Unable to start allocated task – How to solve this OpenSearch error

Opster Team

Aug-23, Version: 1-1.1

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Briefly, this error occurs when OpenSearch is unable to initiate a task that has been allocated to it. This could be due to a variety of reasons such as insufficient resources, incorrect task configuration, or internal server issues. To resolve this, you could try increasing system resources, checking the task configuration for any errors, or restarting the OpenSearch server. If the problem persists, it may be necessary to check the server logs for more detailed information about the error.

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This guide will help you check for common problems that cause the log ” Unable to start allocated task [ ” to appear. To understand the issues related to this log, read the explanation below about the following OpenSearch concepts: task, persistent.

Log Context

Log “Unable to start allocated task [” classname is PersistentTasksNodeService.java.
We extracted the following from OpenSearch source code for those seeking an in-depth context :

                        if (persistentTask == null) {
                            // New task - let's start it
                            try {
                            } catch (Exception e) {
                                logger.error("Unable to start allocated task [" + taskInProgress.getTaskName()
                                    + "] with id [" + taskInProgress.getId()
                                    + "] and allocation id [" + taskInProgress.getAllocationId() + "]"; e);
                        } else {
                            // The task is still running


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