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Edits and notes on client/server time sync.

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git-svn-id: svn+ssh://src.earth.threerings.net/narya/trunk@1397 542714f4-19e9-0310-aa3c-eee0fc999fb1
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Michael Bayne
2002-05-28 21:56:07 +00:00
parent f0d7b8642b
commit f9980f9353
1 changed files with 102 additions and 64 deletions
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Presents Notes -*- outline -*-
* TODO
Pass cause back to client somehow via FailureResponse in Client.requestFailed
- Pass cause back to client somehow via FailureResponse in
Client.requestFailed
clientWillLogff becomes clientMayLogoff?
- clientWillLogff becomes clientMayLogoff?
Look into nbio waking up all sockets when any data comes in.
- Look into nbio waking up all sockets when any data comes in.
(maybe) Allow piggybacking of object subscription onto service defined
responses (like moveTo request).
- (maybe) Allow piggybacking of object subscription onto service defined
responses (like moveTo request).
(maybe) Allow better server side control of subscription management (to
ensure that clients don't remain subscribed to objects they should no
longer be susbcribed to; like scenes they've departed from).
- (maybe) Allow better server side control of subscription management (to
ensure that clients don't remain subscribed to objects they should no
longer be susbcribed to; like scenes they've departed from).
Sort out support for server-side modifiable only fields to DObject.
- Sort out support for server-side modifiable only fields to DObject.
Create a CompoundEvent that allows packaging up of multiple events to be
dispatched in unison. Build dobj source generator and have it add versions
of all update methods that take a compound event to which to append the
event rather than dispatching them directly.
- Create a CompoundEvent that allows packaging up of multiple events to be
dispatched in unison. Build dobj source generator and have it add
versions of all update methods that take a compound event to which to
append the event rather than dispatching them directly.
Maybe make AuthResponseData a Streamable instead of a DObject.
- Maybe make AuthResponseData a Streamable instead of a DObject.
Have the LocationRegistry register the LocationProvider rather than doing
it via a config file. Perhaps lose the config file element altogether.
- Have the LocationRegistry register the LocationProvider rather than
doing it via a config file. Perhaps lose the config file element
altogether.
Think about Subscriber business and whether or not DObject needs a list of
subscribers or if there's a better way to handle removedLastSubscriber()
on the client side and not taint the server side with all dat crap.
- Think about Subscriber business and whether or not DObject needs a list
of subscribers or if there's a better way to handle
removedLastSubscriber() on the client side and not taint the server side
with all dat crap.
* Server-side event concentrator
The client objects will not subscribe directly, but will subscribe through
the concentrator so that, at least, it can create a single
ForwardEventNotification for each Event being dispatched to a group of
clients. Optimally, it would be able to flatten that notification as well
and the byte array can be written to the socket of each of the individual
clients rather than creating a separate byte array for each client. This
will require a special "flattened notification" that can be inserted into
the queue to preserve message ordering but then is simply sent rather than
flattened and sent.
- The client objects will not subscribe directly, but will subscribe
through the concentrator so that, at least, it can create a single
ForwardEventNotification for each Event being dispatched to a group of
clients. Optimally, it would be able to flatten that notification as
well and the byte array can be written to the socket of each of the
individual clients rather than creating a separate byte array for each
client. This will require a special "flattened notification" that can be
inserted into the queue to preserve message ordering but then is simply
sent rather than flattened and sent.
* Marshaller
Consider how the dobject marshaller deals with classes loaded and reloaded
using flushable classloaders.
- Consider how the dobject marshaller deals with classes loaded and
reloaded using flushable classloaders.
Also consider whether access to the marshaller cache needs to be
synchronized.
Also consider whether access to the marshaller cache needs to be
synchronized.
* Check into "connection closed by peer" thread exiting on client
* TypedObjectFactory
Maybe modify so that types are assigned automatically even if everything
has to be registered in a single place, since it pretty much does anyway.
- Maybe modify so that types are assigned automatically even if everything
has to be registered in a single place, since it pretty much does
anyway.
* Client network mgmt
Client perform all network ops on own thread, will call back to main code
through Observer interface to notify of state changes in the
authentication process/connectedness:
- Client perform all network ops on own thread, will call back to main
code through Observer interface to notify of state changes in the
authentication process/connectedness:
public interface ClientObserver
{
public void didConnect ();
public void connectionFailed ();
public void didLogon ();
public void logonFailed ();
public void didDisconnect ();
public void didLogoff ();
}
public interface ClientObserver
{
public void didConnect ();
public void connectionFailed ();
public void didLogon ();
public void logonFailed ();
public void didDisconnect ();
public void didLogoff ();
}
* DObject class generation
Distributed objects are defined like a class with a set of public data
members which is then converted into an actual class with get/set methods
for each member.
- Distributed objects are defined like a class with a set of public data
members which is then converted into an actual class with get/set
methods for each member.
public dclass GameObject
{
public int[] players;
public String description;
}
public dclass GameObject
{
public int[] players;
public String description;
}
becomes
becomes
public class GameObject extends DObject
{
public void setPlayers (int[] players);
public void setPlayersAt (int index, int value);
public int[] getPlayers ();
public int getPlayersAt (int index);
public class GameObject extends DObject
{
public void setPlayers (int[] players);
public void setPlayersAt (int index, int value);
public int[] getPlayers ();
public int getPlayersAt (int index);
public void setDescription (String description);
public String getDescription ();
}
public void setDescription (String description);
public String getDescription ();
}
* 5/27/2002
** Synchronizing time between client and server
- After authentication, client begins a process of establishing the time
differential between the client clock and the server clock.
- The client sends a PING packet, noting the time immediately prior to
delivering the packet over the network.
- The server notes the at which the PING packet was unserialized. It
supplies that time to the constructed PONG packet which then notes the
time immediately prior to serialization and uses that to deliver to the
client the server time and the number of milliseconds that passed
between the unserialization of the PING packet and the serialization
(and subsequent network delivery) of the PONG packet.
- The client can then subtract the server processing time from the total
round trip delay, divide the round trip delay by two, adjust the server
time stamp accordingly and then obtain the client/server time
differential.
- The client then repeats this process some small number of times (five)
to attempt to account for spurious differences in upstream
vs. downstream transmission times and finally settles on a dT that will
be used for the duration of the session.
- We assume that the session will not last long enough for clock drift on
either the client or server to become significant when compared to the
error in the original time differential measurement.
- We'll want to use the high-precision timing services once we have those
because we don't want unnecessary error introduced into our ping and
pong time stamps by the unreliable granularity of
System.currentTimeMillis().