code: public IpcLogEntry addTag(Tag tag) {
      this.additionalTags.put(tag.key(), tag.value());
      return this;
    }
docs: Add custom tags to the request metrics. Note, IPC metrics already have many tags and it
  is not recommended for users to tack on additional context. In particular, any additional
  tags should have a <b>guaranteed</b> low cardinality. If additional tagging causes these
  metrics to exceed limits, then you may lose all visibility into requests.