One more question. From the Mesos code it doesn’t look like events are being split or combined, so given I have a client that gives me access to the individual chunks, is it safe to assume that each chunk contains exactly one event? Because that would make parsing the events a lot easier for me.
Thanks, Dario > On Sep 1, 2015, at 8:42 AM, [email protected] wrote: > > Hi Vinod, > > thanks for the explanation, I got it now. > > Thanks, > Dario > > On 31.08.2015, at 23:47, Vinod Kone <[email protected] > <mailto:[email protected]>> wrote: > >> I think you might be confused with the HTTP chunked encoding and RecordIO >> encoding. Most HTTP client libraries dechunk the stream before presenting it >> to the application. So the application needs to know the encoding of the >> dechunked data to be able to process it. >> >> In Mesos's case, the server (master here) can encode it in JSON or Protobuf. >> We wanted to have a consistent way to encode both these formats and >> Record-IO format was the one we settled on. Note that this format is also >> used by the Twitter streaming API >> <https://dev.twitter.com/streaming/overview/processing> (see delimited >> messages section). >> >> HTH, >> >> On Mon, Aug 31, 2015 at 2:09 PM, Dario Rexin <[email protected] >> <mailto:[email protected]>> wrote: >> Hi Vino, >> >>> On Aug 31, 2015, at 9:36 PM, Vinod Kone <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>> Hi Dario, >>> >>> Can you test with "curl --no-buffer" option? Looks like your stdout might >>> be line-buffered. >> >> that did the trick, thanks! >> >>> >>> The reason we used record-io formatting is to be consistent in how we >>> stream protobuf and json encoded data. >>> >> >> How does simple chunked encoding prevent you from doing this? >> >> Thanks, >> Dario >> >>> On Fri, Aug 28, 2015 at 2:04 PM, <[email protected] >>> <mailto:[email protected]>> wrote: >>> Anand, >>> >>> thanks for the explanation. I didn't think about the case when you have to >>> split a message, now it makes sense. >>> >>> But the case I observed with curl is still weird. Even when splitting a >>> message, it should still receive both parts almost at the same time. Do you >>> have any idea why it could behave like this? >>> >>> On 28.08.2015, at 21:31, Anand Mazumdar <[email protected] >>> <mailto:[email protected]>> wrote: >>> >>>> Dario, >>>> >>>> Most HTTP libraries/parsers ( including one that Mesos uses internally ) >>>> provide a way to specify a default size of each chunk. If a Mesos Event is >>>> too big , it would get split into smaller chunks and vice-versa. >>>> >>>> -anand >>>> >>>>> On Aug 28, 2015, at 11:51 AM, [email protected] >>>>> <mailto:[email protected]> wrote: >>>>> >>>>> Anand, >>>>> >>>>> in the example from my first mail you can see that curl prints the size >>>>> of a message and then waits for the next message and only when it >>>>> receives that message it will print the prior message plus the size of >>>>> the next message, but not the actual message. >>>>> >>>>> What's the benefit of encoding multiple messages in a single chunk? You >>>>> could simply create a single chunk per event. >>>>> >>>>> Cheers, >>>>> Dario >>>>> >>>>> On 28.08.2015, at 19:43, Anand Mazumdar <[email protected] >>>>> <mailto:[email protected]>> wrote: >>>>> >>>>>> Dario, >>>>>> >>>>>> Can you shed a bit more light on what you still find puzzling about the >>>>>> CURL behavior after my explanation ? >>>>>> >>>>>> PS: A single HTTP chunk can have 0 or more Mesos (Scheduler API) Events. >>>>>> So in your example, the first chunk had complete information about the >>>>>> first “event”, followed by partial information about the subsequent >>>>>> event from another chunk. >>>>>> >>>>>> As for the benefit of using RecordIO format here, how else do you think >>>>>> we could have de-marcated two events in the response ? >>>>>> >>>>>> -anand >>>>>> >>>>>> >>>>>>> On Aug 28, 2015, at 10:01 AM, [email protected] >>>>>>> <mailto:[email protected]> wrote: >>>>>>> >>>>>>> Anand, >>>>>>> >>>>>>> thanks for the explanation. I'm still a little puzzled why curl behaves >>>>>>> so strange. I will check how other client behave as soon as I have a >>>>>>> chance. >>>>>>> >>>>>>> Vinod, >>>>>>> >>>>>>> what exactly is the benefit of using recordio here? Doesn't it make the >>>>>>> content-type somewhat wrong? If I send 'Accept: application/json' and >>>>>>> receive 'Content-Type: application/json', I actually expect to receive >>>>>>> only json in the message. >>>>>>> >>>>>>> Thanks, >>>>>>> Dario >>>>>>> >>>>>>> On 28.08.2015, at 18:13, Vinod Kone <[email protected] >>>>>>> <mailto:[email protected]>> wrote: >>>>>>> >>>>>>>> I'm happy to add the "\n" after the event (note it's different from >>>>>>>> chunk) if that makes CURL play nicer. I'm not sure about the "\r" part >>>>>>>> though? Is that a nice to have or does it have some other benefit? >>>>>>>> >>>>>>>> The design doc is not set in the stone since this has not been >>>>>>>> released yet. So definitely want to do the right/easy thing. >>>>>>>> >>>>>>>> On Fri, Aug 28, 2015 at 7:53 AM, Anand Mazumdar <[email protected] >>>>>>>> <mailto:[email protected]>> wrote: >>>>>>>> Dario, >>>>>>>> >>>>>>>> Thanks for the detailed explanation and for trying out the new API. >>>>>>>> However, this is not a bug. The output from CURL is the encoding used >>>>>>>> by Mesos for the events stream. From the user doc >>>>>>>> <https://github.com/apache/mesos/blob/master/docs/scheduler_http_api.md>: >>>>>>>> >>>>>>>> "Master encodes each Event in RecordIO format, i.e., string >>>>>>>> representation of length of the event in bytes followed by JSON or >>>>>>>> binary Protobuf (possibly compressed) encoded event. Note that the >>>>>>>> value of length will never be ‘0’ and the size of the length will be >>>>>>>> the size of unsigned integer (i.e., 64 bits). Also, note that the >>>>>>>> RecordIO encoding should be decoded by the scheduler whereas the >>>>>>>> underlying HTTP chunked encoding is typically invisible at the >>>>>>>> application (scheduler) layer.“ >>>>>>>> >>>>>>>> If you run CURL with tracing enabled i.e. —trace, the output would be >>>>>>>> something similar to this: >>>>>>>> >>>>>>>> <= Recv header, 2 bytes (0x2) >>>>>>>> 0000: 0d 0a .. >>>>>>>> <= Recv data, 115 bytes (0x73) >>>>>>>> 0000: 36 64 0d 0a 31 30 35 0a 7b 22 73 75 62 73 63 72 6d..105.{"subscr >>>>>>>> 0010: 69 62 65 64 22 3a 7b 22 66 72 61 6d 65 77 6f 72 ibed":{"framewor >>>>>>>> 0020: 6b 5f 69 64 22 3a 7b 22 76 61 6c 75 65 22 3a 22 k_id":{"value":" >>>>>>>> 0030: 32 30 31 35 30 38 32 35 2d 31 30 33 30 31 38 2d 20150825-103018- >>>>>>>> 0040: 33 38 36 33 38 37 31 34 39 38 2d 35 30 35 30 2d 3863871498-5050- >>>>>>>> 0050: 31 31 38 35 2d 30 30 31 30 22 7d 7d 2c 22 74 79 1185-0010"}},"ty >>>>>>>> 0060: 70 65 22 3a 22 53 55 42 53 43 52 49 42 45 44 22 pe":"SUBSCRIBED" >>>>>>>> 0070: 7d 0d 0a }.. >>>>>>>> <others >>>>>>>> >>>>>>>> In the output above, the chunks are correctly delimited by ‘CRLF' (0d >>>>>>>> 0a) as per the HTTP RFC. As mentioned earlier, the output that you >>>>>>>> observe on stdout with CURL is of the Record-IO encoding used for the >>>>>>>> events stream ( and is not related to the RFC ): >>>>>>>> >>>>>>>> event = event-size LF >>>>>>>> event-data >>>>>>>> >>>>>>>> Looking forward to more bug reports as you try out the new API ! >>>>>>>> >>>>>>>> -anand >>>>>>>> >>>>>>>>> On Aug 28, 2015, at 12:56 AM, Dario Rexin <[email protected] >>>>>>>>> <mailto:[email protected]>> wrote: >>>>>>>>> >>>>>>>>> -1 (non-binding) >>>>>>>>> >>>>>>>>> I found a breaking bug in the new HTTP API. The messages do not >>>>>>>>> conform to the HTTP standard for chunked transfer encoding. in RFC >>>>>>>>> 2616 Sec. 3 (http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html >>>>>>>>> <http://www.w3.org/Protocols/rfc2616/rfc2616-sec3.html>) a chunk is >>>>>>>>> defined as: >>>>>>>>> >>>>>>>>> chunk = chunk-size [ chunk-extension ] CRLF >>>>>>>>> chunk-data CRLF >>>>>>>>> >>>>>>>>> The HTTP API currently sends a chunk as: >>>>>>>>> >>>>>>>>> chunk = chunk-size LF >>>>>>>>> chunk-data >>>>>>>>> >>>>>>>>> A standard conform HTTP client like curl can’t correctly interpret >>>>>>>>> the data as a complete chunk. In curl it currently looks like this: >>>>>>>>> >>>>>>>>> 104 >>>>>>>>> {"subscribed":{"framework_id":{"value":"20150820-114552-16777343-5050-43704-0000"}},"type":"SUBSCRIBED"}20 >>>>>>>>> {"type":"HEARTBEAT”}666 >>>>>>>>> …. waiting … >>>>>>>>> {"offers":{"offers":[{"agent_id":{"value":"20150820-114552-16777343-5050-43704-S0"},"framework_id":{"value":"20150820-114552-16777343-5050-43704-0000"},"hostname":"localhost","id":{"value":"20150820-114552-16777343-5050-43704-O0"},"resources":[{"name":"cpus","role":"*","scalar":{"value":8},"type":"SCALAR"},{"name":"mem","role":"*","scalar":{"value":15360},"type":"SCALAR"},{"name":"disk","role":"*","scalar":{"value":2965448},"type":"SCALAR"},{"name":"ports","ranges":{"range":[{"begin":31000,"end":32000}]},"role":"*","type":"RANGES"}],"url":{"address":{"hostname":"localhost","ip":"127.0.0.1","port":5051},"path":"\/slave(1)","scheme":"http"}}]},"type":"OFFERS”}20 >>>>>>>>> … waiting … >>>>>>>>> {"type":"HEARTBEAT”}20 >>>>>>>>> … waiting … >>>>>>>>> >>>>>>>>> It will receive a couple of messages after successful registration >>>>>>>>> with the master and the last thing printed is a number (in this case >>>>>>>>> 666). Then after some time it will print the first offers message >>>>>>>>> followed by the number 20. The explanation for this behavior is, that >>>>>>>>> curl can’t interpret the data it gets from Mesos as a complete chunk >>>>>>>>> and waits for the missing data. So it prints what it thinks is a >>>>>>>>> chunk (a message followed by the size of the next messsage) and keeps >>>>>>>>> the rest of the message until another message arrives and so on. The >>>>>>>>> fix for this is to terminate both lines, the message size and the >>>>>>>>> message data, with CRLF. >>>>>>>>> >>>>>>>>> Cheers, >>>>>>>>> Dario >>>>>>>> >>>>>>>> >>>>>> >>>> >>> >> >>
