1<?xml version="1.0" encoding="US-ASCII"?> 2<!DOCTYPE rfc SYSTEM "xml2rfc/rfc2629.dtd"> 3<?xml-stylesheet type='text/xsl' href='xml2rfc/rfc2629.xslt'?> 4<?rfc toc="yes"?> 5<?rfc strict="yes"?> 6<?rfc symrefs="yes"?> 7<?rfc sortrefs="yes" ?> 8<?rfc compact="yes" ?> 9<?rfc subcompact="yes" ?> 10<rfc category="info" docName="draft-stone-memcache-udp-01" ipr="none"> 11 12 <front> 13 14 <title abbrev="Memcache Over UDP"> Memcache Binary Protocol: Extensions for UDP </title> 15 16 <author fullname="Aaron Stone" surname="Aaron Stone" role="editor"> 17 <organization>Six Apart, Ltd.</organization> 18 <address> 19 <postal> 20 <street>548 4th Street</street> 21 <city>San Francisco</city> 22 <region>CA</region> 23 <code>94107</code> 24 <country>USA</country> 25 </postal> 26 <email>[email protected]</email> 27 </address> 28 </author> 29 30 <date day="14" month="December" year="2007" /> 31 32 <area>Applications</area> 33 34 <keyword>memcache memcached cache udp</keyword> 35 36 <abstract> 37 <t> 38 This memo explains extensions to the memcache binary protocol for use in a UDP environment. 39 </t> 40 41 <t> 42 Memcache is a high performance key-value cache. It is intentionally a 43 dumb cache, optimized for speed only. Applications using memcache do 44 not rely on it for data -- a persistent database with guaranteed reliability 45 is strongly recommended -- but applications can run much faster when 46 cached data is available in memcache. 47 </t> 48 </abstract> 49 </front> 50 51 <middle> 52 <section anchor="introduction" title="Introduction"> 53 <t> 54 Memcache is a high performance key-value cache. It is intentionally a 55 dumb cache, optimized for speed only. Applications using memcache do 56 not rely on it for data -- a persistent database with guaranteed reliability 57 is strongly recommended -- but applications can run much faster when 58 cached data is available in memcache. 59 </t> 60 <t> 61 Sites may find that, due to their network architecture or application usage patterns, 62 the stateless <xref target="UDP"/> protocol better suits their needs. This document 63 provides extensions and descriptions of use of the <xref target="MEMCACHE">memcache protocol</xref> 64 in a UDP environment. 65 </t> 66 <t> 67 It is a goal of this document to provide sufficient information in each UDP packet 68 as to avoid any requirement for statefulness on the part of the server nor significant 69 caching of outstanding packets on the part of the client. 70 </t> 71 <section anchor="conventions" title="Conventions Used In This Document"> 72 <t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 73 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 74 document are to be interpreted as described in <xref target="KEYWORDS"/>. 75 </t> 76 </section> 77 </section> 78 79 <section anchor="values" title="Defined Values"> 80 <section anchor="value-magic" title="Magic Byte"> 81 <t> 82 The magic bytes remains the same as in <xref target="MEMCACHE"/>. 83 </t> 84 </section> 85 86 <section anchor="value-status" title="Response Status"> 87 <t> 88 Additional status values: 89 <list hangIndent="8" style="hanging"> 90 <t hangText="0x0004">Value is larger than a single response packet</t> 91 </list> 92 </t> 93 </section> 94 95 <section anchor="value-opcodes" title="Command Opcodes"> 96 <t> 97 Additional opcode values: 98 <list hangIndent="8" style="hanging"> 99 <t hangText="0x0C">Get Range</t> 100 <t hangText="0x0D">Set Range</t> 101 </list> 102 </t> 103 </section> 104 105 <section anchor="value-types" title="Data Types"> 106 <t> 107 There are no new data types in this extension. 108 </t> 109 </section> 110 </section> 111 112 <section anchor="commands" title="Commands"> 113 114 <section anchor="command-get" title="Get Response"> 115 <t> 116 This section extends the behavior of the Get and GetQ commands as described in 117 <xref target="MEMCACHE" x:sec="command-get"/>. 118 </t> 119 120 <t> 121 When a Get or GetQ request is made via UDP, and the value of the key for which 122 the request was made is larger than can be placed into a single UDP packet (noting 123 that the protocol header must also be counted), a Get Range response packet 124 MUST be sent instead of the Get response packet. In this instance: 125 <list style="numbers"> 126 <t>The Status field of the response header MUST be 0x0004.</t> 127 <t>The Offset field of the GetR response extras MUST be 0.</t> 128 <t>The Length field of the GetR response extras, and the data contained in 129 the Value field of the packet, SHOULD be the maximum 130 allowed length of a UDP packet, less the space required by the header 131 and extras; however it MAY be any amount below this maximum.</t> 132 <t>The Total value length field of the response extras MUST be the 133 actual length of the complete value.</t> 134 </list> 135 </t> 136 137 <t> 138 The client, upon receipt of a Get Range response bearing Status 0x004 139 and a Message ID corresponding to its Get request, shall then know that 140 it has received only the first portion of the value. The client MAY choose 141 to request the remaining portion of the value by sending one or more Get Range requests. 142 </t> 143 </section> 144 145 <section anchor="command-getr-request" title="Get Range Request"> 146 <t> 147 The Get Range request is primarily intended for use over a UDP transport 148 to request byte ranges of the value for a key. In the event that the Data version 149 check fails to match that of the key, an error MUST be returned. 150 </t> 151 <t> 152 <figure> 153 <preamble>Extra data for get range request:</preamble> 154 <artwork> 155 Byte/ 0 | 1 | 2 | 3 | 156 / | | | | 157 |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| 158 +---------------+---------------+---------------+---------------+ 159 0| Flags | 160 +---------------+---------------+---------------+---------------+ 161 4| Data version check | 162 | | 163 +---------------+---------------+---------------+---------------+ 164 12| Offset | 165 +---------------+---------------+---------------+---------------+ 166 16| Length | 167 +---------------+---------------+---------------+---------------+ 168 Total 20 bytes 169 </artwork></figure> 170 </t> 171 </section> 172 173 <section anchor="command-getr-response" title="Get Range Response"> 174 <t> 175 The Get Range request is primarily intended for use over a UDP transport 176 to indicate the location of the bytes of the value for a key contained in 177 a given packet. A client receives enough information in each Get Range 178 extras to construct an appropriately sized buffer in its own memory and 179 blindly insert the contents of the packet at the given byte offset. 180 </t> 181 <t> 182 <figure> 183 <preamble>Extra data for get range response:</preamble> 184 <artwork> 185 Byte/ 0 | 1 | 2 | 3 | 186 / | | | | 187 |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| 188 +---------------+---------------+---------------+---------------+ 189 0| Flags | 190 +---------------+---------------+---------------+---------------+ 191 4| Data version check | 192 | | 193 +---------------+---------------+---------------+---------------+ 194 12| Offset | 195 +---------------+---------------+---------------+---------------+ 196 16| Length | 197 +---------------+---------------+---------------+---------------+ 198 20| Total value length | 199 +---------------+---------------+---------------+---------------+ 200 Total 24 bytes 201 </artwork></figure> 202 </t> 203 </section> 204 205 </section> 206 207 <section anchor="security" title="Security Considerations"> 208 <t> 209 This document does not introduce any new security considerations 210 beyond those discussed in <xref target="MEMCACHE" x:sec="security"/>. 211 </t> 212 </section> 213 214 </middle> 215 216 <back> 217 <references title="Normative References"> 218 <dwdrfc-ref anchor='UDP' src='http://xml.resource.org/public/rfc/bibxml/reference.RFC.0768.xml'/> 219 <dwdrfc-ref anchor='KEYWORDS' src='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'/> 220 <!-- FIXME: Get a draft reference for the base document. --> 221 <dwdrfc-ref anchor='MEMCACHE' src='http://xml.resource.org/public/rfc/bibxml/reference.RFC.2119.xml'/> 222 </references> 223 </back> 224 225</rfc> 226 227