The Logs Collected By 'loki.source.journal' Cannot Be Processed By 'loki.process'

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What's wrong?

You are testing the combination of 'loki.source.journal' and 'loki.process' in your demo, but you are facing an issue where you can obtain the log stream through Loki, but you cannot get the tag from the log. This raises a question whether Alloy supports the combination of these two modules in the first place.

Understanding the issue

The issue you are facing is likely due to the way you are configuring the 'loki.source.journal' and 'loki.process' modules. In your demo, you are using a static label in the 'stage.static_labels' module of the 'loki.process' module. However, the logs collected by 'loki.source.journal' are not being processed correctly by 'loki.process'.

Analyzing the configuration

Let's take a closer look at your configuration:

loki.relabel "journal" {
  forward_to = []

    rule {
        source_labels = ["__journal__systemd_unit"]
        target_label  = "unit"
    }

    rule {
        action        = "keep"
        source_labels = ["__journal__systemd_unit"]
        regex         = "prometheus.service"
    }

    rule {
        source_labels = ["__journal__hostname"]
        target_label  = "hostname"
    }
}

loki.source.journal "read"  {
  forward_to    = [loki.process.journal_process.receiver]
  relabel_rules = loki.relabel.journal.rules
  max_age       = "24h"
}


loki.process "journal_process" {

	stage.logfmt {
		mapping = { "level" = "" }
	}

	stage.labels {
		values = { 
			log_level = "level",
		}
	}

	stage.static_labels {
		values = {
			test01 = "log_collector",
		}
	}

    forward_to = [loki.write.grafana_loki.receiver]
}

In this configuration, you are using the 'loki.relabel' module to define a set of rules for relabeling the logs collected by 'loki.source.journal'. The rules are defined in the 'loki.relabel.journal.rules' variable.

However, in the 'loki.process' module, you are not using the 'loki.relabel' module to apply the relabeling rules to the logs. Instead, you are using a static label in the 'stage.static_labels' module.

Steps to reproduce

To reproduce the issue, you can follow these steps:

  1. Create a new Loki demo with the 'loki.source.journal' and 'loki.process' modules.
  2. Configure the 'loki.source.journal' module to collect logs from a journal source.
  3. Configure the 'loki.process' module to process the logs collected by 'loki.source.journal'.
  4. Use a static label in the 'stage.static_labels' module of the 'loki.process' module.
  5. Observe that the logs collected by 'loki.source.journal' are not being processed correctly by 'loki.process'.

System information

  • Loki version: v1.8.1

Software version

  • Loki version: v1.8.1

Configuration

loki.relabel "journal" {
  forward_to = []

    rule {
        source_labels = ["__journal__systemd_unit"]
        target_label  = "unit"
    }

    rule {
        action        = "keep"
        source_labels = ["__journal__systemd_unit"]
        regex         = "prometheus.service"
    }

    rule {
        source_labels = ["__journal__hostname"]
        target_label  = "hostname"
    }
}

loki.source.journal "read"  {
  forward_to    = [loki.process.journal_process.receiver]
  relabel_rules = loki.relabel.journal.rules
  max_age       = "24h"
}


loki.process "journal_process" {

	stage.logfmt {
		mapping = { "level" = "" }
	}

	stage.labels {
		values = { 
			log_level = "level",
		}
	}

	stage.static_labels {
		values = {
			test01 = "log_collector",
		}
	}

    forward_to = [loki.write.grafana_loki.receiver]
}

Logs

Troubleshooting

To troubleshoot the issue, you can try the following:

  1. Check the Loki logs for any errors or warnings related to the 'loki.source.journal' and 'loki.process' modules.
  2. Verify that the 'loki.relabel' module is being applied correctly to the logs collected by 'loki.source.journal'.
  3. Check that the 'loki.process' module is processing the logs correctly.
  4. Try using a different label in the 'stage.static_labels' module of the 'loki.process' module.

Q: What is the issue with the logs collected by 'loki.source.journal' not being processed by 'loki.process'?

A: The issue is likely due to the way you are configuring the 'loki.source.journal' and 'loki.process' modules. In your demo, you are using a static label in the 'stage.static_labels' module of the 'loki.process' module, but the logs collected by 'loki.source.journal' are not being processed correctly by 'loki.process'.

Q: Why is the 'loki.relabel' module not being applied correctly to the logs collected by 'loki.source.journal'?

A: The 'loki.relabel' module is not being applied correctly to the logs collected by 'loki.source.journal' because you are not using the 'loki.relabel' module in the 'loki.process' module. Instead, you are using a static label in the 'stage.static_labels' module.

Q: How can I troubleshoot the issue with the logs collected by 'loki.source.journal' not being processed by 'loki.process'?

A: To troubleshoot the issue, you can try the following:

  1. Check the Loki logs for any errors or warnings related to the 'loki.source.journal' and 'loki.process' modules.
  2. Verify that the 'loki.relabel' module is being applied correctly to the logs collected by 'loki.source.journal'.
  3. Check that the 'loki.process' module is processing the logs correctly.
  4. Try using a different label in the 'stage.static_labels' module of the 'loki.process' module.

Q: What are some common mistakes that can cause the logs collected by 'loki.source.journal' not to be processed by 'loki.process'?

A: Some common mistakes that can cause the logs collected by 'loki.source.journal' not to be processed by 'loki.process' include:

  1. Not using the 'loki.relabel' module in the 'loki.process' module.
  2. Using a static label in the 'stage.static_labels' module of the 'loki.process' module instead of using the 'loki.relabel' module.
  3. Not verifying that the 'loki.relabel' module is being applied correctly to the logs collected by 'loki.source.journal'.
  4. Not checking that the 'loki.process' module is processing the logs correctly.

Q: How can I resolve the issue with the logs collected by 'loki.source.journal' not being processed by 'loki.process'?

A: To resolve the issue, you can try the following:

  1. Use the 'loki.relabel' module in the 'loki.process' module.
  2. Verify that the 'loki.relabel' module is being applied correctly to the logs collected by 'loki.source.journal'.
  3. Check that the 'loki.process' module is processing the logs correctly.
  4. Try using a different label in the 'stage.static_labels' module of the 'loki.process' module.

Q: What are some best practices for configuring the 'loki.source.journal' and 'loki.process' modules?

A: Some best practices for configuring the 'loki.source.journal' and 'loki.process' modules include:

  1. Using the 'loki.relabel' module to apply relabeling rules to the logs collected by 'loki.source.journal'.
  2. Verifying that the 'loki.relabel' module is being applied correctly to the logs collected by 'loki.source.journal'.
  3. Checking that the 'loki.process' module is processing the logs correctly.
  4. Using a different label in the 'stage.static_labels' module of the 'loki.process' module instead of using a static label.

By following these best practices and troubleshooting the issue, you should be able to resolve the problem and get the logs collected by 'loki.source.journal' processed by 'loki.process'.