Sequence ID calibration for mis-ordered requests
draft-mzhang-nfsv4-sequence-id-calibration-01

Network File System Version 4                              M. Zhang, Ed.
Internet-Draft                                              J. Yang, Ed.
Intended status: Standards Track                         C. Tangudu, Ed.
Expires: 9 September 2023                             K. Parambattu, Ed.
                                                 Huawei Technologies Co.
                                                            8 March 2023

            Sequence ID calibration for mis-ordered requests
             draft-mzhang-nfsv4-sequence-id-calibration-01

Abstract

   This document updates RFC8881, Network File System (NFS) version 4
   minor version 1, by adding two operations to prevent the client from
   destroying session when getting the reply of a mis-ordered request
   with NFS4ERR_SEQ_MISORDERED.

   In NFSv4 minor version 1, sequence ID is used to ensure that the size
   of the needed reply cache is tightly bounded.  If the server gets a
   mis-ordered request, the client will often break the session and
   establish a new session with the server.  This approach results in a
   significant burden on the client and the server.  During the process
   of session rebuilding, IO performance will be affected.  This is
   especially troublesome when network latency is substantial, as, for
   example when client and server are in different locations.  This
   document will propose extensions to NFSv4 that would allow client
   reconnection to be dispensed with.

Requirements Language

   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 RFC 2119 [RFC2119].

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at https://datatracker.ietf.org/drafts/current/.

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   Internet-Drafts are draft documents valid for a maximum of six months
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   This Internet-Draft will expire on 9 September 2023.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Operations for Seqence ID calibration . . . . . . . . . . . .   4
     2.1.  Operation 59: SEQENCE_QUERY-Query sequence ID of designated
           session and slot for calibration  . . . . . . . . . . . .   4
       2.1.1.  ARGUMENTS . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.2.  RESULTS . . . . . . . . . . . . . . . . . . . . . . .   4
       2.1.3.  DESCRIPTION . . . . . . . . . . . . . . . . . . . . .   4
       2.1.4.  IMPLEMENTATION  . . . . . . . . . . . . . . . . . . .   5
     2.2.  Operation 15:CB_SEQUENCE_QUERY- Query backchannel sequence
           ID of designated session and slot for calibration . . . .   6
       2.2.1.  ARGUMENT  . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.2.  RESULT  . . . . . . . . . . . . . . . . . . . . . . .   6
       2.2.3.  DESCRIPTION . . . . . . . . . . . . . . . . . . . . .   6
       2.2.4.  IMPLEMENTATION  . . . . . . . . . . . . . . . . . . .   7
   3.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   4.  Security Considerations . . . . . . . . . . . . . . . . . . .   8
   5.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   8
   6.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
     6.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     6.2.  Informative References  . . . . . . . . . . . . . . . . .   8
   Appendix A.  An Appendix  . . . . . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

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1.  Introduction

   In NFSv4 minor version 1, according to RFC 8881, Error code
   NFS4ERR_SEQ_MISORDERED is returned by three operations.

   *  The first operation is CREATE_SESSION. csa_sequence is one
      argument of this operation, which is used for serializing
      CREATE_SESSION via a per-client ID sequence number by the client.
      In CREATE_SESSION request, csa_sequence should be equal to ether
      the sequence ID in the client ID's slot(a retry), or the slot's
      sequence ID + 1(correct normal request).  Otherwise,
      NFS4ERR_SEQ_MISORDERED will be returned from the server.

   *  The second operation is SEQUENCE. sa_sequenceid is one argument of
      this operation.  In SEQUENCE request, If the difference between
      sa_sequenceid and the server's cached sequence ID at the slot ID
      is two (2) or more, or if sa_sequenceid is less than the cached
      sequence ID (accounting for wraparound of the unsigned sequence ID
      value), then the server MUST return NFS4ERR_SEQ_MISORDERED.

   *  The third operation is CB_ SEQUENCE, which is similar to SEQUENCE.
      csa_sequenceid is one argument of this operation.  In CB_ SEQUENCE
      request, If the difference between csa_sequenceid and the client's
      cached sequence ID at the slot ID is two (2) or more, or if
      csa_sequenceid is less than the cached sequence ID (accounting for
      wraparound of the unsigned sequence ID value), then the client
      MUST return NFS4ERR_SEQ_MISORDERED.

   Mis-order requests may happen as a result of network partition,
   software bug, etc.  For such request, the operations subsequent to
   SEQUENCE, if any, are not processed, and so slots state (sequence ID,
   cached reply) are not changed.  That means, requests before this mis-
   ordered one were processed correctly and the session state was
   correct.  In the current implementation, for most of the clients,
   this error code will trigger the requester breaking the session and
   creating a new session.  This process unacceptably interferes with
   ongoing IO operations, especially for the IOs on the normal slots.

   For example of a persistent session, there are several slots on a
   session.  Requests on the slots are being processed correctly and
   replies are being received normally.  Suppose on one slot of them, a
   mis-ordered request is received by the server and a response with
   NFS4ERR_SEQ_MISORDERED error returns to the client.  Then, the client
   is going to destroy the session and establish a new session.  Before
   the new session is ready, new requests will not be performed until
   the pending operations finished.  The effects on IOs of normal slots
   will become dramatic especially in network latency is substantial,
   as, for example when client and server are in different locations.

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   The client has to break the session because it does not know what
   sequence is expected for that session and slot.  This current cached
   sequence information would be available to the client eliminating any
   need to break the session.

   Two operations, SEQENCE_QUERY and CB_SEQENCE_QUERY, are added to
   query sequence ID cached when getting NFS4ERR_SEQ_MISORDERED error.

2.  Operations for Seqence ID calibration

2.1.  Operation 59: SEQENCE_QUERY-Query sequence ID of designated
      session and slot for calibration

2.1.1.  ARGUMENTS

   struct SEQUENCE_QUERY4args {

   sessionid4 sqa_sessionid;

   slotid4 sqa_slotid;

   };

2.1.2.  RESULTS

   struct SEQUENCE_QUERY4resok {

   sessionid4 sqr_sessionid;

   slotid4 sqr_slotid;

   sequenceid4 sqr_sequenceid;

   };

   union SEQUENCE_QUERY4res switch (nfsstat4 sqr_status) {

   case NFS4_OK: SEQUENCE_QUERY4resok sqr_resok4;

   default: void;

   };

2.1.3.  DESCRIPTION

   The SEQUENCE_QUERY operation is used by the client to query sequence
   ID cached for designated session and slot.

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   SEQUENCE_QUERY MUST appear as the sole operation type of any COMPOUND
   in which it appears.  Multiple SEQUENCE_QUERY operations can be used
   in one COMPOUND to query multiple sequence IDs cached for multiple
   slots.  The error NFS4ERR_NOT_ONLY_OP will be returned when that
   constraint is not met.  Operations other than SEQUENCE,
   SEQENCE_QUERY, BIND_CONN_TO_SESSION, EXCHANGE_ID, CREATE_SESSION, and
   DESTROY_SESSION, MUST NOT appear as the first operation in a
   COMPOUND.

   If SEQUENCE_QUERY is received on a connection not associated with the
   session via CREATE_SESSION or BIND_CONN_TO_SESSION, and connection
   association enforcement is enabled (see Section 18.35), then the
   server returns NFS4ERR_CONN_NOT_BOUND_TO_SESSION.

   The sqa_sessionid argument identifies the session to which this
   request applies.  The sqr_sessionid result MUST equal sqa_sessionid.

   The sqa_slotid argument is the index in the reply cache for the
   request.  The sqr_slotid result MUST equal sqa_slotid.

   The sqr_sequenceid field is the cached sequence ID on the slot.  The
   client SHOULD use this value to calibrate sa_sequenceid in the next
   SEQUENCE operation, that is, sqr_sequenceid+1 SHOULD be used as the
   sequence ID of the next request on this slot.

2.1.4.  IMPLEMENTATION

   For CREATE_SESSION, SEQUENCE operations, if the sequence ID in the
   request is mis-ordered(see RFC8881 18.46.3 Section), the replier will
   fail the request by NFS4ERR_SEQ_MISORDERED and keep the reply cache
   unchanged on the slot of this session.  When getting
   NFS4ERR_SEQ_MISORDERED error code in the response, the client SHOULD
   query the cached sequence ID of the slot and session by
   SEQUENCE_QUERY to calibrate its sequence ID for the subsequent
   requests.  That is, the sequence ID in next request on this slot
   SHOULD be sqr_sequenceid+1.

   SEQUENCE_QUERY will leave the state of the slot (sequence ID, cached
   reply) unchanged and lease of state related to the client ID not
   renewed.

   If the client is querying an unknown session ID to the server, the
   server SHOULD return NFS4ERR_BADSESSION in the response.

   If the client is attempting to access a slot the replier does not
   have in its slot table (It is possible the slot may have been
   retired), NFS4ERR_BADSLOT SHOULD be returned in the response.

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2.2.  Operation 15:CB_SEQUENCE_QUERY- Query backchannel sequence ID of
      designated session and slot for calibration

2.2.1.  ARGUMENT

   struct CB_SEQUENCE_QUERY4args {

   sessionid4 csqa_sessionid;

   slotid4 csqa_slotid;

   };

2.2.2.  RESULT

   struct CB_SEQUENCE_QUERY4resok {

   sessionid4 csqr_sessionid;

   slotid4 csqr_slotid;

   sequenceid4 csqr_sequenceid;

   };

   union CB_SEQUENCE_QUERY4res switch (nfsstat4 csqr_status) {

   case NFS4_OK: CB_SEQUENCE_QUERY4resok csqr_resok4;

   default: void;

   };

2.2.3.  DESCRIPTION

   CB_SEQUENCE_QUERY is used to calibrate sequence ID of the call back
   request of the server for the backchannel of the session.

   For each CB_COMPOUND request, the first operation MUST be CB_SEQUENCE
   or CB_SEQUENCE_QUERY.  If any other operation is in the first
   position of CB_COMPOUND except CB_SEQUENCE_QUERY and CB_SEQUENCE,
   NFS4ERR_OP_NOT_IN_SESSION MUST be returned.

   If the first operation is CB_SEQUENCE, CB_SEQUENCE MUST appear once.
   The error NFS4ERR_SEQUENCE_POS MUST be returned when CB_SEQUENCE is
   found in any position in a CB_COMPOUND beyond the first.  If the
   first operation of a CB_COMPOUND is CB_SEQUENCE_QUERY,
   CB_SEQUENCE_QUERY MUST be the sole operation type.  There can be

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   multiple CB_SEQUENCE_QUERY in this CB_COMPOUND to request multiple
   cached sequence IDs of designated sessions and slots.  If any other
   operations are found in this CB_COMPOUND, NFS4ERR_NOT_ONLY_OP MUST be
   returned.

   The csqa_sessionid argument identifies the session to which this
   request applies.  The csqr_sessionid result MUST equal
   csqa_sessionid.

   The csqa_slotid argument is the index in the reply cache for the
   request.  The csqr_slotid result MUST equal sqa_slotid.

   The csqr_sequenceid field is the cached sequence ID on the slot.  The
   server SHOULD use this value to calibrate csa_sequenceid in the next
   SEQUENCE operation, that is, csqr_sequenceid+1 SHOULD be used as the
   sequence ID of the next request on this slot.

2.2.4.  IMPLEMENTATION

   For CB_SEQUENCE operations, if the sequence ID in the call back
   request is mis-ordered(see RFC8881 20.9 Section), the client will
   fail this request by NFS4ERR_SEQ_MISORDERED and keep the reply cache
   unchanged on the slot of this session.  When getting
   NFS4ERR_SEQ_MISORDERED error code in the response, the server SHOULD
   query the cached sequence ID of the slot and session by
   CB_SEQUENCE_QUERY to calibrate its sequence ID for the subsequent
   requests.  That is, the sequence ID in next call back request on this
   slot should be csqr_sequenceid+1.  CB_SEQUENCE_QUERY will leave the
   state of the slot (sequence ID, cached reply) unchanged and the reply
   of CB_SEQUENCE_QUERY will not renew the lease of state related to the
   client ID on the server side.

   If the server is querying an unknown session ID to the client, the
   client SHOULD return NFS4ERR_BADSESSION in the response.

   If the server is attempting to access a slot the client does not have
   in its slot table (It is possible the slot may have been retired),
   NFS4ERR_BADSLOT SHOULD be returned in the response.

3.  IANA Considerations

   This memo includes no request to IANA.

   Note to RFC Editor: this section may be removed on publication as an
   RFC.

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4.  Security Considerations

   All considerations from RFC 8881 security relative sections
   [RFC8881].

5.  Acknowledgements

   The authors would like to acknowledge David Noveck for reviews of the
   various versions of the draft.

6.  References

6.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC8881]  Noveck, D., Ed. and C. Lever, "Network File System (NFS)
              Version 4 Minor Version 1 Protocol", RFC 8881,
              DOI 10.17487/RFC8881, August 2020,
              <https://www.rfc-editor.org/info/rfc8881>.

6.2.  Informative References

Appendix A.  An Appendix

Authors' Addresses

   Zhang Mingqian (editor)
   Huawei Technologies Co.
   China
   Email: zhangmingqian.zhang@huawei.com

   Yang Jing (editor)
   Huawei Technologies Co.
   China
   Email: yangjing8@huawei.com

   Sai Chakravarthy Tangudu (editor)
   Huawei Technologies Co.
   India
   Email: sai.chakravarthy.tangudu@huawei.com

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   Rijesh Kunhi Parambattu (editor)
   Huawei Technologies Co.
   India
   Email: rijesh.kunhi.parambattu@huawei.com

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