/// <summary>
/// Build the sitemap tree structure using a top-down DFS approach using a supervisor
/// that controls concurrency and accounts for error recovery and
/// retrials.
/// </summary>
public CrawlingResult Crawl(CrawlerTaskInfo taskInfo)
{
// baseUrl is validated in the controller,
// so it's safe to create an Uri instance from it.
var root = new Uri(taskInfo.BaseUrl);
// sitemap is the root of the hierarchy.
var sitemap = new NodeInfo(root);
var queue = new ConcurrentQueue <NodeInfo>();
queue.Enqueue(sitemap);
var queueProcessor = new QueueProcessor(
provider,
logger,
root,
taskInfo.MaxDepth,
queue,
configuration.GetValue <int>("QueueProcessorConcurrencyLevel"),
configuration.GetValue <int>("FailuresMaxRetries"),
configuration.GetValue <int>("QueueIdleTime")
);
queueProcessor.Start();
return(new CrawlingResult {
Sitemap = sitemap
});
}
/// <summary>
/// Spawn tasks to crawl each level of the tree at the time. Maintain a list
/// of previously found URLs to avoid infinite loops.
/// </summary>
public CrawlingResult Crawl(CrawlerTaskInfo taskInfo)
{
// baseUrl is validated in the controller,
// so it's safe to create an Uri instance from it.
var root = new Uri(taskInfo.BaseUrl);
var domain = new UriBuilder(root.Scheme, root.Host).Uri;
// sitemap is the root of the hierarchy.
var sitemap = new NodeInfo(root);
var queue = new List <NodeInfo> {
sitemap
};
var paths = new HashSet <string> {
root.AbsolutePath
};
var depth = 0;
// MaxDepth equals zero means all the way down in the tree.
while ((taskInfo.MaxDepth == 0 || ++depth <= taskInfo.MaxDepth) && queue.Count > 0)
{
// Spawn a thread (task) for each node in this level.
var tasks = new List <Task <string> >();
foreach (var node in queue)
{
tasks.Add(Task <string> .Run(() => CrawlNode(node)));
}
Task.WaitAll(tasks.ToArray());
var next = new List <NodeInfo>();
for (var j = 0; j < queue.Count; j++)
{
if (tasks[j].Result != null)
{
var nodeUris = Utils.GetAbsoluteUrisFromHtml(domain, tasks[j].Result);
var childrenUris = new HashSet <Uri>(nodeUris);
foreach (var uri in childrenUris)
{
var child = new NodeInfo(uri);
queue[j].AddChild(child);
// Add it to the next iteration iff it hasn't been found and it
// is in the same domain.
if (domain.Host == uri.Host && !paths.Contains(uri.AbsolutePath))
{
paths.Add(uri.AbsolutePath);
next.Add(child);
}
}
}
}
queue = next;
}
return(new CrawlingResult {
Sitemap = sitemap
});
}
/// <summary>
/// Build the sitemap tree structure using a top-down DFS approach.
/// Thread safety is at the level class.
/// </summary>
public CrawlingResult Crawl(CrawlerTaskInfo taskInfo)
{
// baseUrl is validated in the controller,
// so it's safe to create an Uri instance from it.
var root = new Uri(taskInfo.BaseUrl);
var domain = new UriBuilder(root.Scheme, root.Host).Uri;
// sitemap is the root of the hierarchy.
var sitemap = new NodeInfo(root);
paths = new HashSet <string>()
{
root.AbsolutePath
};
DfsAsync(sitemap, 0, taskInfo.MaxDepth, domain);
return(new CrawlingResult {
Sitemap = sitemap
});
}
