presto-resource-group-managers/src/main/java/io/prestosql/plugin/resourcegroups/FileResourceGroupConfigurationManager.java/FileResourceGroupConfigurationManager/FileResourceGroupConfigurationManager
class FileResourceGroupConfigurationManager:    @Inject
    public FileResourceGroupConfigurationManager(ClusterMemoryPoolManager memoryPoolManager, FileResourceGroupConfig config)
    {
        super(memoryPoolManager);
        requireNonNull(config, "config is null");

        ManagerSpec managerSpec;
        try {
            managerSpec = CODEC.fromJson(Files.readAllBytes(Paths.get(config.getConfigFile())));
        }
        catch (IOException e) {
            throw new UncheckedIOException(e);
        }
        catch (IllegalArgumentException e) {
            Throwable cause = e.getCause();
            if (cause instanceof UnrecognizedPropertyException) {
                UnrecognizedPropertyException ex = (UnrecognizedPropertyException) cause;
                String message = format("Unknown property at line %s:%s: %s",
                        ex.getLocation().getLineNr(),
                        ex.getLocation().getColumnNr(),
                        ex.getPropertyName());
                throw new IllegalArgumentException(message, e);
            }
            if (cause instanceof JsonMappingException) {
                // remove the extra "through reference chain" message
                if (cause.getCause() != null) {
                    cause = cause.getCause();
                }
                throw new IllegalArgumentException(cause.getMessage(), e);
            }
            throw e;
        }

        this.rootGroups = managerSpec.getRootGroups();
        this.cpuQuotaPeriod = managerSpec.getCpuQuotaPeriod();
        validateRootGroups(managerSpec);
        this.selectors = buildSelectors(managerSpec);
    }