IParitionLoadBalancingStrategy Interface

Reference

Definition

Namespace:: Microsoft.Azure.Documents.ChangeFeedProcessor.PartitionManagement

Assembly:: Microsoft.Azure.Documents.ChangeFeedProcessor.dll

Package:: Microsoft.Azure.DocumentDB.ChangeFeedProcessor v2.4.0

Important

Some information relates to prerelease product that may be substantially modified before it’s released. Microsoft makes no warranties, express or implied, with respect to the information provided here.

A strategy defines which leases should be taken by the current host in a certain moment.

public interface IParitionLoadBalancingStrategy

type IParitionLoadBalancingStrategy = interface

Public Interface IParitionLoadBalancingStrategy

Examples

public class CustomStrategy : IParitionLoadBalancingStrategy
{
    private string hostName;
    private string hostVersion;
    private TimeSpan leaseExpirationInterval;

    private const string VersionPropertyKey = "version";

    public IEnumerable<ILease> SelectLeasesToTake(IEnumerable<ILease> allLeases)
    {
        var takenLeases = this.FindLeasesToTake(allLeases);
        foreach (var lease in takenLeases)
        {
            lease.Properties[VersionPropertyKey] = this.hostVersion;
        }

        return takenLeases;
    }

    private IEnumerable<ILease> FindLeasesToTake(IEnumerable<ILease> allLeases)
    {
        List<ILease> takenLeases = new List<ILease>();
        foreach (var lease in allLeases)
        {
            if (string.IsNullOrWhiteSpace(lease.Owner) || this.IsExpired(lease))
            {
                takenLeases.Add(lease);
            }

            if (lease.Owner != this.hostName)
            {
                var ownerVersion = lease.Properties[VersionPropertyKey];
                if (ownerVersion < this.hostVersion)
                {
                    takenLeases.Add(lease);
                }

                // more logic for leases owned by other hosts
            }
        }

        return takenLeases;
    }

    private bool IsExpired(ILease lease)
    {
        return lease.Timestamp.ToUniversalTime() + this.leaseExpirationInterval < DateTime.UtcNow;
    }
}

Remarks

It can set new Properties for all returned leases if needed, including currently owned leases.

Methods

SelectLeasesToTake(IEnumerable<ILease>)

Select leases that should be taken for processing. This method will be called periodically with LeaseAcquireInterval

Applies to

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