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From Alex Plehanov <plehanov.a...@gmail.com>
Subject Re: Thin client: compute support
Date Thu, 28 Nov 2019 07:02:50 GMT
> Since all thin client operations are inherently async, we should be able
to cancel any of them
It's illogical to have such ability. What should do cancel operation of
cancel operation? Moreover, sometimes it's dangerous, for example, create
cache operation should never be canceled. There should be an explicit set
of processes that we can cancel: queries, transactions, tasks, services.
The lifecycle of services is more complex than the lifecycle of tasks. With
services, I suppose, we can't use request cancelation, so tasks will be the
only process with an exceptional pattern.

> The request would be "execute task with specified node filter" - simple
and efficient.
It's not simple: every compute or service request should contain complex
node filtering logic, which duplicates the same logic for cluster API.
It's not efficient: for example, we can't implement forPredicate()
filtering in this case.


ср, 27 нояб. 2019 г. в 19:25, Pavel Tupitsyn <ptupitsyn@apache.org>:

> >  The request is already processed (task is started), we can't cancel the
> request
> The request is not "start a task". It is "execute task" (and get result).
> Same as "cache get" - you get a result in the end, we don't "start cache
> get" then "end cache get".
>
> Since all thin client operations are inherently async, we should be able to
> cancel any of them
> by sending another request with an id of prior request to be cancelled.
> That's why I'm advocating for this approach - it will work for anything, no
> special cases.
> And it keeps "happy path" as simple as it is right now.
>
> Queries are different because we retrieve results in pages, we can't do
> them as one request.
> Transactions are also different because client controls when they should
> end.
> There is no reason for task execution to be a special case like queries or
> transactions.
>
> >  we always need to send 2 requests to server to execute the task
> Nope. We don't need to get nodes on client at all.
> The request would be "execute task with specified node filter" - simple and
> efficient.
>
>
> On Wed, Nov 27, 2019 at 4:31 PM Alex Plehanov <plehanov.alex@gmail.com>
> wrote:
>
> > >  We do cancel a request to perform a task. We may and should use this
> to
> > cancel any other request in future.
> > The request is already processed (task is started), we can't cancel the
> > request. As you mentioned before, we already do almost the same for
> queries
> > (close the cursor, but not cancel the request to run a query), it's
> better
> > to do such things in a common way. We have a pattern: start some process
> > (query, transaction), get id of this process, end process by this id. The
> > "Execute task" process should match the same pattern. In my opinion,
> > implementation with two-way requests is the best option to match this
> > pattern (we can even reuse OP_RESOURCE_CLOSE operation type in this
> case).
> > Sometime in the future, we will need two-way requests for some other
> > functionality (continuous queries, event listening, etc). But even
> without
> > two-way requests introducing some process id (task id in our case) will
> be
> > closer to existing pattern than canceling tasks by request id.
> >
> > > So every new request will apply those filters on server side, using the
> > most recent set of nodes.
> > In this case, we always need to send 2 requests to server to execute the
> > task. First - to get nodes by the filter, second - to actually execute
> the
> > task. It seems like overhead. The same will be for services. Cluster
> group
> > remains the same if the topology hasn't changed. We can use this fact and
> > bind "execute task" request to topology. If topology has changed - get
> > nodes for new topology and retry request.
> >
> > вт, 26 нояб. 2019 г. в 17:44, Pavel Tupitsyn <ptupitsyn@apache.org>:
> >
> > > >  After all, we don't cancel request
> > > We do cancel a request to perform a task. We may and should use this to
> > > cancel any other request in future.
> > >
> > > > Client uses some cluster group filtration (for example forServers()
> > > cluster group)
> > > Please see above - Aleksandr Shapkin described how we store
> > > filtered cluster groups on client.
> > > We don't store node IDs, we store actual filters. So every new request
> > will
> > > apply those filters on server side,
> > > using the most recent set of nodes.
> > >
> > > var myGrp = cluster.forServers().forAttribute("foo"); // This does not
> > > issue any server requests, just builds an object with filters on client
> > > while (true) myGrp.compute().executeTask("bar"); // Every request
> > includes
> > > filters, and filters are applied on the server side
> > >
> > > On Tue, Nov 26, 2019 at 1:42 PM Alex Plehanov <plehanov.alex@gmail.com
> >
> > > wrote:
> > >
> > > > > Anyway, my point stands.
> > > > I can't agree. Why you don't want to use task id for this? After all,
> > we
> > > > don't cancel request (request is already processed), we cancel the
> > task.
> > > So
> > > > it's more convenient to use task id here.
> > > >
> > > > > Can you please provide equivalent use case with existing "thick"
> > > client?
> > > > For example:
> > > > Cluster consists of one server node.
> > > > Client uses some cluster group filtration (for example forServers()
> > > cluster
> > > > group).
> > > > Client starts to send periodically (for example 1 per minute)
> long-term
> > > > (for example 1 hour long) tasks to the cluster.
> > > > Meanwhile, several server nodes joined the cluster.
> > > >
> > > > In case of thick client: All server nodes will be used, tasks will be
> > > load
> > > > balanced.
> > > > In case of thin client: Only one server node will be used, client
> will
> > > > detect topology change after an hour.
> > > >
> > > >
> > > > вт, 26 нояб. 2019 г. в 11:50, Pavel Tupitsyn <ptupitsyn@apache.org>:
> > > >
> > > > > >  I can't see any usage of request id in query cursors
> > > > > You are right, cursor id is a separate thing.
> > > > > Anyway, my point stands.
> > > > >
> > > > > > client sends long term tasks to nodes and wants to do it with
> load
> > > > > balancing
> > > > > I still don't get it. Can you please provide equivalent use case
> with
> > > > > existing "thick" client?
> > > > >
> > > > >
> > > > > On Mon, Nov 25, 2019 at 11:59 PM Alex Plehanov <
> > > plehanov.alex@gmail.com>
> > > > > wrote:
> > > > >
> > > > > > > And it is fine to use request ID to identify compute tasks (as
> we
> > > do
> > > > > with
> > > > > > query cursors).
> > > > > > I can't see any usage of request id in query cursors. We send
> query
> > > > > request
> > > > > > and get cursor id in response. After that, we only use cursor id
> > (to
> > > > get
> > > > > > next pages and to close the resource). Did I miss something?
> > > > > >
> > > > > > > Looks like I'm missing something - how is topology change
> > relevant
> > > to
> > > > > > executing compute tasks from client?
> > > > > > It's not relevant directly. But there are some cases where it
> will
> > be
> > > > > > helpful. For example, if client sends long term tasks to nodes
> and
> > > > wants
> > > > > to
> > > > > > do it with load balancing it will detect topology change only
> after
> > > > some
> > > > > > time in the future with the first response, so load balancing
> will
> > no
> > > > > work.
> > > > > > Perhaps we can add optional "topology version" field to the
> > > > > > OP_COMPUTE_EXECUTE_TASK request to solve this problem.
> > > > > >
> > > > > >
> > > > > > пн, 25 нояб. 2019 г. в 22:42, Pavel Tupitsyn <
> ptupitsyn@apache.org
> > >:
> > > > > >
> > > > > > > Alex,
> > > > > > >
> > > > > > > > we will mix entities from different layers (transport layer
> and
> > > > > request
> > > > > > > body)
> > > > > > > I would not call our message header (which includes the id)
> > > > "transport
> > > > > > > layer".
> > > > > > > TCP is our transport layer. And it is fine to use request ID to
> > > > > identify
> > > > > > > compute tasks (as we do with query cursors).
> > > > > > >
> > > > > > > > we still can't be sure that the task is successfully started
> > on a
> > > > > > server
> > > > > > > The request to start the task will fail and we'll get a
> response
> > > > > > indicating
> > > > > > > that right away
> > > > > > >
> > > > > > > > we won't ever know about topology change
> > > > > > > Looks like I'm missing something - how is topology change
> > relevant
> > > to
> > > > > > > executing compute tasks from client?
> > > > > > >
> > > > > > > On Mon, Nov 25, 2019 at 10:17 PM Alex Plehanov <
> > > > > plehanov.alex@gmail.com>
> > > > > > > wrote:
> > > > > > >
> > > > > > > > Pavel, in this case, we will mix entities from different
> layers
> > > > > > > (transport
> > > > > > > > layer and request body), it's not very good. The same
> behavior
> > we
> > > > can
> > > > > > > > achieve with generated on client-side task id, but there will
> > be
> > > no
> > > > > > > > inter-layer data intersection and I think it will be easier
> to
> > > > > > implement
> > > > > > > on
> > > > > > > > both client and server-side. But we still can't be sure that
> > the
> > > > task
> > > > > > is
> > > > > > > > successfully started on a server. We won't ever know about
> > > topology
> > > > > > > change,
> > > > > > > > because topology changed flag will be sent from server to
> > client
> > > > only
> > > > > > > with
> > > > > > > > a response when the task will be completed. Are we accept
> that?
> > > > > > > >
> > > > > > > > пн, 25 нояб. 2019 г. в 19:07, Pavel Tupitsyn <
> > > ptupitsyn@apache.org
> > > > >:
> > > > > > > >
> > > > > > > > > Alex,
> > > > > > > > >
> > > > > > > > > I have a simpler idea. We already do request id handling in
> > the
> > > > > > > protocol,
> > > > > > > > > so:
> > > > > > > > > - Client sends a normal request to execute compute task.
> > > Request
> > > > ID
> > > > > > is
> > > > > > > > > generated as usual.
> > > > > > > > > - As soon as task is completed, a response is received.
> > > > > > > > >
> > > > > > > > > As for cancellation - client can send a new request (with
> new
> > > > > request
> > > > > > > ID)
> > > > > > > > > and (in the body) pass the request ID from above
> > > > > > > > > as a task identifier. As a result, there are two responses:
> > > > > > > > > - Cancellation response
> > > > > > > > > - Task response (with proper cancelled status)
> > > > > > > > >
> > > > > > > > > That's it, no need to modify the core of the protocol. One
> > > > request
> > > > > -
> > > > > > > one
> > > > > > > > > response.
> > > > > > > > >
> > > > > > > > > On Mon, Nov 25, 2019 at 6:20 PM Alex Plehanov <
> > > > > > plehanov.alex@gmail.com
> > > > > > > >
> > > > > > > > > wrote:
> > > > > > > > >
> > > > > > > > > > Pavel, we need to inform the client when the task is
> > > completed,
> > > > > we
> > > > > > > need
> > > > > > > > > the
> > > > > > > > > > ability to cancel the task. I see several ways to
> implement
> > > > this:
> > > > > > > > > >
> > > > > > > > > > 1. Сlient sends a request to the server to start a task,
> > > server
> > > > > > > return
> > > > > > > > > task
> > > > > > > > > > id in response. Server notifies client when task is
> > completed
> > > > > with
> > > > > > a
> > > > > > > > new
> > > > > > > > > > request (from server to client). Client can cancel the
> task
> > > by
> > > > > > > sending
> > > > > > > > a
> > > > > > > > > > new request with operation type "cancel" and task id. In
> > this
> > > > > case,
> > > > > > > we
> > > > > > > > > > should implement 2-ways requests.
> > > > > > > > > > 2. Client generates unique task id and sends a request to
> > the
> > > > > > server
> > > > > > > to
> > > > > > > > > > start a task, server don't reply immediately but wait
> until
> > > > task
> > > > > is
> > > > > > > > > > completed. Client can cancel task by sending new request
> > with
> > > > > > > operation
> > > > > > > > > > type "cancel" and task id. In this case, we should
> decouple
> > > > > request
> > > > > > > and
> > > > > > > > > > response on the server-side (currently response is sent
> > right
> > > > > after
> > > > > > > > > request
> > > > > > > > > > was processed). Also, we can't be sure that task is
> > > > successfully
> > > > > > > > started
> > > > > > > > > on
> > > > > > > > > > a server.
> > > > > > > > > > 3. Client sends a request to the server to start a task,
> > > server
> > > > > > > return
> > > > > > > > id
> > > > > > > > > > in response. Client periodically asks the server about
> task
> > > > > status.
> > > > > > > > > Client
> > > > > > > > > > can cancel the task by sending new request with operation
> > > type
> > > > > > > "cancel"
> > > > > > > > > and
> > > > > > > > > > task id. This case brings some overhead to the
> > communication
> > > > > > channel.
> > > > > > > > > >
> > > > > > > > > > Personally, I think that the case with 2-ways requests is
> > > > better,
> > > > > > but
> > > > > > > > I'm
> > > > > > > > > > open to any other ideas.
> > > > > > > > > >
> > > > > > > > > > Aleksandr,
> > > > > > > > > >
> > > > > > > > > > Filtering logic for OP_CLUSTER_GROUP_GET_NODE_IDS looks
> > > > > > > > overcomplicated.
> > > > > > > > > Do
> > > > > > > > > > we need server-side filtering at all? Wouldn't it be
> better
> > > to
> > > > > send
> > > > > > > > basic
> > > > > > > > > > info (ids, order, flags) for all nodes (there is
> relatively
> > > > small
> > > > > > > > amount
> > > > > > > > > of
> > > > > > > > > > data) and extended info (attributes) for selected list of
> > > > nodes?
> > > > > In
> > > > > > > > this
> > > > > > > > > > case, we can do basic node filtration on client-side
> > > > > (forClients(),
> > > > > > > > > > forServers(), forNodeIds(), forOthers(), etc).
> > > > > > > > > >
> > > > > > > > > > Do you use standard ClusterNode serialization? There are
> > also
> > > > > > metrics
> > > > > > > > > > serialized with ClusterNode, do we need it on thin
> client?
> > > > There
> > > > > > are
> > > > > > > > > other
> > > > > > > > > > interfaces exist to show metrics, I think it's redundant
> to
> > > > > export
> > > > > > > > > metrics
> > > > > > > > > > to thin clients too.
> > > > > > > > > >
> > > > > > > > > > What do you think?
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > >
> > > > > > > > > > пт, 22 нояб. 2019 г. в 20:15, Aleksandr Shapkin <
> > > > > lexwert@gmail.com
> > > > > > >:
> > > > > > > > > >
> > > > > > > > > > > Alex,
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > I think you can create a new IEP page and I will fill
> it
> > > with
> > > > > the
> > > > > > > > > Cluster
> > > > > > > > > > > API details.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > In short, I’ve introduced several new codes:
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > Cluster API is pretty straightforward:
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_IS_ACTIVE = 5000
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_CHANGE_STATE = 5001
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_CHANGE_WAL_STATE = 5002
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_GET_WAL_STATE = 5003
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > Cluster group codes:
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_GROUP_GET_NODE_IDS = 5100
> > > > > > > > > > >
> > > > > > > > > > > OP_CLUSTER_GROUP_GET_NODE_INFO = 5101
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > The underlying implementation is based on the thick
> > client
> > > > > logic.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > For every request, we provide a known topology version
> > and
> > > if
> > > > > it
> > > > > > > has
> > > > > > > > > > > changed,
> > > > > > > > > > >
> > > > > > > > > > > a client updates it firstly and then re-sends the
> > filtering
> > > > > > > request.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > Alongside the topVer a client sends a serialized nodes
> > > > > projection
> > > > > > > > > object
> > > > > > > > > > >
> > > > > > > > > > > that could be considered as a code to value mapping.
> > > > > > > > > > >
> > > > > > > > > > > Consider: [{Code = 1, Value= [“DotNet”, “MyAttribute”},
> > > > > {Code=2,
> > > > > > > > > > Value=1}]
> > > > > > > > > > >
> > > > > > > > > > > Where “1” stands for Attribute filtering and “2” –
> > > > > > serverNodesOnly
> > > > > > > > > flag.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > As a result of request processing, a server sends
> nodeId
> > > > UUIDs
> > > > > > and
> > > > > > > a
> > > > > > > > > > > current topVer.
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > When a client obtains nodeIds, it can perform a
> NODE_INFO
> > > > call
> > > > > to
> > > > > > > > get a
> > > > > > > > > > >
> > > > > > > > > > > serialized ClusterNode object. In addition there should
> > be
> > > a
> > > > > > > > different
> > > > > > > > > > API
> > > > > > > > > > >
> > > > > > > > > > > method for accessing/updating node metrics.
> > > > > > > > > > >
> > > > > > > > > > > чт, 21 нояб. 2019 г. в 12:32, Sergey Kozlov <
> > > > > > skozlov@gridgain.com
> > > > > > > >:
> > > > > > > > > > >
> > > > > > > > > > > > Hi Pavel
> > > > > > > > > > > >
> > > > > > > > > > > > On Thu, Nov 21, 2019 at 11:30 AM Pavel Tupitsyn <
> > > > > > > > > ptupitsyn@apache.org>
> > > > > > > > > > > > wrote:
> > > > > > > > > > > >
> > > > > > > > > > > > > 1. I believe that Cluster operations for Thin
> Client
> > > > > protocol
> > > > > > > are
> > > > > > > > > > > already
> > > > > > > > > > > > > in the works
> > > > > > > > > > > > > by Alexandr Shapkin. Can't find the ticket though.
> > > > > > > > > > > > > Alexandr, can you please confirm and attach the
> > ticket
> > > > > > number?
> > > > > > > > > > > > >
> > > > > > > > > > > > > 2. Proposed changes will work only for Java tasks
> > that
> > > > are
> > > > > > > > already
> > > > > > > > > > > > deployed
> > > > > > > > > > > > > on server nodes.
> > > > > > > > > > > > > This is mostly useless for other thin clients we
> have
> > > > > > (Python,
> > > > > > > > PHP,
> > > > > > > > > > > .NET,
> > > > > > > > > > > > > C++).
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > I don't guess so. The task (execution) is a way to
> > > > implement
> > > > > > own
> > > > > > > > > layer
> > > > > > > > > > > for
> > > > > > > > > > > > the thin client application.
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > > We should think of a way to make this useful for
> all
> > > > > clients.
> > > > > > > > > > > > > For example, we may allow sending tasks in some
> > > scripting
> > > > > > > > language
> > > > > > > > > > like
> > > > > > > > > > > > > Javascript.
> > > > > > > > > > > > > Thoughts?
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > The arbitrary code execution from a remote client
> must
> > be
> > > > > > > protected
> > > > > > > > > > > > from malicious code.
> > > > > > > > > > > > I don't know how it could be designed but without
> that
> > we
> > > > > open
> > > > > > > the
> > > > > > > > > hole
> > > > > > > > > > > to
> > > > > > > > > > > > kill cluster.
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > > > On Thu, Nov 21, 2019 at 11:21 AM Sergey Kozlov <
> > > > > > > > > skozlov@gridgain.com
> > > > > > > > > > >
> > > > > > > > > > > > > wrote:
> > > > > > > > > > > > >
> > > > > > > > > > > > > > Hi Alex
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > The idea is great. But I have some concerns that
> > > > probably
> > > > > > > > should
> > > > > > > > > be
> > > > > > > > > > > > taken
> > > > > > > > > > > > > > into account for design:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >    1. We need to have the ability to stop a task
> > > > > execution,
> > > > > > > > smth
> > > > > > > > > > like
> > > > > > > > > > > > > >    OP_COMPUTE_CANCEL_TASK  operation (client to
> > > server)
> > > > > > > > > > > > > >    2. What's about task execution timeout? It may
> > > help
> > > > to
> > > > > > the
> > > > > > > > > > cluster
> > > > > > > > > > > > > >    survival for buggy tasks
> > > > > > > > > > > > > >    3. Ignite doesn't have roles/authorization
> > > > > functionality
> > > > > > > for
> > > > > > > > > > now.
> > > > > > > > > > > > But
> > > > > > > > > > > > > a
> > > > > > > > > > > > > >    task is the risky operation for cluster (for
> > > > security
> > > > > > > > > reasons).
> > > > > > > > > > > > Could
> > > > > > > > > > > > > we
> > > > > > > > > > > > > >    add for Ignite configuration new options:
> > > > > > > > > > > > > >       - Explicit turning on for compute task
> > support
> > > > for
> > > > > > thin
> > > > > > > > > > > protocol
> > > > > > > > > > > > > >       (disabled by default) for whole cluster
> > > > > > > > > > > > > >       - Explicit turning on for compute task
> > support
> > > > for
> > > > > a
> > > > > > > node
> > > > > > > > > > > > > >       - The list of task names (classes) allowed
> to
> > > > > execute
> > > > > > > by
> > > > > > > > > thin
> > > > > > > > > > > > > client.
> > > > > > > > > > > > > >    4. Support the labeling for task that may help
> > to
> > > > > > > > investigate
> > > > > > > > > > > issues
> > > > > > > > > > > > > on
> > > > > > > > > > > > > >    cluster (the idea from IEP-34 [1])
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > 1.
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
> https://cwiki.apache.org/confluence/display/IGNITE/IEP-34+Thin+client%3A+transactions+support
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > On Thu, Nov 21, 2019 at 10:58 AM Alex Plehanov <
> > > > > > > > > > > > plehanov.alex@gmail.com>
> > > > > > > > > > > > > > wrote:
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Hello, Igniters!
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > I have plans to start implementation of Compute
> > > > > interface
> > > > > > > for
> > > > > > > > > > > Ignite
> > > > > > > > > > > > > thin
> > > > > > > > > > > > > > > client and want to discuss features that should
> > be
> > > > > > > > implemented.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > We already have Compute implementation for
> > > > binary-rest
> > > > > > > > clients
> > > > > > > > > > > > > > > (GridClientCompute), which have the following
> > > > > > > functionality:
> > > > > > > > > > > > > > > - Filtering cluster nodes (projection) for
> > compute
> > > > > > > > > > > > > > > - Executing task by the name
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > I think we can implement this functionality in
> a
> > > thin
> > > > > > > client
> > > > > > > > as
> > > > > > > > > > > well.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > First of all, we need some operation types to
> > > > request a
> > > > > > > list
> > > > > > > > of
> > > > > > > > > > all
> > > > > > > > > > > > > > > available nodes and probably node attributes
> (by
> > a
> > > > list
> > > > > > of
> > > > > > > > > > nodes).
> > > > > > > > > > > > Node
> > > > > > > > > > > > > > > attributes will be helpful if we will decide to
> > > > > implement
> > > > > > > > > analog
> > > > > > > > > > of
> > > > > > > > > > > > > > > ClusterGroup#forAttribute or
> > > > ClusterGroup#forePredicate
> > > > > > > > methods
> > > > > > > > > > in
> > > > > > > > > > > > the
> > > > > > > > > > > > > > thin
> > > > > > > > > > > > > > > client. Perhaps they can be requested lazily.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > From the protocol point of view there will be
> two
> > > new
> > > > > > > > > operations:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_CLUSTER_GET_NODES
> > > > > > > > > > > > > > > Request: empty
> > > > > > > > > > > > > > > Response: long topologyVersion, int
> > > > > minorTopologyVersion,
> > > > > > > int
> > > > > > > > > > > > > nodesCount,
> > > > > > > > > > > > > > > for each node set of node fields (UUID nodeId,
> > > Object
> > > > > or
> > > > > > > > String
> > > > > > > > > > > > > > > consistentId, long order, etc)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_CLUSTER_GET_NODE_ATTRIBUTES
> > > > > > > > > > > > > > > Request: int nodesCount, for each node: UUID
> > nodeId
> > > > > > > > > > > > > > > Response: int nodesCount, for each node: int
> > > > > > > attributesCount,
> > > > > > > > > for
> > > > > > > > > > > > each
> > > > > > > > > > > > > > node
> > > > > > > > > > > > > > > attribute: String name, Object value
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > To execute tasks we need something like these
> > > methods
> > > > > in
> > > > > > > the
> > > > > > > > > > client
> > > > > > > > > > > > > API:
> > > > > > > > > > > > > > > Object execute(String task, Object arg)
> > > > > > > > > > > > > > > Future<Object> executeAsync(String task, Object
> > > arg)
> > > > > > > > > > > > > > > Object affinityExecute(String task, String
> cache,
> > > > > Object
> > > > > > > key,
> > > > > > > > > > > Object
> > > > > > > > > > > > > arg)
> > > > > > > > > > > > > > > Future<Object> affinityExecuteAsync(String
> task,
> > > > String
> > > > > > > > cache,
> > > > > > > > > > > Object
> > > > > > > > > > > > > > key,
> > > > > > > > > > > > > > > Object arg)
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Which can be mapped to protocol operations:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_COMPUTE_EXECUTE_TASK
> > > > > > > > > > > > > > > Request: UUID nodeId, String taskName, Object
> arg
> > > > > > > > > > > > > > > Response: Object result
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_COMPUTE_EXECUTE_TASK_AFFINITY
> > > > > > > > > > > > > > > Request: String cacheName, Object key, String
> > > > taskName,
> > > > > > > > Object
> > > > > > > > > > arg
> > > > > > > > > > > > > > > Response: Object result
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > The second operation is needed because we
> > sometimes
> > > > > can't
> > > > > > > > > > calculate
> > > > > > > > > > > > and
> > > > > > > > > > > > > > > connect to affinity node on the client-side
> > > (affinity
> > > > > > > > awareness
> > > > > > > > > > can
> > > > > > > > > > > > be
> > > > > > > > > > > > > > > disabled, custom affinity function can be used
> or
> > > > there
> > > > > > can
> > > > > > > > be
> > > > > > > > > no
> > > > > > > > > > > > > > > connection between client and affinity node),
> but
> > > we
> > > > > can
> > > > > > > make
> > > > > > > > > > best
> > > > > > > > > > > > > effort
> > > > > > > > > > > > > > > to send request to target node if affinity
> > > awareness
> > > > is
> > > > > > > > > enabled.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Currently, on the server-side requests always
> > > > processed
> > > > > > > > > > > synchronously
> > > > > > > > > > > > > and
> > > > > > > > > > > > > > > responses are sent right after request was
> > > processed.
> > > > > To
> > > > > > > > > execute
> > > > > > > > > > > long
> > > > > > > > > > > > > > tasks
> > > > > > > > > > > > > > > async we should whether change this logic or
> > > > introduce
> > > > > > some
> > > > > > > > > kind
> > > > > > > > > > > > > two-way
> > > > > > > > > > > > > > > communication between client and server (now
> only
> > > > > one-way
> > > > > > > > > > requests
> > > > > > > > > > > > from
> > > > > > > > > > > > > > > client to server are allowed).
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Two-way communication can also be useful in the
> > > > future
> > > > > if
> > > > > > > we
> > > > > > > > > will
> > > > > > > > > > > > send
> > > > > > > > > > > > > > some
> > > > > > > > > > > > > > > server-side generated events to clients.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > In case of two-way communication there can be
> new
> > > > > > > operations
> > > > > > > > > > > > > introduced:
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_COMPUTE_EXECUTE_TASK (from client to server)
> > > > > > > > > > > > > > > Request: UUID nodeId, String taskName, Object
> arg
> > > > > > > > > > > > > > > Response: long taskId
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > OP_COMPUTE_TASK_FINISHED (from server to
> client)
> > > > > > > > > > > > > > > Request: taskId, Object result
> > > > > > > > > > > > > > > Response: empty
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > The same for affinity requests.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > Also, we can implement not only execute task
> > > > operation,
> > > > > > but
> > > > > > > > > some
> > > > > > > > > > > > other
> > > > > > > > > > > > > > > operations from IgniteCompute (broadcast, run,
> > > call),
> > > > > but
> > > > > > > it
> > > > > > > > > will
> > > > > > > > > > > be
> > > > > > > > > > > > > > useful
> > > > > > > > > > > > > > > only for java thin client. And even with java
> > thin
> > > > > client
> > > > > > > we
> > > > > > > > > > should
> > > > > > > > > > > > > > whether
> > > > > > > > > > > > > > > implement peer-class-loading for thin clients
> > (this
> > > > > also
> > > > > > > > > requires
> > > > > > > > > > > > > two-way
> > > > > > > > > > > > > > > client-server communication) or put classes
> with
> > > > > executed
> > > > > > > > > > closures
> > > > > > > > > > > to
> > > > > > > > > > > > > the
> > > > > > > > > > > > > > > server locally.
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > > > What do you think about proposed protocol
> > changes?
> > > > > > > > > > > > > > > Do we need two-way requests between client and
> > > > server?
> > > > > > > > > > > > > > > Do we need support of compute methods other
> than
> > > > > "execute
> > > > > > > > > task"?
> > > > > > > > > > > > > > > What do you think about peer-class-loading for
> > thin
> > > > > > > clients?
> > > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > >
> > > > > > > > > > > > > > --
> > > > > > > > > > > > > > Sergey Kozlov
> > > > > > > > > > > > > > GridGain Systems
> > > > > > > > > > > > > > www.gridgain.com
> > > > > > > > > > > > > >
> > > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > >
> > > > > > > > > > > > --
> > > > > > > > > > > > Sergey Kozlov
> > > > > > > > > > > > GridGain Systems
> > > > > > > > > > > > www.gridgain.com
> > > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > >
> > > > > > > > > > > --
> > > > > > > > > > > Alex.
> > > > > > > > > > >
> > > > > > > > > >
> > > > > > > > >
> > > > > > > >
> > > > > > >
> > > > > >
> > > > >
> > > >
> > >
> >
>

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