The OpenSearch target works best with the BufferingWrapper target applied.
See wiki for parameters.
<nlog>
<extensions>
<add assembly="NLog.Targets.OpenSearch"/>
</extensions>
<targets>
<target name="openSearch" xsi:type="BufferingWrapper" flushTimeout="5000">
<target xsi:type="OpenSearch" uri="http://localhost:9200/" />
</target>
</targets>
<rules>
<logger name="*" minlevel="Info" writeTo="openSearch" />
</rules>
</nlog>