<s>
Avro	B-Operating_System
is	O
a	O
row-oriented	O
remote	B-Operating_System
procedure	I-Operating_System
call	I-Operating_System
and	O
data	B-Application
serialization	I-Application
framework	B-Architecture
developed	O
within	O
Apache	B-Application
's	I-Application
Hadoop	I-Application
project	O
.	O
</s>
<s>
It	O
uses	O
JSON	B-General_Concept
for	O
defining	O
data	O
types	O
and	O
protocols	O
,	O
and	O
serializes	B-Application
data	O
in	O
a	O
compact	O
binary	O
format	O
.	O
</s>
<s>
Its	O
primary	O
use	O
is	O
in	O
Apache	B-Application
Hadoop	I-Application
,	O
where	O
it	O
can	O
provide	O
both	O
a	O
serialization	B-Application
format	O
for	O
persistent	B-General_Concept
data	I-General_Concept
,	O
and	O
a	O
wire	B-Application
format	I-Application
for	O
communication	O
between	O
Hadoop	B-Application
nodes	B-Protocol
,	O
and	O
from	O
client	O
programs	O
to	O
the	O
Hadoop	B-Application
services	O
.	O
</s>
<s>
Avro	B-Operating_System
uses	O
a	O
schema	B-Application
to	O
structure	O
the	O
data	O
that	O
is	O
being	O
encoded	O
.	O
</s>
<s>
It	O
has	O
two	O
different	O
types	O
of	O
schema	B-Application
languages	O
;	O
one	O
for	O
human	O
editing	O
(	O
Avro	B-Operating_System
IDL	O
)	O
and	O
another	O
which	O
is	O
more	O
machine-readable	B-General_Concept
based	O
on	O
JSON	B-General_Concept
.	O
</s>
<s>
It	O
is	O
similar	O
to	O
Thrift	B-Protocol
and	O
Protocol	B-Protocol
Buffers	I-Protocol
,	O
but	O
does	O
not	O
require	O
running	O
a	O
code-generation	O
program	O
when	O
a	O
schema	B-Application
changes	O
(	O
unless	O
desired	O
for	O
statically-typed	O
languages	O
)	O
.	O
</s>
<s>
Apache	O
Spark	O
SQL	O
can	O
access	O
Avro	B-Operating_System
as	O
a	O
data	O
source	O
.	O
</s>
<s>
An	O
Avro	B-Operating_System
Object	B-Application
Container	I-Application
File	I-Application
consists	O
of	O
:	O
</s>
<s>
one	O
or	O
more	O
file	O
data	B-General_Concept
blocks	I-General_Concept
.	O
</s>
<s>
A	O
file	B-General_Concept
header	I-General_Concept
consists	O
of	O
:	O
</s>
<s>
Four	O
bytes	O
,	O
ASCII	B-Protocol
'	O
O	O
 '	O
,	O
'	O
b	O
 '	O
,	O
'	O
j	O
 '	O
,	O
followed	O
by	O
the	O
Avro	B-Operating_System
version	O
number	O
which	O
is	O
1	O
(	O
0x01	O
)	O
(	O
Binary	O
values	O
0x4F	O
0x62	O
0x6A	O
0x01	O
)	O
.	O
</s>
<s>
File	O
metadata	O
,	O
including	O
the	O
schema	B-Application
definition	O
.	O
</s>
<s>
For	O
data	B-General_Concept
blocks	I-General_Concept
Avro	B-Operating_System
specifies	O
two	O
serialization	B-Application
encodings	O
:	O
binary	O
and	O
JSON	B-General_Concept
.	O
</s>
<s>
For	O
debugging	O
and	O
web-based	O
applications	O
,	O
the	O
JSON	B-General_Concept
encoding	O
may	O
sometimes	O
be	O
appropriate	O
.	O
</s>
<s>
Avro	B-Operating_System
schemas	B-Application
are	O
defined	O
using	O
JSON	B-General_Concept
.	O
</s>
<s>
Schemas	B-Application
are	O
composed	O
of	O
primitive	O
types	O
(	O
null	O
,	O
boolean	O
,	O
int	O
,	O
long	O
,	O
float	O
,	O
double	O
,	O
bytes	O
,	O
and	O
string	O
)	O
and	O
complex	O
types	O
(	O
record	O
,	O
enum	O
,	O
array	O
,	O
map	O
,	O
union	O
,	O
and	O
fixed	O
)	O
.	O
</s>
<s>
Simple	O
schema	B-Application
example	O
:	O
</s>
<s>
Data	O
in	O
Avro	B-Operating_System
might	O
be	O
stored	O
with	O
its	O
corresponding	O
schema	B-Application
,	O
meaning	O
a	O
serialized	O
item	O
can	O
be	O
read	O
without	O
knowing	O
the	O
schema	B-Application
ahead	O
of	O
time	O
.	O
</s>
<s>
Serialization	B-Application
:	O
</s>
<s>
File	O
"	O
users.avro	O
"	O
will	O
contain	O
the	O
schema	B-Application
in	O
JSON	B-General_Concept
and	O
a	O
compact	O
binary	O
representation	O
of	O
the	O
data	O
:	O
</s>
<s>
Deserialization	B-Application
:	O
</s>
<s>
Though	O
theoretically	O
any	O
language	O
could	O
use	O
Avro	B-Operating_System
,	O
the	O
following	O
languages	O
have	O
APIs	O
written	O
for	O
them	O
:	O
</s>
<s>
In	O
addition	O
to	O
supporting	O
JSON	B-General_Concept
for	O
type	O
and	O
protocol	O
definitions	O
,	O
Avro	B-Operating_System
includes	O
experimental	O
support	O
for	O
an	O
alternative	O
interface	B-General_Concept
description	I-General_Concept
language	I-General_Concept
(	O
IDL	O
)	O
syntax	O
known	O
as	O
Avro	B-Operating_System
IDL	O
.	O
</s>
<s>
Previously	O
known	O
as	O
GenAvro	O
,	O
this	O
format	O
is	O
designed	O
to	O
ease	O
adoption	O
by	O
users	O
familiar	O
with	O
more	O
traditional	O
IDLs	O
and	O
programming	O
languages	O
,	O
with	O
a	O
syntax	O
similar	O
to	O
C/C	O
++	O
,	O
Protocol	B-Protocol
Buffers	I-Protocol
and	O
others	O
.	O
</s>
<s>
The	O
Apache	B-Operating_System
Avro	I-Operating_System
logo	O
is	O
from	O
the	O
defunct	O
British	O
aircraft	O
manufacturer	O
Avro	B-Operating_System
(	O
originally	O
A.V.	O
</s>
<s>
Football	O
team	O
Avro	B-Operating_System
F.C.	O
</s>
