Network Working Group K. Evans
Request for Comments: 2372 J. Klein
Category: Informational Tandem Computers
J. Lyon
Microsoft
July 1998
Transaction Internet Protocol - Requirements and
Supplemental Information
Status of this Memo
This memo provides information for the Internet community. It does
not specify an Internet standard of any kind. Distribution of this
memo is unlimited.
Copyright Notice
Copyright (C) The Internet Society (1998). All Rights Reserved.
Abstract
This document describes the purpose (usage scenarios), and
requirements for the Transaction Internet Protocol [1]. It is
intended to help qualify the necessary features and functions of the
protocol. It also provides supplemental information to aid
understanding and facilitate implementation of the TIP protocol.
Table of Contents
1. Introduction 2
2. The Transaction Internet Protocol 3
3. Scope 4
4. Anticipated Usage of TIP 4
5. TIP Compliant Systems 4
6. Relationship to the X/Open DTP Model 5
7. Example TIP Usage Scenario 5
8. TIP Transaction Recovery 9
9. TIP Transaction and Application Message Serialisation 10
10. TIP Protocol and Local Actions 10
11. Security Considerations 11
12. TIP Requirements 11
References 14
Authors' Addresses 15
Comments 15
A. An Example TIP Transaction Manager API 16
Full Copyright Statement 24
Evans, et. al. Informational [Page 1]RFC 2372 TIP Requirements and Supplemental Information July 1998
1. Introduction
Transactions are a very useful programming paradigm, greatly
simplifying the writing of distributed applications. When
transactions are employed, no matter how many distributed application
components participate in a particular unit-of-work, the number of
possible outcomes is reduced to only two; that is, either all of the
work completed successfully, or none of it did (this characteristic
is known as atomicity). Applications programming is therefore much
less complex since the programmer does not have to deal with a
multitude of possible failure scenarios. Typically, transaction
semantics are provided by some underlying system infrastructure
(usually in the form of products such as Transaction Processing
Monitors, and/or Databases). This infrastructure deals with failures,
and performs the necessary recovery actions to guarantee the property
of atomicity. The use of transactions enables the development of
reliable distributed applications which would otherwise be difficult,
if not impossible.
A key technology required to support distributed transactions is the
two-phase commit protocol (2-pc). 2-pc protocols have been used in
commercial Transaction Processing (TP) systems for many years, and
are well understood (e.g. the LU6.2 2-pc (syncpoint) protocol was
first implemented more than 12 years ago). Today a number of
different 2-pc protocols are supported by a variety of TP monitor and
database products. 2-pc is used between the components participating
in a distributed unit-of-work (transaction) to ensure agreement by
all parties regarding the outcome of that work (regardless of any
failure).
Today both standard and proprietary 2-pc protocols exist. These
protocols typically employ a "one-pipe" model. That is, the
transaction and application protocols are tightly-integrated,
executing over the same communications channel. An application may
use only the particular communications mechanism associated with the
transaction protocol. The standard protocols (OSI TP, LU6.2) are
complex, with a large footprint and extensive configuration and
administration requirements. For these reasons they are not very
widely deployed. The net of all this is restricted application
flexibility and interoperability if transactions are to be used.
Applications may wish to use a number of communications protocols for
which there are no transactional variants (e.g. HTTP), and be
deployed in very heterogeneous application environments.
In summary, transactions greatly simplify the programming of
distributed applications, and the 2-pc protocol is a key
transactional technology. Current 2-pc protocols only offer
transaction semantics to a limited set of applications, operating
Evans, et. al. Informational [Page 2]
RFC 2372 TIP Requirements and Supplemental Information July 1998
within a special-purpose (complex, homogeneous) infrastructure, using
a particular set of intercommunication protocols. The restrictions
thus imposed by current 2-pc protocols limits the widespread use of
the transaction paradigm, thereby inhibiting the development of new
distributed business applications.
(See [2] for more information re transactions, atomicity, and two-
phase commit protocols in general.)
2. The Transaction Internet Protocol (TIP)
TIP is a 2-pc protocol which is intended to provide ubiquitous
distributed transaction support, in a heterogeneous (networked)
environment. TIP removes the restrictions of current 2-pc protocols
and enables the development of new distributed business applications.
This goal is achieved primarily by satisfying two key requirements:
1) Keep the protocol simple (yet functionally sufficient). If the
protocol is complex it will not be widely deployed or quickly
adopted. Simplicity also means suitability to a wide range of
application environments.
2) Enable the protocol to be used with any applications
communications protocol (e.g. HTTP). This ensures heterogeneous
environments can participate in distributed work.
TIP does not reinvent the 2-pc protocol itself, the well-known
presumed-abort 2-pc protocol is used as a basis. Rather the novelty
and utility of TIP is in its separation from the application
communications protocol (the two-pipe model).
+-------------+ Application Communication +-------------+
| Application |---------------------------| Application |
| Program | "Pipe 1" | Program |
+-------------+ +-------------+
| |
| TIP TM API TIP TM API |
| |
+-----------------+ TIP 2-pc Protocol +-----------------+
| TIP Transaction |-----------------------| TIP Transaction |
| Manager | "Pipe 2" | Manager |
+-----------------+ +-----------------+
Fig 1: The two-pipe nature of TIP
Evans, et. al. Informational [Page 3]RFC 2372 TIP Requirements and Supplemental Information July 1998
3. Scope
TIP does not describe how business transactions or electronic
commerce are to be conducted on the internet, it specifies only the
2-pc transaction protocol (which is an aid in the development of such
applications). e.g. TIP does not provide a mechanism for non-
repudiation. Such protocols might be a subject for subsequent IETF
activity, once the requirements for general electronic commerce are
better understood. TIP does not preclude the later definition of
these protocols.
TIP does not specify Application Programming Interfaces (note that an
example TIP TM API is included in this document (Appendix A), as an
aid to understanding).
4. Anticipated Usage of TIP
As described above, transactions are a very useful tool in
simplifying the programming of distributed applications. TIP is
therefore targeted at any application that involves distributed work.
Such applications may comprise components executing within a single
system, across a corporate intranet, across the internet, or any
other distributed system configuration. The application may be of
"enterprise" class (requiring high-levels of performance and
availability), or be less demanding. TIP is intended to be generally
applicable, meeting the requirements of any application type which
would benefit from the provision of transaction semantics.
5. TIP Compliant Systems
There are two classes of TIP compliant Transaction Manager system:
1) Client-only systems. Those which provide an application
interface to demarcate TIP transactions, but which do not offer
access to local recoverable resources. Such a lightweight
implementation is useful for systems which host client
applications only (e.g. desktop machines). Such client systems may
be unreliable, and are not appropriate as transaction coordinators
(their unavailability might cause resources on other transaction
participant systems to remain locked and unavailable). These so-
called "volatile client" systems therefore delegate the
responsibility to coordinate the transaction (and recover from
failures), to other "full" (server) TIP system implementations.
For these lightweight systems, only the TIP IDENTIFY, BEGIN,
COMMIT, and ABORT commands are needed; no transaction log is
required.
Evans, et. al. Informational [Page 4]RFC 2372 TIP Requirements and Supplemental Information July 1998
2) Server systems. Those which offer the above support, plus TIP
transaction coordination and recovery services. These systems may
also provide access to recoverable resources (e.g. relational
databases). Server systems support all TIP commands, and provide a
recoverable transaction log.
A TIP compliant Transaction Manager (TM), will also supply
application programming interfaces to demarcate transactions (e.g.
the X/Open TX interface [3]), plus commands to generate TIP URLs, to
PUSH/PULL TIP transactions, and to set the current TIP transaction
context. TIP support can be added to TMs with existing APIs and 2-pc
protocols, and transactions may comprise both proprietary and TIP
transaction branches (it is assumed existing TM implementations will
provide "TIP gateway" facilities which will coordinate between TIP
and other transaction protocols).
6. Relationship to the X/Open DTP Model
The X/Open Distributed Transaction Processing (DTP) Model [4] defines
four components: 1) Application Program (AP), 2) Transaction Manager
(TM), 3) Resource Manager (RM), and 4) Communications Resource
Manager (CRM). In this model, TIP defines a TM to TM interoperability
protocol, which is independent of application communications (there
is no such equivalent protocol specified by X/Open, where all
transaction and application communication occurs between CRMs (the
one-pipe model)). Programmatic interfaces between the AP and TM/RM
are unaffected by, and may be used with TIP. The TM to RM interaction
is defined via the X/Open XA interface specification [5]. TIP is
compatible with XA, and a TIP transaction may comprise applications
accessing multiple RMs where the XA interface is being used to
coordinate the RM transaction branches.
7. Example TIP Usage Scenario
It is expected that a typical internet usage of TIP will involve
applications using the agency model. In this model, the client node
itself is not directly involved in the TIP protocol at all, and does
not need the services of a local TIP TM. Instead, an agency (server)
application handles the dialogue with the client, and is responsible
for the coordination of the TIP transaction. The agency works with
other service providers to deliver the service to the client. e.g. as
a Travel Agency acts as an intermediate between airlines/hotels/etc
and the customer. A big benefit of this model is that the agency is
trusted by the service providers, and there are fewer such agencies
(compared to user clients), so issues of security and performance are
reduced.
Evans, et. al. Informational [Page 5]RFC 2372 TIP Requirements and Supplemental Information July 1998
Consider a Travel Agency example. A client running a web browser on a
network PC accesses the Travel Agency web page. Via pages served up
by the agency (which may in turn be constructed from pages provided
by the airline and hotel servers), the client creates an itinerary
involving flights and hotel choices. Finally, the client clicks the
"make reservation" button. At this point the following sequence of
events occurs (user-written application code is invoked by the
various web servers, via any of the standard or proprietary
techniques available (e.g. CGI)):
1) The travel agency begins a local transaction, and gets a TIP URL
for this transaction (both of these functions are performed using
the API of the local TM. e.g. "tip_xid_to_url()" would return the
TIP URL for the local transaction). The TIP URL contains the
listening endpoint IP address of the local TM and the transaction
identifier of the local transaction.
2) The travel agency application sends a request to the airline
server (via some protocol (e.g. HTTP)), requesting the
"book_flight" service, passing the flights selected by the client,
and the TIP URL (obtained in 1. above).
3) The request is received by the airline server which invokes the
book_flight application. This application retrieves the TIP URL
from the input data, and passes this on a "tip_pull()" API request
to its local TM. The tip_pull() function causes the following to
occur:
a. the local TM creates a local transaction (under which the
work will be performed),
b. if a TIP connection does not already exist to the superior
(travel agency) TM (as identified via the IP address passed in
the TIP URL), one is created and an IDENTIFY exchange occurs
(if multiplexing is to be used on the connection, this is
followed by a MULTIPLEX exchange),
c. a PULL command is sent to the superior TM,
d. in response to the PULL, the superior TM associates the
subordinate (airline) TM with the transaction (by associating
the connection with the transaction), and sends a PULLED
response to the subordinate TM,
e. the subordinate TM returns control to the book_flight
application, which is now executing in the context of the newly
created local transaction.
Evans, et. al. Informational [Page 6]RFC 2372 TIP Requirements and Supplemental Information July 1998
4) The book_flight application does its work (which may involve
access to a recoverable resource manager (e.g. an RDBMS), in which
case the local TM will associate the RM with the local transaction
(via the XA interface or whatever)).
5) The book_flight application returns to the travel agency
application indicating success.
6) Steps 2-5 are then repeated with the hotel server "book_room"
application. At the conclusion of this, the superior TM has
registered two subordinate TMs as participants in the transaction,
there are TIP connections between the agency TM and the airline
and hotel TMs, and there are inflight transactions at the airline
and hotel servers. [Note that steps 2-5 and 6 could be performed
in parallel.]
7) The travel agency application issues a "commit transaction"
request (using the API of the local TM). The local TM sends a
PREPARE command on the TIP connections to the airline and hotel
TMs (as these are registered as subordinate transaction
participants).
8) The TMs at the airline and hotel servers perform the
necessary steps to prepare their local recoverable resources (e.g.
by issuing xa_prepare() requests). If successful, the subordinate
TMs change their TIP transaction state to Prepared, and log
recovery information (e.g. local and superior transaction branch
identifiers, and the IP address of the superior TM). The
subordinate TMs then send PREPARED commands to the superior TM.
9) If both subordinates respond PREPARED, the superior TM logs that
the transaction is Committed, with recovery information (e.g.
local and subordinate transaction identifiers, and subordinate TM
IP addresses). The superior TM then sends COMMIT commands on the
two subordinate TIP connections.
10) The TMs at the airline and hotel servers perform the
necessary steps to commit their local recoverable resources (e.g.
by issuing xa_commit() requests). The subordinate TMs forget the
transaction. The subordinate TMs then send COMITTED commands to
the superior TM.
11) The superior TM forgets the transaction. The TIP connections
between the superior and subordinate TMs return to Idle state
(not associated with any transaction). The superior TM returns
success to the travel agency application "commit transaction"
request.
Evans, et. al. Informational [Page 7]RFC 2372 TIP Requirements and Supplemental Information July 1998
12) The travel agency application returns "reservation made" to the
client.
This example illustrates the use of PULL. If PUSH were to be used
instead, events 2) and 3) above would change as follows:
2) The travel agency application:
a. passes the TIP URL obtained in 1. above, together with the
listening endpoint address of the TM at the airline server, to
its local TM via a "tip_push()" API request. The tip_push()
function causes the following to occur:
i. if a TIP connection does not already exist to the
subordinate (airline server) TM (as identified via the IP
address passed on the tip_push), one is created and an
IDENTIFY exchange occurs (if multiplexing is to be used on
the connection, this is followed by a MULTIPLEX exchange),
ii. a PUSH command is sent to the subordinate TM,
iii. in response to the PUSH, the subordinate TM creates a
local transaction, associates this transaction with the
connection, and sends a PUSHED response to the superior
TM,
iv. in response to the PUSHED response, the superior TM
associates the subordinate TM with the transaction,
v. the superior TM returns control to the travel agency
application.
b. the travel agency application sends a request to the airline
server (via some protocol (e.g. HTTP)), requesting the
"book_flight" service, passing the flights selected by the
client, and the TIP URL (obtained in 1 above).
3) The request is received by the airline server which invokes the
book_flight application. This application retrieves the TIP URL
from the input data, and passes this on a "tip_pull()" API request
to its local TM. Since the local TM has already "seen" this URL
(it was already pushed), it simply returns to the book_flight
application, which is now executing in the context of the
previously created local transaction.
Evans, et. al. Informational [Page 8]RFC 2372 TIP Requirements and Supplemental Information July 1998
[Note that although in this example the transaction coordinator role
is performed by a node which is also a participant in the transaction
(the Travel Agency), other configurations are possible (e.g. where
the transaction coordinator role is performed by a non-participant
3rd-party node).]
8. TIP Transaction Recovery
Until the transaction reaches the Prepared state, any failure results
in the transaction being aborted. If an error occurs once the
transaction has reached the Prepared state, then transaction recovery
must be performed. Recovery behaviour is different for superior and
subordinate; the details depend upon the outcome of the transaction
(committed or aborted), and the precise point at which failure
occurs.
In the travel agency application for example, if the connection to
the hotel server fails before the COMMIT command has been received by
the hotel TM, then (once the connection is restored):
1) The superior (travel agency) TM sends a RECONNECT command
(passing the subordinate transaction identifier (recovered from
the transaction log if necessary)).
2) The subordinate (hotel) TM responds RECONNECTED (since it never
received the COMMIT command, and still has the transaction in
Prepared state (if the failure had occurred after the subordinate
had responded COMMITTED, then the subordinate would have forgotten
the transaction, and responded NOTRECONNECTED to the RECONNECT
command)).
3) The superior TM sends a COMMIT command. The subordinate TM
commits the transaction and responds COMMITTED. The transaction is
now resolved.
4) If the subordinate TM restores the connection to the superior TM
before receiving a RECONNECT command, then it may send a QUERY
command. In this case, the superior TM will respond QUERIEDEXISTS,
and the subordinate TM should wait for the superior to send a
RECONNECT command. If the transaction had been aborted, then the
superior may respond QUERIEDNOTFOUND, in which case the
subordinate should abort the transaction (note that the superior
is not obliged to send a RECONNECT command for an aborted
transaction (i.e. it could just forget the transaction after
sending ABORT and before receiving an ABORTED response)).
Evans, et. al. Informational [Page 9]RFC 2372 TIP Requirements and Supplemental Information July 1998
There are failure circumstances in which the client application (the
one calling "commit") may not receive a response indicating the final
outcome of the transaction (even though the transaction itself is
successfully completed). This is a common problem, and one not unique
to TIP. In such circumstances, it is up to the application to
ascertain the final outcome of the transaction (a TIP TM may
facilitate this by providing some implementation specific mechanism.
e.g. writing the outcome to a user-log).
9. TIP Transaction and Application Message Serialisation
A relationship exists between TIP commands and application messages:
a TIP transaction must not be committed until it is certain that all
participants have properly registered, and have finished work on the
transaction. Because of the two-pipe nature of TIP, this behaviour
cannot necessarily be enforced by the TIP system itself (although it
may be possible in some implementations). It is therefore incumbent
upon the application to behave properly. Generally, an application
must not:
1) call it's local TMs "commit" function when it has any requests
associated with the transaction still outstanding.
2) positively respond to a transactional request from a partner
application prior to having registered it's local TM with the
transaction.
10. TIP Protocol and Local Actions
In order to ensure that transaction atomicity is properly guaranteed,
a system implementing TIP must perform other local actions at certain
points in the protocol exchange. These actions pertain to the
creation and deletion of transaction "log-records" (the necessary
information which survives failures and ensures that transaction
recovery is correctly executed). The following information regarding
the relationship between the TIP protocol and logging events is
advisory, and is not intended to be definitive (see [2] for more
discussion on this subject):
1) before sending a PREPARED response, the system should create
a prepared-recovery-record for the transaction.
2) having created a prepared-recovery-record, this record should not
be deleted until after:
a. an ABORT message is received; or
b. a COMMIT message is received; or
c. a QUERIEDNOTFOUND response is received.
Evans, et. al. Informational [Page 10]RFC 2372 TIP Requirements and Supplemental Information July 1998
3) the system should not send a COMMITTED or NOTRECONNECTED message
if a prepared-recovery-record exists.
4) before creating a commit-recovery-record for the transaction, the
system should have received a PREPARED response.
5) before sending a COMMIT message in Prepared state, the system
should have created a commit-recovery-record for the transaction.
6) having created a commit-recovery-record, this record should not be
deleted until after:
a. a COMMITTED message is received; or
b. a NOTRECONNECTED message is received.
11. Security Considerations
The means by which applications communicate and perform distributed
work are outside the scope of the TIP protocol. The mechanisms used
for authentication and authorisation of clients to access programs
and information on a particular system are part of the application
communications protocol and the application execution infrastructure.
Use of the TIP protocol does not affect these considerations.
Security relates to the TIP protocol itself inasmuch that systems
require to protect themselves from the receipt of unauthorised TIP
commands, or the impersonation of a trusted partner TIP TM. Probably
the worst consequence of this is the possibility of undetected data
inconsistency resulting from violations of the TIP commitment
protocol (e.g. a COMMIT command is injected on a TIP connection in
place of an ABORT command). TIP uses the Transport Layer Security
protocol [6] to restrict access to only trusted partners (i.e. to
control from which remote endpoints TIP transactions will be
accepted, and to verify that an end-point is genuine), and to encrypt
TIP commands. Usage of TLS (or not) is negotiated between partner TIP
TMs. See [1] for details of how TLS is used with TIP.
TIP TM implementations will also likely provide local means to time-
out and abort transactions which have not completed within some time
period (thereby preventing unavailability of resources due to
malicious intent). Transaction time-out also serves as a means of
deadlock resolution.
12. TIP Requirements
Most of these requirements stem from the primary objective of making
transactions a ubiquitous system service, available to all
application classes (much as TCP may be assumed to be available
everywhere). In general this requires imposing as few restrictions
Evans, et. al. Informational [Page 11]RFC 2372 TIP Requirements and Supplemental Information July 1998
regarding the use of TIP as possible (applications should not be
required to execute in some "special" environment in order to use
transactions), and keeping the protocol simple and efficient. This
enables the widespread implementation of TIP (it's cheap to do), on a
wide range of systems (it's cheap to run).
1) Application Communications Protocol Independence
The TIP protocol must be defined independently of the
communications protocol used for transferring application data, to
allow TIP usage in conjunction with any application protocol. It
must be possible for applications using arbitrary communications
protocols to begin, end, and propagate TIP transactions.
This implies that the TIP protocol employ a 2-pipe model of
operation. This model requires the separation of application
communications and transaction coordination, into two discrete
communication channels (pipes). This separation enables the use of
the transaction coordination protocol (TIP), with any application
communications protocol (e.g. HTTP, ODBC, plain TCP/UDP, etc).
2) Support for Transaction Semantics
The TIP protocol must provide the functionality of the de-facto
standard presumed-abort 2-pc protocol, to guarantee transactional
atomicity even in the event of failure. It should provide a means
to construct the transaction tree, as well as provide commitment
and recovery functions.
3) Application Transaction Propagation and Interoperability
In order to facilitate protocol independence, application
interoperability, and provide a means for TIP transaction context
propagation, a standard representation of the TIP transaction
context information is required (in the form of a URL). This
information must include the listening endpoint address of the
partner TIP TM, and transaction identifier information.
4) Ease of Implementation
The TIP protocol must be simple to implement. It should support
only those features necessary to provide a useful, performant 2-pc
protocol service. The protocol should not add complexity in the
form of extraneous optimisations.
Evans, et. al. Informational [Page 12]RFC 2372 TIP Requirements and Supplemental Information July 1998
5) Suitability for All Application Classes
The TIP protocol should be complete and robust enough not only for
electronic commerce on the web, but also for intranet applications
and for traditional TP applications spanning heterogenous
transaction manager environments. The protocol should be
performant and scaleable enough to meet the needs of low to very
high throughput applications.
a. the TIP protocol should support the concept of client-only
transaction participants (useful for ultra-lightweight
implementations on low-end platforms).
b. since some clients may be unreliable, TIP must provide support
for delegation of transaction coordination (to a more reliable
(trusted) node).
c. the TIP protocol must scale between 1 and n (> 1) concurrent
transactions per TCP connection.
d. TIP commands should be able to be concatenated (pipelined).
e. TIP should be compatible with the X/Open XA interface.
6) Security
The TIP protocol must be compatible with existing security
mechanisms, potentially including encryption, firewalls, and
authorization mechanisms (e.g. TLS may be used to authenticate the
sender of a TIP command, and for encryption of TIP commands).
Nothing in the protocol definition should prevent TIP working
within any security environment.
7) TIP Protocol Transport Independence
It would be beneficial to some applications to allow the TIP
protocol to flow over different transport protocols. The benefit
is when using different transport protocols for the application
data, the same transport can be used for the TIP 2PC protocol. TIP
must therefore not preclude use with other transport protocols.
8) Recovery
Recovery semantics need to be defined sufficiently to avoid
ambiguous results in the event of any type of communications
transport failure.
Evans, et. al. Informational [Page 13]RFC 2372 TIP Requirements and Supplemental Information July 1998
9) Extensibility
The TIP protocol should be able to be extended, whilst maintaining
compatibility with previous versions.
References
[1] Lyon, J., Evans, K., and J. Klein, "The Transaction Internet
Protocol Version 3.0", RFC 2371, July 1998.
[2] Transaction Processing: Concepts and Techniques. Morgan
Kaufmann Publishers. (ISBN 1-55860-190-2). J. Gray, A. Reuter.
[3] X/Open CAE Specification, April 1995, Distributed Transaction
Processing: The TX Specification. (ISBN 1-85912-094-6).
[4] X/Open Guide, November 1993, Distributed Transaction Processing:
Reference Model Version 2. (ISBN 1-85912-019-9).
[5] X/Open CAE Specification, December 1991, Distributed Transaction
Processing: The XA Specification. (ISBN 1-872630-24-3).
[6] Dierks, T., et. al., "The TLS Protocol Version 1.0", Work in
Progress.
Evans, et. al. Informational [Page 14]RFC 2372 TIP Requirements and Supplemental Information July 1998
Authors' Addresses
Keith Evans
Tandem Computers Inc, LOC 252-30
5425 Stevens Creek Blvd
Santa Clara, CA 95051-7200, USA
Phone: +1 (408) 285 5314
Fax: +1 (408) 285 5245
EMail: Keith.Evans@Tandem.Com
Johannes Klein
Tandem Computers Inc.
10555 Ridgeview Court
Cupertino, CA 95014-0789, USA
Phone: +1 (408) 285 0453
Fax: +1 (408) 285 9818
EMail: Johannes.Klein@Tandem.Com
Jim Lyon
Microsoft Corporation
One Microsoft Way
Redmond, WA 98052-6399, USA
Phone: +1 (206) 936 0867
Fax: +1 (206) 936 7329
EMail: JimLyon@Microsoft.Com
Comments
Please send comments on this document to the authors at
<JimLyon@Microsoft.Com>, <Keith.Evans@Tandem.Com>,
<Johannes.Klein@Tandem.Com>, or to the TIP mailing list at
<Tip@Tandem.Com>. You can subscribe to the TIP mailing list by
sending mail to <Listserv@Lists.Tandem.Com> with the line
"subscribe tip <full name>" somewhere in the body of the message.
Evans, et. al. Informational [Page 15]
RFC 2372 TIP Requirements and Supplemental Information July 1998
Appendix A. An Example TIP Transaction Manager Application Programming
Interface.
Note that this API is included solely for informational purposes, and
is not part of the formal TIP specification (TIP conformant
implementations are free to define alternative APIs).
1) tip_open() - establish a connection to a TIP TM.
Synopsis
int tip_open ([out] tip_handle_t *ptiptm)
Parameters
ptiptm [out]
Pointer to the TIP TM handle.
Description
tip_open() establishes a connection to a TIP TM. The call
returns a handle which identifies the TIP TM. This function
must be called before any work can be performed on a TIP
transaction.
Return Values
[TIPOK]
Connection has been successfully established.
[TIPNOTCONNECTED]
User has been disconnected from the TIP TM.
[TIPNOTCONFIGURED]
TIP TM has not been configured.
[TIPTRANSIENT]
Too many openers; re-try the open.
[TIPERROR]
An unexpected error occurred.
2) tip_close() - close a connection to a TIP TM.
Synopsis
int tip_close([in] tip_handle_t handle)
Parameters
handle [in]
The TIP TM handle.
Description
tip_close() closes a connection to a TIP TM. All outstanding
requests associated with that connection will be cancelled.
Return Values
[TIPOK]
Connection has been successfully closed.
[TIPINVALIDPARM]
Invalid connection handle specified.
[TIPERROR]
An unexpected error occurred.
Evans, et. al. Informational [Page 16]RFC 2372 TIP Requirements and Supplemental Information July 1998
3) tip_push() - export a local transaction to a remote node and
return a TIP transaction identifier for the
associated remote transaction.
Synopsis
int tip_push ([in] tip_handle_t TM,
[in] char *tm_url,
[in] void *plocal_xid,
[out] char *pxid_url,
[in] unsigned int url_length)
Parameters
TM [in]
The TIP TM handle.
tm_url [in]
Pointer to the TIP URL of the remote transaction manager.
A TIP URL for a transaction manager takes the form:
TIP://<host>[:<port>]
plocal_xid [in]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
pxid_url [out]
Pointer to the TIP URL of the associated remote
transaction. A TIP URL for a transaction takes the form:
TIP://<host>[:<port>]/<transaction identifier>
url_length [in]
The size in bytes of the buffer for the remote
transaction URL.
Description
tip_push() exports (pushes) a local transaction to a remote
node. If a local transaction identifier is not supplied, the
caller's current transaction context is used. The call returns
a TIP URL for the associated remote transaction. The TIP
transaction identifier may be passed on application requests to
the remote node (as part of a TIP URL). The receiving process
uses this information in order to do work on behalf of the
transaction.
Return Values
[TIPOK]
Transaction has been successfully pushed to the remote
node.
[TIPINVALIDXID]
An invalid transaction identifier has been provided.
[TIPNOCURRENTTX]
Process is currently not associated with a transaction
(and none was supplied).
[TIPINVALIDHANDLE]
Invalid connection handle specified.
[TIPNOTPUSHED]
Evans, et. al. Informational [Page 17]RFC 2372 TIP Requirements and Supplemental Information July 1998
Transaction could not be pushed to the remote node.
[TIPNOTCONNECTED]
Caller has been disconnected from the TIP TM.
[TIPINVALIDURL]
Invalid endpoint URL is provided.
[TIPTRANSIENT]
Transient error occurred; re-try the operation.
[TIPTRUNCATED]
Insufficient buffer size is specified for the TIP
transaction identifier.
[TIPERROR]
An unexpected error occurred.
4) tip_pull() - create a local transaction and join it with the TIP
transaction.
Synopsis
int tip_pull([in] tip_handle_t TM,
[in] char *pxid_url,
[out] void *plocal_xid,
[in] unsigned int xid_length)
Parameters
TM [in]
The TIP TM handle.
pxid_url [in]
Pointer to the TIP URL of the associated remote
transaction. A TIP URL for a transaction takes the form:
TIP://<host>[:<port>]/<transaction identifier>
plocal_xid [out]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
xid_length [in]
The size in bytes of the buffer for the local transaction
identifier.
Description
tip_pull() creates a local transaction and joins the local
transaction with the TIP transaction (the caller becomes a
subordinate participant in the TIP transaction). The remote TIP
TM is identified via the URL (*pxid_url). The local transaction
identifier is returned. If a local transaction has already been
created for the TIP transaction identifier supplied, then
[TIPOK] is returned (with the local transaction identifier),
and no other action is taken.
Return Values
[TIPOK]
The local transaction has been successfully created
and joined with the TIP transaction.
[TIPINVALIDHANDLE]
Evans, et. al. Informational [Page 18]RFC 2372 TIP Requirements and Supplemental Information July 1998
Invalid connection handle specified.
[TIPTRUNCATED]
Insufficient buffer size is specified for the local
transaction identifier.
[TIPNOTPULLED]
Joining of the local transaction with the TIP
transaction has failed.
[TIPNOTCONNECTED]
Caller has been disconnected from the TIP TM.
[TIPINVALIDURL]
Invalid URL has been supplied.
[TIPTRANSIENT]
Transient error occurred; retry the operation.
[TIPERROR]
An unexpected error occurred.
5) tip_pull_async() - create a local transaction and join it with the
TIP transaction. Control is returned to the
caller as soon as a local transaction is
created.
Synopsis
int tip_pull_async ([in] tip_handle_t TM
[in] char *pxid_url,
[out] void *plocal_xid,
[in] unsigned int xid_length)
Parameters
TM [in]
The TIP gateway handle.
pxid_url [in]
Pointer to the TIP URL of the associated remote
transaction. A TIP URL for a transaction takes the form:
TIP://<host>[:<port>]/<transaction identifier>
plocal_xid [out]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
xid_length [in]
The size in bytes of the buffer for the local transaction
identifier.
Description
tip_pull_async() creates a local transaction and joins the
local transaction with the TIP transaction (the caller
becomes a subordinate participant in the TIP transaction). The
remote TIP TM is identified via the URL (*pxid_url). The local
transaction identifier is returned. A call to tip_pull_async()
returns immediately after the local transaction has been
created (before the TIP PULL protocol command is sent). A
subsequent call to tip_pull_complete() must be issued to check
Evans, et. al. Informational [Page 19]RFC 2372 TIP Requirements and Supplemental Information July 1998
for successful completion of the pull request.
Return Values
[TIPOK]
The local transaction has been successfully created.
[TIPINVALIDHANDLE]
Invalid connection handle specified.
[TIPNOTCONNECTED]
User has been disconnected from the TIP TM.
[TIPINVALIDURL]
Invalid URL has been supplied.
[TIPTRANSIENT]
Transient error has occurred; retry the operation.
[TIPTRUNCATED]
Insufficient buffer size is specified for the local
transaction identifier.
[TIPERROR]
An unexpected error occurred.
6) tip_pull_complete() - check whether a previous tip_pull_async()
request has been successfully completed.
Synopsis
int tip_pull_complete ([in] tip_handle_t TM,
[in] void *plocal_xid)
Parameters
TM [in]
The TIP TM handle.
plocal_xid [in]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
Description
tip_pull_complete() checks whether a previous call to
tip_pull_async() has been successfully completed. i.e. whether
the local transaction has been successfully joined with the TIP
transaction. The caller supplies the local transaction
identifier returned by the previous call to tip_pull_async().
Repeated calls to tip_pull_complete() for the same local
transaction identifier are idempotent.
Return Values
[TIPOK]
The local transaction has been successfully joined with
the TIP transaction.
[TIPINVALIDHANDLE]
Invalid connection handle specified.
[TIPINVALIDXID]
An invalid transaction identifier has been provided.
[TIPNOTPULLED]
Joining of the local transaction with the TIP transaction
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has failed. The local transaction has been aborted.
[TIPNOTCONNECTED]
Caller has been disconnected from the TIP TM.
[TIPERROR]
An unexpected error occurred.
7) tip_xid_to_url() - return a TIP transaction identifier for a local
transaction identifier.
Synopsis
int tip_xid_to_url ([in] tip_handle_t TM,
[in] void *plocal_xid,
[out] char *pxid_url,
[in] unsigned int url_length)
Parameters
TM [in]
The TIP TM handle.
plocal_xid [in]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
pxid_url [out]
Pointer to the TIP URL of the local transaction.
A TIP URL for a transaction takes the form:
TIP://<host>[:<port>]/<transaction identifier>
url_length [in]
The size in bytes of the buffer for the TIP URL.
Description
tip_xid_to_url() returns a TIP transaction identifier for a
local transaction identifier. The TIP transaction identifier
can be passed to remote applications to enable them to do work
on the transaction. e.g. to pull the local transaction to the
remote node. If a local transaction identifier is not supplied,
the caller's current transaction context is used. The constant
TIPURLSIZE defines the size of a TIP transaction identifier in
bytes. This value is implementation specific.
Return Values
[TIPOK]
TIP transaction identifier has been returned.
[TIPNOTCONNECTED]
Caller has been disconnected from the TIP TM.
[TIPNOCURRENTTX]
Process is currently not associated with a transaction
(and none was supplied).
[TIPINVALIDXID]
An invalid local transaction identifier has been
supplied.
[TIPTRUNCATED]
Insufficient buffer size is specified for the TIP
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transaction identifier.
[TIPERROR]
An unexpected error occurred.
8) tip_url_to_xid() - return a local transaction identifier for a TIP
transaction identifier.
Synopsis
int tip_url_to_xid ([in] tip_handle_t TM,
[in] char *pxid_url,
[out] void *plocal_xid,
[in] unsigned int xid_length)
Parameters
TM [in]
The TIP TM handle.
pxid_url [in]
Pointer to the TIP URL of the local transaction. A TIP
URL for a transaction takes the form:
TIP://<host>[:<port>]/<transaction identifier>
plocal_xid [out]
Pointer to the local transaction identifier. The
structure of the transaction identifier is defined by the
local transaction manager.
xid_length [in]
The size in bytes of the buffer for the local transaction
identifier.
Description
tip_url_to_xid() returns a local transaction identifier for a
TIP transaction identifier (note that the local transaction
must have previously been created via a tip_push(), or tip_pull
(or tip_pull_async()). The constant TIPXIDSIZE defines the size
of a local transaction identifier in bytes. This value is
implementation specific.
Return Values
[TIPOK]
Local transaction identifier is returned.
[TIPINVALIDURL]
An invalid TIP transaction identifier has been provided.
[TIPTRUNCATED]
Insufficient buffer size is specified for the local
transaction identifier.
[TIPERROR]
An unexpected error occurred.
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9) tip_get_tm_url() - get the name of the local TIP transaction
manager in TIP URL form.
Synopsis
int tip_get_tm_url ([in] tip_handle_t TM,
[out] char *tm_url,
[in] int tm_len);
Parameters
TM[in]
The TIP TM handle.
tm_url [in]
Pointer to the TIP URL of the local transaction manager. A
TIP URL for a transaction manager takes the form:
TIP://<host>[:<port>]
tm_len [out]
The size in bytes of the buffer for the TIP URL of the local
transaction manager.
Description
tip_get_tm_url() gets the name of the local transaction
manager in TIP URL form (i.e. TIP://<host>[:<port>])
Return Values
[TIPOK]
The name of the local transaction manager has been
successfully returned.
[TIPTRUNCATED]
The name of the local transaction manager has been
truncated due to insufficient buffer size. Retry the
operation with larger buffer size.
Evans, et. al. Informational [Page 23]RFC 2372 TIP Requirements and Supplemental Information July 1998
Full Copyright Statement
Copyright (C) The Internet Society (1998). All Rights Reserved.
This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph are
included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing
the copyright notice or references to the Internet Society or other
Internet organizations, except as needed for the purpose of
developing Internet standards in which case the procedures for
copyrights defined in the Internet Standards process must be
followed, or as required to translate it into languages other than
English.
The limited permissions granted above are perpetual and will not be
revoked by the Internet Society or its successors or assigns.
This document and the information contained herein is provided on an
"AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
Evans, et. al. Informational [Page 24]
