Upgrade to Apache Client 5
The release of the Apache Client 5.0 in February 2020 introduced some breaking changes, including namespace changes. For example the org.apache.http.impl.client.CloseableHttpClient was moved to org.apache.hc.client5.http.impl.classic.CloseableHttpClient. Thus, there are some efforts necessary to migrate from previous versions to version 5.
Since the default instrumentation of inspectIT Ocelot only addresses the Apache Client 4, you have to include an additional configuration to instrument version 5 for traces and metrics.
You can find the configuration in GitHub: inspectit-ocelot-apache-client5-configuration
Find more information about the migration from version 4 to version 5 on https://hc.apache.org.