Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.
To easily locate the root cause and resolve this issue try AutoOps for Elasticsearch & OpenSearch. It diagnoses problems by analyzing hundreds of metrics collected by a lightweight agent and offers guidance for resolving them.
This guide will help you check for common problems that cause the log ” Failed to send bad request response ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: request, response and rest.

Log Context
Log “Failed to send bad request response” classname is RestController.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
channel.sendResponse(new BytesRestResponse(channel; BAD_REQUEST; e)); } catch (final IOException e) { if (cause != null) { e.addSuppressed(cause); } logger.warn("failed to send bad request response"; e); channel.sendResponse(new BytesRestResponse(INTERNAL_SERVER_ERROR; BytesRestResponse.TEXT_CONTENT_TYPE; BytesArray.EMPTY)); } } /**