Count number of json objects in output - json

Question

I am using Ansible's vmware_cluster_info to give the following json. I need to be able to count the number of hosts in a cluster. Cluster names will change.
{
"ansible_facts": {
"discovered_interpreter_python": "/usr/bin/python"
},
"changed": false,
"clusters": {
"Cluster1": {
"drs_default_vm_behavior": "fullyAutomated",
"ha_restart_priority": [
"medium"
],
"ha_vm_failure_interval": [
50
],
"ha_vm_max_failure_window": [
0
],
"ha_vm_max_failures": [
10
],
"ha_vm_min_up_time": [
90
],
"ha_vm_monitoring": "vmMonitoringOnly",
"ha_vm_tools_monitoring": [
"vmAndAppMonitoring"
],
"hosts": [
{
"folder": "/Datacenter/host/Cluster1",
"name": "host1"
},
{
"folder": "/Datacenter/host/Cluster1",
"name": "host2"
},
{
"folder": "/Datacenter/host/Cluster1",
"name": "host3"
},
{
"folder": "/Datacenter/host/Cluster1",
"name": "host4"
}
],
"resource_summary": {
"cpuCapacityMHz": 144000,
},
"tags": [],
"vsan_auto_claim_storage": false
}
},
"invocation": {
"module_args": {
"cluster_name": "Cluster1",
}
}
}
I have tried:
- debug:
msg: "{{ cluster_info.clusters.[].hosts.name | length }}"
- debug:
msg: "{{ cluster_info.clusters.*.hosts.name | length }}"
Both give me template error while templating string... Also, any suggestions on tutorials, etc to learn how to parse json would be appreciated. It seems to be a difficult topic for me. Any ideas?

Answer 1

one similar approach to what you were trying is by using json_query. I understand you want to print the count of hosts, so the .name is not needed in your code:
- name: print count of hosts
debug:
var: cluster_info.clusters | json_query('*.hosts') | first | length
json_query returns a list, this is why we pass it to first before length.