> > Does this mean that when a client is sending more than one in-flight >> request per connection, the server does not guarantee that responses will >> be sent in the same order as requests? > > > No - the server does provide this guarantee - i.e., responses will always > be sent in the same order as requests received on the same TCP connection. > *"The > server guarantees that on a single TCP connection, requests will be > processed in the order they are sent and responses will return in that > order as well."* The subsequent statements just describe how this is > achieved (i.e., we process only one request at a time in the API handlers). >
To further clarify: the above is true even if the client sends more than on in-flight request per connection. > > On Thu, Feb 18, 2016 at 5:59 AM, Ivan Dyachkov <i...@dyachkov.org> wrote: > >> Thanks Ben. >> >> As I mentioned, I'm developing a kafka library and not using standard >> java producer. >> >> My question is really about protocol guarantees. >> >> /Ivan >> >> ----- Original message ----- >> From: Ben Stopford <b...@confluent.io> >> To: users@kafka.apache.org >> Subject: Re: Kafka response ordering guarantees >> Date: Wed, 17 Feb 2016 14:48:59 -0800 >> >> So long as you set max.inflight.requests.per.connection = 1 Kafka should >> provide strong ordering within a partition (so use the same key for >> messages that should retain their order). There is a bug currently raised >> agaisnt this feature though where there is an edge case that can cause >> ordering issues. >> >> https://issues.apache.org/jira/browse/KAFKA-3197 >> > On 17 Feb 2016, at 07:17, Ivan Dyachkov <d...@dyachkov.org> wrote: >> > >> > Hello all. >> > >> > I'm developing a kafka client and have a question about kafka server >> guarantees. >> > >> > A statement from >> https://cwiki.apache.org/confluence/display/KAFKA/A+Guide+To+The+Kafka+Protocol#AGuideToTheKafkaProtocol-Network >> makes me a bit confused: >> > >> > "The server guarantees that on a single TCP connection, requests will >> be processed in the order they are sent and responses will return in that >> order as well. The broker's request processing allows only a single >> in-flight request per connection in order to guarantee this ordering. Note >> that clients can (and ideally should) use non-blocking IO to implement >> request pipelining and achieve higher throughput. i.e., clients can send >> requests even while awaiting responses for preceding requests since the >> outstanding requests will be buffered in the underlying OS socket buffer. >> All requests are initiated by the client, and result in a corresponding >> response message from the server except where noted." >> > >> > Does this mean that when a client is sending more than one in-flight >> request per connection, the server does not guarantee that responses will >> be sent in the same order as requests? >> > >> > In other words, if I have a strictly monotonically increasing integer >> as a correlation id for all requests, can I rely on Kafka that correlation >> id in responses will also have this property? >> > >> > Thanks. >> > >> > /Ivan >> >> >
