Interesting – what is the JobManager submission bounded by? Does it only allow 
a certain number of submissions per second, or is there a number of threads it 
accepts?

// ah

From: Robert Metzger <rmetz...@apache.org>
Sent: Tuesday, August 11, 2020 4:46 AM
To: Hailu, Andreas [Engineering] <andreas.ha...@ny.email.gs.com>
Cc: user@flink.apache.org; Shah, Siddharth [Engineering] 
<siddharth.x.s...@ny.email.gs.com>
Subject: Re: JobManager refusing connections when running many jobs in parallel?

Thanks for checking.

Your analysis sounds correct. The JM is busy processing job submissions, 
resulting in other submissions not being accepted.

Increasing rest.connection-timeout should resolve your problem.


On Fri, Aug 7, 2020 at 1:59 AM Hailu, Andreas 
<andreas.ha...@gs.com<mailto:andreas.ha...@gs.com>> wrote:
Thanks for pointing this out. We had a look - the nodes in our cluster have a 
cap of 65K open files and we aren’t breaching 50% per metrics, so I don’t 
believe this is the problem.

The connection refused error makes us think it’s some process using a thread 
pool for the JobManager hitting capacity on a port somewhere. This sound 
correct? Is there a config for us to increase the pool size?
________________________________
From: Robert Metzger <rmetz...@apache.org<mailto:rmetz...@apache.org>>
Sent: Wednesday, July 29, 2020 1:52:53 AM
To: Hailu, Andreas [Engineering]
Cc: user@flink.apache.org<mailto:user@flink.apache.org>; Shah, Siddharth 
[Engineering]
Subject: Re: JobManager refusing connections when running many jobs in parallel?

Hi Andreas,

Thanks for reaching out .. this should not happen ...
Maybe your operating system has configured low limits for the number of 
concurrent connections / sockets. Maybe this thread is helpful: 
https://stackoverflow.com/questions/923990/why-do-i-get-connection-refused-after-1024-connections<https://urldefense.proofpoint.com/v2/url?u=https-3A__stackoverflow.com_questions_923990_why-2Ddo-2Di-2Dget-2Dconnection-2Drefused-2Dafter-2D1024-2Dconnections&d=DwMFaQ&c=7563p3e2zaQw0AB1wrFVgyagb2IE5rTZOYPxLxfZlX4&r=hRr4SA7BtUvKoMBP6VDhfisy2OJ1ZAzai-pcCC6TFXM&m=BIYf5yz3admb-1ZnilWzxDnW3JB8d8VkHSSBMPTHaQI&s=bwNr69eekHCEpop2wur_LkAkIxqza-OjwNmG7cv8atc&e=>
 (there might better SO threads, I didn't put much effort into searching :) )

On Mon, Jul 27, 2020 at 6:31 PM Hailu, Andreas 
<andreas.ha...@gs.com<mailto:andreas.ha...@gs.com>> wrote:
Hi team,

We’ve observed that when we submit a decent number of jobs in parallel from a 
single Job Master, we encounter job failures due with Connection Refused 
exceptions. We’ve seen this behavior start at 30 jobs running in parallel. It’s 
seemingly transient, however, as upon several retries the job succeeds. The 
surface level error varies, but digging deeper in stack traces it looks to stem 
from the Job Manager no longer accepting connections.

I’ve included a couple of examples below from failed jobs’ driver logs, with 
different errors stemming from a connection refused error:

First example: 15 Task Managers/2 cores/4096 Job Manager memory/12288 Task 
Manager memory - 30 jobs submitted in parallel, each with parallelism of 1
Job Manager is running @ d43723-563.dc.gs.com<http://d43723-563.dc.gs.com>: 
Using job manager web tracking url <a href="http://d43723-563.dc.gs.com:41268";> 
Job Manager Web Interface  (http://d43723-563.dc.gs.com:41268) </a>
org.apache.flink.client.program.ProgramInvocationException: Could not retrieve 
the execution result. (JobID: 1dfef6303cf0e888231d4c57b4b4e0e6)
at 
org.apache.flink.client.program.rest.RestClusterClient.submitJob(RestClusterClient.java:255)
at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:338)
at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:326)
at 
org.apache.flink.client.program.ContextEnvironment.execute(ContextEnvironment.java:62)
...
Caused by: org.apache.flink.runtime.concurrent.FutureUtils$RetryException: 
Could not complete the operation. Number of retries has been exhausted.
at 
org.apache.flink.runtime.concurrent.FutureUtils.lambda$retryOperationWithDelay$8(FutureUtils.java:273)
at 
java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:760)
at 
java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:736)
at 
java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
at 
java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:1977)
at 
org.apache.flink.runtime.rest.RestClient.lambda$submitRequest$1(RestClient.java:341)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.DefaultPromise.notifyListener0(DefaultPromise.java:511)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.DefaultPromise.notifyListeners0(DefaultPromise.java:504)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.DefaultPromise.notifyListenersNow(DefaultPromise.java:483)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.DefaultPromise.notifyListeners(DefaultPromise.java:424)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.DefaultPromise.tryFailure(DefaultPromise.java:121)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.fulfillConnectPromise(AbstractNioChannel.java:327)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:343)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKey(NioEventLoop.java:644)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeysOptimized(NioEventLoop.java:591)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.processSelectedKeys(NioEventLoop.java:508)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:470)
at 
org.apache.flink.shaded.netty4.io.netty.util.concurrent.SingleThreadEventExecutor$5.run(SingleThreadEventExecutor.java:909)
... 1 more
Caused by: java.util.concurrent.CompletionException: 
org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannel$AnnotatedConnectException:
 Connection refused: 
d43723-563.dc.gs.com/10.47.126.221:41268<http://d43723-563.dc.gs.com/10.47.126.221:41268>
at 
java.util.concurrent.CompletableFuture.encodeThrowable(CompletableFuture.java:292)
at 
java.util.concurrent.CompletableFuture.completeThrowable(CompletableFuture.java:308)
at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:943)
at 
java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
... 16 more
Caused by: 
org.apache.flink.shaded.netty4.io.netty.channel.AbstractChannel$AnnotatedConnectException:
 Connection refused: 
d43723-563.dc.gs.com/10.47.126.221:41268<http://d43723-563.dc.gs.com/10.47.126.221:41268>
at sun.nio.ch.SocketChannelImpl.checkConnect(Native Method)
at sun.nio.ch.SocketChannelImpl.finishConnect(SocketChannelImpl.java:717)
at 
org.apache.flink.shaded.netty4.io.netty.channel.socket.nio.NioSocketChannel.doFinishConnect(NioSocketChannel.java:327)
at 
org.apache.flink.shaded.netty4.io.netty.channel.nio.AbstractNioChannel$AbstractNioUnsafe.finishConnect(AbstractNioChannel.java:340)
... 6 more
Caused by: java.net.ConnectException: Connection refused

Second example: 30 Task Managers/2 cores/4096 Job Manager memory/12288 Task 
Manager memory - 60 jobs submitted in parallel, each with parallelism of 1
Job Manager is running @ d43723-484.dc.gs.com<http://d43723-484.dc.gs.com>: 
Using job manager web tracking url <a href="http://d43723-484.dc.gs.com:36757";> 
Job Manager Web Interface  (http://d43723-484.dc.gs.com:36757) </a>
org.apache.flink.client.program.ProgramInvocationException: Could not retrieve 
the execution result. (JobID: 9c4a797df26b510a92a843c756dc4b3d)
at 
org.apache.flink.client.program.rest.RestClusterClient.submitJob(RestClusterClient.java:255)
at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:338)
at org.apache.flink.client.program.ClusterClient.run(ClusterClient.java:326)
at 
org.apache.flink.client.program.ContextEnvironment.execute(ContextEnvironment.java:62)
...
Caused by: org.apache.flink.runtime.client.JobSubmissionException: Failed to 
submit JobGraph.
at 
org.apache.flink.client.program.rest.RestClusterClient.lambda$submitJob$8(RestClusterClient.java:382)
at 
java.util.concurrent.CompletableFuture.uniExceptionally(CompletableFuture.java:870)
at 
java.util.concurrent.CompletableFuture$UniExceptionally.tryFire(CompletableFuture.java:852)
at 
java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
at 
java.util.concurrent.CompletableFuture.completeExceptionally(CompletableFuture.java:1977)
at 
org.apache.flink.runtime.concurrent.FutureUtils.lambda$retryOperationWithDelay$8(FutureUtils.java:263)
at 
java.util.concurrent.CompletableFuture.uniWhenComplete(CompletableFuture.java:760)
at 
java.util.concurrent.CompletableFuture$UniWhenComplete.tryFire(CompletableFuture.java:736)
at 
java.util.concurrent.CompletableFuture.postComplete(CompletableFuture.java:474)
at java.util.concurrent.CompletableFuture.postFire(CompletableFuture.java:561)
at 
java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:929)
at 
java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
... 3 more
Caused by: org.apache.flink.runtime.rest.util.RestClientException: [Could not 
upload job files.]
at org.apache.flink.runtime.rest.RestClient.parseResponse(RestClient.java:389)
at 
org.apache.flink.runtime.rest.RestClient.lambda$submitRequest$3(RestClient.java:373)
at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
at 
java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
... 4 more
... (this pattern repeats for number of unique JobIDs)
Caused by: org.apache.flink.runtime.rest.util.RestClientException: [Could not 
upload job files.]
at org.apache.flink.runtime.rest.RestClient.parseResponse(RestClient.java:389)
at 
org.apache.flink.runtime.rest.RestClient.lambda$submitRequest$3(RestClient.java:373)
at java.util.concurrent.CompletableFuture.uniCompose(CompletableFuture.java:952)
at 
java.util.concurrent.CompletableFuture$UniCompose.tryFire(CompletableFuture.java:926)
at 
java.util.concurrent.CompletableFuture$Completion.run(CompletableFuture.java:442)
at 
java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
at 
java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
at java.lang.Thread.run(Thread.java:745)
...
26 05:46:39,734 [CASHFLOW-18394] WARN  FlinkClusterStateMonitor - Error while 
attempting to fetch job details for job 4d20537a676df2855e29b31b1de1ead5
com.gs.ep.data.lake.refinerlib.restful.RestfulException: failed connecting to 
http://d43723-484.dc.gs.com:36757/jobs/4d20537a676df2855e29b31b1de1ead5 after 1 
time(s)
Caused by: java.net.ConnectException: Connection refused
at java.net.PlainSocketImpl.socketConnect(Native Method)
at java.net.AbstractPlainSocketImpl.doConnect(AbstractPlainSocketImpl.java:350)
at 
java.net.AbstractPlainSocketImpl.connectToAddress(AbstractPlainSocketImpl.java:206)
at java.net.AbstractPlainSocketImpl.connect(AbstractPlainSocketImpl.java:188)
at java.net.SocksSocketImpl.connect(SocksSocketImpl.java:392)
at java.net.Socket.connect(Socket.java:589)
at java.net.Socket.connect(Socket.java:538)
at sun.net.NetworkClient.doConnect(NetworkClient.java:180)

These connection refusal exceptions and their transient nature makes me think 
that it might be a network-related issue. It’s not uncommon for us to need to 
run 100+ jobs in parallel. How can we investigate what’s causing the Job 
Manager to periodically refuse connections? I can see a Netty package in the 
first example’s stack trace – is there any option we can tune?

____________

Andreas Hailu
Data Lake Engineering | Goldman Sachs & Co.


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