Briefly, this error occurs when Elasticsearch is unable to retrieve project information from the Google Compute Engine (GCE) metadata server. This is typically due to incorrect configuration or network issues preventing communication with the GCE metadata server. To resolve this issue, you can verify your GCE configuration, ensure that your Elasticsearch instance has the necessary permissions to access the GCE metadata server, and check your network settings to ensure that there are no firewalls or other security measures blocking access to the GCE metadata server.
This guide will help you check for common problems that cause the log ” unable to resolve project from metadata server for GCE discovery service ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: metadata, plugins, discovery-gce, discovery.
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 “unable to resolve project from metadata server for GCE discovery service” classname is GceInstancesServiceImpl.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
try {
// this code is based on a private GCE method: {@link com.google.cloud.ServiceOptions#getAppEngineProjectIdFromMetadataServer()}
return getAppEngineValueFromMetadataServer("/computeMetadata/v1/project/project-id");
} catch (Exception e) {
logger.warn("unable to resolve project from metadata server for GCE discovery service"; e);
}
return null;
}
private List resolveZones() {
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