We limit the number of concurrent blob downloads per node and per recovery, but if a user configures too many concurrent recoveries they may run out of per-node download permits which yields the following message:

> Unable to acquire permit to use snapshot files during recovery, this recovery will recover index files from the source node. Ensure snapshot files can be used during recovery by setting [indices.recovery.max_concurrent_snapshot_file_downloads] to be no greater than [25]

The `[25]` here is wrong, the 25 permits are shared across all inbound recoveries so we should divide the suggested value by `cluster.routing.allocation.node_concurrent_incoming_recoveries`. In extreme cases the user may have configured so many concurrent recoveries that the only reasonable limit is zero, and in that case we should suggest setting `indices.recovery.use_snapshots: false` instead.


server/src/main/java/org/elasticsearch/indices/recovery/RecoverySettings.java
}
            return maxBytesPerSec.getStringRep();
        },
        Property.Dynamic,
        Property.NodeScope
    );
    /**
     * Controls the maximum number of file chunk requests that can be sent concurrently from the source node to the target node.
     */
    public static final Setting<Integer> INDICES_RECOVERY_MAX_CONCURRENT_FILE_CHUNKS_SETTING = Setting.intSetting(
        "indices.recovery.max_concurrent_file_chunks",
        2,
        1,
        8,
        Property.Dynamic,
        Property.NodeScope
    );
    /**
     * Controls the maximum number of operation chunk requests that can be sent concurrently from the source node to the target node.
     */
    public static final Setting<Integer> INDICES_RECOVERY_MAX_CONCURRENT_OPERATIONS_SETTING = Setting.intSetting(
        "indices.recovery.max_concurrent_operations",
        1,
        1,
        4,
        Property.Dynamic,
        Property.NodeScope
    );
    /**
     * how long to wait before retrying after issues cause by cluster state syncing between nodes