feat: fetch only the root block (#48)

SPARK is about retrieval testing not load testing.

Currently, more than 90% of retrievals fail on timeout or server errors.
There is little value in checking whether we can download the entire
CAR file, it's more important to know whether SPs are advertising FIL+
deals to IPNI and accept HTTP-based retrieval requests.

SPARK is also not able to fetch and verify CAR files larger than 200MB,
which further reduced the value of fetching full CAR files.

Let's fetch the root block for the time being.
- This should significantly reduce the load on "good" SPs.
- It provides enough data allowing "bad" SPs to fix their setup.


Signed-off-by: Miroslav Bajtoš <[email protected]>

lib/spark.js

@@ -140,6 +140,9 @@ export default class Spark {
       statusCode: null
     }
     const searchParams = new URLSearchParams({
+      // See https://github.com/filecoin-project/lassie/blob/main/docs/HTTP_SPEC.md#dag-scope-request-query-parameter
+      // Only the root block at the end of the path is returned after blocks required to verify the specified path segments.
+      'dag-scope': 'block',
       protocols: retrieval.protocol,
       providers: retrieval.providerAddress
     })

test/spark.js

@@ -3,7 +3,7 @@
 import Spark from '../lib/spark.js'
 import { test } from 'zinnia:test'
 import { assertInstanceOf, assertEquals, assertArrayIncludes } from 'zinnia:assert'
-import { SPARK_VERSION, MAX_CAR_SIZE } from '../lib/constants.js'
+import { SPARK_VERSION } from '../lib/constants.js'
 
 test('getRetrieval', async () => {
   const round = {
@@ -82,6 +82,7 @@ test('fetchCAR', async () => {
   assertEquals(requests, [{ url: URL }])
 })
 
+/* Disabled as long as we are fetching the top-level block only
 test('fetchCAR exceeding MAX_CAR_SIZE', async () => {
   const URL = 'url'
   const fetch = async url => {
@@ -110,6 +111,7 @@ test('fetchCAR exceeding MAX_CAR_SIZE', async () => {
   assertEquals(stats.carChecksum, null)
   assertEquals(stats.statusCode, 200)
 })
+*/
 
 test('submitRetrieval', async () => {
   const requests = []