That is, I know the map's server and RatisServer run on the same process, and try to bypass the serde and network process but locally submit a request with Message.
Best, tison. tison <[email protected]> 于2022年10月1日周六 17:41写道： > Another direction can be, is it possible to submit a request to RaftServer > locally, and thus not need to pipe a request from replicated map's client, > map's server (i.e. RatisClient), and RatisServer? > > Best, > tison. > > > tison <[email protected]> 于2022年9月30日周五 19:03写道： > >> Thank you. I'll check the technical details. >> >> For the application framework, I find a possible way to add an external >> watch manager who gets notified from callbacks registered to the state >> machine. Although, this way asks the client to establish one more >> connection to the watch manager (even if in the same process, different >> port). >> >> Best, >> tison. >> >> >> Tsz Wo Sze <[email protected]> 于2022年9月30日周五 18:30写道： >> >>> > However, still I don't know what "watch an index" actually means. How >>> can I obtain the index in the first place? What condition I will receive a >>> one-shot response from? >>> >>> A log index can be obtained by RaftClientReply.getLogIndex(), which >>> returns the raft log index corresponding to a write request. The work flow >>> is like below: >>> >>> 1. A client sends a (write) request and then gets back a RaftClientReply >>> r -- at that moment the request may only have been replicated to a MAJORITY >>> of servers as specified by the Raft Algorithm. >>> >>> 2. A user application may have a more strict replication requirement. >>> For example, it may want the request to be replicated to ALL the servers, >>> instead of a MAJORITY. It may call >>> watch(r.getLogIndex(), ReplicationLevel.ALL) in order to watch for the >>> replication ALL condition. >>> >>> We also have MAJORITY_COMMITTED and ALL_COMMITTED replication levels. >>> COMMITTED means that the server's commit-index has been increased at least >>> the watched index. >>> >>> Hope it helps. >>> Tsz-Wo >>> >>> On Fri, Sep 30, 2022 at 5:43 PM tison <[email protected]> wrote: >>> >>>> Hi Tsz-Wo, >>>> >>>> Thanks for your reply! >>>> >>>> I think in this way I can implement a one-shot watcher. >>>> >>>> The similar functionality in etcd defines as: >>>> >>>> rpc Watch(stream WatchRequest) returns (stream WatchResponse); >>>> >>>> ... and this is why I use "full-duplex server-client communication" in >>>> the subject - Is it possible for a Ratis client opens a connection to do >>>> something like this? >>>> >>>> > AsyncApi.watch >>>> >>>> Yes. IIRC I asked questions about this "watch" function years ago and >>>> understand it's not "watch a key" :) >>>> >>>> However, still I don't know what "watch an index" actually means. How >>>> can I obtain the index in the first place? What condition I will receive a >>>> one-shot response from? >>>> >>>> Best, >>>> tison. >>>> >>>> >>>> Tsz Wo Sze <[email protected]> 于2022年9月30日周五 15:17写道： >>>> >>>>> Hi tison, >>>>> >>>>> Since Ratis server is asynchronous event-driven. We may implement "watch >>>>> a key" using the AsyncApi [1]: >>>>> 1. Client sends a "watch a key" request by client.a >>>>> sync().sendReadOnly(..). >>>>> 2. StateMachine won't complete the future until the key satisfies the >>>>> watch condition. >>>>> >>>>> One problem is that the async read calls in Ratis are ordered. Thus, >>>>> the other ordered async calls sent by the same client would not be >>>>> completed before the "watch a key" request is completed. Of course, >>>>> we may work around it by creating a new client. A better solution is to >>>>> support unordered async read (a new feature) in Ratis. >>>>> >>>>> Note that Ratis already supports unordered AsyncApi.watch(..), which >>>>> can watch for the replication level of the given log index. Therefore, it >>>>> is easy to add the new feature for supporting unordered async read. >>>>> >>>>> What do you think? >>>>> >>>>> Tsz-Wo >>>>> >>>>> [1] >>>>> https://github.com/apache/ratis/blob/master/ratis-client/src/main/java/org/apache/ratis/client/api/AdminApi.java >>>>> >>>>> >>>>> On Fri, Sep 30, 2022 at 2:21 PM tison <[email protected]> wrote: >>>>> >>>>>> Hi, >>>>>> >>>>>> I'm trying to write a replicated map based on Ratis. >>>>>> >>>>>> One thing that blocks me here is that I'm trying to implement >>>>>> something like "watch a key". While Ratis support basic RPC between >>>>>> server >>>>>> and client, it's a one-shot RPC call. I have two ideas here but both >>>>>> seems >>>>>> not easy to implement: >>>>>> >>>>>> 1. Take the client connection and send back key changes even if the >>>>>> client doesn't round-robin query it. However, the Rpc details in under >>>>>> encapsulation and never intend to be used. >>>>>> 2. Wrapper an RMap server over the Ratis server. However, in this >>>>>> case, It's the RMap server that should be responsible for initiating and >>>>>> managing the connection. Ratis server encapsulates this detail and the >>>>>> only >>>>>> way I can imagine is the RMap server as a proxy, but it's quite clumsy to >>>>>> have one more hop. >>>>>> >>>>>> Looking forward to your ideas. >>>>>> >>>>>> Best, >>>>>> tison. >>>>>> >>>>>
