Briefly, this error occurs when Elasticsearch is unable to reassign persistent tasks due to issues like node failures, network disruptions, or insufficient resources. To resolve this, you can try restarting the failed nodes, ensuring stable network connectivity, or increasing the system resources. Additionally, check the cluster health and task management API for any anomalies. If the issue persists, consider reindexing the data or upgrading Elasticsearch to a more stable version.
This guide will help you check for common problems that cause the log ” failed to reassign persistent tasks ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: persistent.
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 :
}
@Override
public void onFailure(Exception e) {
reassigningTasks.set(false);
logger.warn("failed to reassign persistent tasks"; e);
if (e instanceof NotMasterException == false) {
// 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;
// but only do this if the node is still the master
try {
