Add support for retention by size (#182)

* Add support for retention by size

[feature] Prometheus 2.7.0 now supports setting retention by size in
addition to time.

* Fix some long lines issues

* Fix some issues with long lines.
* Ignore long lines in ansible-lint.

Author: SuperQ

.ansible-lint

@@ -0,0 +1,3 @@
+---
+skip_list:
+- '204'

README.md

@@ -34,6 +34,7 @@ All variables which can be overridden are stored in [defaults/main.yml](defaults
 | `prometheus_web_listen_address` | "0.0.0.0:9090" | Address on which prometheus will be listening |
 | `prometheus_web_external_url` | "" | External address on which prometheus is available. Useful when behind reverse proxy. Ex. `http://example.org/prometheus` |
 | `prometheus_storage_retention` | "30d" | Data retention period |
+| `prometheus_storage_retention_size` | "0" | Data retention period by size |
 | `prometheus_config_flags_extra` | {} | Additional configuration flags passed to prometheus binary at startup |
 | `prometheus_alertmanager_config` | [] | Configuration responsible for pointing where alertmanagers are. This should be specified as list in yaml format. It is compatible with official [<alertmanager_config>](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#alertmanager_config) |
 | `prometheus_alert_relabel_configs` | [] | Alert relabeling rules. This should be specified as list in yaml format. It is compatible with the official [<alert_relabel_configs>](https://prometheus.io/docs/prometheus/latest/configuration/configuration/#alert_relabel_configs) |

defaults/main.yml

@@ -8,6 +8,10 @@ prometheus_web_listen_address: "0.0.0.0:9090"
 prometheus_web_external_url: ''
 
 prometheus_storage_retention: "30d"
+# Available since Prometheus 2.7.0
+# [EXPERIMENTAL] Maximum number of bytes that can be stored for blocks. Units
+# supported: KB, MB, GB, TB, PB.
+prometheus_storage_retention_size: "0"
 
 prometheus_config_flags_extra: {}
 # prometheus_config_flags_extra:

molecule/alternative/playbook.yml

@@ -11,6 +11,7 @@
     prometheus_web_listen_address: "127.0.0.1:9090"
     prometheus_web_external_url: "http://127.0.0.1:9090/prometheus"
     prometheus_storage_retention: "60d"
+    prometheus_storage_retention_size: "1GB"
     prometheus_config_flags_extra:
       alertmanager.timeout: 10s
       web.enable-admin-api:

tasks/preflight.yml

@@ -20,8 +20,17 @@
 
 - name: Fail when prometheus_config_flags_extra duplicates parameters set by other variables
   fail:
-    msg: "Whooops. You are duplicating configuration. Please look at your prometheus_config_flags_extra and check against other variables in defaults/main.yml"
-  with_items: [ 'storage.tsdb.retention', 'storage.tsdb.path', 'storage.local.retention', 'storage.local.path', 'config.file', 'web.listen-address', 'web.external-url' ]
+    msg: >
+      Whooops. You are duplicating configuration. Please look at your prometheus_config_flags_extra
+      and check against other variables in defaults/main.yml
+  with_items:
+    - 'storage.tsdb.retention'
+    - 'storage.tsdb.path'
+    - 'storage.local.retention'
+    - 'storage.local.path'
+    - 'config.file'
+    - 'web.listen-address'
+    - 'web.external-url'
   when: item in prometheus_config_flags_extra.keys()
 
 - name: Get all file_sd files from scrape_configs
@@ -30,14 +39,19 @@
 
 - name: Fail when file_sd targets are not defined in scrape_configs
   fail:
-    msg: "Oh, snap! `{{ item.key }}` couldn't be found in your scrape configs. Please ensure you provided all targets from prometheus_targets in prometheus_scrape_configs"
+    msg: >
+      Oh, snap! `{{ item.key }}` couldn't be found in your scrape configs. Please ensure you provided
+      all targets from prometheus_targets in prometheus_scrape_configs
   when: not prometheus_config_dir + "/file_sd/" + item.key + ".yml" in file_sd_files
   #  when: not item | basename | splitext | difference(['.yml']) | join('') in prometheus_targets.keys()
   with_dict: "{{ prometheus_targets }}"
 
 - name: Fail when prometheus_alertmanager_config is empty, but prometheus_alert_rules is specified
   debug:
-    msg: "There's no use in defining alerting rules if you're not going to use them! Be sure to specify a prometheus_alertmanager_config in defaults/main.yml if you're going to define prometheus_alert_rules"
+    msg: >
+      There's no use in defining alerting rules if you're not going to use them! Be sure to
+      specify a prometheus_alertmanager_config in defaults/main.yml if you're going to define
+      prometheus_alert_rules
   when:
     - prometheus_alertmanager_config == []
     - prometheus_alert_rules != []

templates/prometheus.service.j2

@@ -13,7 +13,12 @@ ExecReload=/bin/kill -HUP $MAINPID
 ExecStart=/usr/local/bin/prometheus \
   --config.file={{ prometheus_config_dir }}/prometheus.yml \
   --storage.tsdb.path={{ prometheus_db_dir }} \
+{% if prometheus_version | version_compare('2.7.0', '>=') %}
+  --storage.tsdb.retention.time={{ prometheus_storage_retention }} \
+  --storage.tsdb.retention.size={{ prometheus_storage_retention_size }} \
+{% else %}
   --storage.tsdb.retention={{ prometheus_storage_retention }} \
+{% endif %}
   --web.console.libraries={{ prometheus_config_dir }}/console_libraries \
   --web.console.templates={{ prometheus_config_dir }}/consoles \
   --web.listen-address={{ prometheus_web_listen_address }} \