Spring Boot app cannot connect to Daemon in Docker container

I have instrumented a Spring Boot application with XRay. I run a Docker container with a proxy to XRay using the instructions on https://docs.aws.amazon.com/xray/latest/devguide/xray-daemon-local.html. But my application cannot connect to the XRay daemon in the docker container. The daemon in the docker container start up logs the following:

```
2022-02-01T10:51:23Z [Info] Initializing AWS X-Ray daemon 3.3.3
2022-02-01T10:51:23Z [Info] Using buffer memory limit of 19 MB
2022-02-01T10:51:23Z [Info] 304 segment buffers allocated
2022-02-01T10:51:23Z [Info] Using region: eu-central-1
2022-02-01T10:51:23Z [Info] HTTP Proxy server using X-Ray Endpoint : https://xray.eu-central-1.amazonaws.com
2022-02-01T10:51:23Z [Info] Starting proxy http server on 127.0.0.1:2000
```

My application tries to connect but fails with the following exception:
```
2022-02-01 11:52:59.150 ERROR 48013 --- [pool-2-thread-1] c.a.x.s.sampling.pollers.RulePoller : Encountered error polling GetSamplingRules:
com.amazonaws.xray.internal.XrayClientException: Could not serialize and send request.
at com.amazonaws.xray.internal.UnsignedXrayClient.sendRequest(UnsignedXrayClient.java:142)
at com.amazonaws.xray.internal.UnsignedXrayClient.getSamplingRules(UnsignedXrayClient.java:112)
at com.amazonaws.xray.strategy.sampling.pollers.RulePoller.pollRule(RulePoller.java:100)
at com.amazonaws.xray.strategy.sampling.pollers.RulePoller.lambda$start$0(RulePoller.java:72)
at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
at java.base/java.util.concurrent.FutureTask.runAndReset(FutureTask.java:305)
at java.base/java.util.concurrent.ScheduledThreadPoolExecutor$ScheduledFutureTask.run(ScheduledThreadPoolExecutor.java:305)
at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1128)
at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:628)
at java.base/java.lang.Thread.run(Thread.java:829)
Caused by: java.net.ConnectException: Connection refused (Connection refused)
```

When I run the xray daemon locally on my system everything works and traces are uploaded to AWS. Anyone an idea?

Start with the AWS X-Ray daemon Docker instructions linked in the issue and compare them with the Spring Boot application's connection settings. Investigate the daemon log showing the proxy bound to 127.0.0.1:2000 and the application's Connection refused error. Done means the application connects to the container and traces are uploaded to AWS.

Written by the indexing model from the issue text.