# ElasticSearch fails to start with java.lang.IllegalStateException: failed to create child event loop

**URL:** <https://discuss.elastic.co/t/elasticsearch-fails-to-start-with-java-lang-illegalstateexception-failed-to-create-child-event-loop/218797>\
**Category:** Elasticsearch\
**Created:** [February 11, 2020, 3:08pm UTC](https://discuss.elastic.co/t/elasticsearch-fails-to-start-with-java-lang-illegalstateexception-failed-to-create-child-event-loop/218797 "2020-02-11T15:08:26Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![code31415926535](https://avatars.discourse-cdn.com/v4/letter/c/a183cd/32.png) [@code31415926535](https://discuss.elastic.co/u/code31415926535)\
**Post date:** [February 11, 2020, 3:08pm UTC](https://discuss.elastic.co/t/elasticsearch-fails-to-start-with-java-lang-illegalstateexception-failed-to-create-child-event-loop/218797/1 "2020-02-11T15:08:26Z")

</div>

Hello. I am trying to run Elasticsearch on a fresh windows 10 machine but I get the following error:

```
org.elasticsearch.bootstrap.StartupException: java.lang.IllegalStateException: failed to create a child event loop
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:163) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.execute(Elasticsearch.java:150) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.cli.EnvironmentAwareCommand.execute(EnvironmentAwareCommand.java:86) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.cli.Command.mainWithoutErrorHandling(Command.java:125) ~[elasticsearch-cli-7.5.2.jar:7.5.2]
        at org.elasticsearch.cli.Command.main(Command.java:90) ~[elasticsearch-cli-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:115) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.main(Elasticsearch.java:92) ~[elasticsearch-7.5.2.jar:7.5.2]
Caused by: java.lang.IllegalStateException: failed to create a child event loop
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:88) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47) ~[?:?]
        at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:59) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:78) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:73) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:60) ~[?:?]
        at org.elasticsearch.transport.netty4.Netty4Transport.doStart(Netty4Transport.java:130) ~[?:?]
        at org.elasticsearch.xpack.core.security.transport.netty4.SecurityNetty4Transport.doStart(SecurityNetty4Transport.java:81) ~[?:?]
        at org.elasticsearch.xpack.security.transport.netty4.SecurityNetty4ServerTransport.doStart(SecurityNetty4ServerTransport.java:43) ~[?:?]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.transport.TransportService.doStart(TransportService.java:230) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.node.Node.start(Node.java:688) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.start(Bootstrap.java:293) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:378) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-7.5.2.jar:7.5.2]
        ... 6 more
Caused by: io.netty.channel.ChannelException: failed to open a new selector
        at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:181) ~[?:?]
        at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:147) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:138) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:37) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:84) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47) ~[?:?]
        at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:59) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:78) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:73) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:60) ~[?:?]
        at org.elasticsearch.transport.netty4.Netty4Transport.doStart(Netty4Transport.java:130) ~[?:?]
        at org.elasticsearch.xpack.core.security.transport.netty4.SecurityNetty4Transport.doStart(SecurityNetty4Transport.java:81) ~[?:?]
        at org.elasticsearch.xpack.security.transport.netty4.SecurityNetty4ServerTransport.doStart(SecurityNetty4ServerTransport.java:43) ~[?:?]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.transport.TransportService.doStart(TransportService.java:230) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.node.Node.start(Node.java:688) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.start(Bootstrap.java:293) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:378) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-7.5.2.jar:7.5.2]
        ... 6 more
Caused by: java.io.IOException: Unable to establish loopback connection
        at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:94) ~[?:?]
        at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:61) ~[?:?]
        at java.security.AccessController.doPrivileged(AccessController.java:554) ~[?:?]
        at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:171) ~[?:?]
        at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50) ~[?:?]
        at java.nio.channels.Pipe.open(Pipe.java:155) ~[?:?]
        at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127) ~[?:?]
        at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44) ~[?:?]
        at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:179) ~[?:?]
        at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:147) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:138) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:37) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:84) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47) ~[?:?]
        at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:59) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:78) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:73) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:60) ~[?:?]
        at org.elasticsearch.transport.netty4.Netty4Transport.doStart(Netty4Transport.java:130) ~[?:?]
        at org.elasticsearch.xpack.core.security.transport.netty4.SecurityNetty4Transport.doStart(SecurityNetty4Transport.java:81) ~[?:?]
        at org.elasticsearch.xpack.security.transport.netty4.SecurityNetty4ServerTransport.doStart(SecurityNetty4ServerTransport.java:43) ~[?:?]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.transport.TransportService.doStart(TransportService.java:230) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.node.Node.start(Node.java:688) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.start(Bootstrap.java:293) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:378) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-7.5.2.jar:7.5.2]
        ... 6 more
Caused by: java.net.ConnectException: Connection timed out: connect
        at sun.nio.ch.Net.connect0(Native Method) ~[?:?]
        at sun.nio.ch.Net.connect(Net.java:493) ~[?:?]
        at sun.nio.ch.Net.connect(Net.java:482) ~[?:?]
        at sun.nio.ch.SocketChannelImpl.connect(SocketChannelImpl.java:732) ~[?:?]
        at java.nio.channels.SocketChannel.open(SocketChannel.java:194) ~[?:?]
        at sun.nio.ch.PipeImpl$Initializer$LoopbackConnector.run(PipeImpl.java:127) ~[?:?]
        at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:76) ~[?:?]
        at sun.nio.ch.PipeImpl$Initializer.run(PipeImpl.java:61) ~[?:?]
        at java.security.AccessController.doPrivileged(AccessController.java:554) ~[?:?]
        at sun.nio.ch.PipeImpl.<init>(PipeImpl.java:171) ~[?:?]
        at sun.nio.ch.SelectorProviderImpl.openPipe(SelectorProviderImpl.java:50) ~[?:?]
        at java.nio.channels.Pipe.open(Pipe.java:155) ~[?:?]
        at sun.nio.ch.WindowsSelectorImpl.<init>(WindowsSelectorImpl.java:127) ~[?:?]
        at sun.nio.ch.WindowsSelectorProvider.openSelector(WindowsSelectorProvider.java:44) ~[?:?]
        at io.netty.channel.nio.NioEventLoop.openSelector(NioEventLoop.java:179) ~[?:?]
        at io.netty.channel.nio.NioEventLoop.<init>(NioEventLoop.java:147) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:138) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.newChild(NioEventLoopGroup.java:37) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:84) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:58) ~[?:?]
        at io.netty.util.concurrent.MultithreadEventExecutorGroup.<init>(MultithreadEventExecutorGroup.java:47) ~[?:?]
        at io.netty.channel.MultithreadEventLoopGroup.<init>(MultithreadEventLoopGroup.java:59) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:78) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:73) ~[?:?]
        at io.netty.channel.nio.NioEventLoopGroup.<init>(NioEventLoopGroup.java:60) ~[?:?]
        at org.elasticsearch.transport.netty4.Netty4Transport.doStart(Netty4Transport.java:130) ~[?:?]
        at org.elasticsearch.xpack.core.security.transport.netty4.SecurityNetty4Transport.doStart(SecurityNetty4Transport.java:81) ~[?:?]
        at org.elasticsearch.xpack.security.transport.netty4.SecurityNetty4ServerTransport.doStart(SecurityNetty4ServerTransport.java:43) ~[?:?]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.transport.TransportService.doStart(TransportService.java:230) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.common.component.AbstractLifecycleComponent.start(AbstractLifecycleComponent.java:59) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.node.Node.start(Node.java:688) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.start(Bootstrap.java:293) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Bootstrap.init(Bootstrap.java:378) ~[elasticsearch-7.5.2.jar:7.5.2]
        at org.elasticsearch.bootstrap.Elasticsearch.init(Elasticsearch.java:159) ~[elasticsearch-7.5.2.jar:7.5.2]
        ... 6 more

```

I get this error when running a freshly extracted zip with no configuration changes. My environment:

Windows 10: 17134.1246  
Elasticsearch: 7.5.2-windows-x86-64  
I am running ES form the command line using: .\elasticsearch.bat

I have tried changing the port and hostname. I've also tried to change the transport port and transport username with no success. This issue is most likely environment specific but I am out of ideas as to what could cause this issue.

Could you provide some ideas?

---

<div class="post-metadata">

**Author:** ![code31415926535](https://avatars.discourse-cdn.com/v4/letter/c/a183cd/32.png) [@code31415926535](https://discuss.elastic.co/u/code31415926535)\
**Post date:** [February 12, 2020, 2:32pm UTC](https://discuss.elastic.co/t/elasticsearch-fails-to-start-with-java-lang-illegalstateexception-failed-to-create-child-event-loop/218797/2 "2020-02-12T14:32:40Z")

</div>

I managed to find a workaround by

1. Disabling the Firewall.
2. Starting Elasticsearch.
3. Enabling the Firewall again.

Subsequent runs of Elasticsearch worked just fine with firewall enabled (which is weird).

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [March 11, 2020, 2:32pm UTC](https://discuss.elastic.co/t/elasticsearch-fails-to-start-with-java-lang-illegalstateexception-failed-to-create-child-event-loop/218797/3 "2020-03-11T14:32:42Z")

</div>

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