I have a Java 8 Spring Boot service.

It is hosted on AWS, in Kubernetes v1.13, Docker v18.06.3-ce.

Yesterday for 10 or even more hours I had a bunch of intermittent UnknownHostExceptions when trying to send http requests from my service to both internal and external services.

The exception happened at least for 5 different host names.

Today I had no issues.

In the service logs I can not find anything other than something like this:

java.net.UnknownHostException: example.com

Also, not sure if it is relevant, but the service is using Spring Boot Apache Camel v2.22.0 to send these requests. Here is a piece of code which sends them:

    Exchange exchange = template.send(url, exchange1 -> {
        exchange1.getIn().setHeaders(headers);
        exchange1.getIn().setHeader(Exchange.HTTP_METHOD, httpMethod.toString());
        exchange1.getIn().setBody(body);
    });

Mvn dependencies for Apache Camel:

    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-spring-boot</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-spring-boot-starter</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-stream</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-core</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-script</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>
    <dependency>
        <groupId>org.apache.camel</groupId>
        <artifactId>camel-http4</artifactId>
        <version>${apache.camel.version}</version>
    </dependency>

Any ideas what can be the cause of these intermittent UnknownHostExceptions? Please let me know what pieces of info would be helpful to find out the root cause of the issue.

P.S. Service was working fine for more than a year. No recent code changes. At least for this logic above.