| /** |
| * <p>This package contains classes for providing some fault tolerance |
| * to S4 PEs.</p> |
| * <p>The current approach is based on <b>checkpointing</b>.</p> |
| * <p>Checkpoints are taken periodically (configurable by time or |
| * frequency of application events), and when restarting an S4 node, |
| * saved checkpoints are automatically and lazily restored.</p> |
| * <p><b>Lazy restoration</b> is triggered by an application event to a PE |
| * that has not yet been restored.</p> |
| * <p>Checkpoints are stored in storage backends. Storage backends may |
| * implement eager techniques to prefetch checkpoint data to be |
| * recovered. Storage backends can be implemented for various kinds of systems, |
| * and must implement the {@link org.apache.s4.core.ft.StateStorage} interface. |
| * They are pluggable throught the module system. |
| * <p> |
| * The application programmer must take care of marking as <b>transient</b> |
| * the fields that do not have to be persisted (or cannot be persisted). |
| * <p>Storage backends are pluggable and we provide some default |
| * implementations in this package</p> |
| */ |
| package org.apache.s4.core.ft; |
