Added python script for setting up global DNS in multi-region / multi…

…-cluster k8s

cloud/kubernetes/yb-multiregion-k8s-setup.py

@@ -0,0 +1,74 @@
+#!/usr/bin/env python
+
+import distutils.spawn
+import json
+import os
+from subprocess import check_call,check_output
+from sys import exit
+from time import sleep
+
+# Replace the following with your own k8s cluster contexts
+contexts = {
+    'us-west1-b': 'gke_yugabyte_us-west1-b_yugabytedb1',
+    'us-central1-b': 'gke_yugabyte_us-central1-b_yugabytedb2',
+    'us-east1-b': 'gke_yugabyte_us-east1-b_yugabytedb3',
+}
+
+# Replace the following with your own `zone`: `region` names
+regions = {
+    'us-west1-b': 'us-west1',
+    'us-central1-b': 'us-central1',
+    'us-east1-b': 'us-east1',
+}
+
+# Set the path to the directory where the generated yaml files will be stored
+generated_files_dir = './generated'
+
+try:
+    os.mkdir(generated_files_dir)
+except OSError:
+    pass
+
+# Create a load balancer for the DNS pods in each k8s cluster.
+for zone, context in contexts.items():
+    check_call(['kubectl', 'create', 'namespace', 'yb-demo-'+zone, '--context', context])
+    check_call(['kubectl', 'apply', '-f', 'yb-dns-lb.yaml', '--context', context])
+
+# Set up each load balancer to forward DNS requests for zone-scoped namespaces to the
+# relevant cluster's DNS server, using the external IP of the internal load balancers 
+dns_ips = dict()
+for zone, context in contexts.items():
+    external_ip = ''
+    while True:
+        external_ip = check_output(['kubectl', 'get', 'svc', 'kube-dns-lb', '--namespace', 'kube-system', '--context', context, '--template', '{{range .status.loadBalancer.ingress}}{{.ip}}{{end}}'])
+        if external_ip:
+            break
+        print  'Waiting for DNS load balancer IP in %s...' % (zone)
+        sleep(10)
+    print 'DNS endpoint for zone %s: %s' % (zone, external_ip)
+    dns_ips[zone] = external_ip
+
+# Update each cluster's DNS configuration with an appropriate configmap. Note
+# that we have to ensure that the local cluster is not added to its own configmap 
+# since those requests do not go through the load balancer. Finally, we have to delete the
+# existing DNS pods in order for the new configuration to take effect.
+for zone, context in contexts.items():
+    remote_dns_ips = dict()
+    for z, ip in dns_ips.items():
+        if z == zone:
+            continue
+        remote_dns_ips['yb-demo-'+z+'.svc.cluster.local'] = [ip]
+    config_filename = '%s/dns-configmap-%s.yaml' % (generated_files_dir, zone)
+    with open(config_filename, 'w') as f:
+        f.write("""\
+apiVersion: v1
+kind: ConfigMap
+metadata:
+  name: kube-dns
+  namespace: kube-system
+data:
+  stubDomains: |
+    %s
+""" % (json.dumps(remote_dns_ips)))
+    check_call(['kubectl', 'apply', '-f', config_filename, '--namespace', 'kube-system', '--context', context])
+    check_call(['kubectl', 'delete', 'pods', '-l', 'k8s-app=kube-dns', '--namespace', 'kube-system', '--context', context])