add etc tunning options

https://coreos.com/etcd/docs/latest/tuning.html

etcd_snapshot_count
and
ionice priority

roles/etcd/defaults/main.yml

@@ -22,6 +22,13 @@ etcd_script_dir: "{{ bin_dir }}/etcd-scripts"
 etcd_heartbeat_interval: "250"
 etcd_election_timeout: "5000"
 
+#etcd_snapshot_count: "10000"
+
+# Parameters for ionice
+# -c takes an integer between 0 and 3 or one of the strings none, realtime, best-effort or idle.
+# -n takes an integer between 0 (highest priority) and 7 (lowest priority)
+#etcd_ionice: "-c2 -n0"
+
 etcd_metrics: "basic"
 
 # Limits

roles/etcd/templates/etcd-events.env.j2

@@ -13,6 +13,9 @@ ETCD_NAME={{ etcd_member_name }}-events
 ETCD_PROXY=off
 ETCD_INITIAL_CLUSTER={{ etcd_events_peer_addresses }}
 ETCD_AUTO_COMPACTION_RETENTION={{ etcd_compaction_retention }}
+{% if etcd_snapshot_count is defined %}
+ETCD_SNAPSHOT_COUNT={{ etcd_snapshot_count }}
+{% endif %}
 
 # TLS settings
 ETCD_TRUSTED_CA_FILE={{ etcd_cert_dir }}/ca.pem

roles/etcd/templates/etcd.env.j2

@@ -13,6 +13,9 @@ ETCD_NAME={{ etcd_member_name }}
 ETCD_PROXY=off
 ETCD_INITIAL_CLUSTER={{ etcd_peer_addresses }}
 ETCD_AUTO_COMPACTION_RETENTION={{ etcd_compaction_retention }}
+{% if etcd_snapshot_count is defined %}
+ETCD_SNAPSHOT_COUNT={{ etcd_snapshot_count }}
+{% endif %}
 
 # TLS settings
 ETCD_TRUSTED_CA_FILE={{ etcd_cert_dir }}/ca.pem

roles/etcd/templates/etcd.j2

@@ -17,5 +17,8 @@
 {% endif %}
   --name={{ etcd_member_name | default("etcd") }} \
   {{ etcd_image_repo }}:{{ etcd_image_tag }} \
+{% if etcd_ionice is defined %}
+  /bin/ionice {{ etcd_ionice }} \
+{% endif %}
   /usr/local/bin/etcd \
   "$@"