Additional Logjam inputs

Logjam also offers additional input options apart from the main logjam-device for logging input.

Most of these are part of the (optional) logjam-fhttpd component.

Frontend metrics

logjam-fhttpd provides the /logjam/ajax and /logjam/page endpoints for general frontend metrics requests.

/logjam/page should be called (from the browser) after the page load is completed
/logjam/ajax should be called after the completion of an AJAX call (e.g. to obtain additional information that should be displayed after some interaction on the page)

HTTP Payload

As this endpoint is intended to receive metrics from within a browser it is likely subject to CORS (Cross-Origin Resource Sharing). Generally browsers limit the connection to other domains to certain types of request based on whether the target server allows the connection. This requires the server to maintain a list of allowed origins. To keep the configuration footprint small the endpoint is providing a safe simple request format.

For a request to be considered simple it needs to be limited to a small selection of supported HTTP Verbs, HTTP request headers as well as a limited selection of allowed content types.

This endpoint is intended to be used by adding the URL as an image into the DOM of the HTML page. This will subsequently cause the browser to perform an HTTP GET request. The payload is appended to the URL in the form of a query string that contains form data.

Format of the payload:

Field	type/unit	mandatory/optional
&v	int	mandatory, must be `1`
&logjam_request_id	string	mandatory
&logjam_action	string	mandatory
&viewport_height	int	optional
&viewport_width	int	optional
&html_nodes	int	optional
&script_nodes	int	optional
&style_nodes	int	optional
&rts	int	optional

If the HTTP request was successfully processed it returns a valid HTTP response (200 status code) for a image/gif 1x1 pixel size image. In the case of an issue with processing it returns a "Bad Request" HTTP response (400 status code) with a description of the error in the response body.

rts field

The rts field is an important field used by both known processors.

For `page` messages

It is a comma-separated string of 16 integer values representing UNIX timestamps (time since epoch). Each timestamp corresponds to a specific browserevent:

index in rts	event
0	navigationStart
1	fetchStart
2	domainLookupStart
3	domainLookupEnd
4	connectStart
5	connectEnd
6	requestStart
7	responseStart
8	responseEnd
9	domLoading
10	domInteractive
11	domContentLoadedEventStart
12	domContentLoadedEventEnd
13	domComplete
14	loadEventStart
15	loadEventEnd

For `ajax` messages

It is a comma-separated string of 2 integer values representing UNIX timestamps (time since epoch).

index in rts	event
0	ajax start
1	ajax end

Published Logjam message

Routing field	value
Routing key prefix	`"frontend"`
Routing key message type	`"ajax"` or `"page"`

The data section of the message is JSON in the following format:

{
  "v": 1,
  "logjam_request_id": "",
  "logjam_action": "",
  "html_nodes": 0,
  "script_nodes": 0,
  "style_nodes": 0,
  "user_agent": "",
  "started_ms": 0,
  "started_at": "0000-00-00T00:00:00+00:00",
  "rts": ""
}

The payload can contain additional fields as other form parameters in the query string get automatically added to the payload as well.

Known processors

logjam-prometheus-exporter

Currently logjam-prometheus-exporter is processing these Logjam messages to provide Prometheus metrics for both page and ajax performance data. It parses the rts field to extract the page time for page requests and ajax time for ajax requests.

page time is defined as loadEventEnd - navigationStart, or if navigationStart is 0 as loadEventEnd - fetchStart.
ajax time is defined as ajax end - ajax start

Both are then used to create the following metrics:

message type	metric name
`ajax` messages	logjam:action:ajax_time_distribution_seconds
`ajax` messages	logjam:application:ajax_time_distribution_seconds
`page` messages	logjam:action:page_time_distribution_seconds
`page` messages	logjam:application:page_time_distribution_seconds

logjam-importer

The logjam-importer stores request data in a MongoDB instance, which is then used as the backing datastore for logjam_app itself. The data from frontend messages is extracted to both provide timings information for page loads as well as individual components (rts (all 16 segments are used for page timings)).

Other fields are also stored in the database to be used within logjam_app, such as html_nodes, script_nodes, style_nodes and user_agent.

Mobile/native metrics

logjam-fhttpd provides the /logjam/mobile endpoint for metrics from mobile clients (specifically native clients, e.g. Android or iOS).

HTTP Payload

A valid request must be a HTTP request with an application/json content type. No Logjam specific headers are required.

Currently defined fields:

{
  "meta": {
    "os": "",
    "device": "",
    "version": "",
    "internal_build": false
  },
  "histograms": [
    {
      "name": "",
      "begin": "",
      "end": "",
      "buckets": [
        {
          "start_value": 0,
          "end_value": 0,
          "count": 0
        }
      ]
    }
  ],
  "gauges": [
    {
      "name": "",
      "metrics": [
        {
          "value": 0,
          "timestamp": ""
        }
      ]
    }
  ]
}

Published Logjam message

Routing field	value
Routing key	`"mobile"`

Currently fhttpd forces a synthetic appenv for the mobile message: mobile-production

The data section of the message is the body of the HTTP request as documented above.

Known processors

Currently logjam-prometheus-exporter is processing these Logjam messages to provide Prometheus metrics.

It supports the following incoming metrics and translates them into Prometheus metrics:

metric name in logjam message	metric type	prometheus metric name
`application_time_firstdraw_ms`	histogram	`logjam:mobile:application_time_firstdraw_ms`
`application_resume_time_ms`	histogram	`logjam:mobile:application_resume_time_ms`
`application_hang_time_ms`	histogram	`logjam:mobile:application_hang_time_ms`

The prometheus metrics have the version and internalBuild labels.

WebVitals

logjam-fhttpd provides the /logjam/webvitals endpoint for metrics from browsers about WebVitals.

HTTP Payload

As this endpoint is intended to receive metrics from within a browser it is likely subject to CORS (Cross-Origin Resource Sharing). Generally browsers limit the connection to other domains to certain types of request based on whether the target server allows the connection. This requires the server to maintain a list of allowed origins. To keep the configuration footprint small the endpoint is providing a safe simple request format.

For a request to be considered simple it needs to be limited to a small selection of supported HTTP Verbs, HTTP request headers as well as a limited selection of allowed content types.

A request should be of the following format:

A HTTP POST request
The Content-Type must be application/x-www-form-urlencoded or multipart/formdata
The payload should either be a query string (in form encoded format) or a form encoded text in the body of the request.

Format of the payload:

Field	type/unit	mandatory/optional
&logjam_request_id	string	mandatory
&logjam_action	string	mandatory
&metrics[].id	string	mandatory (within a metric)
&metrics[].fid	float (in milliseconds)	optional (within a metric)
&metrics[].lcp	float (in milliseconds)	mandatory (within a metric)
&metrics[].cls	float (score 0.0-1.0)	mandatory (within a metric)

Example (single metric)

Linebreaks are only added for readability.

logjam_action=someAction%23call
&logjam_request_id=some-app-preview-4ca101ebe46e4bdaaebe95df9cc7fe83
&metrics%5B%5D.id=241f3328-d781-4c77-8470-be48739ddfc3
&metrics%5B%5D.cls=0
&metrics%5B%5D.fid=891.2476906688746
&metrics%5B%5D.lcp=0

Example (multiple metrics)

logjam_action=someAction%23call
&logjam_request_id=some-app-preview-4ca101ebe46e4bdaaebe95df9cc7fe83
&metrics%5B0%5D.id=241f3328-d781-4c77-8470-be48739ddfc3
&metrics%5B0%5D.cls=0
&metrics%5B0%5D.fid=891.2476906688746
&metrics%5B0%5D.lcp=0
&metrics%5B1%5D.id=241f3328-d781-4c77-8470-be48739ddfc3
&metrics%5B1%5D.lcp=1202.24333333334
&metrics%5B1%5D.fid=0
&metrics%5B1%5D.cls=0

Published Logjam message

Routing field	value
Routing key prefix	`"frontend"`
Routing key message type	`"webvitals"`

The data section of the message is JSON in the following format:

{
  "started_ms": 0,
  "started_at": "0000-00-00T00:00+00:00",
  "logjam_request_id": "some-app-preview-dddeeefff",
  "logjam_action_id": "someAction#call",
  "metrics": [
    {
      "id": "webvitals-id-000dddeee111222333222",
      "lcp": 0.0
    },
    {
      "id": "webvitals-id-000dddeee111222333444",
      "fid": 0.0
    },
    {
      "id": "webvitals-id-000dddeee1112223335555",
      "cls": 0.0
    }
  ]
}

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additional-inputs.md

additional-inputs.md

Additional Logjam inputs

Frontend metrics

HTTP Payload

rts field

For `page` messages

For `ajax` messages

Published Logjam message

Known processors

logjam-prometheus-exporter

logjam-importer

Mobile/native metrics

HTTP Payload

Published Logjam message

Known processors

WebVitals

HTTP Payload

Example (single metric)

Example (multiple metrics)

Published Logjam message

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additional-inputs.md

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additional-inputs.md

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Additional Logjam inputs

Frontend metrics

HTTP Payload

rts field

For page messages

For ajax messages

Published Logjam message

Known processors

logjam-prometheus-exporter

logjam-importer

Mobile/native metrics

HTTP Payload

Published Logjam message

Known processors

WebVitals

HTTP Payload

Example (single metric)

Example (multiple metrics)

Published Logjam message

For `page` messages

For `ajax` messages