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Subject: Prelim minutes of 11/25 meeting
The prelim minutes are attached. Please give comments befor the weekend. -- ---------------------------------------------------- Tom Rutt email: firstname.lastname@example.org; email@example.com Tel: +1 732 801 5744 Fax: +1 732 774 5133Title: Draft Agenda to WSRM TC Conference Call – May 06, 2003
Prelim Minutes WSRM TC Conference Call –
The meeting of the WSRM TC took place by teleconference
Tuesday Nov 25, from to 6:30 PM Eastern Standard Time
(UTC - 5)
WSRM Meeting - Conference call Dial-in numbers:
Toll Free: 1-800-361-5659
International: 1-913 312 4155
<![if !supportLists]>0 <![endif]>Draft Agenda:
Draft Agenda to WSRM TC Conference Call –
1 Roll Call (late arrival no longer counts by OASIS rules)
2 Minutes Discussion
2.1 Appointment of Minute Taker
2.2 Approval of previous meeting minutes
3 Discussion of Vote for CD .52
4 Discussions of Issues
<![if !supportLists]>1 <![endif]>Roll Call
Meeting is quorate.
<![if !supportLists]>2 <![endif]>Minutes Discussion
<![if !supportLists]>2.1 <![endif]>Appointment of Minute Taker
Tom Rutt will take minutes.
Minutes need to serve as the only outputs.
<![if !supportLists]>2.2 <![endif]>Approval of previous meeting minutes
Jishnu moved to accept the 11/18 minutes. Sunil seconded.
No opposition, 11/18 minutes approved.
<![if !supportLists]>3 <![endif]>Discussion of Vote for .52 CD
82% of voting members has responded yes.
We will have a committee a CD at .
The reason was to legitimize the demo.
Sunil stated he did not want a public announcement.
The demo will serve as the publicity.
Keep inside committee.
After the vote, Iwasa will take document, and change the name to committee draft .52.
<![if !supportLists]>4 <![endif]>Discussion of Issues
<![if !supportLists]>4.1 <![endif]>Rel 33
Jacques new proposal from email:
My proposal for Rel33:
- We need first to define "delivery" of a message (also needed for other RM features):
"action of transferring the responsibility to process further a message,
from the RMP and onto the next processor entity. This action marks
the end of the RMP processing for this message. The time at which this action
occurs must be clearly identifiable so that the next message processor
can always establish in which order two deliveries are made.
Examples of delivery are: pushing the message in a queue accessible by an application,
calling back an application component, storing the message in a database where
it is accessible by the next processor."
Then the Ack semantics is simply:
"An acknowledgement is sent for a message or made available to its Sender
after the delivery action is successful and complete for this message."
So its aligned with (4) from Sunil below:
1) "make it available to the application/user".
2) "make it available to the next layer".
3) "RMP passing responsibility for the message to the user"
[I copied this from the Tom's meeting minutes as Pete W. saying so]
4) "Transferring the responsibility to the next layer".
[i vaguely recollect someone saying it in the call.]
Sunil stated he is happy with it.
Jacques moved to accept this proposal, above to resolve Rel 33. Sunil seconded.
No opposition motion passes.
<![if !supportLists]>4.1 <![endif]>Rel 50: Semantics of ExpiryTime:
Jacques email (with edits from discussions):
Rel 50: (solution c) Semantics of ExpiryTime:
ExpiryTime indicates the ultimate date after which the receiver RMP MUST
NOT deliver a received message to the application.
After a message has been sent for the first time, ExpiryTime in a message
MUST NOT be modified in any case by the Sender, when resending the message:
two messages with same ID (duplicates) MUST have same ExpiryTime.
When a message expires on the Sender side before being sucessfully sent,
a Sender RMP MUST NOT send it or resend it, and must communicate a delivery failure
to the Sender application.
- Given the above definition of ExpiryTime, in case duplicate elimination is required,
when a received message is processed, it is sufficient to only check for its duplicates
among IDs of past messages that have not expired yet at the time of the duplicate check.
Jacques moved to resolve issue Rel 50 with the above proposal. Sunil seconded.
No opposition, motion passes.
<![if !supportLists]>4.2 <![endif]>Rel 52: (New rules for persistence)(also, related "timing issues")
Jacques Email from Nov 20:
Rel 52: (Solution c)(New rules for persistence, also, related "timing issues")
Q1: When can a recipient "forget" about a sequence?
How long must an out-of-order message be stored prior to giving up on
ever delivering it to the application?
Answer: see Rel57.
Q2: How do these time windows relate to the TTL (expiration) of an individual message?
Answer: see Rel50 and Rel57.
Q3: Within what window will a duplicate be detected?
[Short Answer:] duplicates will be detected over all non-expired messages.
Since by definition, messages that are expired before the RMP processing is over
will not be made available to the application, and because ExpiryTime is identical across
duplicates, there is no risk ever to deliver two duplicates to the receiver application,
when restricting the duplicate check over the IDs of non-expired messages.
General rule for persisting the ID of a message:
The duplicate elimination feature requires persisting the message ID
(GroupId and optionally the Sequence Number), after the message
has been processed and delivered (made available) to the application.
The general rule about message ID persistence, is that an RMP
MUST persist the ID of a message at least until the message expires
regardless whether the message has been delivered or not to the application.
It is RECOMMENDED that an RMP removes the ID of a singleton message
(message with GroupId but no SequenceNumber) from its persistent store after it expires.
However, unlike for singletons, it is RECOMMENDED to NOT remove the ID of a message that
belongs to a non-singleton group, when the message expires. The reason is, message IDs
for groups can be stored efficiently as intervals of integers.
NOTE: For groups, duplicate checks may be made over all past messages of the group,
whether expired or not, without loss of performance. The check will in fact be faster,
because not discarding expired IDs means fewer intervals to look up.
General rules for terminating a group, and for removing the state of a group:
NOTE: these termination rules apply to both ordered and unordered groups.
NOTE: In all termination cases (t1, t2, t3, t4) below, it is not necessary to remember
the ExpiryTime of all messages of a group, as only the maximum of all ExpiryTime values
NOTE:Termination of a group, and removal of its state are two distinct events.
- When a group terminates, both in sender and receiver, no message is expected to be
sent or received for this group anymore. If a message is received after the
termination of a group, with same GroupId as the terminated group, it is considered
by the Receiver as belonging to a new group (the Receiver is not required
to verify that a new GroupId value has not already been used in a previous group,
as this test is impractical).
- When the state of a group is removed, any trace of the group (including status, groupId,
current sequence number, as well as all received message IDs for the group
e.g. SequenceNumber intervals) are removed, and therefore not available anymore for
duplicate checks. State removal may occur either at termination time or later,
depending on the following rules.
Triggering event: GroupExpiryTime is over.
Receiver side: The RMP MUST NOT accept any new message for this group and MUST
terminate the group. It is RECOMMENDED that its state be removed as soon as possible.
No duplicate check needs to be done against that group ever. If a "late duplicate" arrives,
it would never be delivered to the application, as its ExpiryTime, which is always earlier
than GroupExpiryTime, would have expired.
Sender side: The group MUST be terminated, and its state removed from the RMP.
Triggering event: GroupMaxIdleTime is over.
Receiver side: Except for an ordered group that is out-of-order (see this case in Rel52),
the group MUST be terminated. But unlike (t1), some of its
past messages may not have expired yet, and therefore their ID still be needed
for duplicate checks. If we define max(all ExpiryTime) as the max of all ExpiryTimes
of messages already received for a group, an RMP MUST persist the state of a group
even after termination of the group, at least until max(all ExpiryTime), in case
duplicate elimination is required.
Sender side: The group MUST be immediately terminated, and its state is removed from the RMP
when either (1) the time elapsed since the last sent message (including retries) exceeds
GroupMaxIdleTime, or (2) for an ordered group, a message has failed to be successfully
delivered (as described in Rel 57), whichever occurs first.
Triggering event: the RMP receives a status="end" message. The group had either
GroupExpiryTime or GroupMaxIdleTime specified.
Note that such an event only tells that "no greater seq number will ever be received after",
but late messages may still arrive for this group.
Subcase t3.1: The group was complete on receiver side.
Receiver side: The group MUST be terminated.
However, its state is removed according to (t1) or (t2), depending which termination
criterion was given.
Sender side: The group is also known to be complete, and MUST be terminated.
However, if guaranteed delivery was required, all sent messages must either have been
acknowledged, or been faulted, before termination.
Subcase t3.2: The group was not complete on receiver side.
Then the receiver RMP and sender RMP MUST apply rules of (t1) or (t2), depending which one
of GroupExpiryTime or GroupMaxIdleTime was specified.
Triggering event: the RMP receives a status="end" message. The group had neither
GroupExpiryTime nor GroupMaxIdleTime specified.
Subcase t4.1: The group was complete on receiver side.
Receiver side: The group MUST be terminated. The date of removal of its state
is based on rules for (t2).
Sender side: see subcase t3.1 above.
Subcase t4.2: The group was not complete on receiver side.
This event, by itself, does not cause the termination of the group.
There was no time to discuss the details of this proposal. It is left for further email discussion on how many parameters are required.
<![if !supportLists]>4.3 <![endif]>Rel 57: Ordering and Missing Message Behavior
Jacques mail from Nov 20::
Rel 57: (Solution c) Ordering and Missing Message Behavior
the RMP will wait until expiration of the earliest ExpiryTime of the
out-of-order messages. All subsequent out-of-order messages will then be discarded.
However, a shortage in storage resources may lead to discard out-of-order
messages before the group terminates.
Given the definition of Guaranteed Ordered Delivery, a message must not be delivered
to the receiver application if not all previous messages were.
Therefore in case a Receiver RMP decides to not wait any longer for a missing
message, the already received out-of-order messages for the group MUST not be delivered
to the application, and can be discarded.
[NOTE 1: we could have discarded only the "subsequent" messages - i.e. with greater
seq numbers than the one expired. Indeed, "previous" out-of-order messages still have
a chance to be delivered to the app when the missing message arrives,
but the group is broken anyway, and future messages will not be accepted.
In addition, the fact that a pending message expires makes it likely that the
missing message also expires soon. So there is little benefit in keeping the prior
messages to the expired one. In addition, that makes the RMP implementation more complex.]
On the Receiver side, as soon as the earliest ExpiryTime of pending (stored)
out-of-order messages has expired, all the pending and future out-of-order messages,
MUST not be delivered to the application.
The RMP MUST terminate the out-of-order group as early as convenient after this date,
and out-of-order messages must be discarded.
(see Rel 52 for definition of group temination)
When sending messages for an ordered group, the Receiver MAY decide to NOT resend a
non-acknowledged message before all the previous messages with smaller sequence numbers
have been acknowledged. It MAY also decide to resend a non-acknowledged message
only when the total number of non-acknowledged messages is below a threshold that
is implementation dependent.
On the Sender side, the RMP MUST terminate an ordered group as early as possible after
one of these events occurs, whichever comes first:
(1) a message for the group has not been acknowledged after the last retry plus a
buffer time (e.g. retryinterval).
(2)the ExpiryTime of a message to be sent or resent for the group, has expired before
the message has been acknowledged.
Deciding that a message has "Not been acknowledged" must require a failed poll request
from the Sender, in case the reply pattern is "poll", or must exhaust the expected
delay in receiving a multiple-acknowledgement.
NOTE 2: discarding of out-of-order messages of a group, and more generally terminating a
group, does not mean yet the removal of the group state, as message IDs may still
be needed for duplicate checks.
Sunil: The decision of discard out of order sequence is only using the expiry time of individual messages.
This is not the only criteria to end sequence of group. The group expiry time can occur while out of order sequence is waiting.
Jacques, if expiry time is earlier of group, then the only problem is for group max idle time.
Rel 57 might need a bit more work.
Bob F: this wording made expiry time the dominant parameter for storage. If we are going to be throwing things ouf for expiry time, what would the group expiry time add.
Max Idle time: message waiting with expiry before max idle, can end up with same conundrum, max idle must
Be set that none expires while the idle time is being waited for.
Bob F: Consider, utilize only expiry times for the management of groups.
Tom R: Is there a requirement for the additional control of max Idle or group expiry
Doug B: I am having trouble understanding. I have trouble with a gap between messages resulting in error. We have a general problem if, we allow the sender to stop retrying after the first attempt, the sender could think the messages are lost when they have made it to the other end.
Jacques, in control of receiver, but not acked, the sender is in the dark on out of order messages. This is not an issue, the first missing message has not been acked, that is why the sequence is out of order, all the subsequent might or might not have arrived. The sender must assume that all are lost. However it should resend the first message until it is acked. There is a caveat on that, always possible message has been delivered while the sender has not received ack.
It is always possible that a message has been well received, but the sender has not been acked.
A more serious misunderstanding, which we can prevent, is that they think it has been delivered but in fact it has not been delivered.
Doug has problem why anyone can discern between lost message and lost ack. Sender must behave as if it has not happened.
Jacques: agree sender should consider message as lost. However it as received before, the protocol should work.
Tom: the use of expiry time only, would require that it be monotonic. This was considered to be too strong.
Bob F : conditions. If we did not have messageExpiry, but only group expiry this has problem. The problem with setting group expiry time for an idle interval, is that these time depend on what the message expiry time is. The cases of one greater than another is on case. Other errors and complexity are added by each parameter.
Jacques: I wish we could make bare boned simple. Expiry time at message level is needed. However, a group is open, an rmp has to manage state for this group. If the group is not active for a long time, you still have to decide when to get rid of the group.
Bob F: why to we need to retain group state.
Jacques. We need for duplicate elimination.
Tom: should we add a new enum to the status for the group: “destroy group”.
Rell 52 and Rel 57 are too new to vote on.
How many parameters do we really need.
We need expiry time for each message.
Do we need other group parameters, to simplify matters (e.g. to not require imposing monotonic expiry time)
We are making assumptions, I would like to keep it open as much as possible.
Jacques. If the user does not specify any of these parameters, they must use the end to stop the group. This needs more discussion.
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