Rosa Seohwa Kang created FLINK-38109:
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Summary: BlobServer isn't associated with the correct bind-host
Key: FLINK-38109
URL: https://issues.apache.org/jira/browse/FLINK-38109
Project: Flink
Issue Type: Bug
Components: Runtime / Coordination
Affects Versions: 1.11.0
Environment: !image-2025-07-16-18-23-30-302.png|width=654,height=135!
Reporter: Rosa Seohwa Kang
In a flink cluster, if the JobManager bind-host is configured with an address,
this creates a mismatch where clients expect to connect to BlobServer at same
address, but it's actually bound to localhost. The BlobServer becomes
unreachable to clients, causing "Could not connect to BlobServer" errors.
This can be reproduced when uploading a JAR file to the cluster for UDF
registration, and configuring the JobManager bind-host to an external address.
Example:
```
package com.shopify.flink.examples.functions.asynchttpfunction;
import org.apache.flink.configuration.Configuration;
import org.apache.flink.configuration.RestOptions;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.table.api.bridge.java.StreamTableEnvironment;
public class RosaTestFunction {
public static void main(final String[] args) throws Exception {
// Configuration for connecting to the local session cluster
final Configuration configuration = new Configuration();
// Configure REST client to connect to the local session cluster
configuration.set(RestOptions.ADDRESS,
"flink-examples-flinkbook.root.shopify.dev.internal");
configuration.set(RestOptions.PORT, 7100); // REST API port
configuration.setString("jobmanager.bind-host",
"flink-examples-flinkbook.root.shopify.dev.internal");
configuration.setString("taskmanager.bind-host",
"flink-examples-flinkbook.root.shopify.dev.internal");
StreamExecutionEnvironment env =
StreamExecutionEnvironment.getExecutionEnvironment(configuration);
StreamTableEnvironment tableEnv = StreamTableEnvironment.create(env);
tableEnv.executeSql("""
CREATE FUNCTION example_custom
AS 'com.shopify.flink.examples.shared.ExampleCustomFunction'
LANGUAGE JAVA
USING JAR
'file:///Users/rosa/src/github.com/Shopify/flink-examples/sql/pipelines/flinksql-example/jars/shared.jar';""");
tableEnv.executeSql("SELECT example_custom(1,2) as
sum_result;").print();
}
}
```
Root cause:
The BlobServer bind-host is set to use the Jobmanager bind-host, however isn't
assigned the correct host in the PekkoRpcService.
[BlobServer.java](https://github.com/apache/flink/blob/master/flink-runtime/src/main/java/org/apache/flink/runtime/blob/BlobServer.java#L218-L220)
```
String bindHost =
(String)config.getOptional(JobManagerOptions.BIND_HOST).orElseGet(NetUtils::getWildcardIPAddress);
```
[PekkoRpcService.java](https://github.com/apache/flink/blob/master/flink-rpc/flink-rpc-akka/src/main/java/org/apache/flink/runtime/rpc/pekko/PekkoRpcService.java#L477-L486)
```
private Tuple2<String, String> extractAddressHostname(ActorRef actorRef) {
final String actorAddress = PekkoUtils.getRpcURL(actorSystem, actorRef);
final String hostname;
Option<String> host = actorRef.path().address().host();
if (host.isEmpty()) {
hostname = "localhost";
} else {
hostname = host.get();
}
return Tuple2.of(actorAddress, hostname);
}
```
Proposed solution:
Add a `blob.server.bind-host` configuration option similar to the existing
bind-host solution introduced in
[FLINK-15911](https://issues.apache.org/jira/browse/FLINK-15911).
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