Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which analyzes 2 JSON files to detect many errors.
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This guide will help you check for common problems that cause the log ” No ec2 metadata returned from ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: cloud-aws, discovery-ec2, metadata, node and plugins.
Overview
Metadata in Elasticsearch refers to additional information stored for each document. This is achieved using the specific metadata fields available in Elasticsearch. The default behavior of some of these metadata fields can be customized during mapping creation.
Examples
Using _meta meta-field for storing application-specific information with the mapping:
PUT /my_index?pretty
{
"mappings": {
"_meta": {
"domain": "security",
"release_information": {
"date": "18-01-2020",
"version": "7.5"
}
}
}
}Notes
- In version 2.x, Elasticsearch had a total 13 meta fields available, which are: _index, _uid, _type, _id, _source, _size, _all, _field_names, _timestamp, _ttl, _parent, _routing, _meta
- In version 5.x, _timestamp and _ttl meta fields were removed.
- In version 6.x, the _parent meta field was removed.
- In version 7.x, _uid and _all meta fields were removed.
Log Context
Log “no ec2 metadata returned from {}” classname is Ec2CustomNodeAttributes.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
in = urlConnection.getInputStream();
BufferedReader urlReader = new BufferedReader(new InputStreamReader(in; StandardCharsets.UTF_8));
String metadataResult = urlReader.readLine();
if (metadataResult == null || metadataResult.length() == 0) {
logger.error("no ec2 metadata returned from {}"; url);
return null;
}
ec2Attributes.put("aws_availability_zone"; metadataResult);
} catch (IOException e) {
logger.debug("failed to get metadata for [placement/availability-zone]"; e);
