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Network Working Group Aaron Stone, Ed. Internet-Draft Six Apart, Ltd. Intended status: Informational December 14, 2007 Expires: June 16, 2008 Memcache Binary Protocol: Extensions for UDP draft-stone-memcache-udp-01 Abstract This memo explains extensions to the memcache binary protocol for use in a UDP environment. 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. Status of This Memo This Internet-Draft is submitted in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF). Note that other groups may also distribute working documents as Internet-Drafts. The list of current Internet- Drafts is at http://datatracker.ietf.org/drafts/current/. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." This Internet-Draft will expire on June 16, 2008. Copyright Notice Copyright (c) 2007 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of publication of this document. Please review these documents carefully, as they describe your rights and restrictions with respect to this document. Code Components extracted from this document must Aaron Stone Expires June 16, 2008 [Page 1]  Internet-Draft Memcache Over UDP December 2007 include Simplified BSD License text as described in Section 4.e of the Trust Legal Provisions and are provided without warranty as described in the Simplified BSD License. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 1.1. Conventions Used In This Document . . . . . . . . . . . . 2 2. Defined Values . . . . . . . . . . . . . . . . . . . . . . . 3 2.1. Magic Byte . . . . . . . . . . . . . . . . . . . . . . . 3 2.2. Response Status . . . . . . . . . . . . . . . . . . . . . 3 2.3. Command Opcodes . . . . . . . . . . . . . . . . . . . . . 3 2.4. Data Types . . . . . . . . . . . . . . . . . . . . . . . 3 3. Commands . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Get Response . . . . . . . . . . . . . . . . . . . . . . 3 3.2. Get Range Request . . . . . . . . . . . . . . . . . . . . 4 3.3. Get Range Response . . . . . . . . . . . . . . . . . . . 4 4. Security Considerations . . . . . . . . . . . . . . . . . . . 5 5. Normative References . . . . . . . . . . . . . . . . . . . . 5 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 1. Introduction 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. Sites may find that, due to their network architecture or application usage patterns, the stateless [UDP] protocol better suits their needs. This document provides extensions and descriptions of use of the memcache protocol [MEMCACHE] in a UDP environment. It is a goal of this document to provide sufficient information in each UDP packet as to avoid any requirement for statefulness on the part of the server nor significant caching of outstanding packets on the part of the client. 1.1. Conventions Used In This Document 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 [KEYWORDS]. Aaron Stone Expires June 16, 2008 [Page 2]  Internet-Draft Memcache Over UDP December 2007 2. Defined Values 2.1. Magic Byte The magic bytes remains the same as in [MEMCACHE]. 2.2. Response Status Additional status values: 0x0004 Value is larger than a single response packet 2.3. Command Opcodes Additional opcode values: 0x0C Get Range 0x0D Set Range 2.4. Data Types There are no new data types in this extension. 3. Commands 3.1. Get Response This section extends the behavior of the Get and GetQ commands as described in [MEMCACHE]. When a Get or GetQ request is made via UDP, and the value of the key for which the request was made is larger than can be placed into a single UDP packet (noting that the protocol header must also be counted), a Get Range response packet MUST be sent instead of the Get response packet. In this instance: 1. The Status field of the response header MUST be 0x0004. 2. The Offset field of the GetR response extras MUST be 0. 3. The Length field of the GetR response extras, and the data contained in the Value field of the packet, SHOULD be the maximum allowed length of a UDP packet, less the space required by the header and extras; however it MAY be any amount below this maximum. 4. The Total value length field of the response extras MUST be the actual length of the complete value. The client, upon receipt of a Get Range response bearing Status 0x004 and a Message ID corresponding to its Get request, shall then know Aaron Stone Expires June 16, 2008 [Page 3]  Internet-Draft Memcache Over UDP December 2007 that it has received only the first portion of the value. The client MAY choose to request the remaining portion of the value by sending one or more Get Range requests. 3.2. Get Range Request The Get Range request is primarily intended for use over a UDP transport to request byte ranges of the value for a key. In the event that the Data version check fails to match that of the key, an error MUST be returned. Extra data for get range request: 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| Data version check | | | +---------------+---------------+---------------+---------------+ 12| Offset | +---------------+---------------+---------------+---------------+ 16| Length | +---------------+---------------+---------------+---------------+ Total 20 bytes 3.3. Get Range Response The Get Range request is primarily intended for use over a UDP transport to indicate the location of the bytes of the value for a key contained in a given packet. A client receives enough information in each Get Range extras to construct an appropriately sized buffer in its own memory and blindly insert the contents of the packet at the given byte offset. Aaron Stone Expires June 16, 2008 [Page 4]  Internet-Draft Memcache Over UDP December 2007 Extra data for get range response: 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| Data version check | | | +---------------+---------------+---------------+---------------+ 12| Offset | +---------------+---------------+---------------+---------------+ 16| Length | +---------------+---------------+---------------+---------------+ 20| Total value length | +---------------+---------------+---------------+---------------+ Total 24 bytes 4. Security Considerations This document does not introduce any new security considerations beyond those discussed in [MEMCACHE]. 5. Normative References [KEYWORDS] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [MEMCACHE] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [UDP] Postel, J., "User Datagram Protocol", STD 6, RFC 768, August 1980. Author's Address Aaron Stone (editor) Six Apart, Ltd. 548 4th Street San Francisco, CA 94107 USA Email: aaron@serendipity.palo-alto.ca.us Aaron Stone Expires June 16, 2008 [Page 5]