Briefly, this error occurs when Elasticsearch is trying to run a health check or monitor, but a similar process is already running. This is a built-in mechanism to prevent resource overuse. It’s not necessarily a problem unless it’s happening frequently, which could indicate that your checks are taking too long. To resolve this, you can optimize your Elasticsearch cluster to perform checks faster, increase the interval between checks, or reduce the number of checks. Also, ensure that your system has sufficient resources to handle these operations.
This guide will help you check for common problems that cause the log ” skipping monitor as a check is already in progress ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: monitor, routing, allocation, cluster.
Overview
In Elasticsearch, routing refers to document routing. When you index a document, Elasticsearch will determine which shard the document should be routed to for indexing.
The shard is selected based on the following formula:
shard = hash(_routing) % number_of_primary_shards
Where the default value of _routing is _id.
It is important to know which shard the document is routed to, because Elasticsearch will need to determine where to find that document later on for document retrieval requests.
Examples
In twitter index with 2 primary shards, the document with _id equal to “440” gets routed to the shard number:
shard = hash( 440 ) % 2
PUT twitter/_doc/440
{
...
}Notes and good things to know
- In order to improve search speed, you can create custom routing. For example, you can enable custom routing that will ensure that only a single shard will be queried (the shard that contains your data).
- To create custom routing in Elasticsearch, you will need to configure and define that not all routing will be completed by default settings. ( v <= 5.0)
PUT my_index/customer/_mapping
{
"order":{
"_routing":{
"required":true
}
}
}- This will ensure that every document in the “customer” type must specify a custom routing. For Elasticsearch version 6 or above you will need to update the same mapping as:
PUT my_index/_mapping
{
"order":{
"_routing":{
"required":true
}
}
}Log Context
Log “skipping monitor as a check is already in progress” classname is DiskThresholdMonitor.java.
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
}
// TODO find a better way to limit concurrent updates (and potential associated reroutes) while allowing tests to ensure that
// all ClusterInfo updates are processed and never ignored
if (checkInProgress.compareAndSet(false; true) == false) {
logger.info("skipping monitor as a check is already in progress");
return;
}
if (diskThresholdSettings.isEnabled() == false) {
removeExistingIndexBlocks();
