Logs

Almost everything is logged inside the system journal. Recent logs are available using journalctl and services can be inspected using systemctl command.

As root use journalctl to see messages from agents, rootfull and rootless modules. As rootless UNIX user (eg. traefik1), use journalctl --user to see messages only from systemd user session.

By default a Loki instance is installed inside the leader node, it collects the logs from all cluster nodes. A rootfull Promtail container runs as a node service on all nodes, including the leader one. It sends all logs to the Loki server.

Logs of nodes, modules and the whole cluster can be read from the Logs page, or with the api-server-logs command. The following command prints the last lines of log produced by module traefik1 and waits for further lines, like a tail -f:

api-server-logs logs -e module -n traefik1

See api-server-logs -h for more command invocation styles.

It is also possible to query the logs of all nodes and modules with the logcli command.

Get the list of existing node identifiers:

# logcli labels node_id -q
1
2

Get the list of modules:

# logcli labels module_id -q
ldapproxy1
loki1
traefik1

Example log search for module ldapproxy1:

# logcli query -q --no-labels '{module_id="ldapproxy1"} | json | line_format "{{.MESSAGE}}"'

The string wrapped by '' is the log query. It is expressed in LogQL.

Forwarding

On an active Loki instance, it is possible to enable two forwarding services. When forwarders are active and the leader node changes, they are automatically migrated to the new leader node.

By default, these forwarders are disabled.

Syslog server

This service can be enabled either from the cluster admin interface or through the API using the following examples:

# api-cli run module/loki1/set-syslog-forwarder --data '{"active": true, "address": "127.0.0.1", "port": "514", "protocol": "udp", "format": "rfc3164", "start_time": "2024-01-01T00:00:00.00Z"}'

Configuration parameters

active: Boolean to enable or disable the forwarder (e.g., true or false).
address: The IP address of the Syslog server.
port: The port on which the Syslog server listens.
protocol: Protocol to use (e.g., udp or tcp).
format: Log format (e.g., rfc3164 or rfc5424).
start_time: The time from which logs should be forwarded. (ISO 8601)

It can be also stopped through API:

# api-cli run module/loki1/set-syslog-forwarder --data '{"active": false}'

Cloud Log Manager

Cloud Log Manager forwarder is available only with a subscription, and if the subscription expires or is removed, the forwarder is automatically stopped.

Similarly, this service can be enabled from the cluster admin interface or through the API with examples like the following:

# api-cli run module/loki1/set-clm-forwarder --data '{"active": true, "address": "https://nar.nethesis.it", "teant": "example", "start_time": "2024-07-12T00:00:00.000000Z"}'

Configuration parameters

active: Boolean to enable or disable the forwarder (e.g., true or false).
address: The URL of the Cloud Log Manager.
tenant: The tenant identifier.
start_time: The time from which logs should be forwarded. (ISO 8601)

It can be also stopped through API:

# api-cli run module/loki1/set-clm-forwarder --data '{"active": false}'

When Loki is installed, it generates a unique identifier that is used on the Cloud Log Manager. You can find this identifier on Cloud Log Manager settings panel or using the following command:

# redis-cli hget module/$(redis-cli --raw get cluster/default_instance/loki)/environment CLOUD_LOG_MANAGER_HOSTNAME

Troubleshooting

Check the status of forwarders using loki agent:

runagent -m loki1
systemctl --user status *forwarder.service