public static ClientAddressSource ofHeader(CharSequence header) {
        checkArgument(requireNonNull(header, "header").length() > 0, "empty header");
        return new ClientAddressSource(HttpHeaderNames.of(header));
    }
Returns a {@link ClientAddressSource} which indicates the value of the specified {@code header}
in a request will be used to determine a client address.
core/src/main/java/com/linecorp/armeria/server/ClientAddressSource.java