![]() ![]() (The exception appear in the producer, I don't have a consumer in this application. I have tried to set 40 MB, but I still get the exception. If the message size is about 15 MB I get a MessageSizeTooLargeException. MySignaling.I send String-messages to Kafka V. Check this out: let pc = new RTCPeerConnection(.) So, what can be done to retrieve this information? The answer lies within the SDP blob. Create and exchange offer/answer here.īut sadly, it doesn’t because Firefox and all other browsers currently don’t support the object API yet, that has been borrowed from the ORTC specification. Let maximumMessageSize = pc.sctp.maxMessageSize ĭc.send(new Uint8Array(maximumMessageSize)) So, the following example should work, right? let pc = new RTCPeerConnection(.) It maps to the attribute from the SDP and is exactly what a user application needs to look for. In the W3C WebRTC spec, there’s an RTCSctpTransport object which has a field called maxMessageSize. More precisely, that value must be available before an application even tries to send a message or it would be a guessing game… Maximum Message Size Indication But having a size limit requires knowledge about this limitation. Nevertheless, this size limitation may be increased in the future. Changing this requires changes to the W3C WebRTC specification. Therefore, when you want to send a large file as a whole, there’s an enormous backpressure due to the fact that the file’s data needs to be in memory when calling the send method. Why is there a limitation? Well, theoretically we can support much more but the limiting factor is available memory and the fact that the RTCDataChannel API of WebRTC is too high-level, meaning it’s not possible to send or receive a message in chunks. Thanks to the new EOR feature Firefox now supports receiving up to 1 GiB messages. It is not the cleanest of solutions but it should be adequate and will be removed after Firefox ESR has EOR support. A detection algorithm has been added, so Firefox will fall back to use PPID-based fragmentation/reassembly when needed: in case the maximum message size attribute in the remote SDP is missing and 256 incoming streams have been negotiated for the SCTP association, it is assumed that the other peer is an older Firefox browser. But hold on a second… sending large messages from Firefox to Firefox was possible before, wasn’t it? Yep, that’s true, with help of the deprecated PPID-based fragmentation/reassembly mechanism. With EOR handling, one major benefit is of course being able to send and receive large messages. He decided that it was about time to add support to at least one of the browsers. Lennart had gained experience in writing a standalone data channel implementation with EOR handling when he implemented RAWRTC. While the ndata extension is currently in the specification process, it’s making good progress and there’s no excuse for holding back proper EOR handling anymore. Must be larger than, or a broker can accept messages it cannot replicate, potentially resulting. : 1048576 (1 MiB) Maximum message size a broker can replicate. All messages exchanged in the chat would arrive after the lengthy process of sending a gigantic file has been completed. : 1073741824 (1 GiB) Size of a Kafka data file. This phenomenon is also known as head-of-line blocking and makes sending large messages quite painful if other channels need to keep exchanging messages frequently, for example in a real-time chat with file-sending capability. Unfortunately, none of the browsers today support the SCTP ndata extension yet, so a single data channel message will monopolise the whole SCTP association. Let's first look into our Kafka setup before jumping to configuration. For this tutorial, we're using Kafka v2.5. However, if there's a requirement to send large messages, we need to tweak these configurations as per our requirements. ![]() For more technical information on this and how one can work around this, take a look at Lennart’s previous blog posting. Kafka configuration limits the size of messages that it's allowed to send. This is sadly the case for all popular data channel implementations at the moment and results in harsh size limitations for data channel messages. Thus, every implementation needs to pay attention to this flag or message integrity will be violated. Its API provides an EOR flag which stands for end of record and tells us whether a message is partial or complete. SCTP is the transport protocol used for exchanging WebRTC data channel messages. ![]() The good news is that bug 979417, a big contribution by Lennart Grahl, has landed in Firefox 57, which adds EOR handling to Firefox data channels. See here for a very good explanation of the problem. Especially if the data channel had been established between Firefox and Chrome. Until very recently you had to be careful about the maximum message size you could send over a WebRTC data channel. ← View all posts NovemLarge Data Channel Messages Contributed by Nils Ohlmeier, Hacking on real time communications since 2002 ![]()
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