- All Implemented Interfaces:
public enum TopicOverloadPolicy extends java.lang.Enum<TopicOverloadPolicy>A policy to deal with an overloaded topic; so topic where there is no place to store new messages.
This policy can only be used in combination with the
The reliable topic uses a
Ringbufferto store the messages. A ringbuffer doesn't track where readers are, so it has no concept of a slow consumers. This provides many advantages like high performance reads, but it also gives the ability to the reader to re-read the same message multiple times in case of an error.
A ringbuffer has a limited, fixed capacity. A fast producer may overwrite old messages that are still being read by a slow consumer. To prevent this, we may configure a time-to-live on the ringbuffer (see
Once the time-to-live is configured, the
TopicOverloadPolicycontrols how the publisher is going to deal with the situation that a ringbuffer is full and the oldest item in the ringbuffer is not old enough to get overwritten.
Keep in mind that this retention period (time-to-live) can keep messages from being overwritten, even though all readers might have already completed reading.
Enum Constant Summary
Enum Constants Enum Constant Description
BLOCKThe caller will wait till there space in the ringbuffer.
DISCARD_NEWESTThe message that was to be published is discarded.
DISCARD_OLDESTUsing this policy, a message that has not expired can be overwritten.
ERRORThe publish call immediately fails.
All Methods Static Methods Concrete Methods Modifier and Type Method Description
valueOf(java.lang.String name)Returns the enum constant of this type with the specified name.
values()Returns an array containing the constants of this enum type, in the order they are declared.
Methods inherited from class java.lang.Enum
clone, compareTo, equals, finalize, getDeclaringClass, hashCode, name, ordinal, toString, valueOf
Enum Constant Detail
public static final TopicOverloadPolicy DISCARD_OLDESTUsing this policy, a message that has not expired can be overwritten. No matter the retention period set, the overwrite will just overwrite the item.
This can be a problem for slow consumers because they were promised a certain time window to process messages. But it will benefit producers and fast consumers since they are able to continue. This policy sacrifices the slow producer in favor of fast producers/consumers.
public static final TopicOverloadPolicy DISCARD_NEWESTThe message that was to be published is discarded.
public static final TopicOverloadPolicy BLOCKThe caller will wait till there space in the ringbuffer.
public static final TopicOverloadPolicy ERRORThe publish call immediately fails.
public static TopicOverloadPolicy values()Returns an array containing the constants of this enum type, in the order they are declared. This method may be used to iterate over the constants as follows:
for (TopicOverloadPolicy c : TopicOverloadPolicy.values()) System.out.println(c);
- an array containing the constants of this enum type, in the order they are declared
public static TopicOverloadPolicy valueOf(java.lang.String name)Returns the enum constant of this type with the specified name. The string must match exactly an identifier used to declare an enum constant in this type. (Extraneous whitespace characters are not permitted.)
name- the name of the enum constant to be returned.
- the enum constant with the specified name
java.lang.IllegalArgumentException- if this enum type has no constant with the specified name
java.lang.NullPointerException- if the argument is null