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.


test/framework/src/main/java/org/elasticsearch/test/MockLogAppender.java
private final List<WrappedLoggingExpectation> expectations;
    public MockLogAppender() {
        super("mock", null, null, false, Property.EMPTY_ARRAY);
        /*
         * We use a copy-on-write array list since log messages could be appended while we are setting up expectations. When that occurs,
         * we would run into a concurrent modification exception from the iteration over the expectations in #append, concurrent with a
         * modification from #addExpectation.
         */
        expectations = new CopyOnWriteArrayList<>();
    }
    public void addExpectation(LoggingExpectation expectation) {
        expectations.add(new WrappedLoggingExpectation(expectation));
    }
    @Override
    public void append(LogEvent event) {
        for (LoggingExpectation expectation : expectations) {
            expectation.match(event);
        }
    }
    public void assertAllExpectationsMatched() {
        for (LoggingExpectation expectation : expectations) {
            expectation.assertMatched();
        }
    }
    public interface LoggingExpectation {