
Most
of
maintenance
are
there
and
willing
to
to
help
you
whenever
possible.
There
is
also
slack
channel.
That's
part
of
the
cncf
slack.
You
can
find
some
help
from
some
of
the
maintenance.
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This
is
a
very
interesting
cell
application
that
can
help
a
lot
of
areas.
It's
also
very
interesting
to
see
the
topics
of
dns
can
be
expanded
into
other
areas
of
security
and
machine
learning
by
the
way
in
2021.
We
are
also
participating
in
google
summer
code
in
this
year.
The
topic
of
google
summer
code
for
coding
us
is
acme
support,
which
is
cme
support.
You
should
be
able
to
obtain
or
renew
your
certificate
automatically
without
any
manual
intervention,
which
is
acme
support.
A
Plugins
we
switched
back
to
2020
the
google
summer
code
and
the
coordinates
the
student
actually
posts
a
very
interesting
web
page
to
to
list
all
his
source
code
for
this
server
application.
He
set
up
several
components.
The
first
component
is
recording
a
server
plugs,
a
plugin
which
is
written
in
gola.
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He
set
up
another
server,
which
is
a
python
server,
exposing
a
resource
api.
The
reason
he
set
up
independent
server
in
python
is
in
machine
learning.
Most
of
implementations
are
actually
done
in
python
cipher
pass,
so
he
decided
that
it's
not
the
best
interest
to
reinvent
the
bill
to
to
put
everything
into
gola,
so
instead
he
set
up
an
individual
server
so
that
it's
easy
to
reuse
the
existing
infrastructure
in
machine
learning
and
allow
coordinates
to
talk
to
the
machine
learning
server
through
the
restful
api.
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Finally,
dns
is
very
pervasive
in
id
infrastructure,
which
means
you
can
find
dns
from
anywhere
in
any
organization
and
in
any
way,
for
example,
you
can
find
dns
in
your
id
organization.
You
can
find
dinners
in
your
deployment
of
kubernetes.
You
can
find
the
dns
in
your
cloud
vendor's
native
services.
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Let's
say
you
have
a
service
or
cluster
deployed,
let's
say
iews
and
you
want
to
migrate
to
google
cloud
or
maybe
migrate,
a
part
of
service
into
microsoft
azure.
So
how
would
you
do
that?
If
you
don't
have
a
dns
which
is
in
direction
in
place
at
the
beginning?
You
may
need
to
do
a
lot
of
change.
You
may
need
to
notify
your
users
about
ids
that
you
have
translation,
but
with
dns.
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The
initial
setup
function
are
pretty
straightforward,
but
the
main
processing
of
the
dns
queries
is
a
serve
dns
function.
This
function
takes
the
query
message
as
well
as
a
response
writer,
which
is
a
function.
You
should
be
able
to
process
the
dns
request
and
return
the
response,
or,
if
you,
if
you
decided
that
your
plugin
is
not
going
to
process
this
dns
request,
you
will
pass
it
down
the
chain,
allow
the
next
plugin
to
process
it.
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Further,
this
is
the
setup
function
and
the
init
function,
as
you
can
see,
it's
pretty
straightforward
for
unit
function.
Since
we
named
this
plugin
as
demo,
we
pass
a
demo
as
a
stream.
We
also
set
the
dns
as
the
server
type
the
setup
is.
The
function
will
build
processor
configuration
since
in
this
demo
plugin.
We
are
not
going
to
pass
any
configuration
parameters.
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We
take
the
dns
request,
that's
the
dns.msd.
We
will.
We
will
also
pass
the
dns
response
writer,
which
allows
you
to
decide
what
to
do
for
the
for
this.
For
this
plugin,
the
first
thing
you
need
to
do
is
to
construct
a
request
state.
This
is
done
by
the
first
line
of
state
equals
request
data
request,
which
is
state.
You
are
able
to
find
the
name
of
the
query,
and
you
now
you
can
start
deciding
what
to
do
with
the
response.
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We
already
decide
what
to
do
so,
we'll
pass
through
the
answers
and
go
through
the
response
writer
to
to
do
that.
If
we
decided
that
we
don't
want
to
reply,
then
all
we
need
to
do
is
to
just
pass
through
the
plug-in
chain
and
allow
for
and
allow
the
next
plugin
to
pick
up
and
the
process
further.
But
in
this
case
we
are
going
to
do
that.
So
we
will
return
the
answers
ourselves.
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With
the
demo
plugin
in
place,
you
can
build
the
binary,
but
you
also
need
a
core
file
by
default.
All
the
plugins
are
disabled,
initially
so,
which
means
in
order
to
enable
demo.
You
should
at
least
place
demo
in
your
profile.
We
set
up
the
port
number
of
1053
so
that
we
can
listen
to
this
port.
If
you
want
to
listen
to
the
default
for
number
53,
you
should
change
the
configuration.
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The
next
step
is
to
build
with
scola,
since
sometimes,
if
you're,
using
linux
or
using
mac,
it
may
not
be
exactly
straightforward
to
set
up
a
go
line
environment.
If
you
don't
want
to
bother-
and
you
already
have
docking
installed,
you
can
actually
use
docker
to
run
this
one
line
command
to
build
a
binary.
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If
you
try
it
yourself,
you
will
find
out
that
that,
if
you
do
the
query
from
external
networks,
the
return
the
returned
id
will
be
8.8.8.8
and
they
feel,
if
you
query
the,
if
you
create
example.out
from
your
internal
network,
then
the
response
will
be
1.1.1.1
and
that's
exactly
the
service
discovery
we
talked
about.
It
gives
you
a
lot
of
flexibility
and
allow
you
to
decide
what
to
response
and
the
point
in
service
the
way
you.
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Want
the
whole
source
code
of
demo
plugin
is
available
on
github.
You
should
be
able
to
check
by
yourself.
It
consists
of
readme
as
well
as
other
details,
and
if
you
take
a
further
look,
you
can
notice
that
the
total
line
code
is
about
less
than
80
lines.
So
that
gives
you
enough
detail
to
allow
you
to
write
on
your
own.