real-logic/Aeron

Efficient reliable UDP unicast, UDP multicast, and IPC message transport

Martin Thompson

@mjpt777

@pieceofchum We only answer cluster questions to those on a support contract.

David Raymond

@pieceofchum

ok np

William

@ilove7412369_twitter

I think there is a bug in aeron IPC.
I run aeron archive on the channel say ipc stream id 1001

I publish thing in order,
but the subscriber read message 100057 before 100055, out of order and shown in log

The archive, however is totally in correct order.
Aeron version i use is 1.28.2

i wonder if such is a know issue or not.

Martin Thompson

@mjpt777

@ilove7412369_twitter We are not aware of such an issue. We have tests that assert the correct order. You can use the LogInspector on the log buffers to see contents. Are you certain the logic of your usage is correct? Subscriptions are not concurrent so each thread requires its own instance.

William

@ilove7412369_twitter

Thanks, i will investigate further.

Judd Gaddie

@juddgaddie

I have been looking at the design of the TimerService in Aeron Cluster and it places strict requirements on the ClusteredService to always call scheduleTimer in the same sequence after a replay or snapshot and subsequent replay.
The constraint of a ClusteredService to not do anything completely non-deterministic i.e. new Random() etc - feels reasonable to me.

However, it also requires ClusteredService to record and restore all its state in a snapshot in order to correctly call scheduleTimer() for it to be reliable. While strictly speaking the snapshot of a ClusteredService should store its entire state. Sometimes a user may only store a subset of the ClusteredService state when snapshotted, this may still result in correct behavior of the ClusteredService however it may not be a deterministic sequence of “schedule” and “cancel” calls to the TimerService therefore it may be doing NoOps when an attempt to schedule following the loading of the snapshot.

I did see the javadoc on the Cluster does hint at this.

Martin Thompson

@mjpt777

@juddgaddie The timers are recorded in the snapshot managed by the consensus module. The service does not need to worry about that.

Judd Gaddie

@juddgaddie

It needs to worry about it a little bit as the state of the ClusteredService needs to be in sync with the state of the timers in the consensus module (at least wrt the sequence of calls to schedule and cancel and correlationIds used). Otherwise because of expiredTimerCountByCorrelationIdMap in the consensus module some scheduled timers may be ignored.

Martin Thompson

@mjpt777

@juddgaddie You can take this up as a support issue as this is not the place to discuss. I'm not sure you are using things correctly.

Judd Gaddie

@juddgaddie

Fair enough, thanks

feyyaz91

@feyyaz91

Hello there, is there a way to use ReplayMerge when the live publication is on a different media driver to the archived recording? At the moment i am aware the recording and publication must share a media driver to successfully merge

William

@ilove7412369_twitter

Is it illegal to modify the buffer of the callback onFragment?

Martin Thompson

@mjpt777

@ilove7412369_twitter The buffer should be considered readonly.

Ivan Zemlyanskiy

@QIvan

hi! Happy New year, guys!
if you recall I asked some time ago about restarting archive and ports issue, when with java md everything worked fine, but with C md didn't (you said because C md is a way faster than Java one and that's cause of the problem)
Could you help to clarify this scenario: I create an aeron instance (with Aeron.connect()) and add a subscription for an endpoint let's say 10.1.1.1:1234, I work with it for some time, then I close the subscription, close the aeron instance and repeat everything once again. A question: what should I do, and should I, before I start everything over?
thank you in advance

Todd L. Montgomery

@tmontgomery

@QIvan you will want to wait until the counter associated with the channel has get removed.

Ivan Zemlyanskiy

@QIvan

but if I closed the aeron where can I get the CounterReader from?

I mean, I tried to do it with aeron.countersReader(), but I got a segFault =)

Martin Thompson

@mjpt777

@QIvan Same way AeronStat does it.

Ivan Zemlyanskiy

@QIvan

ahhh... you're right, now I feel stupid =)
thank you!

zaradai

@zaradai

Q, Possible bug?
aeron_driver_receiver.c
aeron_driver_receiver_on_add_publication_image

if ensure capacity fails, the error is logged but then continues to inc the array ptr which will surely fail. Should the capacity check be separated and skip the images array update?

Lorenzo Nicora

@nicusX

Hi everybody! Apologies for the newbie question. I am trying to run some of the samples in AWS, between separate EC2 instances, same subnet.
Ping/Pong works perfectly, but I cannot make BasicPublisher/BasicSubscriber talk each other, even via simple unicast UDP.

Publisher (10.0.101.101):

java -cp ./aeron-all-1.32.0-SNAPSHOT.jar \
     -Daeron.sample.embeddedMediaDriver=true \
     -Daeron.sample.channel="aeron:udp?endpoint=10.0.101.101:9000" \
     io.aeron.samples.BasicPublisher

Subscriber (10.0.101.201):

java -cp ./aeron-all-1.32.0-SNAPSHOT.jar \
   -Daeron.sample.embeddedMediaDriver=true \
   -Daeron.sample.channel="aeron:udp?endpoint=10.0.101.101:9000" \
   io.aeron.samples.BasicSubscriber

The subscriber always fails to connect:

io.aeron.exceptions.ChannelEndpointException: ERROR - AeronException : ERROR - channel error - Cannot assign requested address (at java.base/sun.nio.ch.Net.bind0(Native Method)): aeron:udp?endpoint=10.0.101.101:9000

Security Groups, NACL and routing seems to be ok. The two instances can ping each other and can send UDP on port 9000 with netcat. I also tried specifying the interface explicitly and nothing changes (instances have a single network interface, anyhow).

I am sure I am missing something stupid.

Todd L. Montgomery

@tmontgomery

subscriber should use 10.0.101.201. You are using the publisher IP (10.0.101.101). So, use 10.0.101.201 for both if that IP is the subscriber IP

Lorenzo Nicora

@nicusX

Many thanks @tmontgomery
I must say this was not obvious at all, looking at all samples and the wiki. Everything uses localhost that does make not obvious whether it's the publisher or the recipient

Todd L. Montgomery

@tmontgomery

endpoint is explained in https://github.com/real-logic/aeron/wiki/Channel-Configuration#configuration-properties

just FYI

Lorenzo Nicora

@nicusX

Thanks. I read that.
Re-reading "The socket address to which publications will send messages and from which subscriptions will receive messages" now I understand the subtlety. But it wasn't massively obvious.
(I don't want to criticise. Please, just get this as a newbie feedback)

Todd L. Montgomery

@tmontgomery

thanks! If you have any suggestions on where that info should be, feel free to let us know

i.e. where would you have expected it, etc.

Lorenzo Nicora

@nicusX

The endpoint paragraph on the wiki is fine. Clarifying the "socket address" is the subscriber (recipient) machine would have helped

Martin Thompson

@mjpt777

@nicusX I've just added that.

Lorenzo Nicora

@nicusX

Cool

Martin Thompson

@mjpt777

@zaradai Thanks, I've pushed a fix.

Mendel Monteiro-Beckerman

@MendelMonteiro

Hi, has there ever been any interest in being able to set QoS traffic classes on the sockets created by Aeron?

Todd L. Montgomery

@tmontgomery

@MendelMonteiro nothing that anyone has been willing to sponsor development on. But if interested in sponsoring it, we could look into it.

Mendel Monteiro-Beckerman

@MendelMonteiro

@tmontgomery thanks for the reply. I'll get in touch if sponsorship is an option.

William

@ilove7412369_twitter

i look at the stats:
sessionId=-1385188173 streamId=1001 channel=aeron:ipc?term-length=268435456 : pub-pos (sampled):251:1694624000 pub-lmt:251:1694623552

is that when it publish reach the pub-lmt, it will take tons of time for the archive to create new memory mapped file and zero them out causing such 10 s?

any ways to avoid?

William

@ilove7412369_twitter

sorry problem solved

Ivan Zemlyanskiy

@QIvan

hi! a quick question if you don't mind:
should in theory the taggedReplicate work with C Media Driver?
I'm getting a timeout exception on my even basic tests, while with Java MD everything is just fine.
thanks.

Martin Thompson

@mjpt777

This room is not being used to answer Aeron questions. Questions can go to our support channels or Stackoverflow which we may eventually get round to.

This room is being reserved for discussions with public contributors.

Martin Thompson

@mjpt777

We are considering shutting down this room. For now we will keep it open but will no longer be giving out free support.

Ivan Zemlyanskiy

@QIvan

oh, cool! glad to read it! It would be awesome if Aeron tag would become more popular on SO

I hope that'd be a good start https://stackoverflow.com/questions/65780369/aeron-should-in-the-taggedreplicate-work-with-c-media-driver =)

Martin Thompson

@mjpt777

@QIvan Please stop posting here if it is not related to contributions.

Ivan Zemlyanskiy

@QIvan

ok, sorry. Speaking about contributions, a little feedback about reading with Aeron:
why do we need this errorHandler in TermReader https://github.com/real-logic/aeron/blob/master/aeron-client/src/main/java/io/aeron/logbuffer/TermReader.java#L82 ?
I found it very inconveniet, because when I read with my own FH and I throw an exception, I want to use my own try-catch block around a poll, not the global errorHandler which I provided for Aeron and excpect handle aeron related exceptions.

Martin Thompson

@mjpt777

@QIvan This is really a question and not a contribution. I'll allow grace just this once. Look at the following: https://github.com/real-logic/aeron/blob/master/aeron-client/src/main/java/io/aeron/Aeron.java#L1124

William

@ilove7412369_twitter

Aeron archive replay seems quite slow when remote replicate from say Tokyo to SG. Is it not a right use of that? Any way should be better way to do for a higher throughput?

Martin Thompson

@mjpt777

@ilove7412369_twitter As previous stated we will not be offering free consultancy in the room any longer. This room is reserved for public contributor discussions. If you need support we have a commercial offering.

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