vert.x getting - failed to create a child event loop

Question

I am creating about 150 files of around 5MB sizes. Vertx file APIs gives an exception randomly after creating 10-15 files "failed to create a child event loop".

(I am using vertx3 and java8)

Below is my code snippet (After I get a callback then only I call the function again to create the next file. So, file creation is never concurrent):

Vertx.vertx().fileSystem().writeFile(filepath,
       Buffer.buffer(dataList.toString()), result -> {
 if (result.succeeded()) {
   System.out.println("File written");
 } else {
  System.err.println("Oh oh ..." + result.cause());
 }
 lambda.callback();
});

Below is my exception stack trace:

java.lang.IllegalStateException: failed to create a child event loop
    at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:68)
    at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:49)
    at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:61)
    at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:52)
    at io.vertx.core.impl.VertxImpl.<init>(VertxImpl.java:132)
    at io.vertx.core.impl.VertxImpl.<init>(VertxImpl.java:126)
    at io.vertx.core.impl.VertxImpl.<init>(VertxImpl.java:122)
    at io.vertx.core.impl.VertxFactoryImpl.vertx(VertxFactoryImpl.java:34)
    at io.vertx.core.Vertx.vertx(Vertx.java:78)
    at rc_datawarehouse.CsvToJsonChunkWriter.writeCsvChunkToFiles(CsvToJsonChunkWriter.java:73)
    at rc_datawarehouse.CsvToJsonReadWrite.lambda$2(CsvToJsonReadWrite.java:119)
    at rc_datawarehouse.CsvToJsonReadWrite$$Lambda$16/1470881859.handle(Unknown Source)
    at io.vertx.core.file.impl.AsyncFileImpl.handleData(AsyncFileImpl.java:335)
    at io.vertx.core.file.impl.AsyncFileImpl.lambda$doRead$285(AsyncFileImpl.java:320)
    at io.vertx.core.file.impl.AsyncFileImpl$$Lambda$17/1067800899.handle(Unknown Source)
    at io.vertx.core.file.impl.AsyncFileImpl$2.lambda$done$289(AsyncFileImpl.java:408)
    at io.vertx.core.file.impl.AsyncFileImpl$2$$Lambda$18/1632681662.handle(Unknown Source)
    at io.vertx.core.impl.ContextImpl.lambda$wrapTask$15(ContextImpl.java:314)
    at io.vertx.core.impl.ContextImpl$$Lambda$5/1780132728.run(Unknown Source)
    at io.netty.util.concurrent.SingleThreadEventExecutor.runAllTasks(SingleThreadEventExecutor.java:357)
    at io.netty.channel.nio.NioEventLoop.run(NioEventLoop.java:357)
    at io.netty.util.concurrent.SingleThreadEventExecutor$2.run(SingleThreadEventExecutor.java:111)
    at java.lang.Thread.run(Unknown Source)
Caused by: io.netty.channel.ChannelException: failed to open a new selector
    at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:128)
    at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:120)
    at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:87)
    at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:64)
    ... 22 more
Caused by: java.io.IOException: Unable to establish loopback connection
    at sun.nio.ch.PipeImpl$Initializer.run(Unknown Source)
    at sun.nio.ch.PipeImpl$Initializer.run(Unknown Source)
    at java.security.AccessController.doPrivileged(Native Method)
    at sun.nio.ch.PipeImpl.<init>(Unknown Source)
    at sun.nio.ch.SelectorProviderImpl.openPipe(Unknown Source)
    at java.nio.channels.Pipe.open(Unknown Source)
    at sun.nio.ch.WindowsSelectorImpl.<init>(Unknown Source)
    at sun.nio.ch.WindowsSelectorProvider.openSelector(Unknown Source)
    at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:126)
    ... 25 more
Caused by: java.net.SocketException: No buffer space available (maximum connections reached?): connect
    at sun.nio.ch.Net.connect0(Native Method)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.Net.connect(Unknown Source)
    at sun.nio.ch.SocketChannelImpl.connect(Unknown Source)
    at java.nio.channels.SocketChannel.open(Unknown Source)
    at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(Unknown Source)
    ... 34 more

score 2 · Accepted Answer · answered Dec 15 '15 at 17:24

2

I got my answer from the forum here (Thanks Jez)

Vertx.vertx() is the culprit. It creates a new vertx every time leading to multiple eventloops which seems to be the problem.

I cached it in a variable, rather than using Vertx.vertx() every time and it worked

cachedVertx.fileSystem().writeFile(...)

answered Dec 15 '15 at 17:24

prasun

7,073
9
41
59

Vertx.vertx() wouldn't create any event loops. Event loop queue and thread is created only when you deploy a Verticle with method Vertx#deployVerticle. And why do you want to cache vertx instance when the variable is already in the parent Abstract class from your verticle, unless you don't have any other variable with the same name (vertx) – Sai Karthik Mar 17 '21 at 16:44

vert.x getting - failed to create a child event loop

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