Initial support for DAG based workflows

examples/dag-coinflip.yaml

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+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: dag-diamond-coinflip-
+spec:
+  entrypoint: diamond
+  templates:
+  - name: coinflip
+    steps:
+    - - name: flip-coin
+        template: flip-coin
+    - - name: heads
+        template: heads
+        when: "{{steps.flip-coin.outputs.result}} == heads"
+      - name: tails
+        template: coinflip
+        when: "{{steps.flip-coin.outputs.result}} == tails"
+  - name: flip-coin
+    script:
+      image: python:3.6
+      command: [python]
+      source: |
+        import random
+        result = "heads" if random.randint(0,1) == 0 else "tails"
+        print(result)
+  - name: heads
+    container:
+      image: alpine:3.6
+      command: [sh, -c]
+      args: ["echo \"it was heads\""]
+  - name: diamond
+    dag:
+      tasks:
+      - name: A
+        template: coinflip
+      - name: B
+        dependencies: [A]
+        template: coinflip
+      - name: C
+        dependencies: [A]
+        template: coinflip
+      - name: D
+        dependencies: [B, C]
+        template: coinflip

examples/dag-diamond-steps.yaml

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+# The following workflow executes a diamond workflow, with each
+# node comprising of three parallel fan-in fan-out steps.
+# 
+#           *
+#         / | \
+#       A1 A2  A3
+#         \ | /
+#           *
+#         /   \ 
+#       /       \
+#      *         *
+#    / | \     / | \
+#  B1  B2 B3  C1 C2 C3
+#    \ | /     \ | /
+#      *         *
+#       \       /
+#         \   /
+#           *
+#         / | \
+#       D1 D2  D3
+#         \ | /
+#           *
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: dag-diamond-steps-
+spec:
+  entrypoint: diamond
+  templates:
+  - name: echo
+    inputs:
+      parameters:
+      - name: message
+    container:
+      image: alpine:3.7
+      command: [echo, "{{inputs.parameters.message}}"]
+  - name: echo-thrice
+    inputs:
+      parameters:
+      - name: message
+    steps:
+    - - name: echo
+        template: echo
+        arguments:
+          parameters:
+          - {name: message, value: "{{inputs.parameters.message}}{{item}}"}
+        withItems: [1,2,3]
+  - name: diamond
+    dag:
+      tasks:
+      - name: A
+        template: echo-thrice
+        arguments:
+          parameters: [{name: message, value: A}]
+      - name: B
+        dependencies: [A]
+        template: echo-thrice
+        arguments:
+          parameters: [{name: message, value: B}]
+      - name: C
+        dependencies: [A]
+        template: echo-thrice
+        arguments:
+          parameters: [{name: message, value: C}]
+      - name: D
+        dependencies: [B, C]
+        template: echo-thrice
+        arguments:
+          parameters: [{name: message, value: D}]

examples/dag-diamond.yaml

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+# The following workflow executes a diamond workflow
+# 
+#   A
+#  / \
+# B   C
+#  \ /
+#   D
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: dag-diamond-
+spec:
+  entrypoint: diamond
+  templates:
+  - name: echo
+    inputs:
+      parameters:
+      - name: message
+    container:
+      image: alpine:3.7
+      command: [echo, "{{inputs.parameters.message}}"]
+  - name: diamond
+    dag:
+      tasks:
+      - name: A
+        template: echo
+        arguments:
+          parameters: [{name: message, value: A}]
+      - name: B
+        dependencies: [A]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: B}]
+      - name: C
+        dependencies: [A]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: C}]
+      - name: D
+        dependencies: [B, C]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: D}]

examples/dag-multiroot.yaml

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+# The following workflow executes a multi-root workflow
+# 
+#   A   B
+#  / \ /
+# C   D
+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: dag-multiroot-
+spec:
+  entrypoint: multiroot
+  templates:
+  - name: echo
+    inputs:
+      parameters:
+      - name: message
+    container:
+      image: alpine:3.7
+      command: [echo, "{{inputs.parameters.message}}"]
+  - name: multiroot
+    dag:
+      tasks:
+      - name: A
+        template: echo
+        arguments:
+          parameters: [{name: message, value: A}]
+      - name: B
+        dependencies:
+        template: echo
+        arguments:
+          parameters: [{name: message, value: B}]
+      - name: C
+        dependencies: [A]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: C}]
+      - name: D
+        dependencies: [A, B]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: D}]

examples/dag-nested.yaml

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+apiVersion: argoproj.io/v1alpha1
+kind: Workflow
+metadata:
+  generateName: dag-nested-
+spec:
+  entrypoint: diamond
+  templates:
+  - name: echo
+    inputs:
+      parameters:
+      - name: message
+    container:
+      image: alpine:3.7
+      command: [echo, "{{inputs.parameters.message}}"]
+  - name: diamond
+    dag:
+      tasks:
+      - name: A
+        template: nested-diamond
+        arguments:
+          parameters: [{name: message, value: A}]
+      - name: B
+        dependencies: [A]
+        template: nested-diamond
+        arguments:
+          parameters: [{name: message, value: B}]
+      - name: C
+        dependencies: [A]
+        template: nested-diamond
+        arguments:
+          parameters: [{name: message, value: C}]
+      - name: D
+        dependencies: [B, C]
+        template: nested-diamond
+        arguments:
+          parameters: [{name: message, value: D}]
+  - name: nested-diamond
+    inputs:
+      parameters:
+      - name: message
+    dag:
+      tasks:
+      - name: A
+        template: echo
+        arguments:
+          parameters: [{name: message, value: "{{inputs.parameters.message}}A"}]
+      - name: B
+        dependencies: [A]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: "{{inputs.parameters.message}}B"}]
+      - name: C
+        dependencies: [A]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: "{{inputs.parameters.message}}C"}]
+      - name: D
+        dependencies: [B, C]
+        template: echo
+        arguments:
+          parameters: [{name: message, value: "{{inputs.parameters.message}}D"}]

hack/wfgraph.py

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+#!/usr/bin/env python3
+
+import argparse
+import json
+import subprocess
+import tempfile
+
+from subprocess import run
+
+template = '''
+<!doctype html>
+
+<meta charset="utf-8">
+<title>%s</title>
+
+<link rel="stylesheet" href="demo.css">
+<script src="http://d3js.org/d3.v3.min.js" charset="utf-8"></script>
+<script src="https://cdnjs.cloudflare.com/ajax/libs/dagre-d3/0.4.17/dagre-d3.js"></script>
+
+<style id="css">
+body {
+  font: 300 14px 'Helvetica Neue', Helvetica;
+}
+
+.node rect,
+.node circle,
+.node ellipse {
+  stroke: #333;
+  fill: #fff;
+  stroke-width: 1px;
+}
+
+.edgePath path {
+  stroke: #333;
+  fill: #333;
+  stroke-width: 1.5px;
+}
+</style>
+
+<h2>%s</h2>
+
+<svg width=960 height=600><g/></svg>
+
+<script id="js">
+// Create a new directed graph
+var g = new dagreD3.graphlib.Graph().setGraph({});
+
+var nodes = 
+  %s
+;
+
+var edges = 
+  %s
+;
+
+nodes.forEach(function(node) {
+  g.setNode(node.id, { 
+    label: node.label,
+    style: node.color,
+  });
+});
+
+edges.forEach(function(edge) {
+  g.setEdge(edge.from, edge.to, {
+    arrowhead: "normal",
+    lineInterpolate: "basis",
+  });
+});
+
+var svg = d3.select("svg"),
+    inner = svg.select("g");
+
+// Set up zoom support
+var zoom = d3.behavior.zoom().on("zoom", function() {
+      inner.attr("transform", "translate(" + d3.event.translate + ")" +
+                                  "scale(" + d3.event.scale + ")");
+    });
+svg.call(zoom);
+
+// Create the renderer
+var render = new dagreD3.render();
+
+// Run the renderer. This is what draws the final graph.
+render(inner, g);
+
+// Center the graph
+var initialScale = 0.75;
+zoom
+  .translate([(svg.attr("width") - g.graph().width * initialScale) / 2, 20])
+  .scale(initialScale)
+  .event(svg);
+svg.attr('height', g.graph().height * initialScale + 40);
+</script>
+
+
+'''
+
+def main():
+    parser = argparse.ArgumentParser(description='Visualize graph of a workflow')
+    parser.add_argument('workflow', type=str, help='workflow name')
+    args = parser.parse_args()
+    res = run(["kubectl", "get", "workflow", "-o", "json", args.workflow  ], stdout=subprocess.PIPE)
+    wf = json.loads(res.stdout.decode("utf-8"))
+    nodes = []
+    edges = []
+    colors = {
+      'Pending': 'fill: #D0D0D0',
+      'Running': 'fill: #A0FFFF',
+      'Failed': 'fill: #f77',
+      'Succeeded': 'fill: #afa',
+      'Skipped': 'fill: #D0D0D0',
+      'Error': 'fill: #f77',
+    }
+    wf_name = wf['metadata']['name']
+    for node_id, node_status in wf['status']['nodes'].items():
+        if node_status['name'] == wf_name:
+            label = node_status['name']
+        else:
+            label = node_status['name'].replace(wf_name, "")
+        node = {'id': node_id, 'label': label, 'color': colors[node_status['phase']]}
+        nodes.append(node)
+        if 'children' in node_status:
+            for child_id in node_status['children']:
+              edge = {'from': node_id, 'to': child_id, 'arrows': 'to'}
+              edges.append(edge)
+    html = template % (wf_name, wf_name, json.dumps(nodes), json.dumps(edges))
+    tmpfile = tempfile.NamedTemporaryFile(suffix='.html', delete=False)
+    tmpfile.write(html.encode())
+    tmpfile.flush()
+    run(["open", tmpfile.name])
+
+
+if __name__ == '__main__':
+    main()