INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Experimental OpenLDAP Foundation
Expires in six months 16 June 2002
LDAPv3 Transactions
<draft-zeilenga-ldap-txn-04.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 2002, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
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Abstract
Lightweight Directory Access Protocol (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
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transactions.
Conventions
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 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 [LDAPTS] 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 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.
Editor's Note:
The object identifiers appearing in this draft are fictious. The
top-level OID 1.1 is be replaced before this draft is published as
an RFC.
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
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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
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
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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
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. IANA Considerations
No IANA assignments are required.
The OID <TBD> was assigned [ASSIGN] by OpenLDAP Foundation under its
IANA assigned private enterprise allocation [PRIVATE] for use in this
specification.
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7. Acknowledgments
The author gratefully acknowledges the contributions made by members
of the Internet Engineering Task Force.
8. Author's Address
The author may be contacted as follows:
Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
9. Normative References
[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.
[LDAPIANA] K. Zeilenga, "IANA Considerations for LDAP",
draft-ietf-ldapbis-iana-xx.txt, a work in progress.
[LDAPTS] J. Hodges, R. Morgan, "Lightweight Directory Access
Protocol (v3): Technical Specification",
draft-ietf-ldapbis-ldapv3-ts-00.txt.
[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.
10. 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.
[ASSIGN] OpenLDAP Foundation, "OpenLDAP OID Delegations",
http://www.openldap.org/foundation/oid-delegate.txt.
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[PRIVATE] IANA, "Private Enterprise Numbers",
http://www.iana.org/assignments/enterprise-numbers.
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