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Body Storage

Lace executors write request and response bodies to a shared filesystem volume. The result JSON contains absolute paths to these files -- no body bytes appear in the result JSON itself.

Path convention

Body files follow the naming pattern:

{run_base_dir}/call_{index}_{request|response}.{ext}
Segment Description
run_base_dir Base directory for this probe run. Configured via result.bodies.dir in lace.config.
index Zero-based call index matching calls[n].index.
request \| response Whether the file contains the request body or response body.
ext File extension derived from the content type (e.g. json, xml, txt, html).

Examples

/probe_runs/abc/call_0_request.json
/probe_runs/abc/call_0_response.json
/probe_runs/abc/call_1_response.html

bodyPath

Both the request record and the response record include a bodyPath field.

Request bodyPath: absolute path to the request body file, or null if no body was sent (typical for GET and DELETE requests).

{
  "request": {
    "url": "https://api.example.com/users",
    "method": "post",
    "headers": {
      "content-type": "application/json"
    },
    "bodyPath": "/probe_runs/abc/call_0_request.json"
  }
}

{
  "request": {
    "url": "https://api.example.com/users",
    "method": "get",
    "headers": {},
    "bodyPath": null
  }
}

Response bodyPath: absolute path to the response body file, or null when the body was not captured.

{
  "response": {
    "status": 200,
    "statusText": "OK",
    "headers": {
      "content-type": "application/json"
    },
    "bodyPath": "/probe_runs/abc/call_0_response.json",
    "responseTimeMs": 145
  }
}

bodyNotCapturedReason

When the response bodyPath is null, the bodyNotCapturedReason field explains why.

Value Meaning
"bodyTooLarge" The response body exceeded the configured size limit and was not written.
"notRequested" The probe configuration did not request body capture for this call.
"timeout" The call timed out before the body could be fully received. 
{
  "response": {
    "status": 200,
    "bodyPath": null,
    "bodyNotCapturedReason": "bodyTooLarge",
    "sizeBytes": 52428800
  }
}

{
  "response": {
    "status": 200,
    "statusText": "OK",
    "headers": {
      "content-type": "application/octet-stream"
    },
    "bodyPath": null,
    "bodyNotCapturedReason": "bodyTooLarge",
    "responseTimeMs": 320,
    "dnsMs": 5,
    "connectMs": 18,
    "tlsMs": 25,
    "ttfbMs": 100,
    "transferMs": 220,
    "sizeBytes": 52428800,
    "dns": {
      "resolvedIps": [
        "10.0.0.1"
      ],
      "resolvedIp": "10.0.0.1"
    },
    "tls": null
  }
}

Configuration

The run base directory is set in lace.config:

[result.bodies]
dir = "./lace_results/bodies"

If not specified, it defaults to the same directory as result.path (which itself defaults to the current directory).

Config key Default Description
result.bodies.dir Same as result.path Directory where body files are written.