Package io.grpc

Class LoadBalancer.Helper

java.lang.Object
io.grpc.LoadBalancer.Helper
Direct Known Subclasses:
ForwardingLoadBalancerHelper
Enclosing class:
LoadBalancer
@ThreadSafe @ExperimentalApi("https://github.com/grpc/grpc-java/issues/1771") public abstract static class LoadBalancer.Helper extends Object
Provides essentials for LoadBalancer implementations.
Since:
1.2.0

  • Constructor Details

    • Helper

      public Helper()

  • Method Details

    • createSubchannel

      public LoadBalancer.Subchannel createSubchannel(LoadBalancer.CreateSubchannelArgs args)
      Creates a Subchannel, which is a logical connection to the given group of addresses which are considered equivalent. The attrs are custom attributes associated with this Subchannel, and can be accessed later through Subchannel.getAttributes().

      The LoadBalancer is responsible for closing unused Subchannels, and closing all Subchannels within LoadBalancer.shutdown().

      It must be called from the Synchronization Context

      Returns:
      Must return a valid Subchannel object, may not return null.
      Since:
      1.22.0

    • createOobChannel

      public abstract ManagedChannel createOobChannel(EquivalentAddressGroup eag, String authority)
      Create an out-of-band channel for the LoadBalancer’s own RPC needs, e.g., talking to an external load-balancer service.

      The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

      Since:
      1.4.0

    • createOobChannel

      public ManagedChannel createOobChannel(List<EquivalentAddressGroup> eag, String authority)
      Create an out-of-band channel for the LoadBalancer's own RPC needs, e.g., talking to an external load-balancer service. This version of the method allows multiple EAGs, so different addresses can have different authorities.

      The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

    • updateOobChannelAddresses

      public void updateOobChannelAddresses(ManagedChannel channel, EquivalentAddressGroup eag)
      Updates the addresses used for connections in the Channel that was created by createOobChannel(EquivalentAddressGroup, String). This is superior to createOobChannel(EquivalentAddressGroup, String) when the old and new addresses overlap, since the channel can continue using an existing connection.
      Throws:
      IllegalArgumentException - if channel was not returned from createOobChannel(io.grpc.EquivalentAddressGroup, java.lang.String)
      Since:
      1.4.0

    • updateOobChannelAddresses

      public void updateOobChannelAddresses(ManagedChannel channel, List<EquivalentAddressGroup> eag)
      Updates the addresses with a new EAG list. Connection is continued when old and new addresses overlap.

    • createResolvingOobChannel

      public ManagedChannel createResolvingOobChannel(String target)
      Creates an out-of-band channel for LoadBalancer's own RPC needs, e.g., talking to an external load-balancer service, that is specified by a target string. See the documentation on ManagedChannelBuilder.forTarget(java.lang.String) for the format of a target string.

      The target string will be resolved by a NameResolver created according to the target string.

      The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

      Since:
      1.20.0

    • createResolvingOobChannelBuilder

      @Deprecated public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(String target)
      Deprecated.
      Use createResolvingOobChannelBuilder(String, ChannelCredentials) instead.
      Creates an out-of-band channel builder for LoadBalancer's own RPC needs, e.g., talking to an external load-balancer service, that is specified by a target string. See the documentation on ManagedChannelBuilder.forTarget(java.lang.String) for the format of a target string.

      The target string will be resolved by a NameResolver created according to the target string.

      The returned oob-channel builder defaults to use the same authority and ChannelCredentials (without bearer tokens) as the parent channel's for authentication. This is different from createResolvingOobChannelBuilder(String, ChannelCredentials).

      The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

      Since:
      1.31.0

    • createResolvingOobChannelBuilder

      public ManagedChannelBuilder<?> createResolvingOobChannelBuilder(String target, ChannelCredentials creds)
      Creates an out-of-band channel builder for LoadBalancer's own RPC needs, e.g., talking to an external load-balancer service, that is specified by a target string and credentials. See the documentation on Grpc.newChannelBuilder(java.lang.String, io.grpc.ChannelCredentials) for the format of a target string.

      The target string will be resolved by a NameResolver created according to the target string.

      The LoadBalancer is responsible for closing unused OOB channels, and closing all OOB channels within LoadBalancer.shutdown().

      Since:
      1.35.0

    • updateBalancingState

      public abstract void updateBalancingState(@Nonnull ConnectivityState newState, @Nonnull LoadBalancer.SubchannelPicker newPicker)
      Set a new state with a new picker to the channel.

      When a new picker is provided via updateBalancingState(), the channel will apply the picker on all buffered RPCs, by calling LoadBalancer.SubchannelPicker.pickSubchannel(LoadBalancer.PickSubchannelArgs).

      The channel will hold the picker and use it for all RPCs, until updateBalancingState() is called again and a new picker replaces the old one. If updateBalancingState() has never been called, the channel will buffer all RPCs until a picker is provided.

      It should be called from the Synchronization Context. Currently will log a warning if violated. It will become an exception eventually. See #5015 for the background.

      The passed state will be the channel's new state. The SHUTDOWN state should not be passed and its behavior is undefined.

      Since:
      1.6.0

    • refreshNameResolution

      public void refreshNameResolution()
      Call NameResolver.refresh() on the channel's resolver.

      It should be called from the Synchronization Context. Currently will log a warning if violated. It will become an exception eventually. See #5015 for the background.

      Since:
      1.18.0

    • ignoreRefreshNameResolutionCheck

      @ExperimentalApi("https://github.com/grpc/grpc-java/issues/8088") @Deprecated public void ignoreRefreshNameResolutionCheck()
      Deprecated.
      Warning has been removed
      Historically the channel automatically refreshes name resolution if any subchannel connection is broken. It's transitioning to let load balancers make the decision. To avoid silent breakages, the channel checks if refreshNameResolution() is called by the load balancer. If not, it will do it and log a warning. This will be removed in the future and load balancers are completely responsible for triggering the refresh. See #8088 for the background.

      This should rarely be used, but sometimes the address for the subchannel wasn't provided by the name resolver and a refresh needs to be directed somewhere else instead. Then you can call this method to disable the short-tem check for detecting LoadBalancers that need to be updated for the new expected behavior.

      Since:
      1.38.0

    • getSynchronizationContext

      public SynchronizationContext getSynchronizationContext()
      Returns a SynchronizationContext that runs tasks in the same Synchronization Context as that the callback methods on the LoadBalancer interface are run in.

      Pro-tip: in order to call SynchronizationContext.schedule(java.lang.Runnable, long, java.util.concurrent.TimeUnit, java.util.concurrent.ScheduledExecutorService), you need to provide a ScheduledExecutorService. getScheduledExecutorService() is provided for your convenience.

      Since:
      1.17.0

    • getScheduledExecutorService

      public ScheduledExecutorService getScheduledExecutorService()
      Returns a ScheduledExecutorService for scheduling delayed tasks.

      This service is a shared resource and is only meant for quick tasks. DO NOT block or run time-consuming tasks.

      The returned service doesn't support shutdown() and shutdownNow(). They will throw if called.

      Since:
      1.17.0

    • getAuthority

      public abstract String getAuthority()
      Returns the authority string of the channel, which is derived from the DNS-style target name. If overridden by a load balancer, getUnsafeChannelCredentials() must also be overridden to call getChannelCredentials() or provide appropriate credentials.
      Since:
      1.2.0

    • getChannelTarget

      public String getChannelTarget()
      Returns the target string of the channel, guaranteed to include its scheme.

    • getChannelCredentials

      public ChannelCredentials getChannelCredentials()
      Returns the ChannelCredentials used to construct the channel, without bearer tokens.
      Since:
      1.35.0

    • getUnsafeChannelCredentials

      public ChannelCredentials getUnsafeChannelCredentials()
      Returns the UNSAFE ChannelCredentials used to construct the channel, including bearer tokens. Load balancers should generally have no use for these credentials and use of them is heavily discouraged. These must be used very carefully to avoid sending bearer tokens to untrusted servers as the server could then impersonate the client. Generally it is only safe to use these credentials when communicating with the backend.
      Since:
      1.35.0

    • getChannelLogger

      public ChannelLogger getChannelLogger()
      Returns the ChannelLogger for the Channel served by this LoadBalancer.
      Since:
      1.17.0

    • getNameResolverArgs

      public NameResolver.Args getNameResolverArgs()
      Returns the NameResolver.Args that the Channel uses to create NameResolvers.
      Since:
      1.22.0

    • getNameResolverRegistry

      public NameResolverRegistry getNameResolverRegistry()
      Returns the NameResolverRegistry that the Channel uses to look for NameResolvers.
      Since:
      1.22.0

    • getMetricRecorder

      @Internal public MetricRecorder getMetricRecorder()
      Returns the MetricRecorder that the channel uses to record metrics.
      Since:
      1.64.0