Add scale thresholds to split etcd and k8s-masters

Also adds calico-rr group if there are standalone etcd nodes.
Now if there are 50 or more nodes, 3 etcd nodes will be standalone.
If there are 200 or more nodes, 2 kube-masters will be standalone.
If thresholds are exceeded, kube-node group cannot add nodes that
belong to etcd or kube-master groups (according to above statements).

contrib/inventory_builder/inventory.py

@@ -40,7 +40,8 @@ import os
 import re
 import sys
 
-ROLES = ['kube-master', 'all', 'k8s-cluster:children', 'kube-node', 'etcd']
+ROLES = ['all', 'kube-master', 'kube-node', 'etcd', 'k8s-cluster:children',
+         'calico-rr']
 PROTECTED_NAMES = ROLES
 AVAILABLE_COMMANDS = ['help', 'print_cfg', 'print_ips', 'load']
 _boolean_states = {'1': True, 'yes': True, 'true': True, 'on': True,
@@ -51,10 +52,18 @@ def get_var_as_bool(name, default):
     value = os.environ.get(name, '')
     return _boolean_states.get(value.lower(), default)
 
+# Configurable as shell vars start
+
 CONFIG_FILE = os.environ.get("CONFIG_FILE", "./inventory.cfg")
+# Reconfigures cluster distribution at scale
+SCALE_THRESHOLD = int(os.environ.get("SCALE_THRESHOLD", 50))
+MASSIVE_SCALE_THRESHOLD = int(os.environ.get("SCALE_THRESHOLD", 200))
+
 DEBUG = get_var_as_bool("DEBUG", True)
 HOST_PREFIX = os.environ.get("HOST_PREFIX", "node")
 
+# Configurable as shell vars end
+
 
 class KargoInventory(object):
 
@@ -74,11 +83,16 @@ class KargoInventory(object):
         if changed_hosts:
             self.hosts = self.build_hostnames(changed_hosts)
             self.purge_invalid_hosts(self.hosts.keys(), PROTECTED_NAMES)
-            self.set_kube_master(list(self.hosts.keys())[:2])
             self.set_all(self.hosts)
             self.set_k8s_cluster()
-            self.set_kube_node(self.hosts.keys())
             self.set_etcd(list(self.hosts.keys())[:3])
+            if len(self.hosts) >= SCALE_THRESHOLD:
+                self.set_kube_master(list(self.hosts.keys())[3:5])
+            else:
+                self.set_kube_master(list(self.hosts.keys())[:2])
+            self.set_kube_node(self.hosts.keys())
+            if len(self.hosts) >= SCALE_THRESHOLD:
+                self.set_calico_rr(list(self.hosts.keys())[:3])
         else:  # Show help if no options
             self.show_help()
             sys.exit(0)
@@ -205,8 +219,32 @@ class KargoInventory(object):
         self.add_host_to_group('k8s-cluster:children', 'kube-node')
         self.add_host_to_group('k8s-cluster:children', 'kube-master')
 
+    def set_calico_rr(self, hosts):
+        for host in hosts:
+            if host in self.config.items('kube-master'):
+                    self.debug("Not adding {0} to calico-rr group because it "
+                               "conflicts with kube-master group".format(host))
+                    continue
+            if host in self.config.items('kube-node'):
+                    self.debug("Not adding {0} to calico-rr group because it "
+                               "conflicts with kube-node group".format(host))
+                    continue
+            self.add_host_to_group('calico-rr', host)
+
     def set_kube_node(self, hosts):
         for host in hosts:
+            if len(self.config['all']) >= SCALE_THRESHOLD:
+                if self.config.has_option('etcd', host):
+                    self.debug("Not adding {0} to kube-node group because of "
+                               "scale deployment and host is in etcd "
+                               "group.".format(host))
+                    continue
+            if len(self.config['all']) >= MASSIVE_SCALE_THRESHOLD:
+                if self.config.has_option('kube-master', host):
+                    self.debug("Not adding {0} to kube-node group because of "
+                               "scale deployment and host is in kube-master "
+                               "group.".format(host))
+                    continue
             self.add_host_to_group('kube-node', host)
 
     def set_etcd(self, hosts):
@@ -275,7 +313,15 @@ print_ips - Write a space-delimited list of IPs from "all" group
 Advanced usage:
 Add another host after initial creation: inventory.py 10.10.1.5
 Delete a host: inventory.py -10.10.1.3
-Delete a host by id: inventory.py -node1'''
+Delete a host by id: inventory.py -node1
+
+Configurable env vars:
+DEBUG                   Enable debug printing. Default: True
+CONFIG_FILE             File to write config to Default: ./inventory.cfg
+HOST_PREFIX             Host prefix for generated hosts. Default: node
+SCALE_THRESHOLD         Separate ETCD role if # of nodes >= 50
+MASSIVE_SCALE_THRESHOLD Separate K8s master and ETCD if # of nodes >= 200
+'''
         print(help_text)
 
     def print_config(self):

contrib/inventory_builder/requirements.yml

@@ -1,48 +0,0 @@
----
-- src: https://gitlab.com/kubespray-ansibl8s/k8s-common.git
-  path: roles/apps
-  scm: git
-
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-dashboard.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-kubedns.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-elasticsearch.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-redis.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-memcached.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-postgres.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-pgbouncer.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-heapster.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-influxdb.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-kubedash.git
-#  path: roles/apps
-#  scm: git
-#
-#- src: https://gitlab.com/kubespray-ansibl8s/k8s-kube-logstash.git
-#  path: roles/apps
-#  scm: git

contrib/inventory_builder/tests/test_inventory.py

@@ -210,3 +210,31 @@ class TestInventory(unittest.TestCase):
 
         self.inv.set_etcd([host])
         self.assertTrue(host in self.inv.config[group])
+
+    def test_scale_scenario_one(self):
+        num_nodes = 50
+        hosts = OrderedDict()
+
+        for hostid in range(1, num_nodes+1):
+            hosts["node" + str(hostid)] = ""
+
+        self.inv.set_all(hosts)
+        self.inv.set_etcd(hosts.keys()[0:3])
+        self.inv.set_kube_master(hosts.keys()[0:2])
+        self.inv.set_kube_node(hosts.keys())
+        for h in range(3):
+            self.assertFalse(hosts.keys()[h] in self.inv.config['kube-node'])
+
+    def test_scale_scenario_two(self):
+        num_nodes = 500
+        hosts = OrderedDict()
+
+        for hostid in range(1, num_nodes+1):
+            hosts["node" + str(hostid)] = ""
+
+        self.inv.set_all(hosts)
+        self.inv.set_etcd(hosts.keys()[0:3])
+        self.inv.set_kube_master(hosts.keys()[3:5])
+        self.inv.set_kube_node(hosts.keys())
+        for h in range(5):
+            self.assertFalse(hosts.keys()[h] in self.inv.config['kube-node'])

contrib/inventory_builder/tox.ini

@@ -11,7 +11,7 @@ deps =
     -r{toxinidir}/test-requirements.txt
 setenv = VIRTUAL_ENV={envdir}
 passenv = http_proxy HTTP_PROXY https_proxy HTTPS_PROXY no_proxy NO_PROXY
-commands = py.test -vv #{posargs:./tests}
+commands = pytest -vv #{posargs:./tests}
 
 [testenv:pep8]
 usedevelop = False

docs/getting-started.md

@@ -23,19 +23,17 @@ Building your own inventory
 
 Ansible inventory can be stored in 3 formats: YAML, JSON, or inifile. There is
 an example inventory located
-[here](https://github.com/kubernetes-incubator/kargo/blob/master/inventory/inventory.example):
+[here](https://github.com/kubernetes-incubator/kargo/blob/master/inventory/inventory.example).
 
-```
-cp -r inventory my_inventory
-cp my_inventory/inventory.example my_inventory/inventory.cfg
-# edit the inventory file as needed
-```
-
-Or you can use an
+You can use an
 [inventory generator](https://github.com/kubernetes-incubator/kargo/blob/master/contrib/inventory_builder/inventory.py)
 to create or modify an Ansible inventory. Currently, it is limited in
 functionality and is only use for making a basic Kargo cluster, but it does
-support creating large clusters. For example:
+support creating large clusters. It now supports
+separated ETCD and Kubernetes master roles from node role if the size exceeds a
+certain threshold. Run inventory.py help for more information.
+
+Example inventory generator usage:
 
 ```
 cp -r inventory my_inventory

docs/large-deployments.md

@@ -27,5 +27,15 @@ For a large scaled deployments, consider the following configuration changes:
   end up with the 'm' skipped for docker as well. This is required as docker does not
   understand k8s units well.
 
+* Add calico-rr nodes if you are deploying with Calico or Canal. Nodes recover
+  from host/network interruption much quicker with calico-rr. Note that
+  calico-rr role must be on a host without kube-master or kube-node role (but
+  etcd role is okay).
+
+* Check out the
+  [Inventory](https://github.com/kubernetes-incubator/kargo/blob/master/docs/getting-started.md#building-your-own-inventory)
+  section of the Getting started guide for tips on creating a large scale
+  Ansible inventory.
+
 For example, when deploying 200 nodes, you may want to run ansible with
 ``--forks=50``, ``--timeout=600`` and define the ``retry_stagger: 60``.