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+ | ===== Distributed Garbage Collection ===== | ||
+ | [[http:// | ||
- | **Motivation** | + | < |
+ | This page is outdated. Please check [[http:// | ||
+ | </ | ||
- | Mobile ad hoc networks represent a new kind of distributed system with distinguishing characteristics that pose new challenges in the field of distributed garbage collection (DGC). In particular, DGC must deal with a highly partial disconnected network topology where remote references may be inaccessible for unpredicted amount of time. DGC mechanisms typically determine the reachability of the remote objects by means of communication between the nodes involved. However, in a mobile setting where disconnections are the rule rather the exception, the system cannot determine how long it should wait for a connection to be restored. At best, the failure will be transitory and the created inaccessible reference will become accessible again by a repaired connection, but at worst the devices may never encounter again - e.g. when a user never comes back to a certain place - and an unbounded amount of inaccessible reference will be accumulated as they move about. | + | ==== Motivation ==== |
- | Knowing when the communication will be restored | + | Mobile ad hoc networks represent a new kind of distributed system with distinguishing characteristics that pose new challenges in the field of distributed garbage collection (DGC). In particular, DGC must deal with a highly partial disconnected network topology where remote references may be inaccessible for unpredicted amount of time. DGC mechanisms typically determine the reachability of the remote objects by means of communication between the nodes involved. However, in a mobile setting where disconnections are the rule rather the exception, the system cannot determine how long it should wait for a connection to be restored. |
- | As a result, we claim that reclaiming remote objects can no longer be a low level concern tackled in a transparent way with a DGC mechanism. | + | Our position is that reclaiming remote objects can no longer be a low level concern tackled in a transparent way via a DGC mechanism. On the contrary, we admit that automatic transparent DGC is irreconcilable with the characteristics intrinsic to mobile networks. Our research proposes a novel treatment of the memory management called |
- | Design | + | ==== Design |
- | Semi-automatic garbage collection is a hybrid approach which relies on an underlying local GC and proposes a non-transparent DGC. The approach can be seen as an extension to the indirect reference counting (Piquer,1991) and network objects (Birrel | + | Semi-automatic garbage collection is a hybrid approach which relies on an underlying local GC and proposes a non-transparent DGC. The approach can be seen as an extension to the indirect reference counting (Piquer,91) and network objects (Birrell |
- | Our approach propose that remote references will be tangible to the developer who will determine the conditions under which a reference is meaningful to the application in order to help the collector to ascertain if the remote object they point to can be reclaimed. Since devices may not be able to communicate at some point in time, when a remote reference is first allocated, both parties in the interaction will establish then a contract with the condition under which the reference is useful to the application. Therefore, if one devices becomes inaccessible because of a broken connection, the other one is aware of the conditions in which the inaccessible reference is still valuable. That is why we talk about remote reference as two party contract since both parties in the interaction know exactly the disposability of a reference after a disconnection without requiring later communication. | + | {{ remoterefint.jpg?430x250 }} |
- | We propose referencing strategies as the language support that allows the developer to decide which collection policy will be applied | + | Since devices may not be able to communicate at some point in time, when a remote |
- | Ongoing | + | We propose // |
- | We are currently exploring the necessary referencing strategies for the developer to annotate remote references with the extra semantic information. We have come up with a tentative classification of referencing strategies that can be found with more detail here, but we are still investigating the semantics of these constructs. | + | ==== Ongoing and Future work ==== |
- | We have also identified | + | We are currently exploring the necessary referencing strategies for the developer to annotate remote references. |
- | Resolving conflicts between client and service provider strategies. | + | There are a number of open issues that are not properly tackled yet by our approach: |
- | Indirect references: passing a reference to a third party. | + | * Resolving conflicts between client and service provider strategies. |
- | Composition mechanism to mark group of remote | + | * Indirect references: passing a reference |
- | Garbage collection | + | * Composition mechanism to mark group of remote |
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+ | ==== Further Reading ==== | ||
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+ | **Semi-Automatic Garbage Collection for Mobile Networks**. Elisa Gonzalez Boix, Tom Van Cutsem, Stijn Mostinckx, Jessie Dedecker, Wolfgang De Meuter, and Theo D' |