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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 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])

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

argument type description default
url string The full URL to Loki in format [${scheme}://][${tenant}[:${token}]]@${host}[:${port}] -
timeout integer Request timeout in milliseconds, e.g. 10000 for 10s 10000
ratio float The ratio between JSON and Protobuf encoded batch requests for pushing logs
Must be a number between (including) 0 (100% JSON) and 1 (100% Protobuf)
This is only relevant for write scenarios.		 0.9
cardinality object The cardinality (unique values) for labels, where the object key is the name of the label and the value is the maximum amount of different values it may have. null

Example:

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

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:

argument type description default
config object An instance of Config which holds the configuration for the client. -

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.

argument type description default
streams integer The amount of streams the pushed batch should contain. -
minSize integer Minimum size in bytes of the raw log lines of the batch. -
maxSize integer Maximum size in bytes of the raw log lines of the batch. -

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

Method client.instantQuery(query, limit)

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

argument type description default
query string The LogQL query to perform. -
limit integer Maxiumum number of entries to return. -

Method client.rangeQuery(query, duration, limit)

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

argument type description default
query string The LogQL query to perform. -
duration string The time span of the range, e.g. 15m, 1h, or 7d. -
limit integer Maxiumum number of entries to return. -

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

Method client.labelsQuery(duration)

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

argument type description default
duration string The time span for which labels should be returned, e.g. 15m, 1h, or 7d. -

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)

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

argument type description default
label string The label name for which to query the values. -
duration string The time span for which label values should be returned, e.g. 15m, 1h, or 7d. -

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)

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

argument type description default
matchers list A list of label matchers used for the query. -
duration string The time span for which the matching series should be returned, e.g. 15m, 1h, or 7d. -

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 label names for generating streams:

name values notes
instance fixed: 1 per k6 worker
format fixed: apache_common, apache_combined, apache_error, rfc3164, rfc5424, json This label defines how the log lines of a stream are formatted.
os fixed: darwin, linux, windows -
namespace variable 1
app variable 1
pod variable 1
language variable 1
word variable 1

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.

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.

Footnotes

  1. The amount of values can be defined in cardinality argument of the client configuration. ↩ ↩2 ↩3 ↩4 ↩5