"curl: (52) Empty reply from server" / timeout when querying ElastiscSearch - elasticsearch

Question

I've ran into an annoying issue with my ElasticSearch (Version 1.5.2): Queries immediately return timeout (when I used python's Requests) or
curl: (52) Empty reply from server
when I used curl.
This only happened when the expected output was large. When I sent a similar (but smaller) query, it came back just fine.
what's going on here? and how can I overcome this?

Answer 1

just open
sudo nano /etc/elasticsearch/elasticsearch.yml
and replace this setting with false
# Enable security features
xpack.security.enabled: false

Answer 2

An other explanation can be making http request when ssl/security is activated on the cluster.
In this case use
curl -X GET "https://localhost:9200/_cluster/health?wait_for_status=yellow&timeout=50s&pretty" --key certificates/elasticsearch-ca.pem -k -u elasticuser
As stated by #FanchenBao, one can read the doc about ELK with SSL.

Answer 3

I meet with the same issue on Elasticsearh 8.1.3, which is the latest version.
I fixed this issue by changing the following setting from true to false in the /config/elasticsearch.yml file:
# Enable security features
xpack.security.enabled: false
I installed elastic by downloading the tar file, and unzip it, then going to the folder of elasticsearch, and running the following command:
./bin/elasticsearch
The first time you run this command, it will change the elasticsearch.yml file with the following content, which means it's a default secruity setting auto generated:
#----------------------- BEGIN SECURITY AUTO CONFIGURATION -----------------------
#
# The following settings, TLS certificates, and keys have been automatically
# generated to configure Elasticsearch security features on 01-05-2022 06:59:12
#
# --------------------------------------------------------------------------------
# Enable security features
xpack.security.enabled: true
xpack.security.enrollment.enabled: true
# Enable encryption for HTTP API client connections, such as Kibana, Logstash, and Agents
xpack.security.http.ssl:
enabled: true
keystore.path: certs/http.p12
# Enable encryption and mutual authentication between cluster nodes
xpack.security.transport.ssl:
enabled: true
verification_mode: certificate
keystore.path: certs/transport.p12
truststore.path: certs/transport.p12
# Create a new cluster with the current node only
# Additional nodes can still join the cluster later
cluster.initial_master_nodes: ["DaMings-MacBook-Pro.local"]
# Allow HTTP API connections from localhost and local networks
# Connections are encrypted and require user authentication
http.host: [_local_, _site_]
# Allow other nodes to join the cluster from localhost and local networks
# Connections are encrypted and mutually authenticated
#transport.host: [_local_, _site_]
#----------------------- END SECURITY AUTO CONFIGURATION -------------------------

Answer 4

This issue was caused by Elastic running out of memory: it simply can't hold all the documents in memory. Unfortunately there's no explicit error code for this case.
There are a bunch of options to work around this (besides adding more memory):
You can tell Elastic to not attach the source, by specifying "_source: false". The results would then just list the relevant documents (and you would need to retrieve them).
You could use "source filtering" to return just part of the documents, if you dont need the whole thing - that worked for me.
You can also just split your query into a bunch of sub-queries. not pretty, but it would do the trick.

Answer 5

When running in Docker you can disable the security by setting the environment variable xpack.security.enabled to false, e.g. in docker-compose.yml:
environment:
- xpack.security.enabled=false
- discovery.type=single-node

Answer 6

In version 6.2, there are more strict checking.
for example:
curl -XPUT -H'Content-Type: application/json' 'http://localhost:9200/us/user/2?pretty=1' -d '{"email" : "mary#jones.com", "name" : "Mary Jones","username" : "#mary"}'
curl: (52) Empty reply from server
if you remove =1:
curl -XPUT -H'Content-Type: application/json' 'http://localhost:9200/us/user/2?pretty' -d '{"email" : "mary#jones.com", "name" : "Mary Jones","username" : "#mary"}'
{
"_index" : "us",
"_type" : "user",
"_id" : "2",
"_version" : 1,
"result" : "created",
"_shards" : {
"total" : 2,
"successful" : 1,
"failed" : 0
},
"_seq_no" : 0,
"_primary_term" : 1
}
it works!

Answer 7

In my case it was because the url scheme https:// was missing in the endpoint url.