Briefly, this error occurs when Elasticsearch cannot find or connect to the specified host. This could be due to incorrect hostname, network issues, or DNS resolution problems. To resolve this, first, verify the hostname and ensure it’s correct. Second, check your network connection and firewall settings to ensure Elasticsearch can reach the host. Lastly, check your DNS settings to ensure the host can be resolved correctly. If the host is a remote server, ensure it’s up and running and accessible from your network.
This guide will help you check for common problems that cause the log ” failed to resolve host {} ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: bulk.
Overview
In Elasticsearch, when using the Bulk API it is possible to perform many write operations in a single API call, which increases the indexing speed. Using the Bulk API is more efficient than sending multiple separate requests. This can be done for the following four actions:
- Index
- Update
- Create
- Delete
Examples
The bulk request below will index a document, delete another document, and update an existing document.
POST _bulk
{ "index" : { "_index" : "myindex", "_id" : "1" } }
{ "field1" : "value" }
{ "delete" : { "_index" : "myindex", "_id" : "2" } }
{ "update" : {"_id" : "1", "_index" : "myindex"} }
{ "doc" : {"field2" : "value5"} }Notes
- Bulk API is useful when you need to index data streams that can be queued up and indexed in batches of hundreds or thousands, such as logs.
- There is no correct number of actions or limits to perform on a single bulk call, but you will need to figure out the optimum number by experimentation, given the cluster size, number of nodes, hardware specs etc.
Log Context
Log “failed to resolve host {}” classname is BulkUdpService.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
InetAddress hostAddressX;
try {
hostAddressX = networkService.resolveBindHostAddress(host);
} catch (IOException e) {
logger.warn("failed to resolve host {}"; e; host);
return;
}
final InetAddress hostAddress = hostAddressX;
PortsRange portsRange = new PortsRange(port);
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