/
protocol-binary.xml
1466 lines (1379 loc) · 61.4 KB
/
protocol-binary.xml
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<?xml version="1.0" encoding="US-ASCII"?>
<!DOCTYPE rfc SYSTEM "xml2rfc/rfc2629.dtd">
<?xml-stylesheet type='text/xsl' href='xml2rfc/rfc2629.xslt'?>
<?rfc toc="yes"?>
<?rfc strict="yes"?>
<?rfc symrefs="yes"?>
<?rfc sortrefs="yes" ?>
<?rfc compact="yes" ?>
<?rfc subcompact="yes" ?>
<rfc category="info" docName="draft-stone-memcache-binary-01" ipr="trust200902">
<front>
<title> Memcache Binary Protocol </title>
<author fullname="Aaron Stone" surname="Stone" role="editor">
<organization>Six Apart, Ltd.</organization>
<address>
<postal>
<street>548 4th Street</street>
<city>San Francisco</city>
<region>CA</region>
<code>94107</code>
<country>USA</country>
</postal>
<email>aaron@serendipity.palo-alto.ca.us</email>
</address>
</author>
<author fullname="Trond Norbye" surname="Norbye" role="editor">
<organization>Sun Microsystems, INC</organization>
<address>
<postal>
<street>Haakon VII g. 7B</street>
<city>Trondheim</city>
<code>NO-7485 Trondheim</code>
<country>Norway</country>
</postal>
<email>trond.norbye@sun.com</email>
</address>
</author>
<date day="28" month="August" year="2008" />
<area>Applications</area>
<keyword>memcache memcached cache</keyword>
<abstract>
<t>
This memo explains the memcache binary protocol for informational
purposes.
</t>
<t>
Memcache is a high performance key-value cache. It is intentionally a
dumb cache, optimized for speed only. Applications using memcache do
not rely on it for data -- a persistent database with guaranteed
reliability is strongly recommended -- but applications can run much
faster when cached data is available in memcache.
</t>
</abstract>
</front>
<middle>
<section anchor="introduction" title="Introduction">
<t>
Memcache is a high performance key-value cache. It is intentionally a
dumb cache, optimized for speed only. Applications using memcache should
not rely on it for data -- a persistent database with guaranteed
reliability is strongly recommended -- but applications can run much
faster when cached data is available in memcache.
</t>
<t>
Memcache was originally written to make
<xref target="LJ">LiveJournal</xref> faster. It now powers all of
the fastest web sites that you love.
</t>
<section anchor="conventions" title="Conventions Used In This Document">
<t>
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in
<xref target="KEYWORDS"/>.
</t>
</section>
</section>
<section anchor="packet" title="Packet Structure">
<figure>
<preamble>General format of a packet:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0/ HEADER /
/ /
/ /
/ /
+---------------+---------------+---------------+---------------+
24/ COMMAND-SPECIFIC EXTRAS (as needed) /
+/ (note length in the extras length header field) /
+---------------+---------------+---------------+---------------+
m/ Key (as needed) /
+/ (note length in key length header field) /
+---------------+---------------+---------------+---------------+
n/ Value (as needed) /
+/ (note length is total body length header field, minus /
+/ sum of the extras and key length body fields) /
+---------------+---------------+---------------+---------------+
Total 24 bytes
</artwork>
</figure>
<figure>
<preamble>Request header:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| Magic | Opcode | Key length |
+---------------+---------------+---------------+---------------+
4| Extras length | Data type | Reserved |
+---------------+---------------+---------------+---------------+
8| Total body length |
+---------------+---------------+---------------+---------------+
12| Opaque |
+---------------+---------------+---------------+---------------+
16| CAS |
| |
+---------------+---------------+---------------+---------------+
Total 24 bytes
</artwork>
</figure>
<figure>
<preamble>Response header:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| Magic | Opcode | Key Length |
+---------------+---------------+---------------+---------------+
4| Extras length | Data type | Status |
+---------------+---------------+---------------+---------------+
8| Total body length |
+---------------+---------------+---------------+---------------+
12| Opaque |
+---------------+---------------+---------------+---------------+
16| CAS |
| |
+---------------+---------------+---------------+---------------+
Total 24 bytes
</artwork>
</figure>
<t>
Header fields:
<list hangIndent="20" style="hanging">
<t hangText="Magic">Magic number.</t>
<t hangText="Opcode">Command code.</t>
<t hangText="Key length">Length in bytes of the text key that follows the command extras.</t>
<t hangText="Status">Status of the response (non-zero on error).</t>
<t hangText="Extras length">Length in bytes of the command extras.</t>
<t hangText="Data type">Reserved for future use (Sean is using this soon).</t>
<t hangText="Reserved">Really reserved for future use (up for grabs).</t>
<t hangText="Total body length">Length in bytes of extra + key + value.</t>
<t hangText="Opaque">Will be copied back to you in the response.</t>
<t hangText="CAS">Data version check.</t>
</list>
</t>
</section>
<section anchor="values" title="Defined Values">
<section anchor="value-magic" title="Magic Byte">
<t>
<list hangIndent="8" style="hanging">
<t hangText="0x80">Request packet for this protocol version</t>
<t hangText="0x81">Response packet for this protocol version</t>
</list>
</t>
<t>
Magic byte / version. For each version of the protocol, we'll use a
different request/response value pair. This is useful for protocol
analyzers to distinguish the nature of the packet from the direction
which it is moving. Note, it is common to run a memcached instance on
a host that also runs an application server. Such a host will both
send and receive memcache packets.
</t>
<t>
The version should hopefully correspond only to different meanings of
the command byte. In an ideal world, we will not change the header
format. As reserved bytes are given defined meaning, the protocol
version / magic byte values should be incremented.
</t>
<t>
Traffic analysis tools are encouraged to identify memcache packets
and provide detailed interpretation if the magic bytes are recognized
and otherwise to provide a generic breakdown of the packet. Note, that
the key and value positions can always be identified even if the magic
byte or command opcode are not recognized.
</t>
</section>
<section anchor="value-status" title="Response Status">
<t>
Possible values of this two-byte field:
<list hangIndent="8" style="hanging">
<t hangText="0x0000">No error</t>
<t hangText="0x0001">Key not found</t>
<t hangText="0x0002">Key exists</t>
<t hangText="0x0003">Value too large</t>
<t hangText="0x0004">Invalid arguments</t>
<t hangText="0x0005">Item not stored</t>
<t hangText="0x0006">Incr/Decr on non-numeric value.</t>
<t hangText="0x0081">Unknown command</t>
<t hangText="0x0082">Out of memory</t>
</list>
</t>
</section>
<section anchor="value-opcodes" title="Command Opcodes">
<t>
Possible values of the one-byte field:
<list hangIndent="8" style="hanging">
<t hangText="0x00">Get</t>
<t hangText="0x01">Set</t>
<t hangText="0x02">Add</t>
<t hangText="0x03">Replace</t>
<t hangText="0x04">Delete</t>
<t hangText="0x05">Increment</t>
<t hangText="0x06">Decrement</t>
<t hangText="0x07">Quit</t>
<t hangText="0x08">Flush</t>
<t hangText="0x09">GetQ</t>
<t hangText="0x0A">No-op</t>
<t hangText="0x0B">Version</t>
<t hangText="0x0C">GetK</t>
<t hangText="0x0D">GetKQ</t>
<t hangText="0x0E">Append</t>
<t hangText="0x0F">Prepend</t>
<t hangText="0x10">Stat</t>
<t hangText="0x11">SetQ</t>
<t hangText="0x12">AddQ</t>
<t hangText="0x13">ReplaceQ</t>
<t hangText="0x14">DeleteQ</t>
<t hangText="0x15">IncrementQ</t>
<t hangText="0x16">DecrementQ</t>
<t hangText="0x17">QuitQ</t>
<t hangText="0x18">FlushQ</t>
<t hangText="0x19">AppendQ</t>
<t hangText="0x1A">PrependQ</t>
</list>
</t>
<t>
As a convention all of the commands ending with "Q" for
Quiet. A quiet version of a command will omit responses
that are considered uninteresting. Whether a given response
is interesting is dependent upon the command. See the
descriptions of the
<xref target="command-get">set commands</xref>
and <xref target="command-set">set commands</xref> for
examples of commands that include quiet variants.
</t>
</section>
<section anchor="value-types" title="Data Types">
<t>
Possible values of the one-byte field:
<list hangIndent="8" style="hanging">
<t hangText="0x00">Raw bytes</t>
</list>
</t>
</section>
</section>
<section title="Commands">
<section anchor="command-introduction" title="Introduction">
<t>
All communication is initiated by a request from the client,
and the server will respond to each request with zero or
multiple packets for each request. If the status code of a response
packet is non-nil, the body of the packet will contain a textual error
message. If the status code is nil, the command opcode will define the
layout of the body of the message.
</t>
<section anchor="command-introduction-example" title="Example">
<t>
The following figure illustrates the packet layout for
a packet with an error message.
</t>
<figure>
<preamble>Packet layout:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x81 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x01 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x09 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
24| 0x4e ('N') | 0x6f ('o') | 0x74 ('t') | 0x20 (' ') |
+---------------+---------------+---------------+---------------+
28| 0x66 ('f') | 0x6f ('o') | 0x75 ('u') | 0x6e ('n') |
+---------------+---------------+---------------+---------------+
32| 0x64 ('d') |
+---------------+
Total 33 bytes (24 byte header, and 9 bytes value)
Field (offset) (value)
Magic (0) : 0x81
Opcode (1) : 0x00
Key length (2,3) : 0x0000
Extra length (4) : 0x00
Data type (5) : 0x00
Status (6,7) : 0x0001
Total body (8-11) : 0x00000009
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000000
Extras : None
Key : None
Value (24-32): The textual string "Not found"
</artwork>
</figure>
</section>
</section>
<section anchor="command-get" title="Get, Get Quietly, Get Key, Get Key Quietly">
<t>
Request:
</t>
<t>
<list style="empty">
<t>MUST NOT have extras.</t>
<t>MUST have key.</t>
<t>MUST NOT have value.</t>
</list>
</t>
<t>
Response (if found):
</t>
<t>
<list style="empty">
<t>MUST have extras.</t>
<t>MAY have key.</t>
<t>MAY have value.</t>
</list>
</t>
<t>
<list style="symbols">
<t>4 byte flags</t>
</list>
</t>
<t>
<figure>
<preamble>Extra data for the get commands:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| Flags |
+---------------+---------------+---------------+---------------+
Total 4 bytes
</artwork>
</figure>
</t>
<t>
The get command gets a single key. The getq command is both mum
on cache miss and quiet, holding its response until a non-quiet
command is issued. Getk and getkq differs from get and getq by
adding the key into the response packet.
</t>
<t>
You're not guaranteed a response to a getq/getkq cache hit until
you send a non-getq/getkq command later, which uncorks the
server and bundles up IOs to send to the client in one go.
</t>
<t>
Clients should implement multi-get (still important for
reducing network roundtrips!) as n pipelined requests, the
first n-1 being getq/getkq, the last being a regular
get/getk. That way you're guaranteed to get a response, and
you know when the server's done. You can also do the naive
thing and send n pipelined get/getks, but then you could potentially
get back a lot of "NOT_FOUND" error code packets.
Alternatively, you can send 'n' getq/getkqs, followed by a
'noop' command.
</t>
<section anchor="command-get-example" title="Example">
<t>
To request the data associated with the key "Hello" the
following fields must be specified in the packet.
</t>
<figure>
<preamble>get request:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x80 | 0x00 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
24| 0x48 ('H') | 0x65 ('e') | 0x6c ('l') | 0x6c ('l') |
+---------------+---------------+---------------+---------------+
28| 0x6f ('o') |
+---------------+
Total 29 bytes (24 byte header, and 5 bytes key)
Field (offset) (value)
Magic (0) : 0x80
Opcode (1) : 0x00
Key length (2,3) : 0x0005
Extra length (4) : 0x00
Data type (5) : 0x00
Reserved (6,7) : 0x0000
Total body (8-11) : 0x00000005
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000000
Extras : None
Key (24-29): The textual string: "Hello"
Value : None
</artwork>
</figure>
<t>If the item exist on the server the following packet is returned,
otherwise a packet with status code != 0 will be returned (see
<xref target="command-introduction">Introduction</xref>)
</t>
<figure>
<preamble>get/getq response:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x81 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
4| 0x04 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x09 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x01 |
+---------------+---------------+---------------+---------------+
24| 0xde | 0xad | 0xbe | 0xef |
+---------------+---------------+---------------+---------------+
28| 0x57 ('W') | 0x6f ('o') | 0x72 ('r') | 0x6c ('l') |
+---------------+---------------+---------------+---------------+
32| 0x64 ('d') |
+---------------+
Total 33 bytes (24 byte header, 4 byte extras and 5 byte value)
Field (offset) (value)
Magic (0) : 0x81
Opcode (1) : 0x00
Key length (2,3) : 0x0000
Extra length (4) : 0x04
Data type (5) : 0x00
Status (6,7) : 0x0000
Total body (8-11) : 0x00000009
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000001
Extras :
Flags (24-27): 0xdeadbeef
Key : None
Value (28-32): The textual string "World"
</artwork>
</figure>
<figure>
<preamble>getk/getkq response:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x81 | 0x00 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
4| 0x04 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x09 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x01 |
+---------------+---------------+---------------+---------------+
24| 0xde | 0xad | 0xbe | 0xef |
+---------------+---------------+---------------+---------------+
28| 0x48 ('H') | 0x65 ('e') | 0x6c ('l') | 0x6c ('l') |
+---------------+---------------+---------------+---------------+
32| 0x6f ('o') | 0x57 ('W') | 0x6f ('o') | 0x72 ('r') |
+---------------+---------------+---------------+---------------+
36| 0x6c ('l') | 0x64 ('d') |
+---------------+---------------+
Total 38 bytes (24 byte header, 4 byte extras, 5 byte key
and 5 byte value)
Field (offset) (value)
Magic (0) : 0x81
Opcode (1) : 0x00
Key length (2,3) : 0x0005
Extra length (4) : 0x04
Data type (5) : 0x00
Status (6,7) : 0x0000
Total body (8-11) : 0x0000000E
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000001
Extras :
Flags (24-27): 0xdeadbeef
Key (28-32): The textual string: "Hello"
Value (33-37): The textual string: "World"
</artwork>
</figure>
</section>
</section>
<section anchor="command-set" title="Set, Add, Replace">
<t>
<list style="empty">
<t>MUST have extras.</t>
<t>MUST have key.</t>
<t>MUST have value.</t>
</list>
</t>
<t>
<list style="symbols">
<t>4 byte flags</t>
<t>4 byte expiration time</t>
</list>
</t>
<figure>
<preamble>Extra data for set/add/replace:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| Flags |
+---------------+---------------+---------------+---------------+
4| Expiration |
+---------------+---------------+---------------+---------------+
Total 8 bytes
</artwork>
</figure>
<t>
If the Data Version Check (CAS) is nonzero, the requested
operation MUST only succeed if the item exists and has a CAS value
identical to the provided value.
</t>
<t>
Add MUST fail if the item already exist.
</t>
<t>
Replace MUST fail if the item doesn't exist.
</t>
<t>
Set should store the data unconditionally if the item exists
or not.
</t>
<t>
Quiet mutations only return responses on failure. Success
is considered the general case and is suppressed when in
quiet mode, but errors should not be allowed to go
unnoticed.
</t>
<section anchor="command-set-example" title="Example">
<t>The following figure shows an add-command for
<list style="empty">
<t>Key: "Hello"</t>
<t>Value: "World"</t>
<t>Flags: 0xdeadbeef</t>
<t>Expiry: in two hours</t>
</list>
</t>
<figure>
<preamble>Add request:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x80 | 0x02 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
4| 0x08 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x12 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
24| 0xde | 0xad | 0xbe | 0xef |
+---------------+---------------+---------------+---------------+
28| 0x00 | 0x00 | 0x1c | 0x20 |
+---------------+---------------+---------------+---------------+
32| 0x48 ('H') | 0x65 ('e') | 0x6c ('l') | 0x6c ('l') |
+---------------+---------------+---------------+---------------+
36| 0x6f ('o') | 0x57 ('W') | 0x6f ('o') | 0x72 ('r') |
+---------------+---------------+---------------+---------------+
40| 0x6c ('l') | 0x64 ('d') |
+---------------+---------------+
Total 42 bytes (24 byte header, 8 byte extras, 5 byte key and
5 byte value)
Field (offset) (value)
Magic (0) : 0x80
Opcode (1) : 0x02
Key length (2,3) : 0x0005
Extra length (4) : 0x08
Data type (5) : 0x00
Reserved (6,7) : 0x0000
Total body (8-11) : 0x00000012
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000000
Extras :
Flags (24-27): 0xdeadbeef
Expiry (28-31): 0x00001c20
Key (32-36): The textual string "Hello"
Value (37-41): The textual string "World"
</artwork>
</figure>
<t>
The response-packet contains no extra data, and the result of the
operation is signaled through the status code. If the command
succeeds, the CAS value for the item is returned in the CAS-field
of the packet.
</t>
<figure>
<preamble>Successful add response:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x81 | 0x02 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x01 |
+---------------+---------------+---------------+---------------+
Total 24 bytes
Field (offset) (value)
Magic (0) : 0x81
Opcode (1) : 0x02
Key length (2,3) : 0x0000
Extra length (4) : 0x00
Data type (5) : 0x00
Status (6,7) : 0x0000
Total body (8-11) : 0x00000000
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000001
Extras : None
Key : None
Value : None
</artwork>
</figure>
</section>
</section>
<section anchor="command-delete" title="Delete">
<t>
<list style="empty">
<t>MUST NOT have extras.</t>
<t>MUST have key.</t>
<t>MUST NOT have value.</t>
</list>
</t>
<t>
Delete the item with the specific key.
</t>
<section anchor="command-delete-example" title="Example">
<t>The following figure shows a delete message for the
item "Hello".</t>
<figure>
<preamble>Delete request:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x80 | 0x04 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
24| 0x48 ('H') | 0x65 ('e') | 0x6c ('l') | 0x6c ('l') |
+---------------+---------------+---------------+---------------+
28| 0x6f ('o') |
+---------------+
Total 29 bytes (24 byte header, 5 byte value)
Field (offset) (value)
Magic (0) : 0x80
Opcode (1) : 0x04
Key length (2,3) : 0x0005
Extra length (4) : 0x00
Data type (5) : 0x00
Reserved (6,7) : 0x0000
Total body (8-11) : 0x00000005
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000000
Extras : None
Key : The textual string "Hello"
Value : None
</artwork>
</figure>
<t>
The response-packet contains no extra data, and the result of the
operation is signaled through the status code.
</t>
</section>
</section>
<section anchor="command-incr" title="Increment, Decrement">
<t>
<list style="empty">
<t>MUST have extras.</t>
<t>MUST have key.</t>
<t>MUST NOT have value.</t>
</list>
</t>
<t>
<list style="symbols">
<t>8 byte value to add / subtract</t>
<t>8 byte initial value (unsigned)</t>
<t>4 byte expiration time</t>
</list>
</t>
<figure>
<preamble>Extra data for incr/decr:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| Amount to add |
| |
+---------------+---------------+---------------+---------------+
8| Initial value |
| |
+---------------+---------------+---------------+---------------+
16| Expiration |
+---------------+---------------+---------------+---------------+
Total 20 bytes
</artwork>
</figure>
<t>
These commands will either add or remove the specified
amount to the requested counter.
</t>
<t>
If the counter does not exist, one of two things may happen:
</t>
<t>
<list style="numbers">
<t>If the expiration value is all one-bits (0xffffffff), the
operation will fail with NOT_FOUND.</t>
<t>For all other expiration values, the operation will succeed
by seeding the value for this key with the provided initial
value to expire with the provided expiration time. The flags
will be set to zero.</t>
</list>
</t>
<figure>
<preamble>incr/decr response body:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 64-bit unsigned response. |
| |
+---------------+---------------+---------------+---------------+
Total 8 bytes
</artwork>
</figure>
<section anchor="command-incr-example" title="Example">
<t>The following figure shows an incr-command for
<list style="empty">
<t>Key: "counter"</t>
<t>Delta: 0x01</t>
<t>Initial: 0x00</t>
<t>Expiry: in two hours</t>
</list>
</t>
<figure>
<preamble>Increment request:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x80 | 0x05 | 0x00 | 0x07 |
+---------------+---------------+---------------+---------------+
4| 0x14 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x1b |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
24| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
28| 0x00 | 0x00 | 0x00 | 0x01 |
+---------------+---------------+---------------+---------------+
32| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
36| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
40| 0x00 | 0x00 | 0x1c | 0x20 |
+---------------+---------------+---------------+---------------+
44| 0x63 ('c') | 0x6f ('o') | 0x75 ('u') | 0x6e ('n') |
+---------------+---------------+---------------+---------------+
48| 0x74 ('t') | 0x65 ('e') | 0x72 ('r') |
+---------------+---------------+---------------+
Total 51 bytes (24 byte header, 20 byte extras, 7 byte key)
Field (offset) (value)
Magic (0) : 0x80
Opcode (1) : 0x05
Key length (2,3) : 0x0007
Extra length (4) : 0x14
Data type (5) : 0x00
Reserved (6,7) : 0x0000
Total body (8-11) : 0x0000001b
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000000
Extras :
delta (24-31): 0x0000000000000001
initial (32-39): 0x0000000000000000
expiration (40-43): 0x00001c20
Key : Textual string "counter"
Value : None
</artwork>
</figure>
<t>
If the key doesn't exist, the server will respond with the
initial value. If not the incremented value will be returned.
Let's assume that the key didn't exist, so the initial value
is returned.
</t>
<figure>
<preamble>Increment response:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x81 | 0x05 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x08 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x05 |
+---------------+---------------+---------------+---------------+
24| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
28| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
Total 32 bytes (24 byte header, 8 byte value)
Field (offset) (value)
Magic (0) : 0x81
Opcode (1) : 0x05
Key length (2,3) : 0x0000
Extra length (4) : 0x00
Data type (5) : 0x00
Status (6,7) : 0x0000
Total body (8-11) : 0x00000008
Opaque (12-15): 0x00000000
CAS (16-23): 0x0000000000000005
Extras : None
Key : None
Value : 0x0000000000000000
</artwork>
</figure>
</section>
</section>
<section anchor="command-quit" title="quit">
<t>
<list style="empty">
<t>MUST NOT have extras.</t>
<t>MUST NOT have key.</t>
<t>MUST NOT have value.</t>
</list>
</t>
<t>
Close the connection to the server.
</t>
<section anchor="command-quit-example" title="Example">
<figure>
<preamble>Quit request:</preamble>
<artwork>
Byte/ 0 | 1 | 2 | 3 |
/ | | | |
|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|0 1 2 3 4 5 6 7|
+---------------+---------------+---------------+---------------+
0| 0x80 | 0x07 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
4| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
8| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
12| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
16| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
20| 0x00 | 0x00 | 0x00 | 0x00 |
+---------------+---------------+---------------+---------------+
Total 24 bytes
Field (offset) (value)
Magic (0) : 0x80
Opcode (1) : 0x07
Key length (2,3) : 0x0000
Extra length (4) : 0x00
Data type (5) : 0x00
Reserved (6,7) : 0x0000
Total body (8-11) : 0x00000000
Opaque (12-15): 0x00000000