 automatically determined based on CPU limits.
If set to 0, all cores on the machine will be used.</p></td></tr><tr id=ProxyConfig-environment_variables><td><div class=field><div class=name><code><a href=#ProxyConfig-environment_variables>environmentVariables</a></code></div><div class=type>map&lt;string,&nbsp;string></div></div></td><td><p>Additional environment variables for the proxy.
Names starting with <code>ISTIO_META_</code> will be included in the generated bootstrap configuration and sent to the XD