com.datastax.driver.core.policies

Class ErrorAwarePolicy.Builder

java.lang.Object

com.datastax.driver.core.policies.ErrorAwarePolicy.Builder

Enclosing class:

ErrorAwarePolicy

public static class ErrorAwarePolicy.Builder
extends Object

Utility class to create a ErrorAwarePolicy.

Constructor Summary

Constructors

Constructor and Description
Builder(LoadBalancingPolicy childPolicy) Creates a ErrorAwarePolicy.Builder instance.

Method Summary

Modifier and Type	Method and Description
ErrorAwarePolicy	build() Creates the ErrorAwarePolicy instance.
ErrorAwarePolicy.Builder	withErrorsFilter(ErrorAwarePolicy.ErrorFilter errorFilter) Provides a filter that will decide which errors are counted towards withMaxErrorsPerMinute(int).
ErrorAwarePolicy.Builder	withMaxErrorsPerMinute(int maxErrorsPerMinute) Defines the maximum number of errors allowed per minute for each host.
ErrorAwarePolicy.Builder	withRetryPeriod(long retryPeriod, TimeUnit retryPeriodTimeUnit) Defines the time during which a host is excluded by the policy once it has exceeded withMaxErrorsPerMinute(int).

Methods inherited from class java.lang.Object

clone, equals, finalize, getClass, hashCode, notify, notifyAll, toString, wait, wait, wait

Constructor Detail

Builder

public Builder(LoadBalancingPolicy childPolicy)

Creates a ErrorAwarePolicy.Builder instance.

Parameters:

childPolicy - the load balancing policy to wrap with error awareness.

Method Detail

withMaxErrorsPerMinute

public ErrorAwarePolicy.Builder withMaxErrorsPerMinute(int maxErrorsPerMinute)

Defines the maximum number of errors allowed per minute for each host.

The policy keeps track of the number of errors on each host (filtered by withErrorsFilter(com.datastax.driver.core.policies.ErrorAwarePolicy.ErrorFilter)) over a sliding 1-minute window. If a host had more than this number of errors, it will be excluded from the query plan for the duration defined by withRetryPeriod(long, TimeUnit).

Default value for the threshold is 1.

Parameters:

maxErrorsPerMinute - the number.

Returns:

this ErrorAwarePolicy.Builder instance, for method chaining.

withRetryPeriod

public ErrorAwarePolicy.Builder withRetryPeriod(long retryPeriod,
                                                TimeUnit retryPeriodTimeUnit)

Defines the time during which a host is excluded by the policy once it has exceeded withMaxErrorsPerMinute(int).

Default value for the retry period is 2 minutes.

Parameters:

retryPeriod - the period of exclusion for a host.

retryPeriodTimeUnit - the time unit for the retry period.

Returns:

this ErrorAwarePolicy.Builder instance, for method chaining.

withErrorsFilter

public ErrorAwarePolicy.Builder withErrorsFilter(ErrorAwarePolicy.ErrorFilter errorFilter)

Provides a filter that will decide which errors are counted towards withMaxErrorsPerMinute(int).

The default implementation will exclude from the error counting, the following exception types:

• QueryConsistencyException and UnavailableException: the assumption is that these errors are most often caused by other replicas being unavailable, not by something wrong on the coordinator;
• InvalidQueryException, AlreadyExistsException, SyntaxError: these are likely caused by a bad query in client code, that will fail on all hosts. Excluding hosts could lead to complete loss of connectivity, rather the solution is to fix the query;
• FunctionExecutionException: similarly, this is caused by a bad function definition and likely to fail on all hosts.

Parameters:

errorFilter - the filter class that the policy will use.

Returns:

this ErrorAwarePolicy.Builder instance, for method chaining.

build

public ErrorAwarePolicy build()

Creates the ErrorAwarePolicy instance.

Returns:

the newly created ErrorAwarePolicy.