INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Experimental OpenLDAP Foundation
Expires: 20 May 2002 20 November 2001
LDAPv3 Transactions
<draft-zeilenga-ldap-txn-03.txt>
Status of Memo
This document is an Internet-Draft and is in full conformance with all
provisions of Section 10 of RFC2026.
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as an Experimental document.
Distribution of this memo is unlimited. Technical discussion of this
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mailing list <ietf-ldapext@netscape.com>. Please send editorial
comments directly to the author <Kurt@OpenLDAP.org>.
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Copyright 2001, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
Abstract
LDAP update operations have atomic properties upon individual entries.
However, it is often desirable to update two or more entries as one
atomic action, a transaction. Transactions are necessary to support a
number of applications including resource provisioning and information
replication. This document defines an LDAP extension to support
transactions.
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Conventions
The key words "SHALL", "SHALL NOT", "MUST", "MUST NOT", "SHOULD",
"SHOULD NOT", "MAY" and "MAY NOT" used in this document are to be
interpreted as described in BCP 14 [RFC2119].
Protocol elements are described using ASN.1 [X.680]. The term
"BER-encoded" means the element is to be encoded using the Basic
Encoding Rules [X.690] under the restrictions detailed in Section 5.1
of [RFC2251].
1. Overview
This document extends LDAP [RFC2251] to allow clients to group a
number of related update operations and have them preformed as one
atomic action, a transaction. The mechanism uses the grouping
mechanism provided by [GROUP] to relate operations of the transaction.
The createGrouping operation is used to obtain a group cookie which is
used to identify operations which are apart of the transaction. The
group cookie can be viewed as a transaction identifier. The
endGrouping operation is used to settle (commit or abort) the
transaction.
This document is a ''work in progress.'' This specification will
likely be significantly enhanced before it progressed. In particular,
clarification of transaction semantics and better error handling will
likely be added. A ''prepare'' capability may also be added.
2. Specification of a Transaction
Servers implementing this specification SHOULD publish the
transactionGroupingType as a value of the supportedGroupingTypes
attribute contained within the Root DSE.
transactionGroupingType ::= 1.1.1 ;; fictious
A client wishing to preform a transaction MUST issue a
createGroupingRequest with a createGroupType of
transactionGroupingType and no createGroupValue. A server which is
willing and able to support transactions SHALL return a
createGroupingResponse with a success result code, a
createGroupCookie, and no createGroupValue. Otherwise the server
SHALL return a non-success result code, no createGroupCookie, and no
createGroupValue.
The client MAY then attach a GroupingControl to subsequent update
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operations (modify or moddn) to indicate that they are to be processed
as part of the transaction per [GROUP], Section 3.5. If the server is
willing and able to attempt to process operation as part of the
transaction, the server SHALL return success. If the server is
unwilling or unable to attempt to process the operation as part of the
transaction, the server SHALL return a non-successful result code.
If the server becomes unwilling or unable to continue the
specification of a transaction, the server SHOULD issue a
endGroupNotice. Any future use of cookie by the client SHALL result
in a response containing a non-success result code.
Upon receipt of a endGroupingNotice, the client SHOULD discontinue all
use of the grouping cookie. The client SHOULD NOT issue an
endGroupingRequest for the grouping cookie as the transaction is null
and void.
A client requests settling of transaction by issuing an
endGroupingRequest where the groupingCookie is the group cookie
identify the transaction. The absence of any endGroupingValue
indicates a commit request. The presence of an empty endGroupValue
indicates an abort request. The endGroupValue MUST be empty if
provided.
The endGroupingResponse of success indicates the settle action was
successfully. No endGroupingValue is provided with the
endGroupingResponse.
3. Transaction Semantics
Upon request to commit the transaction, the server perform the
operations as one atomic action. Operations belonging to the
transaction are applied in the request order. If any operation fails,
the contents of target objects is left unchanged and a non-success
result code is returned indicating the nature of the failure.
There is no requirement that a server serialize transactions. That
is, a server MAY process multiple transactions commit requests (from
one or more clients) acting upon different sets of entries
concurrently. A server MUST ensure concurrent processing of
transactions provides the atomic properties described above. A server
MUST avoid deadlock.
4. Distributed Directory Considerations
The LDAP/X.500 models provide for distributed directory operations
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including server-side chaining and client-side chasing of operations.
This document does not disallow servers from chaining operations which
are part of a transaction. However, if a server does allow such
chaining, it MUST ensure that transaction semantics detailed above are
provided.
This mechanism defined by this document does not support client-side
chasing. Grouping cookies used to identify the transaction are
specific to a particular client/server session.
The LDAP/X.500 models provide for a single-master/multiple-slave
replication architecture. This document states no requirement that
changes made to the directory based upon processing a transaction be
replicated as one atomic action. That is, the client SHOULD NOT
assume tight data consistency nor fast data convergence at slave
servers unless they have a priori knowledge that such is provided.
Though this mechanism could be used to support replication, such use
is not described in this document.
The LDAP/X.500 models do not currently support a multi-master
replication architecture and, hence, not considered by this
specification.
5. Security Considerations
Transactions mechanisms and related grouping operations may be the
target of denial of service attacks. Implementors should provide
safeguards to ensure these mechanisms are not abused.
6. Acknowledgments
The author gratefully acknowledges the contributions made by members
of the Internet Engineering Task Force.
7. Author's Address
The author may be contacted as follows:
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
8. Normative References
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[RFC2119] S. Bradner, "Key Words for use in RFCs to Indicate
Requirement Levels", BCP 14 (also RFC 2119), March 1997.
[RFC2251] M. Wahl, S. Kille, T. Howes, "Lightweight Directory Access
Protocol (v3)", RFC 2251, December 1997.
[GROUP] K. Zeilenga, "LDAPv3: Grouping of Related Operations",
draft-zeilenga-ldap-grouping-xx.txt, a work in progress.
[X.680] ITU-T, "Abstract Syntax Notation One (ASN.1) - Specification
of Basic Notation", X.680, 1994.
[X.690] ITU-T, "Specification of ASN.1 encoding rules: Basic,
Canonical, and Distinguished Encoding Rules", X.690, 1994.
9. Informative References
[X.500] ITU-T, "The Directory: Overview of Concepts, Models, and
Services", X.500, 1993.
[X.501] ITU-T, "The Directory: Models", X.501, 1993.
Copyright 2001, The Internet Society. All Rights Reserved.
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