"docs": [
is a JSONArray
.
What you have
String sSDR = nodeStats.getString("docs");
Change to
JSONObject nodeStats = nodeRoot.getJSONObject("response");
JSONArray jr = (JSONArray) nodeStats.getJSONArray("docs");
for(int i=0;i<jr.length();i++)
{
JSONObject jb = jr.getJSONObject(i);
String id = jb.getString("id");
}