> On April 23, 2014, 10:22 a.m., Ivan Kelly wrote: > > bookkeeper-server/src/main/proto/BookkeeperProtocol.proto, line 104 > > <https://reviews.apache.org/r/17895/diff/2/?file=563033#file563033line104> > > > > You're sending StatusCode twice, every time. Firstly, shouldn't be an > > enum as stated above. Secondly, shouldn't be required. > > Sijie Guo wrote: > > enum > > as the comments above. > > > status code twice. > > the status code for ReadResponse/AddResponse is for individual responses. > if we are going to support kind of batch reads, the status code of Response > means either the whole batch succeed or not while the individual read > responses might have different status codes (e.g OK or NotExists). That is > why it exists two places. > > > required > > as the comments above > > Ivan Kelly wrote: > Per request makes sense. However, in that case, can't you just remove the > per packet status? > > Sijie Guo wrote: > Nope. the packet status indicates whether the packet succeed or not. say > if it is batch read, if the total batch read failed, it would set the whole > packet status to be failed and there would be no individual responses in the > packet since the whole batch failed. > > Ivan Kelly wrote: > Then it should have a different name. Like entryStatus & packetStatus. > But then you also have a consistency problem. What is packetStatus is OK, but > one entryStatus is an error? Will there be a SOME_OK error? In what scenario > would a whole read batch fail? > > Sijie Guo wrote: > if ledger isn't exists, then a packet status with NoSuchLedgerExists is > returned. if ledger exists, but some entries are missing, so ok is returned > for the packet, but NoSuchEntry would be returned for the missing entries. > > Ivan Kelly wrote: > this would be better handled with a batch intermediatory message, defined > like > > message Response { > required BKPacketHeader header = 1; > > optional ReadResponse readResponse = 100; > optional AddResponse addResponse = 101; > optional BatchReadResponse batchReadResponse = 102; > } > > message ReadResponse { > required StatusCode status = 1; > required int64 ledgerId = 2; > required int64 entryId = 3; > optional bytes body = 4; > } > > message BatchReadResponse { > optional StatusCode status = 1; > repeated ReadResponse entries = 2; > } > > message AddResponse { > required StatusCode status = 1; > required int64 ledgerId = 2; > required int64 entryId = 3; > } > > > Sijie Guo wrote: > the point of differentiating the status code in packet from the one in > operations. there are common status codes which are in packet level not > related to individual operations, like 'bad request', 'authentication > failure' etc, in this case they could be handled in packet level rather than > operations level. otherwise, you need to add duplicated logic to handle those > common things in operation responses each time you added new type of > requests. doesn't this make a call for separating packet status from > operation status?
> otherwise, you need to add duplicated logic to handle those common things in > operation responses each time you added new type of requests. You have duplicate logic here anyhow. (PerChannelBookieClient.java:633) It does make some sense to have a packet level status and an op level status. But then they shouldn't share codes. StatusCode should be split into PacketStatusCode and OpStatusCode. > On April 23, 2014, 10:22 a.m., Ivan Kelly wrote: > > bookkeeper-server/src/main/proto/BookkeeperProtocol.proto, line 33 > > <https://reviews.apache.org/r/17895/diff/2/?file=563033#file563033line33> > > > > This should certainly not be an enum. Otherwise we need to bump the > > protocol version each time we add an error code. > > > > Imagine the scenario where both server and client are running 4.3.0. > > Then the server is upgraded with 4.3.1 which a new error EPRINTERONFIRE. It > > sends this to the client who throws a decode error. > > Sijie Guo wrote: > how could being not enum help this? if it is integer, client still has no > idea how to interpret, so it is still invalid response from 4.3.0 client. I > thought we reached an agreement on enum on the ticket, no? > > Ivan Kelly wrote: > So for version and operationtype, enum is ok. These originate at the > client, so if the servers are always upgraded at the client, there's no > interoperability issues. Status codes originate at the server though, so it > is possible for the server to send a statuscode that is unrecognised to a > client. The normal way to handle this would be a "else" or "default:" to pass > this up to the client as a BKException.UnexpectedConditionException. If it's > an enum, this will throw a decode exception in the netty decoder, which is > harder to handle. > > To resolve this on the server side, by checking the version and only > sending errors valid for that version, implies two things. Firstly, every > error code change will require the version to be bumped and secondly, that > there will need to be a list maintained for which errors are valid for each > version. This goes against the motivation for using protobuf in the first > place. > > Sijie Guo wrote: > this is the application level agreement, no? it doesn't matter that u are > using a protobuf protocol or using current protocol, or it also doesn't > matter that u are using an integer or an enum. in any case, the best way is > as you described, you shouldn't send new status code back to an old client, > as the new status code is meaningless to the old client. > > Ivan Kelly wrote: > but how do you know its an old client? Only by bumping the version number > each time you add an error code. In which case you end up with a whole lot of > junk like "if (client.version == X) { send A } else if (client.version == Y) > { send B } else if (client.version ..." which is exactly what protobuf was > designed to avoid (see "A bit of history" on > https://developers.google.com/protocol-buffers/docs/overview). > > Sijie Guo wrote: > a else or default branch would make the behavior unpredictable as an old > client is treating a new status code as some kind of unknown. as you said, > you want to treat them as UnexpectedConditionException. But what does > UnexpectedConditionException means? doesn't it mean the sever already breaks > backward compatibility, since server couldn't satisfy the old client's > request. > > so still, if server wants to be backward compatibility to clients, in any > cases, it needs to know what version of protocol that the client is speaking > and handle them accordingly, not just let client to do their job in an > unexpected way. > > I don't see any elegant solutions without detecting protocol version. if > you have, please describe how not being enum would avoid this. > > Ivan Kelly wrote: > the default behaviour for an unknown error code is something we already > use today. > > https://github.com/apache/bookkeeper/blob/trunk/bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java#L714 > > The client only needs to know that the request failed. the point of the > different error codes is so that the client could take specific recovery > steps. the default behaviour is just to pass the error up. > > Sijie Guo wrote: > the default behavior was there just for all already known status codes. > but it doesn't mean it is correct for any unknown status codes. and when u > are saying 'the client only needs to know that the request failed', you are > making an assumption that there is only one status code indicating OK, other > status code should be taken as failed. but it isn't true. say in an old > protocol, we supported range reads, it responded with OK, list of entry > response (0 = <data>, 1 = missing, 2 = missing, 3 = <data>). if we are going > to improve our protocol to make communication more efficient, we are going to > change the protocol to get rid of transferring missing entries: responding > with PARTIAL_OK, list of existing entries (0 = <data>, 3 = <data>). > > in this case, if server doesn't distinguish the client's protocol, just > respond every range reads with PARTIAL_OK, would did break the compatibility > with old protocol, as old protocol treats it as failure by default behavior. > in order to maintain backward compatibility, server needs to detect the > client's protocol and responds accordingly. as what I said, for backward > compatibility, a protocol doesn't really help if it involves behavior in > application agreement. and a default behavior is not exact right. > > for me, using protocol. it means that it is easy for us to add new > requests type, add new fields in existing requests. besides that, we need to > keep the backward compatibility in our level. > > Ivan Kelly wrote: > when i say that 'the client only needs to know that the request failed', > it means that the client only needs to recognise the statuses which indicate > success. for any request, the status codes which indicate success should > never change. For a read request or add request, only OK is SUCCESS. For > range read, only PARTIAL_OK and OK are success. But the client will never > send a range read request unless it already knows about PARTIAL_OK. > > Sijie Guo wrote: > > “But the client will never send a range read request unless it already > knows about PARTIAL_OK.” > > the example that I made is that the range read introduced with OK, but if > it is going to evolved to have PARTIAL_OK. then that will be an problem. Partial_ok doesn't make sense if you're using the concept of packet status and operation status (as mentioned below). - Ivan ----------------------------------------------------------- This is an automatically generated e-mail. To reply, visit: https://reviews.apache.org/r/17895/#review41130 ----------------------------------------------------------- On April 24, 2014, 7:43 a.m., Sijie Guo wrote: > > ----------------------------------------------------------- > This is an automatically generated e-mail. To reply, visit: > https://reviews.apache.org/r/17895/ > ----------------------------------------------------------- > > (Updated April 24, 2014, 7:43 a.m.) > > > Review request for bookkeeper and Ivan Kelly. > > > Bugs: BOOKKEEPER-582 > https://issues.apache.org/jira/browse/BOOKKEEPER-582 > > > Repository: bookkeeper-git > > > Description > ------- > > - introducing protobuf support for bookkeeper > - for server: introduce packet processor / EnDecoder for different protocol > supports > - for client: change PCBC to use protobuf to send requests > - misc changes for protobuf support > > (bookie server is able for backward compatibility) > > > Diffs > ----- > > bookkeeper-server/pom.xml ebc1198 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/bookie/IndexInMemPageMgr.java > 56487aa > > bookkeeper-server/src/main/java/org/apache/bookkeeper/client/LedgerChecker.java > 28e23d6 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/client/PendingReadOp.java > fb36b90 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/processor/RequestProcessor.java > 241f369 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieProtoEncoding.java > 1154047 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieRequestHandler.java > b922a82 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookieRequestProcessor.java > 8155b22 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/BookkeeperProtocol.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PacketProcessorBase.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PacketProcessorBaseV3.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/PerChannelBookieClient.java > a10f7d5 > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/ReadEntryProcessor.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/ReadEntryProcessorV3.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/WriteEntryProcessor.java > PRE-CREATION > > bookkeeper-server/src/main/java/org/apache/bookkeeper/proto/WriteEntryProcessorV3.java > PRE-CREATION > bookkeeper-server/src/main/proto/BookkeeperProtocol.proto PRE-CREATION > bookkeeper-server/src/main/resources/findbugsExclude.xml 97a6156 > > bookkeeper-server/src/test/java/org/apache/bookkeeper/proto/TestProtoVersions.java > 5fcc445 > > bookkeeper-server/src/test/java/org/apache/bookkeeper/replication/AuditorPeriodicCheckTest.java > 3f8496f > > bookkeeper-server/src/test/java/org/apache/bookkeeper/test/BookieClientTest.java > bc05229 > > bookkeeper-server/src/test/java/org/apache/bookkeeper/test/TestBackwardCompat.java > 8376b46 > compat-deps/bookkeeper-server-compat-4.2.0/pom.xml PRE-CREATION > compat-deps/hedwig-server-compat-4.2.0/pom.xml PRE-CREATION > compat-deps/pom.xml f79582d > hedwig-server/pom.xml 06cf01c > > hedwig-server/src/test/java/org/apache/hedwig/server/TestBackwardCompat.java > 8da109e > > Diff: https://reviews.apache.org/r/17895/diff/ > > > Testing > ------- > > unit tests. backward tests. > > > Thanks, > > Sijie Guo > >
