public static async Task <DependencyFlowGraph> BuildAsync(
List <DefaultChannel> defaultChannels,
List <Subscription> subscriptions,
IRemote barOnlyRemote,
int days)
{
// Dictionary of nodes. Key is the repo+branch
Dictionary <string, DependencyFlowNode> nodes = new Dictionary <string, DependencyFlowNode>(
StringComparer.OrdinalIgnoreCase);
List <DependencyFlowEdge> edges = new List <DependencyFlowEdge>();
// First create all the channel nodes. There may be disconnected
// nodes in the graph, so we must process all channels and all subscriptions
foreach (DefaultChannel channel in defaultChannels)
{
DependencyFlowNode flowNode = GetOrCreateNode(channel.Repository, channel.Branch, nodes);
// Add the build times
if (channel.Id != default(int))
{
BuildTime buildTime = await barOnlyRemote.GetBuildTimeAsync(channel.Id, days);
flowNode.OfficialBuildTime = buildTime.OfficialBuildTime ?? 0;
flowNode.PrBuildTime = buildTime.PrBuildTime ?? 0;
flowNode.GoalTimeInMinutes = buildTime.GoalTimeInMinutes ?? 0;
}
else
{
flowNode.OfficialBuildTime = 0;
flowNode.PrBuildTime = 0;
}
// Add a the output mapping.
flowNode.OutputChannels.Add(channel.Channel.Name);
}
// Process all subscriptions (edges)
foreach (Subscription subscription in subscriptions)
{
// Get the target of the subscription
DependencyFlowNode destinationNode = GetOrCreateNode(subscription.TargetRepository, subscription.TargetBranch, nodes);
// Add the input channel for the node
destinationNode.InputChannels.Add(subscription.Channel.Name);
// Find all input nodes by looking up the default channels of the subscription input channel and repository.
// This may return no nodes if there is no default channel for the inputs.
IEnumerable <DefaultChannel> inputDefaultChannels = defaultChannels.Where(d => d.Channel.Name == subscription.Channel.Name &&
d.Repository.Equals(subscription.SourceRepository, StringComparison.OrdinalIgnoreCase));
foreach (DefaultChannel defaultChannel in inputDefaultChannels)
{
DependencyFlowNode sourceNode = GetOrCreateNode(defaultChannel.Repository, defaultChannel.Branch, nodes);
DependencyFlowEdge newEdge = new DependencyFlowEdge(sourceNode, destinationNode, subscription);
destinationNode.IncomingEdges.Add(newEdge);
sourceNode.OutgoingEdges.Add(newEdge);
edges.Add(newEdge);
}
}
return(new DependencyFlowGraph(nodes.Select(kv => kv.Value).ToList(), edges));
}
public DependencyFlowEdge(DependencyFlowNode from, DependencyFlowNode to, Subscription subscription)
{
Subscription = subscription;
From = from;
To = to;
OnLongestBuildPath = false;
BackEdge = false;
}
public void RemoveEdge(DependencyFlowEdge edge)
{
if (Edges.Remove(edge))
{
edge.From.OutgoingEdges.Remove(edge);
DependencyFlowNode targetNode = edge.To;
edge.To.IncomingEdges.Remove(edge);
RecalculateInputChannels(targetNode);
}
}
/// <summary>
/// Determine and mark the absolute longest build path in the flow graph, based on the Best Case time.
/// </summary>
public void MarkLongestBuildPath()
{
// Find the node with the worst best case time, we will treat it as the starting point and walk down the path
// from this node to a product node
DependencyFlowNode startNode = Nodes.OrderByDescending(n => n.BestCasePathTime).FirstOrDefault();
if (startNode != null)
{
startNode.OnLongestBuildPath = true;
MarkLongestPath(startNode);
}
}
/// <summary>
/// Prune away uninteresting nodes and edges from the graph
/// </summary>
/// <param name="isInterestingNode">Returns true if the node is an interesting node</param>
/// <param name="isInterestingEdge">Returns true if the edge is an interesting edge</param>
/// <remarks>
/// Starting with the set of interesting nodes as indicated by <paramref name="isInterestingNode"/>,
/// remove all edges that are not interesting, and all nodes that are not reachable by an interesting
/// edge.
/// </remarks>
public void PruneGraph(Func <DependencyFlowNode, bool> isInterestingNode,
Func <DependencyFlowEdge, bool> isInterestingEdge)
{
HashSet <DependencyFlowNode> unreachableNodes = new HashSet <DependencyFlowNode>(Nodes);
HashSet <DependencyFlowEdge> unreachableEdges = new HashSet <DependencyFlowEdge>(Edges);
Stack <DependencyFlowNode> nodes = new Stack <DependencyFlowNode>();
// Walk each root
foreach (DependencyFlowNode node in Nodes)
{
if (!isInterestingNode(node))
{
continue;
}
nodes.Push(node);
while (nodes.Count != 0)
{
DependencyFlowNode currentNode = nodes.Pop();
if (!unreachableNodes.Remove(currentNode))
{
// Nothing to do
continue;
}
foreach (var inputEdge in currentNode.IncomingEdges)
{
if (isInterestingEdge(inputEdge))
{
unreachableEdges.Remove(inputEdge);
// Push the inputs onto the stack.
nodes.Push(inputEdge.From);
}
}
}
}
// Now walk the graph and eliminate any edges or nodes that
foreach (var node in unreachableNodes)
{
RemoveNode(node);
}
foreach (var edge in unreachableEdges)
{
RemoveEdge(edge);
}
}
/// <summary>
/// Calculate the longest build path time from each node in the flow graph
/// </summary>
/// <remarks>
/// Starting with the set of root node (nodes with no outgoing edges), compute the
/// longest build path time using a breadth first search
/// </remarks>
public void CalculateLongestBuildPaths()
{
List <DependencyFlowNode> roots = Nodes.Where(n => n.OutgoingEdges.Count == 0).ToList();
Dictionary <DependencyFlowNode, HashSet <DependencyFlowNode> > visitedNodes = new Dictionary <DependencyFlowNode, HashSet <DependencyFlowNode> >();
Queue <DependencyFlowNode> nodesToVisit = new Queue <DependencyFlowNode>();
foreach (DependencyFlowNode root in roots)
{
nodesToVisit.Enqueue(root);
while (nodesToVisit.Count > 0)
{
DependencyFlowNode node = nodesToVisit.Dequeue();
if (visitedNodes.ContainsKey(node))
{
visitedNodes[node].Add(node);
}
else
{
visitedNodes.Add(node, new HashSet <DependencyFlowNode>()
{
node
});
}
foreach (DependencyFlowEdge edge in node.IncomingEdges)
{
DependencyFlowNode child = edge.From;
if (!visitedNodes[node].Contains(child) && !nodesToVisit.Contains(child))
{
if (visitedNodes.ContainsKey(child))
{
visitedNodes[child].UnionWith(visitedNodes[node]);
}
else
{
visitedNodes.Add(child, new HashSet <DependencyFlowNode>(visitedNodes[node]));
}
nodesToVisit.Enqueue(child);
}
}
node.CalculateLongestPathTime();
}
}
}
private void MarkLongestPath(DependencyFlowNode node)
{
// The edges we are interested in are those that haven't been marked as on the longest build path
// and aren't back edges, both of which indicate a cycle
var edgesOfInterest = node.OutgoingEdges.Where(e => !e.OnLongestBuildPath && !e.BackEdge).ToList();
if (edgesOfInterest.Count > 0)
{
DependencyFlowEdge pathEdge = edgesOfInterest.Aggregate((e1, e2) => e1.To.BestCasePathTime > e2.To.BestCasePathTime ? e1: e2);
// Mark the edge and the node as on the longest build path
pathEdge.OnLongestBuildPath = true;
pathEdge.To.OnLongestBuildPath = true;
MarkLongestPath(pathEdge.To);
}
}
private static DependencyFlowNode GetOrCreateNode(
string repo,
string branch,
Dictionary <string, DependencyFlowNode> nodes)
{
string key = $"{repo}@{branch}";
if (nodes.TryGetValue(key, out DependencyFlowNode existingNode))
{
return(existingNode);
}
else
{
DependencyFlowNode newNode = new DependencyFlowNode(repo, branch, Guid.NewGuid().ToString());
nodes.Add(key, newNode);
return(newNode);
}
}
private static DependencyFlowNode GetOrCreateNode(
string repo,
string branch,
Dictionary <string, DependencyFlowNode> nodes)
{
string normalizedBranch = NormalizeBranch(branch);
string key = $"{repo}@{normalizedBranch}";
if (nodes.TryGetValue(key, out DependencyFlowNode existingNode))
{
return(existingNode);
}
else
{
DependencyFlowNode newNode = new DependencyFlowNode(repo, normalizedBranch);
nodes.Add(key, newNode);
return(newNode);
}
}
public void RemoveNode(DependencyFlowNode node)
{
// Remove the node from the list, then remove corresponding edges
if (Nodes.Remove(node))
{
foreach (DependencyFlowEdge incomingEdge in node.IncomingEdges)
{
// Don't use RemoveEdge as it assumes that this node will remain in the graph and
// will cause modification of this IncomingEdges collection while iterating
incomingEdge.From.OutgoingEdges.Remove(incomingEdge);
}
foreach (DependencyFlowEdge outgoingEdge in node.OutgoingEdges)
{
// Don't use RemoveEdge as it assumes that this node will remain in the graph and
// will cause modification of this OutgoingEdges collection while iterating
DependencyFlowNode targetNode = outgoingEdge.To;
targetNode.IncomingEdges.Remove(outgoingEdge);
RecalculateInputChannels(targetNode);
}
}
}
/// <summary>
/// Recalculate the input channels based on the input edges.
/// </summary>
/// <param name="node">Node to calculate the input edges for.</param>
private void RecalculateInputChannels(DependencyFlowNode node)
{
node.InputChannels = new HashSet <string>(node.IncomingEdges.Select(e => e.Subscription.Channel.Name));
}
/// <summary>
/// If pruning the graph is desired, determine whether a node is interesting.
/// </summary>
/// <param name="node">Node</param>
/// <returns>True if the node is interesting, false otherwise</returns>
public static bool IsInterestingNode(string targetChannel, DependencyFlowNode node)
{
return(node.OutputChannels.Any(c => c == targetChannel));
}
/// <summary>
/// Mark the back edges of the graph so that they can be ignored when walking it.
/// Determine the backedges by computing dominators for each node. A node n is said to
/// dominate another node if every path from the start to the other node must go through
/// n.
/// </summary>
public void MarkBackEdges()
{
// In this, we will interpret the root of the graph as those nodes that have no outgoing edges
// (call them 'products'). Connect all of these via a start node.
// Add a start node to the graph (a node that connects all nodes that have no outgoing edges
// We will also reverse the graph by flipping the interpretation of incoming and outgoing.
DependencyFlowNode startNode = new DependencyFlowNode("start", "start", "start");
foreach (DependencyFlowNode node in Nodes)
{
if (!node.OutgoingEdges.Any())
{
DependencyFlowEdge newEdge = new DependencyFlowEdge(node, startNode, null);
startNode.IncomingEdges.Add(newEdge);
node.OutgoingEdges.Add(newEdge);
}
}
Nodes.Add(startNode);
// Dominator set for each node starts with the full set of nodes.
Dictionary <DependencyFlowNode, HashSet <DependencyFlowNode> > dominators = new Dictionary <DependencyFlowNode, HashSet <DependencyFlowNode> >();
foreach (DependencyFlowNode node in Nodes)
{
dominators.Add(node, new HashSet <DependencyFlowNode>(Nodes));
}
Queue <DependencyFlowNode> workList = new Queue <DependencyFlowNode>();
workList.Enqueue(startNode);
while (workList.Count != 0)
{
DependencyFlowNode currentNode = workList.Dequeue();
// Compute a new dominator set for this node. Remember we are
// flipping the interepretation of incoming and outgoing
HashSet <DependencyFlowNode> newDom = null;
IEnumerable <DependencyFlowNode> predecessors = currentNode.OutgoingEdges.Select(e => e.To);
IEnumerable <DependencyFlowNode> successors = currentNode.IncomingEdges.Select(e => e.From);
// Compute the intersection of the dominators for the predecessors
foreach (DependencyFlowNode predNode in predecessors)
{
if (newDom == null)
{
newDom = new HashSet <DependencyFlowNode>(dominators[predNode]);
}
else
{
newDom.IntersectWith(dominators[predNode]);
}
}
if (newDom == null)
{
newDom = new HashSet <DependencyFlowNode>();
}
// Add the current node
newDom.Add(currentNode);
// Compare to the existing dominator set for this node
if (!dominators[currentNode].SetEquals(newDom))
{
dominators[currentNode] = newDom;
// Queue all of the successors
foreach (DependencyFlowNode succ in successors)
{
workList.Enqueue(succ);
}
}
}
// Determine backedges
List <DependencyFlowEdge> toRemove = new List <DependencyFlowEdge>();
foreach (DependencyFlowEdge edge in Edges)
{
if (dominators[edge.To].Contains(edge.From))
{
edge.BackEdge = true;
}
}
// Remove the start node we created and links to it
foreach (DependencyFlowEdge edge in startNode.IncomingEdges)
{
RemoveEdge(edge);
}
RemoveNode(startNode);
}
public DependencyFlowEdge(DependencyFlowNode from, DependencyFlowNode to, Subscription subscription)
{
Subscription = subscription;
From = from;
To = to;
}