Collect syslog lines next to metrics

This makes that we can show the last log entries next to a metric to
detect certain issues such as why a CPU clocks down or why a process
stops for example.

Author: Your Name

provision-contest/ansible/roles/grafana/files/.gitignore

@@ -1,2 +1,3 @@
 /ssl.*
 /grafana.deb
+/loki-linux-amd64.zip

provision-contest/ansible/roles/grafana/files/loki-local-config.yaml

@@ -2,45 +2,26 @@ auth_enabled: false
 
 server:
   http_listen_port: 3100
-  grpc_listen_port: 9096
+  grpc_listen_port: 13100
 
-ingester:
-  lifecycler:
-    address: 127.0.0.1
-    ring:
-      kvstore:
-        store: inmemory
-      replication_factor: 1
-    final_sleep: 0s
-  chunk_idle_period: 5m
-  chunk_retain_period: 30s
-  max_transfer_retries: 0
+common:
+  ring:
+    instance_addr: 127.0.0.1
+    kvstore:
+      store: inmemory
+  replication_factor: 1
+  path_prefix: /tmp/loki
 
 schema_config:
   configs:
-    - from: 2018-04-15
-      store: boltdb
+    - from: 2020-05-15
+      store: tsdb
       object_store: filesystem
-      schema: v11
+      schema: v13
       index:
         prefix: index_
-        period: 168h
+        period: 24h
 
 storage_config:
-  boltdb:
-    directory: /data/loki/index
-
   filesystem:
-    directory: /data/loki/chunks
-
-limits_config:
-  enforce_metric_name: false
-  reject_old_samples: true
-  reject_old_samples_max_age: 168h
-
-chunk_store_config:
-  max_look_back_period: 0s
-
-table_manager:
-  retention_deletes_enabled: false
-  retention_period: 0s
+    directory: /tmp/loki/chunks

provision-contest/ansible/roles/grafana/tasks/main.yml

@@ -19,48 +19,56 @@
   notify: Restart prometheus
 
 # Setup loki which gathers our logs
-- name: Install loki
-  unarchive:
-    src: https://github.com/grafana/loki/releases/download/v2.5.0/loki-linux-amd64.zip
-    dest: /usr/bin/
-    remote_src: true
-    owner: domjudge
-    group: domjudge
-  when: loki
-
-- name: Dir for loki settings
-  file:
-    state: directory
-    path: /etc/grafana/loki/
-    owner: root
-    group: root
-    mode: 0755
-  when: loki
-
-- name: Set loki settings
-  copy:
-    src: loki-local-config.yaml
-    dest: /etc/grafana/loki/
-    owner: root
-    group: root
-    mode: 0644
-  when: loki
-  notify: Restart loki
-
-- name: Setup loki systemd
-  copy:
-    src: loki.service
-    dest: /etc/systemd/system/
-    mode: 0655
-  when: loki
-  notify: Restart loki
-
-- name: Start loki service
-  service:
-    name: loki
-    state: started
-    enabled: true
+- name: Setup loki
   when: loki
+  block:
+    - name: Install loki
+      unarchive:
+        src: loki-linux-amd64.zip
+        dest: /usr/bin/
+        remote_src: false
+        owner: domjudge
+        group: domjudge
+      when: ICPC_IMAGE
+
+    - name: Install loki
+      unarchive:
+        src: https://github.com/grafana/loki/releases/download/v2.5.0/loki-linux-amd64.zip
+        dest: /usr/bin/
+        remote_src: true
+        owner: domjudge
+        group: domjudge
+      when: not ICPC_IMAGE
+    
+    - name: Dir for loki settings
+      file:
+        state: directory
+        path: /etc/grafana/loki/
+        owner: root
+        group: root
+        mode: 0755
+    
+    - name: Set loki settings
+      copy:
+        src: loki-local-config.yaml
+        dest: /etc/grafana/loki/
+        owner: root
+        group: root
+        mode: 0644
+      notify: Restart loki
+    
+    - name: Setup loki systemd
+      copy:
+        src: loki.service
+        dest: /etc/systemd/system/
+        mode: 0655
+      notify: Restart loki
+    
+    - name: Start loki service
+      service:
+        name: loki
+        state: started
+        enabled: true
 
 ## Setup grafana
 - name: Install grafana
@@ -91,8 +99,8 @@
   notify: Restart grafana
 
 - name: Set up grafana datasources
-  synchronize:
-    src: files/grafana/datasources.yml
+  template:
+    src: datasources.yml.j2
     dest: /etc/grafana/provisioning/datasources/default.yml
   notify: Restart grafana
 

provision-contest/ansible/roles/grafana/files/datasources.yml renamed to provision-contest/ansible/roles/grafana/templates/datasources.yml.j2

@@ -48,3 +48,14 @@ datasources:
     version: 1
     # <bool> allow users to edit datasources from the UI.
     editable: true
+{% if loki is defined and loki %}
+  - name: Loki
+    type: loki
+    access: proxy
+    url: http://localhost:3100
+    jsonData:
+      timeout: 60
+      maxLines: 1000
+      httpHeaderName1: Connection
+      httpHeaderName2: Upgrade
+{% endif %}

provision-contest/ansible/roles/prometheus_target_all/defaults/main.yml

@@ -1 +1,4 @@
 prom: true
+GROUP_PREFIXES:
+  - 'online-'
+  - ''

provision-contest/ansible/roles/prometheus_target_all/files/.gitignore

@@ -1,2 +1,3 @@
 *.key
 *.crt
+promtail-linux-amd64.zip

provision-contest/ansible/roles/prometheus_target_all/files/promtail.service

@@ -4,7 +4,7 @@ After=network.target
 
 [Service]
 Type=simple
-ExecStart=/usr/bin/promtail-linux-amd64 --config.file /etc/promtail/promtail-local-config.yaml
+ExecStart=/usr/bin/promtail-linux-amd64 --config.file /etc/promtail/promtail-local-config.yml
 
 [Install]
 WantedBy=multi-user.target

provision-contest/ansible/roles/prometheus_target_all/tasks/main.yml

@@ -55,3 +55,57 @@
     regexp: '^ARGS=""'
     line: 'ARGS="--web.config /etc/prometheus/prometheus-authentication.yml"'
   notify: Restart node-exporter
+
+# Setup promtail which sends our logs
+- name: Setup promtail to ship logs to loki (and grafana)
+  when: prom
+  block:
+    - name: Install promtail
+      unarchive:
+        src: promtail-linux-amd64.zip
+        dest: /usr/bin/
+        remote_src: false
+        owner: domjudge
+        group: domjudge
+      when: ICPC_IMAGE
+
+    - name: Install promtail
+      unarchive:
+        src: https://github.com/grafana/loki/releases/download/v3.0.1/promtail-linux-amd64.zip
+        dest: /usr/bin/
+        remote_src: true
+        owner: domjudge
+        group: domjudge
+      when: not ICPC_IMAGE
+    
+    - name: Dir for promtail settings
+      file:
+        state: directory
+        path: /etc/promtail
+        owner: root
+        group: root
+        mode: 0755
+    
+    - name: Set promtail settings
+      template:
+        src: promtail-local-config.yml.j2
+        dest: /etc/promtail/promtail-local-config.yml
+        owner: root
+        group: root
+        mode: 0644
+      notify: Restart promtail
+    
+    - name: Setup promtail systemd
+      copy:
+        src: promtail.service
+        dest: /etc/systemd/system/
+        mode: 0655
+        owner: root
+        group: root
+      notify: Restart promtail
+    
+    - name: Start promtail service
+      service:
+        name: promtail
+        state: started
+        enabled: true

provision-contest/ansible/roles/prometheus_target_all/templates/promtail-local-config.yaml.j2

@@ -0,0 +1,37 @@
+server:
+  http_listen_port: 9080
+  grpc_listen_port: 19080
+
+positions:
+  filename: /var/tmp/promtail-syslog-positions.yml
+
+clients:
+{% for host in groups["grafana"] %}
+  - url: http://{{ hostvars[host].ansible_host }}:3100/loki/api/v1/push
+{% endfor %}
+
+scrape_configs:
+  - job_name: system
+    static_configs:
+      - labels:
+          __path__: /var/log/**/*log
+{% for group_prefix in GROUP_PREFIXES %}
+{% if ansible_fqdn in groups[group_prefix+'judgehost'] %}
+  - job_name: judgehostlogs
+    static_configs:
+      - labels:
+          __path__: '/opt/domjudge/output/log/*'
+{% endif %}
+{% if ansible_fqdn in groups[group_prefix+'domserver'] %}
+  - job_name: webapplogs
+    static_configs:
+      - labels:
+          __path__: '/opt/domjudge/webapp/var/log/*'
+{% endif %}
+{% endfor %}
+  # See: https://alexandre.deverteuil.net/post/syslog-relay-for-loki/
+  - job_name: syslog
+    syslog:
+      listen_address: 0.0.0.0:1514
+      labels:
+        job: syslog