Add query exporter

metrics/prometheus/exporters/README.md

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+# Install Node-exporter
+
+You'll need to install node exporter for monitoring
+
+1. Download Node Exporter
+As first step, you need to download the Node Exporter binary which is available for Linux in the official Prometheus website here. In the website, you will find a table with the list of available builds. Of our interest in this case, is the node_exporter build for Linux AMD64:
+
+Node Exporter Ubuntu Linux
+
+In this case the latest available version is the 1.7.0. Copy the .tar.gz URL and download it somewhere in your server using wget or cURL:
+
+`wget https://github.com/prometheus/node_exporter/releases/download/v1.7.0/node_exporter-1.7.0.linux-amd64.tar.gz`
+
+2. Extract Node Exporter and move binary
+After downloading the latest version of Node Exporter, proceed to extract the content of the downloaded tar using the following command:
+
+`tar xvf node_exporter-1.7.0.linux-amd64.tar.gz`
+The content of the zip will be extracted in the current directory, the extracted directory will contain 3 files:
+
+LICENSE (license text file)
+node_exporter (binary)
+NOTICE (license text file)
+You only need to move the binary file node_exporter to the /usr/local/bin directory of your system. Switch to the node_exporter directory:
+
+`cd node_exporter-1.7.0.linux-amd64`
+And then copy the binary file with the following command:
+
+`sudo cp node_exporter /usr/local/bin`
+Then you can remove the directory that we created after extracting the zip file content:
+
+# Exit current directory
+`cd ..`
+
+# Remove the extracted directory
+`rm -rf ./node_exporter-1.7.0.linux-amd64`
+3. Create Node Exporter User
+As a good practice, create an user in the system for Node Exporter:
+
+`sudo useradd --no-create-home --shell /bin/false node_exporter`
+And set the owner of the binary node_exporter to the recently created user:
+
+`sudo chown node_exporter:node_exporter /usr/local/bin/node_exporter`
+4. Create and start the Node Exporter service
+The Node Exporter service should always start when the server boots so it will always be available to be scrapped for information. Create the node_exporter.service file with nano:
+
+`sudo nano /etc/systemd/system/node_exporter.service`
+And paste the following content in the file:
+
+```
+[Unit]
+Description=Node Exporter
+Wants=network-online.target
+After=network-online.target
+
+[Service]
+User=node_exporter
+Group=node_exporter
+Type=simple
+ExecStart=/usr/local/bin/node_exporter
+Restart=always
+RestartSec=3
+
+[Install]https://github.com/prometheus/node_exporter/releases/download
+WantedBy=multi-user.target
+```
+
+Close nano and save the changes to the file. Proceed to reload the daemon with:
+
+`sudo systemctl daemon-reload`
+And finally enable the node_exporter service with the following command:
+
+`sudo systemctl enable node_exporter`
+And then start the service:
+
+`sudo systemctl start node_exporter`
+
+`sudo ufw allow 9090`
+`sudo ufw allow 9100`
+
+now go to `http://localhost:9100/metrics`
+
+# Install query exporter
+
+`sudo snap install query-exporter`
+
+Run query exporter
+
+`cd exporters`
+
+`query-exporter config.yaml -H 0.0.0.0`
+
+`sudo ufw allow 9560`

metrics/prometheus/exporters/config.yaml

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+databases:
+  db1:
+    dsn: postgres://postgres:postgres@host.docker.internal:15432/bluesky?sslmode=disable
+
+metrics:
+  repos_fully_indexed:
+    type: gauge
+    description: Repositories fully indexed
+  repos_seen:
+    type: gauge
+    description: Repositories seen
+
+queries:
+  query1:
+    interval: 30
+    databases: [db1]
+    metrics: [repos_fully_indexed]
+    sql: select count(*) as repos_fully_indexed from repos where last_indexed_rev <> '' and (last_indexed_rev >= first_rev_since_reset or first_rev_since_reset is null or first_rev_since_reset = '');
+  query2:
+    interval: 30
+    databases: [db1]
+    metrics: [repos_seen]
+    sql: select count(*) as repos_seen from repos;