Spring Boot app cannot connect to Daemon in Docker container

[haiko]

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?

[wangzlei]

By default XRay Daemon turns on UDP port 2000 for sending trace to XRay and TCP port 2000 for remote sampling rules. I guess you are running Daemon in docker for Mac, so, get error log about Sampling rule poller but still see trace in xray console. There is a known issue that docker for Mac does not map to local TCP port, please try workaround by searching google, such as docker/for-mac#770

If not using remote sampling rule, you can ignore that log.