loki

xk6-loki

A k6 extension for pushing logs to Loki.

Getting started

1. Install xk6

   go install go.k6.io/xk6/cmd/xk6@latest
   

2. Checkout grafana/xk6-loki

   git clone https://github.com/grafana/xk6-loki
   cd xk6-loki
   

3. Build the extension

   make k6
   

Javascript API

Module k6/x/loki

The k6/x/loki module contains the Loki extension to interact with the Loki API. To import the module add

import loki from 'k6/x/loki';

on top of your test file.

Class Config(url, [timeout, ratio, cardinality, labels])

The class Config holds configuration for the Loki client. The constructor takes the following arguments:

Example:

import loki from 'k6/x/loki';
let conf = loki.Config("localhost:3100");

Class Labels(labels)

The class Labels allows the definition of custom labels that can be used instead of the built-in labels. An instance of this class can be passed as fifth argument to the loki.Config constructor.

Example:

import loki from 'k6/x/loki';
let labels = loki.Labels({
  "format": ["json", "logfmt"], // must contain at least one of the supported log formats
  "cluster": ["prod-us-east-0", "prod-eu-west-1"],
  "namespace": ["dev", "staging", "prod"],
  "container": ["nginx", "app-1", "app-2", "app-3"]
});

Class Client(config)

The class Client is a Loki client that can read from and write to a Loki instance. The constructor takes the following arguments:

Example:

import loki from 'k6/x/loki';
let conf = loki.Config("localhost:3100");
let client = loki.Client(conf);

Method client.push()

This function is a shortcut for client.pushParameterized(5, 800*1024, 1024*1024).

Method client.pushParameterized(streams, minSize, maxSize)

Execute a push request (POST /loki/api/v1/push).

The function pushParameterized generates batch of logs and pushes it to the Loki instance. A batch consists of one or more streams which hold multiple log lines. A stream is a set of log lines with a unique set of labels.

minSize and maxSize define the boundaries for a random value of the actual batch size.

Method client.instantQuery(query, limit)

This function is a shortcut for client.instantQueryAt(query, limit, time.Now()) where time.Now() is the current nanosecond.

Method client.instantQueryAt(query, limit, instant)

Execute an instant query (GET /loki/api/v1/query).

Method client.rangeQuery(query, duration, limit)

This function is a shortcut for client.rangeQueryAt(query, duration, limit, time.Now()) where time.Now() is the current nanosecond.

Method client.rangeQueryAt(query, duration, limit, instant)

Execute a range query (GET /loki/api/v1/query_range).

duration defines the range for the query and uses the current timestamp as end and current timestamp - duration as start.

Method client.labelsQuery(duration)

This function is a shortcut for client.labelsQueryAt(duration, time.Now()) where time.Now() is the current nanosecond.

Method client.labelsQueryAt(duration, instant)

Execute a labels query (GET /loki/api/v1/labels).

duration defines the range for the query and uses the current timestamp as end and current timestamp - duration as start.

Method client.labelValuesQuery(label, duration)

This function is a shortcut for client.labelValuesQueryAt(label, duration, time.Now()) where time.Now() is the current nanosecond.

Method client.labelValuesQueryAt(label, duration, instant)

Execute a label values query (GET /loki/api/v1/label//values).

duration defines the range for the query and uses the current timestamp as end and current timestamp - duration as start.

Method client.seriesQuery(matchers, duration)

This function is a shortcut for client.seriesQueryAt(matchers, duration, time.Now()) where time.Now() is the current nanosecond.

Method client.seriesQueryAt(matchers, duration, instant)

Execute a series query (GET /loki/api/v1/series).

duration defines the range for the query and uses the current timestamp as end and current timestamp - duration as start.

Labels

xk6-loki uses the following built-in label names for generating streams:

[^1]: The amount of values can be defined in cardinality argument of the client configuration.

The total amount of different streams is defined by the carthesian product of all label values. Keep in mind that high cardinality impacts the performance of the Loki instance.

Custom labels

Additionally, xk6-loki also supports custom labels that can be used instead of the built-in labels.

See examples/custom-labels.js for a full example with custom labels.

Metrics

The extension collects metrics that are printed in the end-of-test summary in addition to the built-in metrics.

Query metrics

These metrics are collected only for instant and range queries.

Write metrics

Example

import sleep from 'k6';
import loki from 'k6/x/loki';

/**
 * URL used for push and query requests
 * Path is automatically appended by the client
 * @constant {string}
 */
const BASE_URL = `http://localhost:3100`;

/**
 * Client timeout for read and write in milliseconds
 * @constant {number}
 */
const timeout = 5000;

/**
 * Ratio between Protobuf and JSON encoded payloads when pushing logs to Loki
 * @constant {number}
 */
const ratio = 0.5;

/**
 * Cardinality for labels
 * @constant {object}
 */
const cardinality = {
  "app": 5,
  "namespace": 5
};

/**
 * Execution options
 */
export const options = {
  vus: 10,
  iterations: 10,
};

/**
 * Create configuration object
 */
const conf = new loki.Config(BASE_URL, timeout, ratio, cardinality);

/**
 * Create Loki client
 */
const client = new loki.Client(conf);

export default () => {
  // Push a batch of 2 streams with a payload size between 500KB and 1MB
  let res = client.pushParameterized(2, 512 * 1024, 1024 * 1024);
  // A successful push request returns HTTP status 204
  check(res, { 'successful write': (res) => res.status == 204 });
  sleep(1);
}

./k6 run examples/simple.js

You can find more examples in the examples/ folder.