implement download mirrors support (kubernetes-sigs#8474)

* [download] add mechanism to support mirrors

* [calico] support alternate download url

roles/download/defaults/main.yml

@@ -138,6 +138,7 @@ etcd_download_url: "https://github.com/etcd-io/etcd/releases/download/{{ etcd_ve
 flannel_cni_download_url: "https://github.com/flannel-io/cni-plugin/releases/download/{{ flannel_cni_version }}/flannel-{{ image_arch }}"
 cni_download_url: "https://github.com/containernetworking/plugins/releases/download/{{ cni_version }}/cni-plugins-linux-{{ image_arch }}-{{ cni_version }}.tgz"
 calicoctl_download_url: "https://github.com/projectcalico/calicoctl/releases/download/{{ calico_ctl_version }}/calicoctl-linux-{{ image_arch }}"
+calicoctl_alternate_download_url: "https://github.com/projectcalico/calico/releases/download/{{ calico_ctl_version }}/calicoctl-linux-{{ image_arch }}"
 calico_crds_download_url: "https://github.com/projectcalico/calico/archive/{{ calico_version }}.tar.gz"
 crictl_download_url: "https://github.com/kubernetes-sigs/cri-tools/releases/download/{{ crictl_version }}/crictl-{{ crictl_version }}-{{ ansible_system | lower }}-{{ image_arch }}.tar.gz"
 helm_download_url: "https://get.helm.sh/helm-{{ helm_version }}-linux-{{ image_arch }}.tar.gz"
@@ -1120,6 +1121,9 @@ downloads:
     dest: "{{ local_release_dir }}/calicoctl"
     sha256: "{{ calicoctl_binary_checksum }}"
     url: "{{ calicoctl_download_url }}"
+    mirrors:
+    - "{{ calicoctl_alternate_download_url }}"
+    - "{{ calicoctl_download_url }}"
     unarchive: false
     owner: "root"
     mode: "0755"

roles/download/tasks/download_file.yml

@@ -47,11 +47,40 @@
     - download_force_cache
     - not download_localhost
 
+  # We check a number of mirrors that may hold the file and pick a working one at random
+  # This task will avoid logging it's parameters to not leak environment passwords in the log
+  - name: download_file | Validate mirrors
+    uri:
+      url: "{{ mirror }}"
+      method: HEAD
+      validate_certs: "{{ download_validate_certs }}"
+      url_username: "{{ download.username | default(omit) }}"
+      url_password: "{{ download.password | default(omit) }}"
+      force_basic_auth: "{{ download.force_basic_auth | default(omit) }}"
+    delegate_to: "{{ download_delegate if download_force_cache else inventory_hostname }}"
+    run_once: "{{ download_force_cache }}"
+    register: uri_result
+    until: uri_result is success
+    retries: 4
+    delay: "{{ retry_stagger | default(5) }}"
+    environment: "{{ proxy_env }}"
+    no_log: true
+    loop: "{{ download.mirrors | default([download.url]) }}"
+    loop_control:
+      loop_var: mirror
+    ignore_errors: true
+
+  # Ansible 2.9 requires we convert a generator to a list
+  - name: download_file | Get the list of working mirrors
+    set_fact:
+      valid_mirror_urls: "{{ uri_result.results | selectattr('failed', 'eq', False) | map(attribute='mirror') | list }}"
+    delegate_to: "{{ download_delegate if download_force_cache else inventory_hostname }}"
+
   # This must always be called, to check if the checksum matches. On no-match the file is re-downloaded.
   # This task will avoid logging it's parameters to not leak environment passwords in the log
   - name: download_file | Download item
     get_url:
-      url: "{{ download.url }}"
+      url: "{{ valid_mirror_urls | random }}"
       dest: "{{ file_path_cached if download_force_cache else download.dest }}"
       owner: "{{ omit if download_localhost else (download.owner | default(omit)) }}"
       mode: "{{ omit if download_localhost else (download.mode | default(omit)) }}"