alertmanager: set log format to json

Signed-off-by: Jakub Sokołowski <jakub@status.im>

defaults/main.yml

@@ -12,6 +12,7 @@ alertmanager_admin_email: ~
 alertmanager_cont_tag: 'v0.24.0'
 alertmanager_cont_image: 'prom/alertmanager:{{ alertmanager_cont_tag }}'
 alertmanager_cont_log_lvl: 'info'
+alertmanager_cont_log_fmt: 'json'
 
 # Port used for the web ui
 alertmanager_webui_port: 9093

templates/docker-compose.yml.j2

@@ -18,6 +18,7 @@ services:
     command:
       - '--storage.path=/data'
       - '--config.file=/etc/alertmanager.yml'
+      - '--log.format={{ alertmanager_cont_log_fmt }}'
       - '--log.level={{ alertmanager_cont_log_lvl }}'
       - '--web.external-url={{ alertmanager_url }}'
       - '--cluster.advertise-address={{ ansible_local.wireguard.vpn_ip }}:{{ alertmanager_cluster_port }}'