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/test/java/org/elasticsearch/indices/recovery/RecoverySettingsTests.java
}
    }
    public void testDefaultMaxBytesPerSecOnNonDataNode() {
        RecoverySettings recoverySettings = nodeRecoverySettings().withRole(randomFrom("master", "ingest", "ml"))
            .withRandomBandwidths()
            .withRandomMemory()
            .build();
        assertThat(
            "Non-data nodes have a default 40mb rate limit",
            recoverySettings.getMaxBytesPerSec(),
            equalTo(DEFAULT_MAX_BYTES_PER_SEC)
        );
    }
    public void testMaxBytesPerSecOnNonDataNodeWithIndicesRecoveryMaxBytesPerSec() {
        final ByteSizeValue random = randomByteSizeValue();
        assertThat(
            "Non-data nodes should use the defined rate limit when set",
            nodeRecoverySettings().withRole(randomFrom("master", "ingest", "ml"))
                .withIndicesRecoveryMaxBytesPerSec(random)
                .withRandomMemory()
                .build()
                .getMaxBytesPerSec(),
            equalTo(random)
        );
    }
    public void testDefaultMaxBytesPerSecOnDataNode() {
        assertThat(
            "Data nodes that are not dedicated to cold/frozen have a default 40mb rate limit",
            nodeRecoverySettings().withRole(randomFrom("data", "data_hot", "data_warm", "data_content"))
                .withRandomMemory()