Package com.microsoft.azure.eventprocessorhost

Interface ILeaseManager

  • All Known Implementing Classes:
    InMemoryLeaseManager
    public interface ILeaseManager
    If you wish to have EventProcessorHost store leases somewhere other than Azure Storage, you can write your own lease manager using this interface. The Azure Storage managers use the same storage for both lease and checkpoints, so both interfaces are implemented by the same class. You are free to do the same thing if you have a unified store for both types of data. This interface does not specify initialization methods because we have no way of knowing what information your implementation will require. If your implementation needs initialization, you will have to initialize the instance before passing it to the EventProcessorHost constructor.

    • Method Detail

      • getLeaseDurationInMilliseconds

        int getLeaseDurationInMilliseconds()
        The lease duration is mostly internal to the lease manager implementation but may be needed by other parts of the event processor host.
        Returns:
        Duration of a lease before it expires unless renewed, specified in milliseconds.

      • leaseStoreExists

        CompletableFuture<Boolean> leaseStoreExists()
        Does the lease store exist?

        The returned CompletableFuture completes with true if the checkpoint store exists or false if it does not. It completes exceptionally on error.

        Returns:
        CompletableFuture -> true if it exists, false if not

      • createLeaseStoreIfNotExists

        CompletableFuture<Void> createLeaseStoreIfNotExists()
        Create the lease store if it does not exist, do nothing if it does exist.
        Returns:
        CompletableFuture -> null on success, completes exceptionally on error.

      • deleteLeaseStore

        CompletableFuture<Void> deleteLeaseStore()
        Deletes the lease store.
        Returns:
        CompletableFuture -> null on success, completes exceptionally on error.

      • getLease

        CompletableFuture<CompleteLease> getLease​(String partitionId)
        Returns the lease info for the given partition..
        Parameters:
        partitionId - Get the lease info for this partition.
        Returns:
        CompletableFuture -> Lease, completes exceptionally on error.

      • getAllLeases

        CompletableFuture<List<BaseLease>> getAllLeases()
        Returns lightweight BaseLease for all leases, which includes name of owning host and whether lease is expired. An implementation is free to return CompleteLease or its own class derived from CompleteLease, but it is important that getAllLeases run as fast as possible. If it is faster to obtain only the information required for a BaseLease, we heavily recommend doing that.
        Returns:
        CompletableFuture -> list of BaseLease, completes exceptionally on error.

      • createAllLeasesIfNotExists

        CompletableFuture<Void> createAllLeasesIfNotExists​(List<String> partitionIds)
        Create in the store a lease for each of the given partitions, if it does not exist. Do nothing for any lease which exists in the store already.
        Parameters:
        partitionIds - ids of partitions to create lease info for
        Returns:
        CompletableFuture -> null on success, completes exceptionally on error

      • deleteLease

        CompletableFuture<Void> deleteLease​(CompleteLease lease)
        Delete the lease info for a partition from the store. If there is no stored lease for the given partition, that is treated as success.
        Parameters:
        lease - the currently existing lease info for the partition
        Returns:
        CompletableFuture -> null on success, completes exceptionally on error.

      • acquireLease

        CompletableFuture<Boolean> acquireLease​(CompleteLease lease)
        Acquire the lease on the desired partition for this EventProcessorHost.

        Note that it is legal to acquire a lease that is currently owned by another host, which is called "stealing". Lease-stealing is how partitions are redistributed when additional hosts are started.

        The existing Azure Storage implementation can experience races between two host instances attempting to acquire or steal the lease at the same time. To avoid situations where two host instances both believe that they own the lease, acquisition can fail non-exceptionally by returning false and should do so when there is any doubt -- the worst that can happen is that no host instance owns the lease for a short time. This is qualitatively different from, for example, the underlying store throwing an access exception, which is an error and should complete exceptionally.

        Parameters:
        lease - Lease info for the desired partition
        Returns:
        CompletableFuture -> true if the lease was acquired, false if not, completes exceptionally on error.

      • renewLease

        CompletableFuture<Boolean> renewLease​(CompleteLease lease)
        Renew a lease currently held by this host instance.

        If the lease has been taken by another host instance (either stolen or after expiration) or explicitly released, renewLease must return false. With the Azure Storage-based implementation, it IS possible to renew an expired lease that has not been taken by another host, so your implementation can allow that or not, whichever is convenient. If it does not, renewLease should return false.

        Parameters:
        lease - Lease to be renewed
        Returns:
        true if the lease was renewed, false as described above, completes exceptionally on error.

      • releaseLease

        CompletableFuture<Void> releaseLease​(CompleteLease lease)
        Give up a lease currently held by this host.

        If the lease has expired or been taken by another host, releasing it is unnecessary but will succeed since the intent has been fulfilled.

        Parameters:
        lease - Lease to be given up
        Returns:
        CompletableFuture -> null on success, completes exceptionally on error.

      • updateLease

        CompletableFuture<Boolean> updateLease​(CompleteLease lease)
        Update the store with the information in the provided lease.

        It is necessary to currently hold a lease in order to update it. If the lease has been stolen, or expired, or released, it cannot be updated. Lease manager implementations should renew the lease before performing the update to avoid lease expiration during the process.

        Parameters:
        lease - New lease info to be stored
        Returns:
        true if the update was successful, false if lease was lost and could not be updated, completes exceptionally on error.