Edit File: draft-zeilenga-ldap-c-api-concurrency-xx.txt
INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standards Track OpenLDAP Foundation Extends: draft-ietf-ldapext-ldap-c-api-03.txt Expires: 28 March 2000 28 September 1999 LDAP C API Concurrency Extensions <draft-zeilenga-ldap-c-api-concurrency-00.txt> 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This draft document will be submitted to the RFC Editor as a Standards Track document. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extension Working Group mailing list <ietf-ldapext@netscape.com>. Please send editorial comments directly to the author <Kurt@OpenLDAP.org>. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright 1999, The Internet Society. All Rights Reserved. Please see the Copyright section near the end of this document for more information. 2. Abstract This document defines extensions to the LDAP C API to support use in concurrent execution environments. The document describes and defines Zeilenga [Page 1] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 requirements for multiple concurrency levels: thread safe, session thread safe, and operation thread safe. The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", and "MAY" in this document are to be interpreted as described in RFC 2119 [KEYW]. 3. Introduction This document extends the LDAP C API [CAPI] specification to support use in concurrent execution environments. The extensions add powerful concurrent processing capabilities to the simple to use CAPI. This document provides an overview of different levels of concurrent execution support and offers a number of CAPI "features" to provide capabilities at these levels. The remainder of this section describes three levels of concurrent execution: thread safe, session thread safe, operation thread safe APIs. 3.1. Thread Safe An implementation which allows applications to safely execute in concurrent execution environments where the application provides necessary synchronization to ensure serialization of CAPI usage is considered to be "thread safe." Applications may execute non-CAPI calls in concurrent execution contexts when using thread safe implementations. 3.2. Session Thread Safe A "thread safe" implementation which allows CAPI calls associated with different LDAP sessions to proceed asychronously is considered to be "session thread safe." 3.3. Operation Thread Safe A "session thread safe" implementation which allows CAPI calls associated with different LDAP operations to proceed asychronously is considered to be "operation thread safe". 4. Basic Thread Safe Feature Zeilenga [Page 2] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 This section details requirements for the thread safe CAPI feature. Implementations fulfilling these requirements are said to support the LDAP_API_FEATURE_THREAD_SAFE feature and SHOULD advertise this support as detailed below. This feature SHOULD be provided by implementations. Implementations of this feature MUST implement the LDAP error handling extension [ERRNO]. Implementations of this feature MUST allow non-CAPI calls to proceed asynchronously. Implementations of this feature MUST NOT use any non-thread safe call or mechanism provided by C environment or operating system. An example of non-reentrant calls is the UNIX strtok() function. Example of a non-reentrant mechanism is global (i.e.: non-thread specific) errno. 5. Session Thread Safe Feature This section details requirements for the session thread safe CAPI feature. Implementations fulfilling these requirements are said to support the LDAP_API_FEATURE_SESSION_THREAD_SAFE feature and SHOULD advertise this support as detailed below. This feature is RECOMMENDED. 5.1. Prerequisite Features Implementations providing this feature MUST provide and advertise both LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO [ERRNO] and LDAP_API_FEATURE_THREAD_SAFE. 5.2. Atomic Session Handles Implementations providing this feature SHOULD ensure that operations upon a given session handle are atomic. Implementations which provide atomic session handles SHOULD advertise the feature LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES. 5.3. Concurrency Requirements Implementations providing this feature MUST not restrict CAPI calls acting upon a given LDAP session to a particular execution context. Applications MAY use a session handle on any thread. Applications Zeilenga [Page 3] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 MUST NOT assume that operations upon a session are atomic. Implementations providing this feature MUST allow CAPI calls acting upon different LDAP sessions to safely proceed asynchronously. Implementations providing this feature MUST allow CAPI calls not acting upon an LDAP session to safely proceed asynchronously. 6. Operation Thread Safe Feature This section details requirements for the operation thread safe CAPI feature based upon a duplicate session handles mechanism. Implementations fulfilling these requirements are said to support the LDAP_API_FEATURE_DUPLICATE_SESSION_HANDLES feature and SHOULD advertise this support as detailed below. This feature is OPTIONAL. 6.1. Prerequisite Features Implementations of this feature MUST provide and advertise LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO [ERRNO], LDAP_API_FEATURE_THREAD_SAFE, LDAP_API_FEATURE_SESSION_THREAD_SAFE, and LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES. 6.2. Duplicated Session Handles Implementations of this feature MUST support duplicated session handles. As defined in CAPI, a session handle refers to an LDAP session encompassing connections with one or more servers, associated message results, a set of properties (options), and state information. This feature provides a mechanism for a handle to be duplicated. A session handle and its duplicates are considered siblings. Each sibling session handle refers to the same LDAP session and message results. Some properties and state are specific to a handle and others shared between siblings as detailed below. CAPI calls made on a handle are atomic. Calls made on sibling (or other) handles MAY proceed asynchronously. Session handles are duplicated using ldap_dup() and destroyed using ldap_destroy(). Use of duplicated session handles with CAPI calls have the following semantics detailed in the sections below. Zeilenga [Page 4] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 6.2.1. Creating and Destroying duplicated sessions Implementations of this feature are required to provide two new routines: LDAP *ldap_dup( ld ); int ldap_destroy( ld ); Parameters are: ld The session handle The ldap_dup() function returns a duplicate of a session handle. The returned session handle may be used concurrently with the original session handle as described below. ldap_dup returns NULL if it is not able to duplicate the session handle and sets LDAP_OPT_ERROR_NUMBER and ldap_errno indicating the nature of the failure. The ldap_destroy() function destroys the session handle. If the session handle has no siblings, ldap_destroy behaves exactly like ldap_unbind. If the session handle has siblings, the resources assocated with the handle are released and the siblings remain valid. ldap_destroy() returns LDAP_SUCCESS or an error number indicating the nature of failure. Regardless of returned value, the handle SHOULD be considered invalid and MUST not be used in subsequent calls. Attempts to use a destroyed session handle MUST NOT result in LDAP_INVALID_SESSION error being reported. Implementations SHOULD report LDAP_PARAM_ERROR in such cases. 6.2.2. ldap_unbind and siblings When ldap_unbind() is called on a session handle with siblings, the siblings become invalid. The siblings must be destroyed using ldap_destroy(). All attempts to obtain the siblings' LDAP_OPT_ERROR_NUMBER will return LDAP_INVALID_SESSION. Any use other than ldap_destroy() or reading LDAP_OPT_ERROR_NUMBER will fail with an LDAP_INVALID_SESSION error being reported. 6.2.3. ldap_result() Message queues are shared between siblings. Results of operations on a duplicated session handles are accessible to all sibling session handles. Applications desiring results associated with a specific operation SHOULD provide the appropriate msgid to ldap_result(). Applications SHOULD avoid calling ldap_result() with LDAP_RES_ANY as such may "steal" and return results which an operation on a sibling requires to complete. Zeilenga [Page 5] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 6.2.4. Session Options The following CAPI options access values shared between siblings: LDAP_OPT_API_INFO LDAP_OPT_DESC LDAP_OPT_REFERRALS LDAP_OPT_PROTOCOL_VERSION LDAP_OPT_API_FEATURE_INFO LDAP_OPT_HOST_NAME The following CAPI options access values specific to a sibling: LDAP_OPT_DEREF LDAP_OPT_SIZELIMIT LDAP_OPT_TIMELIMIT LDAP_OPT_RESTART LDAP_OPT_CLIENT_CONTROLS LDAP_OPT_SERVER_CONTROLS LDAP_OPT_ERROR_NUMBER LDAP_OPT_ERROR_STRING LDAP_OPT_MATCHED_DN 6.2.4.1. LDAP_OPT_SESSION_REFCNT In addition, implementations MUST provide the READ-ONLY, shared LDAP_OPT_SESSION_REFCNT option. LDAP_OPT_SESSION_REFCNT returns the reference count associated with the supplied session handle argument. The session handle argument is required. The outvalue argument should be a pointer to an integer. Example use: int refcount(LDAP *ld) { #ifdef LDAP_OPT_SESSION_REFCNT if(ld != NULL) { int refcnt, rc; rc = ldap_get_option(ld, LDAP_OPT_SESSION_REFCNT, &refcnt); if(rc == LDAP_OPT_SUCCESS) { return refcnt; } } #endif return -1; } 7. Advertising Features This document REQUIRES that supported features with the name in the form LDAP_API_FEATURE_x be advertised to consumers of the CAPI as Zeilenga [Page 6] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 follows: SHOULD provide the macro LDAP_API_FEATURE_x with the value of 1000 + revision number of this draft (i.e.: 1000+0 for this 0 revision of the draft). MUST provide the CAPI extension "x" when returning API information upon LDAP_OPT_API_INFO option access, and MUST provide feature info for "x" via LDAP_OPT_FEATURE_INFO option mechanism. The feature version provided MUST match the value LDAP_API_FEATURE_x macro where x is replaced appropriately. As implementations may not provide macros for all features, applications SHOULD use LDAP_OPT_API_INFO to determine which features are provided by a given implementation. 8. Changes to the C API specification 8.1. New Symbols This extension introduces the following macros: LDAP_API_FEATURE_ATOMIC_SESSION_HANDLES LDAP_API_FEATURE_DUPLICATE_SESSION_HANDLES LDAP_API_FEATURE_SESSION_THREAD_SAFE LDAP_API_FEATURE_THREAD_SAFE LDAP_API_FEATURE_OPERATION_THREAD_SAFE LDAP_INVALID_SESSION LDAP_OPT_SESSION_REFCNT This extension introduces these new functions: ldap_destroy() ldap_dup() This extension introduces no new typedefs nor structure names. 8.2. Duplicated Session Handles This extension introduces duplicated session handles and requirements for handling duplicated session handles. Semantics of non-duplicated session handles are not affected by this introduction. However, the semantics of calls upon duplicate session handles differs as described in the extension. Zeilenga [Page 7] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 9. Security Considerations None taken, none given. 10. Copyright Copyright 1999, The Internet Society. 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 AUTHORS, 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. 11. Bibliography [CAPI] M. Smith, T. Howes, A. Herron, M. Wahl, A. Anantha, "The C LDAP Application Program Interface", INTERNET-DRAFT, <draft- ietf-ldapext-ldap-c-api-03.txt> + LDAPext discussions, June 1999. [ERRNO] K. Zeilenga, "LDAP C API Error Reporting Extension", INTERNET-DRAFT, <draft-zeilenga-ldap-c-api-errno-00.txt>, June 1999. [KEYW] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. Zeilenga [Page 8] INTERNET-DRAFT LDAP C API Concurrency Extensions 28 September 1999 [LDAP] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. 13. Author's Address Kurt D. Zeilenga OpenLDAP Foundation <Kurt@OpenLDAP.org> This document expires on 28 March 2000. Zeilenga [Page 9] --------------------------------------------------------------------- INTERNET-DRAFT Kurt D. Zeilenga Intended Category: Standards Track OpenLDAP Foundation Extends: draft-ietf-ldapext-ldap-c-api-03.txt Expires: 28 March 2000 28 September 1999 LDAP C API Error Reporting Extension <draft-zeilenga-ldap-c-api-errno-00.txt> 1. Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. This draft document will be submitted to the RFC Editor as a Standards Track document. Distribution of this memo is unlimited. Technical discussion of this document will take place on the IETF LDAP Extension Working Group mailing list <ietf-ldapext@netscape.com>. Please send editorial comments directly to the author <Kurt@OpenLDAP.org>. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. 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.'' The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Copyright 1999, The Internet Society. All Rights Reserved. Please see the Copyright section near the end of this document for more information. 2. Abstract This document defines a manatory extension to the LDAP C API to provide error reporting for all API calls. The mechanism is nonintrusive and can, optionally, support concurrent execution environments. Zeilenga [Page 1] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 The key words ``MUST'', ``MUST NOT'', ``REQUIRED'', ``SHALL'', ``SHALL NOT'', ``SHOULD'', ``SHOULD NOT'', ``RECOMMENDED'', and ``MAY'' in this document are to be interpreted as described in RFC 2119 [KEYW]. 3. Background and Intent of Use The LDAP [LDAP] C API [CAPI] provides an interface which (due to legacy compatibiity issues) does not provide a consistent mechanism for reporting errors. A large number of the calls within the specification have no mechanism to indicate the nature of a failure. The usefulness of a CAPI without a consistent, easy to use, error reporting mechanism is limited. This document defines an mandatory extension to the CAPI. All implementations of the CAPI MUST provide this extension. The extension details additional requirements for error reporting. Implementations MUST fulfill all other CAPI error reporting requirements. 4. Error Handling Extension This extension provides a mechanism that applications MAY use to obtain an LDAP error number indicating the nature of the failure associated with the last failed CAPI call. Implementations MUST provide access to an LDAP error number (CAPI, Section 9) resulting from the last failed CAPI call via the symbol ldap_errno. The last failed CAPI call may be within the global context or within the current execution context. The ldap_errno MUST evaluate to a modifiable lvalue that has type 'int', the value of which is set to a LDAP error number. It is unspecified whether ldap_errno is a macro or an identifier declared with external linkage. If a macro definition is suppressed in order to access an actual object, or a program defines an identifier with the name ldap_errno, the behavior is undefined. Applications MUST access ldap_errno within the same concurrent execution context, commonly a thread, in which the failure occurred. The value of ldap_errno is LDAP_SUCCESS (0) if no API failure has occurred within the supported context and the user has not assigned a value within the supported context. Zeilenga [Page 2] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 Implementations SHALL NOT update the ldap_errno value upon successful CAPI call completion. Implementations providing a current execution context specific ldap_errno MUST advertise the feature LDAP_API_CONTEXT_SPECIFIC_ERRNO as described in Section 6. Implementation of LDAP_API_CONTEXT_SPECIFIC_ERRNO is RECOMMENDED. 4.1. Reporting Server Errors It is not a CAPI failure for a server to return an error number. Implementations SHALL NOT assign error results returned by servers to ldap_errno. 4.2. Implementation Specific Reporting The CAPI specification stated that the caller may obtain an indication of failure of certain calls (see listed below) using implementation specific and/or operating system specific requirements. Implementations are NOT REQUIRED to support any implementation specific and/or operating system mechanism for ANY call detailed by the CAPI specification or its extensions. Affected calls include ldap_init(), ldap_open(), and ber_*(). 4.3. Example The following is an example showing how an application may obtain the error information resulting from a failed CAPI calls: int msgid; LDAP *ld = ldap_init("localhost", 389); if(ld == NULL) { printf("ldap_init failed, ldap_errno=%d (%s)\n", ldap_errno, ldap_err2string(ldap_errno)); printf("unable to initialize LDAP session\n"); return -1; } msgid = ldap_simple_bind(ld, NULL, NULL); if(msgid == -1) { int err = ldap_errno; if (err != LDAP_SUCCESS ) { Zeilenga [Page 3] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 /* API failure */ printf("ldap_simple_bind failure: ldap_errno=%d (%s)\n", err, ldap_err2string(err)); } else { int lderr, rc; printf("ldap_simple_bind failed\n"); rc = ldap_get_option(ld, LDAP_OPT_ERROR_NUMBER, &lderr); if(rc == LDAP_OPT_SUCCESS) { printf(" reason=%d (%s)\n", lderr, ldap_err2string(lderr)); } else { printf("ldap_get_option failed, ldap_errno=%d (%s)\n", ldap_errno, ldap_err2string(ldap_errno)); } } goto unbind; } /* ... */ unbind: if(ldap_unbind(ld) != 0) { printf("ldap_unbind failed, ldap_errno=%d (%s)\n", ldap_errno, ldap_error2str(ldap_errno)); return -1; } return 0; 5. Advertising Features This document REQUIRES that supported features with the name in the form LDAP_API_FEATURE_x be advertised to consumers of the CAPI as follows: SHOULD provide the macro LDAP_API_FEATURE_x with the value of 1000 + revision number of this draft (i.e.: 1000+0 for this 0 revision of the draft). MUST provide the CAPI extension "x" when returning API information upon LDAP_OPT_API_INFO option access, and Zeilenga [Page 4] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 MUST provide feature info for "x" via LDAP_OPT_FEATURE_INFO option mechanism. The feature version provided MUST match the value LDAP_API_FEATURE_x macro where x is replaced appropriately. As implementations may not provide macros for all features, applications SHOULD use LDAP_OPT_API_INFO to determine which features are provided by a given implementation. 6. Changes to the LDAP C API This section provides a summary of changes to the CAPI specification. 6.1. LDAP_API_VERSION LDAP_API_VERSION should be set to the RFC number of this extension if and when it is published as a Standards Track RFC. (see purpose of this draft above). Until such time as this document is published as an RFC, implementations should use the value specified by CAPI plus 100 + 10 * the number of this draft. For the third draft of CAPI and this 0 revision of draft, the value of 2103 ((2000+3) + (100+10*0)) should be used. 6.2. New Symbols This extension introduces two new symbols: LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO ldap_errno LDAP_API_FEATURE_CONTEXT_SPECIFIC_ERRNO is a macro. ldap_errno MAY be a MACRO. This extension indroductes no new functions, typedefs, or structure names. 6.3. Implementation/System Specific Error Handling This extensions removes any requirements that implementations to use implementation and/or operating system specific error reporting mechanisms. Zeilenga [Page 5] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 7. Security Considerations None taken, none given. 8. Copyright Copyright 1999, The Internet Society. 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 AUTHORS, 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. 9. Bibliography [CAPI] M. Smith, T. Howes, A. Herron, M. Wahl, A. Anantha, "The C LDAP Application Program Interface", INTERNET-DRAFT, <draft-ietf-ldapext-ldap-c-api-03.txt> + LDAPext discussions, June 1999. [KEYW] S. Bradner, "Key words for use in RFCs to Indicate Requirement Levels", RFC 2119, March 1997. [LDAP] M. Wahl, T. Howes, S. Kille, "Lightweight Directory Access Protocol (v3)", RFC 2251, December 1997. Zeilenga [Page 6] INTERNET-DRAFT LDAP C API Error Reporting Extension 28 September 1999 10. Author's Address Kurt D. Zeilenga OpenLDAP Foundation <Kurt@OpenLDAP.org> This document expires on 28 March 2000. Zeilenga [Page 7]
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