Failed to set GOMEMLIMIT on M3 Mac

[nicholsn]

What's wrong?

After installing with homebrew and setting up a pipeline to write logs to loki, Alloy fails to send logs and reports an error indicating that the system doesn't support cgroups and cant GOMEMLIMIT.

Steps to reproduce

• Follow default install instructions
• Create the config below and restart the service
• run an app to start generating logs to parse
• check the alloy logs for the error

System information

M3 Macbook arm64

Software version

Grafana Alloy v1.5.1

Configuration

logging {
  level = "warn"
}

local.file_match "log_files" {
  path_targets = [
    { __path__ = "/tmp/app/logs/server.log" },
  ]
}

loki.source.file "log_scraper" {
  targets        = local.file_match.log_files.targets
  forward_to     = [loki.process.log_processor.receiver]
  tail_from_end  = false
}

loki.process "log_processor" {
  // Parse the log line as JSON and extract fields
  stage.json {
    expressions = {
      ts       = "timestamp",
      level    = "level",
      logger   = "name",
      msg      = "message",
      filename = "metadata.filename",
      funcName = "metadata.funcName",
      lineno   = "metadata.lineno",
    }
  }

  // Convert the extracted timestamp to the appropriate format
  stage.timestamp {
    source = "ts"
    format = "2006-01-02 15:04:05,000"
  }

  // Assign extracted fields as labels
  stage.labels {
    values = {
      level    = "",
      logger   = "",
      filename = "",
      funcName = "",
      lineno   = "",
    }
  }

  // Set the log message to the extracted 'msg' field
  stage.output {
    source = "msg"
  }

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

loki.write "loki_output" {
  endpoint {
    url = "http://localhost:3100/loki/api/v1/push"
  }
}

Logs

ts=2024-12-20T06:12:53.964364Z level=error source=github.com/KimMachineGun/[email protected]/memlimit/memlimit.go:117 msg="failed to set GOMEMLIMIT" package=github.com/KimMachineGun/automemlimit/memlimit error="failed to set GOMEMLIMIT: cgroups is not supported on this system"

[nicholsn]

I also used the instructions at https://grafana.com/docs/alloy/latest/configure/macos/#configure-the-alloy-service to edit the homebrew recipe and set GOMEMLIMIT=2750MiB, then brew reinstall --formula alloy , and restart the service. This did not fix the issue and resulted in the same error although a comment in the source code indicated that this envrionment variable should override the cgroup derived setting:

alloy/internal/alloycli/cmd_run.go

Line 221 in 2b42ec4

// Set the memory limit, this will honor GOMEMLIMIT if set

❯ cat /opt/homebrew/etc/alloy/config.env
GOMEMLIMIT=2750MiB

[dehaansa]

This error should be resolved (no longer attempting to use groups & logging the message) in next release #2264

The environment variable should definitely overrule the cgroup behavior (see https://github.com/KimMachineGun/automemlimit/blob/v0.6.1/memlimit/memlimit.go#L146C2-L150C3 ) so I'm surprised that you weren't able to set GOMEMLIMIT in the appropriate way through homebrew services. I'll find some time to test that behavior and see if I can replicate.

[dehaansa]

My tests replicated the behavior, GOMEMLIMIT is not pulled in to the alloy service according to the documentation.

[dehaansa]

I've had a chance to discuss with the team - it looks like the behavior exists in the latest brew service, but will require reinstalling alloy ( see comments in grafana/homebrew-grafana#108 )

[nicholsn]

Thanks for the followup - reinstalling the latest version is working now