INTERNET-DRAFT Kurt D. Zeilenga
Intended Category: Informational OpenLDAP Foundation
Expires: 9 February 2001 9 August 2000
LDAPv3 Transactions
<draft-zeilenga-ldap-txn-00.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 a Standard Track document.
Distribution of this memo is unlimited. Technical discussion of this
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Copyright 2000, The Internet Society. All Rights Reserved.
Please see the Copyright section near the end of this document for
more information.
1. Abstract
LDAP [RFC2251] 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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2. Overview
This document provides a mechanism to allow clients to group a number
of related update operations and have them preformed as 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. The current intent is to eventually publish this
work as an Informational RFC.
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 [RFC2119].
3. Specification of a Transaction
Servers implementing this specification SHOULD publishing
transactionGroupingType as a value of the supportedGroupingTypes
attribute contained within the Root DSE.
transactionGroupingType ::= 1.2.3 ;; 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, 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.
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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 are
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.
4. Transaction Semantics
Upon request to commit the transaction, the server perform the
operations as one atomic action. Operations belonging to the
transaction are processed 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.
5. Distributed Directory Considerations
The LDAP/X.500 model provides for distributed directory operations
including support for server-side chaining and client-side chasing of
operations.
Though 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
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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 model provides 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.
LDAP/X.500 model do not currently support multi-master replication
architectures and, hence, is not supported by this mechanism.
6. 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.
7. References
[RFC2119] S. Bradner, "Key Words for use in RFCs to Indicate
Requirement Levels", Harvard University, 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.
8. Acknowledgments
The author gratefully acknowledges the contributions made by members
of the Internet Engineering Task Force.
9. Additional Information
Discussions regarding these suggestions may directed to the author:
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Kurt D. Zeilenga
OpenLDAP Foundation
<Kurt@OpenLDAP.org>
or the LDAPext Working Group mailing list:
<ietf-ldapext@netscape.com>
Copyright 2000, The Internet Society. All Rights Reserved.
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