ICAP Server Sub-Systems

Many service classes are organized into sub-systems in the ICAP server. These sub-system services are initialized in a specific order defined by:

1. The order number of the sub-system (see enum SubSystem)
2. The priority of the service

The priority can be specified as an attribute of the @SubSystemService annotation. Services with a smaller priority are initialized earlier.

The @SubSystemService annotation only makes sense for singleton classes.

The EblockerServerApp automatically calls all initialization methods of sub-system services in the defined order and installs shutdown-hooks for their shutdown methods.

Service initialization methods are annotated with @SubSystemInit, shutdown methods with @SubSystemShutdown.

Runtime Check During Startup

The SubSystemUsageInterceptor ensures that service methods can only be called after all sub-systems with a lower order number have been initialized.

However, it is not checked whether a service has itself been initialized before any of its methods are called. Some services check this themselves, for example SslService.

See also: AOP in Guice

Startup Example

As an example, below is the current order of initializations of sub-systems and service classes (with priorities in brackets):

HTTP_SERVER
    [-1000]
        common.network.NetworkInterfaceWrapper
    [0]
        http.server.EblockerHttpsServer

DATABASE_CLIENT
    [0]
        common.data.JedisDataSource

EVENT_LISTENER
    [-1]
        http.service.AccessDeniedService
    [0]
        http.service.DeviceService
        common.network.unix.EblockerDnsServer
        http.service.ParentalControlEnforcerService
        http.service.ParentalControlService
        http.service.ParentalControlUsageService
        http.service.ProductInfoService
        common.network.TrafficAccounter
        http.service.UserService
    [10]
        common.blacklist.DomainBlockingService

BACKGROUND_TASKS
    [-1]
        http.service.AppModuleService
        common.update.AutomaticUpdater
        common.data.statistic.BlockedDomainsStatisticService
        common.network.DhcpBindListener
        http.service.MessageCenterService
        common.network.NetworkInterfaceWatchdog
        http.service.ParentalControlAccessRestrictionsService
        common.network.TorController
        common.network.TorExitNodeCountries
    [0]
        app.BackgroundServices
        common.openvpn.server.OpenVpnAddressListener
        common.squid.SquidWarningService

ICAP_SERVER
    [0]
        icap.server.EblockerIcapServer
        icap.filter.FilterManager

NETWORK_STATE_MACHINE
    [25]
        common.network.unix.IpSets
    [50]
        common.malware.MalwareFilterService
    [100]
        common.network.NetworkStateMachine

HTTPS_SERVER
    [0]
        http.server.SSLContextHandler
    [100]
        common.ssl.SslService
    [150]
        common.squid.SquidConfigController
    [200]
        common.openvpn.OpenVpnService

SERVICES
    [0]
        http.service.AnonymousService
        http.service.AutoTrustAppService
        common.blocker.BlockerService
        icap.filter.bpjm.BpjmFilterService
        http.service.DashboardCardService
        common.blacklist.DomainBlockingNetworkService
        common.service.FilterStatisticsService
        http.service.OpenVpnServerService
        http.service.ParentalControlSearchEngineConfigService
        http.service.RegistrationServiceAvailabilityCheck