Before you begin reading this guide, we recommend you run Elasticsearch Error Check-Up which can resolve issues that cause many errors.
This guide will help you check for common problems that cause the log ” Failed to reassign persistent tasks ” to appear. It’s important to understand the issues related to the log, so to get started, read the general overview on common issues and tips related to the Elasticsearch concepts: cluster and persistent.
Advanced users might want to skip right to the common problems section in each concept or try running the Check-Up which analyses ES to pinpoint the cause of many errors and provides suitable actionable recommendations how to resolve them (free tool that requires no installation).
Overview
In Elasticsearch, persistent refers to cluster settings that persist across cluster restarts. This setting is used in Cluster Update API calls. Persistent settings can also be configured in the elasticsearch.yml file.
Examples
## enable shard routing
PUT /_cluster/settings
{
"persistent" : {
"cluster.routing.allocation.enable" : "all"
}
}
## enable rebalancing of shards
PUT /_cluster/settings
{
"persistent" : {
"cluster.routing.rebalance.enable" : "all"
}
}
## limit the heap size for fielddata
PUT /_cluster/settings
{
"persistent" : {
“indices.breaker.fielddata.limit”: "30%"
}
}Log Context
Log “Failed to reassign persistent tasks” classname is PersistentTasksClusterService.java
We extracted the following from Elasticsearch source code for those seeking an in-depth context :
return reassignTasks(currentState);
}
Override
public void onFailure(String source; Exception e) {
logger.warn("failed to reassign persistent tasks"; e);
// There must be a task that's worth rechecking because there was one
// that caused this method to be called and the method failed to assign it
periodicRechecker.rescheduleIfNecessary();
}
Run the Check-Up to get customized recommendations like this:
Run Check-Up
The high disk watermark threshold is about to be reached in specific nodes
Description
There are various “watermark” thresholds on each Elasticsearch cluster. When the high disk watermark threshold has been exceeded, it means disk space is running out. The node will…
Recommendations
Based on your specific ES deployment you should…
X-PUT curl -H [a customized code snippet to resolve the issue]