Unable to release memory bytes buffer

Question

Go 1.18.1

pprof report

 3549.93kB 49.73% 49.73%  3549.93kB 49.73%  src/lag_monitor.PublishLagMetricToDataDog
     514kB  7.20% 56.93%      514kB  7.20%  bufio.NewWriterSize
  512.88kB  7.18% 64.11%   512.88kB  7.18%  encoding/pem.Decode
  512.69kB  7.18% 71.30%  1536.98kB 21.53%  crypto/x509.parseCertificate
  512.50kB  7.18% 78.48%   512.50kB  7.18%  crypto/x509.(*CertPool).AddCert

This piece of code appears to not release memory and based on pprof, the beloew function is the one consuming most memory.Memory graph

func caller() {
 events := make([]string, 0)
 //....
 PublishLagMetricToDataDog(ctx, strings.Join(events, ","))
}

func PublishLagMetricToDataDog(ctx context.Context, events string) error {
msg := `{
    "series": [%v]
}`
b := []byte(msg)
resp, err := http.Post("https://api.datadoghq.com/api/v1/series?api_key="+env.GetDataDogKey(), "application/json", bytes.NewBuffer(b))
if err != nil {
    logger.Error(ctx, "Error submitting event to datadog, err = ", err)
    return err
}
logger.Info(ctx, resp)
return nil
}

Above function is called in a loop. Since there are no global variables, and no reference to the byte slice from PublishLagMetricToDataDog, I am not able to pinpoint the memory leak. I read about Reset() and Truncate(), but this does not release the underlying memory.

Answer 1

You must close the response body for every http response you receive. Not doing so will potentially lead to resource leaks, such as the one you've observed.

Solution:

    resp, err := http.Post("https://api.datadoghq.com/api/v1/series?api_key="+env.GetDataDogKey(), "application/json", bytes.NewBuffer(b))
    if err != nil {
        logger.Error(ctx, "Error submitting event to datadog, err = ", err)
        return err
    }
    logger.Info(ctx, resp)
    _ = resp.Body.Close() // <--- Add this
    return nil
}