Add both the Root CA and the intermediate one into the mongodb CAfile.

mongodb-org/defaults/main.yml

@@ -49,7 +49,6 @@ mongodb_storage_engine: wiredTiger
 
 mongodb_ssl_enabled: False
 mongodb_ssl_letsencrypt_managed: True
-mongodb_letsencrypt_download_ca_file: False
 mongodb_ssl_letsencrypt_ca_url: 'https://letsencrypt.org/certs/lets-encrypt-x3-cross-signed.pem.txt'
 mongodb_ssl_letsencrypt_ca_dir: '{{ mongodb_ssl_cert_dir }}'
 mongodb_ssl_letsencrypt_ca_filename: lets-encrypt-x3-cross-signed.pem
@@ -57,8 +56,8 @@ mongodb_ssl_letsencrypt_ca_filename: lets-encrypt-x3-cross-signed.pem
 mongodb_ssl_mode: requireSSL
 mongodb_ssl_cert_dir: /etc/pki/mongodb
 mongodb_ssl_certkey_file: '{{ mongodb_ssl_cert_dir }}/mongodb.pem'
-# mongodb_ssl_CA_file: '{{ mongodb_ssl_letsencrypt_ca_dir }}/{{ mongodb_ssl_letsencrypt_ca_filename }}'
-mongodb_ssl_CA_file: '/usr/share/ca-certificates/mozilla/DST_Root_CA_X3.crt'
+mongodb_ssl_CA_file: '{{ mongodb_ssl_letsencrypt_ca_dir }}/{{ mongodb_ssl_letsencrypt_ca_filename }}'
+mongodb_ssl_root_CA_file: '/usr/share/ca-certificates/mozilla/DST_Root_CA_X3.crt'
 mongodb_ssl_allowConnectionsWithoutCertificates: 'true'
 mongodb_ssl_disabled_protocols: 'TLS1_0,TLS1_1'
 

mongodb-org/tasks/mongodb-letsencrypt-acmetool.yml

@@ -11,7 +11,11 @@
 
   - name: Get the Letsencrypt CA file if there is no local copy yet
     get_url: url={{ mongodb_ssl_letsencrypt_ca_url }} dest={{ mongodb_ssl_cert_dir }}/{{ mongodb_ssl_letsencrypt_ca_filename }}
-    when: mongodb_letsencrypt_download_ca_file
+    register: build_mongo_ca_file
+
+  - name: Add the Root CA certificate to the mongodb CA file
+    command: cat {{ mongodb_ssl_root_CA_file }} >> {{ mongodb_ssl_cert_dir }}/{{ mongodb_ssl_letsencrypt_ca_filename }}
+    when: build_mongo_ca_file is changed
 
   - name: Verify if the mongodb pem file exists
     stat: path={{ mongodb_ssl_certkey_file }}