Before you begin reading this guide, we recommend you try running the Elasticsearch Error Check-Up which can resolve issues that cause many errors.
This guide will help you check for common problems that cause the log ” Failed to send error response for action clear_sc and request ” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: request, response, scroll and search.
Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).
Overview
In Elasticsearch, the concept of scroll comes into play when you have a large set of search results. Large search results are exhaustive for both the Elasticsearch cluster and the requesting client in terms of memory and processing. The scroll API enables you to take a snapshot of a large number of results from a single search request.
Examples
To perform a scroll search, you need to add the scroll parameter to a search query and specify how long Elasticsearch should keep the search context viable.
GET mydocs-2019/_search?scroll=40s
{
"size": 5000,
"query": {
"match_all": {}
},
"sort": [
{
"_doc": {
"order": "asc"
}
}
]
}This query will return a maximum of 5000 hits. If the scroll is idle for more than 40 seconds, then it will be deleted. The response will return the first page of the results and a scroll ID. You can use the scroll ID to get additional documents from the scroll. You’re able to keep retrieving the documents until you have all of them.
Notes
- Changes made to documents after the scroll will not show up in your results.
- When you are done with the scroll, you can delete it manually using the scroll ID.
DELETE _search/scroll/<scroll_id>
Log Context
Log “Failed to send error response for action [clear_sc] and request [” classname is TransportClearScrollAction.java
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
Override
public void onFailure(Throwable e) {
try {
channel.sendResponse(e);
} catch (Exception e1) {
logger.warn("Failed to send error response for action [clear_sc] and request [" + request + "]"; e1);
}
}
});
}
