public void DownscaleManualExamples(string fromString, string toString)
{
var from = RedisClusterSize.TryParse(fromString).ThrowIfFailure();
var to = RedisClusterSize.TryParse(toString).ThrowIfFailure();
Assert.True(RedisScalingUtilities.IsDownScale(from, to));
}
/// <summary>
/// Decides whether a scaling move is allowed. At this point, we don't know if Azure Cache for Redis business
/// rules allow scaling from the current to the target size. We just decide whether it is reasonable based on
/// our knowledge of our production workload.
///
/// The autoscaler will figure out how to reach the desired plan.
/// </summary>
private bool IsScalingAllowed(
RedisClusterSize currentClusterSize,
RedisClusterSize targetClusterSize,
ModelContext modelContext)
{
// WARNING: order matters in the following if statements. Please be careful.
// Cluster must be able to handle the amount of data we'll give it, with some overhead in case of
// production issues. Notice we don't introduce a per-shard restriction; reason for this is that the shards
// distribute keys evenly.
if (targetClusterSize.ClusterMemorySizeMb < modelContext.MinimumAllowedClusterMemoryMb)
{
return(false);
}
// Cluster must be able to handle the amount of operations needed. Notice we don't introduce a per-shard
// restriction; reason for this is that the shards distribute keys evenly.
if (targetClusterSize.EstimatedRequestsPerSecond < modelContext.MinimumAllowedClusterRps)
{
return(false);
}
// Disallow going over the maximum allowed cluster memory
// NOTE: we only constrain on the target not being over the allowed size, rather than all nodes in the
// path. The reason for this is that our ability to reach all nodes is based on being able to scale above
// any specific memory threshold.
if (modelContext.MaximumAllowedClusterMemoryMb != null && targetClusterSize.ClusterMemorySizeMb > modelContext.MaximumAllowedClusterMemoryMb.Value)
{
return(false);
}
// Always allow not doing anything if it's available.
// NOTE: this is here because in downscale situations we always want to ensure we have the "status quo"
// action available.
if (currentClusterSize.Equals(targetClusterSize))
{
return(true);
}
// Disallow downscales that don't improve cost significantly
if (_configuration.MinimumCostSavingForDownScaling != null)
{
var monthlyCostDelta = targetClusterSize.MonthlyCostUsd - currentClusterSize.MonthlyCostUsd;
if (RedisScalingUtilities.IsDownScale(currentClusterSize, targetClusterSize) && monthlyCostDelta <= 0 && -monthlyCostDelta < _configuration.MinimumCostSavingForDownScaling)
{
return(false);
}
}
return(true);
}
public void LoweringTierIsDownscaling()
{
foreach (var source in RedisClusterSize.Instances)
{
var candidates =
from size in source.ScaleEligibleSizes
where size.Shards == source.Shards && RedisScalingUtilities.IsDownScale(source.Tier, size.Tier)
select size;
foreach (var to in candidates)
{
RedisScalingUtilities.IsDownScale(source, to).Should().BeTrue();
}
}
}
public void RemovingShardsIsDownscaling()
{
foreach (var source in RedisClusterSize.Instances)
{
var candidates =
from size in source.ScaleEligibleSizes
where size.Tier.Equals(source.Tier) && size.Shards < source.Shards
select size;
foreach (var to in candidates)
{
RedisScalingUtilities.IsDownScale(source, to).Should().BeTrue();
}
}
}
