S3 Blobstore "Timeout waiting for connection from pool"

On a system configured to use Amazon S3 blob storage, you may see errors in the logs indicating that the S3 connection pool has run out of resources.

2020-09-17 16:54:19,429+0000 WARN  [qtp143422335-624]  *UNKNOWN org.sonatype.nexus.repository.httpbridge.internal.ViewServlet - Failure servicing: GET /nexus/repository/myrepo/file.xml
com.amazonaws.SdkClientException: Unable to execute HTTP request: Timeout waiting for connection from pool

There was a Nexus property introduced in Repository Manager 3.20 which allows you to increase the size of the S3 connection pool for all S3 blob stores. If you are encountering these errors in your logs we recommend adding this property to the $data-dir/etc/nexus.properties file.

nexus.s3.connection.pool=200

A value of 200 has been sufficient to resolve these errors. Setting this parameter to a higher value may introduce performance problems.

You will need to restart Nexus Repository for this change to take effect.

Or, you can change the individual pool size from the Blob store’s configuration page under Advanced Connection Settings. Type in an integer value for “Max Connection Pool Size”.

NOTE: Changing any configuration on the Blob store does not require restarting Nexus however, the modified blob store will be reloaded. This will terminate any current activities like reading or uploading blobs.