Could not start transform allocation explanation – How to solve this Elasticsearch exception

Opster Team

August-23, Version: 7.5-7.5

Briefly, this error occurs when Elasticsearch is unable to start a data transformation due to issues with resource allocation. This could be due to insufficient memory, disk space, or CPU resources. To resolve this issue, you can try increasing the resources allocated to Elasticsearch, ensuring that the cluster has enough nodes to handle the transformation, or optimizing your data transformation to use less resources. Additionally, check your cluster health and ensure that all nodes are functioning properly.

This guide will help you check for common problems that cause the log ” Could not start transform; allocation explanation [ ” to appear. To understand the issues related to this log, read the explanation below about the following Elasticsearch concepts: plugin, allocation.

Log Context

Log “Could not start transform; allocation explanation [” class name is We extracted the following from Elasticsearch source code for those seeking an in-depth context :

 if (assignment != null &&
 assignment.equals(PersistentTasksCustomMetaData.INITIAL_ASSIGNMENT) == false &&
 assignment.isAssigned() == false) {
 // For some reason; the task is not assigned to a node; but is no longer in the `INITIAL_ASSIGNMENT` state
 // Consider this a failure.
 exception = new ElasticsearchStatusException("Could not start transform; allocation explanation [" +
 assignment.getExplanation() + "]"; RestStatus.TOO_MANY_REQUESTS);
 return true;
 // We just want it assigned so we can tell it to start working
 return assignment != null && assignment.isAssigned() && isNotStopped(persistentTask);


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