/// <summary>
/// Method that removes the expired elements from the DHT. This method search for expired element and add it to a structure,
/// then delete all the expired elements and if a resource remanins without any supplier will be deleted too.
/// </summary>
public void Expire()
{
List <KademliaResource> lr = new List <KademliaResource>();
LinkedList <ExpireIteratorDesc> cleanList = new LinkedList <ExpireIteratorDesc>();
_repository.GetAll <KademliaResource>(lr);
Parallel.ForEach <KademliaResource, ExpireIteratorDesc>(lr,
() => new ExpireIteratorDesc(),
(key, loop, iter_index, iter_desc) =>
{
if (key == null)
{
return(iter_desc);
}
if (iter_desc.TagId == null)
{
iter_desc.TagId = key.Id;
}
List <DhtElement> dhtElementList = key.Urls.ToList();
for (int k = 0; k < dhtElementList.Count; k++)
{
DhtElement delem = dhtElementList[k];
if (DateTime.Compare(delem.Publication.Add(delem.Validity), DateTime.Now) <= 0)
{
iter_desc.Expired.Add(delem);
}
}
if (iter_desc.Expired.Count == key.Urls.Count)
{
iter_desc.ToBeDeleted = true;
}
else
{
iter_desc.ToBeDeleted = false;
}
return(iter_desc);
},
(finalResult) => cleanList.AddLast(finalResult)
);
Parallel.ForEach <ExpireIteratorDesc>(cleanList,
(iter_desc) =>
{
if (iter_desc == null)
{
return;
}
if (iter_desc.ToBeDeleted)
{
DeleteTag(iter_desc.TagId);
}
else
{
_repository.ArrayRemoveByPosition(iter_desc.TagId, "Urls", iter_desc.Expired.ToArray <DhtElement>());
}
}
);
}
/// <summary>
/// Returns the publication time of a Dht Element related to a Resource.
/// </summary>
/// <param name="tagid">Resource Identifier</param>
/// <param name="url">Url of the Dht Element</param>
/// <returns>The publication time of the Dht Element if it exists, the DateTime min value if the element doesn't exist</returns>
public DateTime GetPublicationTime(string tagid, Uri url)
{
KademliaResource rs = Get(tagid);
if (rs != null)
{
DhtElement elem = rs.Urls.ToList().Find(de =>
{
return(de.Url.Equals(url));
}
);
if (elem != null)
{
return(elem.Publication);
}
}
return(DateTime.MinValue);
}
/// <summary>
/// Method that implements the registration of a peer as supplier for a given resource.
/// This method just load the resource and adds the Dht Element if it's not already in the suppliers list.
/// </summary>
/// <param name="tagid">Resource Identifier</param>
/// <param name="url">Url of the supplier</param>
/// <param name="pubtime">Publication Time for the supplier</param>
/// <returns></returns>
public bool Put(string tagid, Uri url, DateTime pubtime)
{
KademliaResource rs = new KademliaResource();
DhtElement dhtElem = new DhtElement(url, pubtime, this._elementValidity);
RepositoryResponse resp = _repository.GetByKey <KademliaResource>(tagid, rs);
if (resp == RepositoryResponse.RepositoryLoad)
{
if (!rs.Urls.Contains(dhtElem))
{
_repository.ArrayAddElement(rs.Id, "Urls", dhtElem);
return(true);
}
else
{
log.Debug("Urls " + url.ToString() + " already known");
}
}
return(false);
}
/// <summary>
/// Checks if the given resource contains the Url in its supplier list
/// </summary>
/// <param name="tagid">Resource identifier</param>
/// <param name="url">Url of the supplier</param>
/// <returns>True if the Peer with the given Url is a supplier for the resource.</returns>
public bool ContainsUrl(string tagid, Uri url)
{
KademliaResource rs = Get(tagid);
DhtElement fakeElem = new DhtElement()
{
Url = url
};
if (rs != null)
{
if (rs.Urls.Contains(fakeElem))
{
return(true);
}
else
{
return(false);
}
}
return(false);
}
/// <summary>
/// Stores a tag as resource into the kademlia repository. If the resource already exists the method tries to add the
/// given Url (with the desired publication time) to the list of suppliers for that resource; if the url is already known
/// the method does nothing. If the resource is new first the method adds it to the repository and then generates a set of
/// keywords related to the new resource. For each generated keyword, if this is already in the repository the tag
/// identifier (that is the resource identifier too) will be added to the related tags list, if the keyword doesn't exist
/// it will be created and its related tags list will contains only the new resource.
/// </summary>
/// <param name="tag">Tag to store in the kademlia resource</param>
/// <param name="peer">Url of the supplier</param>
/// <param name="pubtime">Publication TIme</param>
/// <returns>False if something went wrong, true otherwise</returns>
public bool StoreResource(CompleteTag tag, Uri peer, DateTime pubtime)
{
KademliaResource rs = new KademliaResource();
Console.WriteLine("Storing resource from peer " + peer);
DhtElement dhtElem = new DhtElement(peer, pubtime, this._elementValidity);
RepositoryResponse resp = _repository.GetByKey <KademliaResource>(tag.TagHash, rs);
if (resp == RepositoryResponse.RepositoryLoad)
{
if (!rs.Urls.Contains(dhtElem))
{
_repository.ArrayAddElement(rs.Id, "Urls", dhtElem);
}
else
{
log.Debug("Urls " + peer.ToString() + " already known");
}
}
else if (resp == RepositoryResponse.RepositoryMissingKey)
{
rs = new KademliaResource(tag, dhtElem);
if (_repository.Save(rs) == RepositoryResponse.RepositorySuccess)
{
List <string> pks = new List <string>(generatePrimaryKey(tag));
List <KademliaKeyword> keys = new List <KademliaKeyword>();
if (_repository.GetByKeySet(pks.ToArray(), keys) > 0)
{
foreach (KademliaKeyword k in keys)
{
if (!k.Tags.Contains(rs.Id))
{
_repository.ArrayAddElement(k.Id, "Tags", rs.Id);
}
pks.Remove(k.Id);
}
foreach (String pk in pks)
{
KademliaKeyword localKey = new KademliaKeyword(pk, rs.Id);
_repository.Save(localKey);
}
}
else
{
log.Error("Unexpected reposnde while getting keywords");
return(false);
}
}
else
{
log.Error("Unexpected response while inserting Tag with key " + tag.TagHash);
return(false);
}
}
else
{
log.Error("Unexpected response while testing presence of the key " + tag.TagHash);
return(false);
}
return(true);
}
