@Beta public class PercentileSpeculativeExecutionPolicy extends Object implements SpeculativeExecutionPolicy
This class uses a PerHostPercentileTracker that must be registered with the cluster instance:
PerHostPercentileTracker tracker = PerHostPercentileTracker
.builderWithHighestTrackableLatencyMillis(15000)
.build();
PercentileSpeculativeExecutionPolicy policy = new PercentileSpeculativeExecutionPolicy(tracker, 99.0, 2);
cluster = Cluster.builder()
.addContactPoint("127.0.0.1")
.withSpeculativeExecutionPolicy(policy)
.build();
cluster.register(tracker);
You must register the tracker with the cluster yourself (as shown on the last line above), this class will not
do it itself.
This class is currently provided as a beta preview: it hasn't been extensively tested yet, and the API is still subject to change.
SpeculativeExecutionPolicy.SpeculativeExecutionPlan| Constructor and Description |
|---|
PercentileSpeculativeExecutionPolicy(PerHostPercentileTracker percentileTracker,
double percentile,
int maxSpeculativeExecutions)
Builds a new instance.
|
| Modifier and Type | Method and Description |
|---|---|
void |
close()
Gets invoked at cluster shutdown.
|
void |
init(Cluster cluster)
Gets invoked at cluster startup.
|
SpeculativeExecutionPolicy.SpeculativeExecutionPlan |
newPlan(String loggedKeyspace,
Statement statement)
Returns the plan to use for a new query.
|
public PercentileSpeculativeExecutionPolicy(PerHostPercentileTracker percentileTracker, double percentile, int maxSpeculativeExecutions)
percentileTracker - the component that will record latencies. Note that this policy doesn't register it with the Cluster,
you must do it yourself (see the code example in this class's Javadoc).percentile - the percentile that a request's latency must fall into to be considered slow (ex: 99.0).maxSpeculativeExecutions - the maximum number of speculative executions that will be triggered for a given request (this does not
include the initial, normal request). Must be strictly positive.public SpeculativeExecutionPolicy.SpeculativeExecutionPlan newPlan(String loggedKeyspace, Statement statement)
SpeculativeExecutionPolicynewPlan in interface SpeculativeExecutionPolicyloggedKeyspace - the currently logged keyspace (the one set through either
Cluster.connect(String) or by manually doing a USE query) for
the session on which this plan need to be built. This can be null if
the corresponding session has no keyspace logged in.statement - the query for which to build a plan.public void init(Cluster cluster)
SpeculativeExecutionPolicyinit in interface SpeculativeExecutionPolicycluster - the cluster that this policy is associated with.public void close()
SpeculativeExecutionPolicyThis gives the policy the opportunity to perform some cleanup, for instance stop threads that it might have started.
close in interface SpeculativeExecutionPolicy