Tutorial: Modifying Grafana's Source Code
Tags: grafana, tutorial, opensource, observability
Published: 2023-08-07 10:25:41

## A story of exploration and guesswork.

So this blog is a little different from my usual tutorials…

{% youtube xZ9gwBO3TMM %}

A little background: I have been working with Jacob Marble to test and “demo-fy” his work with InfluxDB 3.0 and the OpenTelemetry ecosystem (If you would like to learn more I highly recommend checking out this [blog](https://www.influxdata.com/blog/opentelemetry-tutorial-collect-traces-logs-metrics-influxdb-3-0-jaeger-grafana/)).

During the project, we identified a need to enable specific Grafana features for InfluxDB data sources, particularly the _trace to logs_ functionality. Grafana is an open-source platform, and one of its major advantages is the ability to modify its source code to suit our unique requirements. However, diving into the codebase of such a robust tool can be overwhelming, even for the most seasoned developers.

Despite the complexity, we embraced the challenge and dove headfirst into Grafana's source code. We tumbled, we stumbled, and we learned a great deal along the way. And now, having successfully modified Grafana to meet our specific project needs, I believe it's time to share this acquired knowledge with you all.

The purpose of this blog is not just to provide you with a step-by-step guide for tweaking Grafana's source code, but also to inspire you to explore and adapt open-source projects to your needs. It's about imparting a method and a mindset, cultivating a culture of curiosity, and encouraging more hands-on learning and problem-solving.

I hope that this guide will empower you to modify Grafana's source code for your projects, thereby expanding the horizons of what's possible with open-source platforms. It’s time to roll up your sleeves and venture into the depths of Grafana's code. 


## The problem

So our problem lies within the [Trace visualisation](https://grafana.com/docs/grafana/latest/panels-visualizations/visualizations/traces/) of Grafana.

![traces](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/08ql725ikv9yoq45la68.png)

As you can see the visualisation performs rather well with InfluxDB except for one button which appears to be disabled:** Logs for this span**. This button is automatically disabled when our trace data source (in this case, Jaeger with InfluxDB 3.0 acting as the [gRPC storage engine](https://www.jaegertracing.io/docs/next-release/deployment/#sidecar-model)) has not been configured with a log data source. A log data source within Grafana is usually represented by default using the [log explorer interface](https://grafana.com/docs/grafana/latest/explore/logs-integration/), common log data sources are; [Loki](https://grafana.com/oss/loki/), [OpenSearch](https://opensearch.org/) and [ElasticSearch](https://www.elastic.co/). So let's head across to the Jaeger data source and configure that…


![data sources](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/4vf82apcwgdhoivo6q1b.png)

Data sources can be navigated to via **Connections -> Data Sources**. We currently have three configured; FlightSQL, InfluxDB and Jaeger. If we open the Jaeger configuration and navigate to the Trace to Logs section we want to essentially be able yo select either InfluxDB or FlightSQL as our Data source. 

![traces to logs](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/w7fizrk8rvp48m1f02do.png)

Houston, we have a problem. It appears Grafana doesn’t recognise InfluxDB as a log data source. Fair enough; only recently has InfluxDB become a viable option for logs. So, what are our options?


1. We lie down, accept the issue, and hope that in the future this feature becomes generic enough to support more data sources.
2. Take action and make the change ourselves. 

Well, by now you know what option we chose.


## The Solution

In this section, I will summarize the steps I took to discover what changes needed to be made. How to implement the changes for your own data source and finally how to build your own custom build of Grafana OSS.


### Discovery

So the first step is to understand where to even begin. Grafana is a huge Open Source platform with many components so I needed to narrow down the search. So the first thing I did was search the Grafana repository for signs of life.


![github](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3y6eeeweio8fg7bm35su.png)

As you can see I made this little discovery by using the keyword **trace**. Which led me to the directory **TraceToLogs**. This led me to this section of code within **[TraceToLogsSettings.tsx](https://github.com/grafana/grafana/blob/main/public/app/core/components/TraceToLogs/TraceToLogsSettings.tsx):**

```typescript

export function TraceToLogsSettings({ options, onOptionsChange }: Props) {

  const supportedDataSourceTypes = [

    'loki',

    'elasticsearch',

    'grafana-splunk-datasource', // external

    'grafana-opensearch-datasource', // external

    'grafana-falconlogscale-datasource', // external

    'googlecloud-logging-datasource', // external

  ];

```

This section of code seems to create a static list of data sources supported by the Trace to Logs feature. We can confirm this by some of the common suspects within the list (Loki, Elasticsearch, etc.). Based on this our first alteration to the Grafana source code should be to add our data sources to this list.

Now as the coding pessimist that I am, I knew this probably wouldn’t be the only change we needed to make but it's a good place to start. So I did the following:



1. I forked the Grafana repo
2. Cloned the repo:

    ```bash

    git clone https://github.com/InfluxCommunity/grafana

    ```


Before I made those modifications I wanted to do some more searching to see if there are any changes I should be making. One line stood out to me in **TraceToLogsSettings** file:

```typescript

  const updateTracesToLogs = useCallback(

    (value: Partial&lt;TraceToLogsOptionsV2>) => {

      // Cannot use updateDatasourcePluginJsonDataOption here as we need to update 2 keys, and they would overwrite each

      // other as updateDatasourcePluginJsonDataOption isn't synchronized

      onOptionsChange({

        ...options,

        jsonData: {

          ...options.jsonData,

          tracesToLogsV2: {

            ...traceToLogs,

            ...value,

          },

          tracesToLogs: undefined,

        },

      });

    },

    [onOptionsChange, options, traceToLogs]

  );

```

It was **TraceToLogsOptionsV2**. When I searched for places this interface was used I found the following entry.

![TraceToLogsOptionsV2](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/3a5pb6qftk3ludc6l29q.png)

So it appears we might also have work to do in the **[createSpanLink.tsx](https://github.com/grafana/grafana/blob/main/public/app/features/explore/TraceView/createSpanLink.tsx#L332)** file. Within I found this section of code, so my question was what exactly is this code doing?


![case statement](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/0k9p2riukestxwcv1bnc.png)

To cut a long story short the case statement essentially tells the trace visualisation to check what log data source has been defined (if any) and to define a query interface relevant to that data source. If the specified data source is not found within this case statement then the button is simply disabled which meant changing the original file won’t be enough as we suspected.

Okay, we have now completed our investigation. Let's move on to the code changes.


### Modification

We have two files to modify:

1. **[TraceToLogsSettings.tsx](https://github.com/grafana/grafana/blob/main/public/app/core/components/TraceToLogs/TraceToLogsSettings.tsx)**
2. **[createSpanLink.tsx](https://github.com/grafana/grafana/blob/main/public/app/features/explore/TraceView/createSpanLink.tsx#L332)**

Let's start with the simplest to tackle and go from there. 


#### TraceToLogsSettings

So this file was relatively simple to change. All we needed to do was modify the static list of supported log input sources like so:

```typescript

export function TraceToLogsSettings({ options, onOptionsChange }: Props) {

  const supportedDataSourceTypes = [

    'loki',

    'elasticsearch',

    'grafana-splunk-datasource', // external

    'grafana-opensearch-datasource', // external

    'grafana-falconlogscale-datasource', // external

    'googlecloud-logging-datasource', // external

    'influxdata-flightsql-datasource', // external

    'influxdb', // external

  ];

```

As you can see I have added two. I ran a quick build of the Grafana project to see how this affected our data source configuration (we will discuss how to build at the end).


![datasource list](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/9nmb6kfl0fbzfo55zrum.png)


Hey presto! We have a result. Now this still didn’t enable the button within our Trace View but we already knew this would requiremore work. 


#### createSpanLink

Now, onto the meat of our modification. For the record, I am not a TypeScript developer. What I do know is that the file has a whole bunch of examples we can use to attempt a blind copy-and-paste job with a few modifications. I ended up doing this for both plugins but to keep the blog short we will focus on the InfluxDB official plugin. 

My hypothesis was to use the Grafana Loki interface as the basis for the InfluxDB interface. The first included adding data source types:

```typescript

import { LokiQuery } from '../../../plugins/datasource/loki/types';

import { InfluxQuery } from '../../../plugins/datasource/influxdb/types';

```

These are easy to locate when Grafana has an official plugin for your data source since it's embedded within the official repository. For our community plugin I had two options: define a static interface within the file or provide more query parameters. I chose the latter.

The next step was to modify the case statement:

```typescript

   // TODO: This should eventually move into specific data sources and added to the data frame as we no longer use the

    //  deprecated blob format and we can map the link easily in data frame.

    if (logsDataSourceSettings && traceToLogsOptions) {

      const customQuery = traceToLogsOptions.customQuery ? traceToLogsOptions.query : undefined;

      const tagsToUse =

        traceToLogsOptions.tags && traceToLogsOptions.tags.length > 0 ? traceToLogsOptions.tags : defaultKeys;

      switch (logsDataSourceSettings?.type) {

        case 'loki':

          tags = getFormattedTags(span, tagsToUse);

          query = getQueryForLoki(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'grafana-splunk-datasource':

          tags = getFormattedTags(span, tagsToUse, { joinBy: ' ' });

          query = getQueryForSplunk(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'influxdata-flightsql-datasource':

            tags = getFormattedTags(span, tagsToUse, { joinBy: ' OR ' });

            query = getQueryFlightSQL(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'influxdb':

            tags = getFormattedTags(span, tagsToUse, { joinBy: ' OR ' });

            query = getQueryForInfluxQL(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'elasticsearch':

        case 'grafana-opensearch-datasource':

          tags = getFormattedTags(span, tagsToUse, { labelValueSign: ':', joinBy: ' AND ' });

          query = getQueryForElasticsearchOrOpensearch(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'grafana-falconlogscale-datasource':

          tags = getFormattedTags(span, tagsToUse, { joinBy: ' OR ' });

          query = getQueryForFalconLogScale(span, traceToLogsOptions, tags, customQuery);

          break;

        case 'googlecloud-logging-datasource':

          tags = getFormattedTags(span, tagsToUse, { joinBy: ' AND ' });

          query = getQueryForGoogleCloudLogging(span, traceToLogsOptions, tags, customQuery);

      }

```

As you can see I added two new cases:** <code>influxdata-flightsql-datasource</code></strong> and<strong> <code>influxdb</code></strong>. I then copied from Loki the two function calls within the case: <code>getFormattedTags<strong> </strong></code>and<strong> <code>getQueryFor</code></strong>. It appeared one I could leave alone (<strong><code>getFormattedTags</code></strong>) as this seemed to be the same for the majority of the cases. However,I would need to define my own <strong><code>getQueryFor</code></strong> function. 

Let's take a look at the new `getQueryForInfluxQL` function that’s called in the `influxdb` case statement:

```typescript

function getQueryForInfluxQL(

  span: TraceSpan,

  options: TraceToLogsOptionsV2,

  tags: string,

  customQuery?: string

): InfluxQuery | undefined {

  const { filterByTraceID, filterBySpanID } = options;

  if (customQuery) {

    return {

      refId: '',

      rawQuery: true,

      query: customQuery,

      resultFormat: 'logs',

    };

  }

  let query = 'SELECT time, "severity_text", body, attributes FROM logs WHERE time >=${__from}ms AND time &lt;=${__to}ms';

  if (filterByTraceID && span.traceID && filterBySpanID && span.spanID) {

            query = 'SELECT time, "severity_text", body, attributes FROM logs WHERE "trace_id"=\'${__span.traceId}\' AND "span_id"=\'${__span.spanId}\' AND time >=${__from}ms AND time &lt;=${__to}ms';

    } else if (filterByTraceID && span.traceID) {

            query = 'SELECT time, "severity_text", body, attributes FROM logs WHERE "trace_id"=\'${__span.traceId}\' AND time >=${__from}ms AND time &lt;=${__to}ms';

    } else if (filterBySpanID && span.spanID) {

            query = 'SELECT time, "severity_text", body, attributes FROM logs WHERE "span_id"=\'${__span.spanId}\' AND time >=${__from}ms AND time &lt;=${__to}ms';

  }

  return {

    refId: '',

    rawQuery: true,

    query: query,

    resultFormat: 'logs',

  };

}

```

So there is quite a lot here, but let me highlight the important parts. First of all, I started with an exact copy of the Loki function. Then, I made the following changes:



1. I changed the return interface from ‘`LokiQuery | undefined`‘ to  ‘ `InfluxQuery | undefined`‘ –the data source type we imported earlier.
2. Next, I focused on the return payload. After some digging within the InfluxQuery type file, I came up with this:

    ```typescript


    return {


        refId: '',


        rawQuery: true,


        query: query,


        resultFormat: 'logs',


      };


    ```


    The InfluxDB data source had a hany parameter which allowed me to define the result format (usually metrics) and also I now knew the data source would be expecting a raw query rather than an expression.

3. Lastly, I had to define the queries which would run when the user clicked the button. These depended on what filter features the user had toggled within the data source settings (filter by traceID, spanID or both). So I modified the `if` statement defined within the Loki function and constructed static InfluxQL queries. From there, I then used the Grafana placeholder variables found within other data sources to make the queries dynamic. Here is an example:

    ```typescript


    if (filterByTraceID && span.traceID && filterBySpanID && span.spanID) {


                query = 'SELECT time, "severity_text", body, attributes FROM logs WHERE "trace_id"=\'${__span.traceId}\' AND "span_id"=\'${__span.spanId}\' AND time >=${__from}ms AND time &lt;=${__to}ms';


    ```


    Full disclosure, it took me a good minute to find out about the **<code>>=${__from}ms</code> </strong>and <strong><code>&lt;=${__to}ms</code></strong>. This ended up being a brute force build and error case. 



### Building

Phew! We’re past the hard bit. Now onto the build process. I have quite a few years of experience with Docker, so this part was stress-free for me, but I imagine it could be daunting for new Docker users. Luckily, Grafana has some easy-to-follow [documentation](https://github.com/grafana/grafana/blob/main/contribute/developer-guide.md) for the task. To paraphrase, these are the steps:



1. Run the following build command (this can take a while and make sure your docker VM has enough memory if using macOS or Windows)

    ```bash


    make build-docker-full  


    ```

2. The build process produces a Docker image called: **grafana/grafana-oss:dev** . We could just use this image, but as a formality, I like to retag the image and push it to my Docker registry.

    ```bash


    docker tag grafana/grafana-oss:dev jaymand13/grafana-oss:dev2


    docker push jaymand13/grafana-oss:dev2


    ```


 This way I have checkpoints when I am brute forcing changes.

There we have it! A fully baked Grafana dev image to try out with our changes.


## The results and conclusion

So after investigating, making the changes, and building our new Grafana container, let's take a look at our results:


![result](https://dev-to-uploads.s3.amazonaws.com/uploads/articles/rfp4zm9yw4t1wni2o012.png)


With our changes, the **Logs for this span** button now activates. We also have this neat little **Log** button that appears next to each span. A confession: the blue **Logs for this span** button currently only works within the Grafana Explorer tab, but the new **Log** link works within our dashboard. To quickly explain the differences; Grafana Dashboards are custom-built by users and can include 1 or many data sources with a variety of different visualisations. Data Explorers on the other hand provide an interface for drill-down and investigation activities like you see in the above screenshot. Still, it’s not a huge problem compared to how little we needed to change to get here. 

And so, we've reached the end of our dive into the intricacies of modifying Grafana's source code. Over the course of this tutorial, I hope you've not only gained a practical understanding of how to customize Grafana for your specific requirements, but also an appreciation for the flexibility and potential of open-source platforms in general.

Remember, in the realm of open-source, there's no limit to how much we can tweak, adjust, and reimagine to suit our needs. I hope this guide serves you well as you delve deeper into your own projects, and that it brings you one step closer to mastering the powerful tool that is Grafana. For me, my journey continues as I now plan to add exemplar support to this OSS build. If you would like to try this out yourself you can find the OpenTelemetry example [here](https://github.com/InfluxCommunity/opentelemetry-demo).