# Tools: Aggregator Failures

## Master Aggregator Fails

If the Master Aggregator node fails and is recoverable, [restart the Master Aggregator](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/restart-node.md).

If it is not recoverable, a Child Aggregator must be promoted to the role of Master Aggregator by running either [AGGREGATOR SET AS MASTER](https://docs.singlestore.com/db/v9.1/reference/sql-reference/cluster-management-commands/aggregator-set-as-master.md) in SQL or [sdb-admin bootstrap-aggregator](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/bootstrap-aggregator.md) on the command line.

## One Child Aggregator Fails

If a Child Aggregator is recoverable, [restart the Child Aggregator](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/restart-node.md).

If it is not recoverable, deploy a new aggregator by [creating a new node](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/create-node.md) and adding it to the cluster [as a Child Aggregator](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/add-aggregator.md).

## Many Aggregators Fail

If more than one aggregator fails, each aggregator can either be [reintroduced](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/add-aggregator.md) or [removed](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/remove-aggregator.md), [created](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/create-node.md), and then [replaced](https://docs.singlestore.com/db/v9.1/reference/singlestore-tools-reference/sdb-admin-commands/add-aggregator.md) one by one.

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Modified at: June 22, 2022

Source: [/db/v9.1/user-and-cluster-administration/dealing-with-cluster-failures/tools-aggregator-failures/](https://docs.singlestore.com/db/v9.1/user-and-cluster-administration/dealing-with-cluster-failures/tools-aggregator-failures/)

(An index of the documentation is available at /llms.txt)