Migrate to ArrowSquid (Substrate)

This is a Substrate guide. EVM guide is available here. ArrowSquid refers to @subsquid/substrate-processor versions 3.x and above. It is not compatible with the FireSquid archive endpoints. Instead, the new version uses SQD Network gateways. See the Supported networks page. The main feature introduced by the ArrowSquid update is the new ability of the processor to ingest unfinalized blocks directly from a network node, instead of waiting for an archive to ingest and serve it first. The processor can now handle forks and rewrite the contents of its database if it happens to have indexed orphaned blocks. This allows SQD-based APIs to become near real-time and respond to the on-chain activity with subsecond latency. Other new features include the new streamlined processor configuration interface and automatic retrieval of execution traces. On the implementation side, the way in which data is fetched has been made more efficient. End-to-end Substrate ArrowSquid examples:

Here is a step-by-step guide for migrating a squid built with an older SDK version to the post-ArrowSquid tooling.

Step 1

Update all packages affected by the update:

npm i @subsquid/substrate-processor@latest @subsquid/typeorm-store@latest

npm i --save-dev @subsquid/substrate-typegen@latest

If your squid uses file-store, please update any related packages to the @latest version.

Step 2

Replace the old setDataSource() processor configuration call with a combination of setGateway() and setRpcEndpoint(). Use a public SQD Network gateway URL for your network. If your squid did not use an RPC endpoint before, find one for your network and set it with setRpcEndpoint(). For Aleph Zero your edit might look like this:

 processor
-  .setDataSource({
-    archive: 'https://aleph-zero.archive.subsquid.io/graphql'
-  })
+  .setGateway('https://v2.archive.subsquid.io/network/aleph-zero')
+  .setRpcEndpoint({
+    url: 'https://aleph-zero-rpc.dwellir.com',
+    rateLimit: 10
+  })

We recommend using a private RPC endpoint for the best performance, e.g. from Dwellir. For squids deployed to SQD Cloud you may also consider using our RPC addon. Your squid will work with just an RPC endpoint, but it will sync significantly slower. With a SQD Network gateway available the processor will only use RPC to retrieve metadata and sync the few most recent blocks not yet made available by the gateway; without it it will retrieve all data from the endpoint.

Step 3

Next, we have to account for the changes in signatures of the data requesting processor methods

Previously, each call of these methods supplied its own fine-grained data fields selector. In the new interface, these calls only request data items, either directly or by relation (for example with the call flag for event-requesting methods). Field selection is now done by the new setFields() method on a per-item-type basis: once for all Calls, once for all Events etc. The setting is processor-wide: for example, all Calls returned by the processor will have the same set of available fields, regardless of whether they were requested directly or as related data. Begin migrating to the new interface by finding all calls to these methods and combining all the field selectors into processor-wide event, call and extrinsic field selectors that request all fields previously requested by individual selectors. Note that call.args and event.args are now requested by default and can be omitted. When done, add a call to setFields() supplying it with the new field selectors. The new field selector format is fully documented on the Field selection page.

Blanket field selections like \{data: \{event: \{extrinsic: true\}\}\} are not supported in ArrowSquid. If you used one of these, please find out which exact fields you use in the batch handler and specifically request them.

Do not include related data requests into the field selection. E.g.

  .setFields({
    event: {
      call: true
    }
  })

will at best fail to compile and at worst make your squid fail due to HTTP 400s from the network gateway.

For example, suppose the processor was initialized with the following three calls:

const processor = new SubstrateBatchProcessor()
  .addCall('Balances.transfer_keep_alive', {
    data: {
      call: {
        origin: true,
        args: true
      }
    }
  } as const)
  .addEvent('Balances.Transfer', {
    data: {
      event: {
        args: true,
        extrinsic: {
          hash: true,
          fee: true
        },
        call: {
          success: true,
          error: true
        }
      }
    }
  } as const)
  .addEvmLog(CONTRACT_ADDRESS,
    filter: [[ abi.events.SomeLog.topic ]],
    {
      data: {
        event: {
          extrinsic: {
            hash: true,
            tip: true
          }
        }
      }
    } as const
  )

then the new global selectors should be added like this:

const processor = new SubstrateBatchProcessor()
  // ... addXXX() calls ...
  .setFields({
    event: \{\},
    call: {
      origin: true,
      success: true,
      error: true
    },
    extrinsic: {
      hash: true,
      fee: true,
      tip: true
    }
  })

Be aware that this operation will not increase the amount of data retrieved from the SQD Network gateway, since previously such coalescence was done under the hood and all fields were retrieved by the processor anyway. In fact, the amount of data should decrease due to a more efficient transfer mechanism employed by ArrowSquid. There are two old field requests that have no direct equivalent in the new interface:

Step 4

Replace the old calls to the data requesting processor methods with calls using the new signatures.

The meaning of passing [] as a set of parameter values has been changed in the ArrowSquid release: now it selects no data. Pass undefined for a wildcard selection:

.addEvent(\{name: []\}) // selects no events
.addEvent(\{\}) // selects all events

Old data request calls will be erased during the process. Make sure to request the appropriate related data with the boolean flags (call for event-requesting methods, events for call-requesting methods and extrinsic, stack for both). Interfaces of data request methods are documented on the Data requests reference page:

Here is a fully updated initialization code for the example processor from step 3:

const processor = new SubstrateBatchProcessor()
  .addCall({
    name: [ 'Balances.transfer_keep_alive' ]
  })
  .addEvent({
    name: [ 'Balances.Transfer' ],
    call: true,
    extrinsic: true
  })
  .addEvmLog({
    address: [ CONTRACT_ADDRESS ],
    topic0: [ abi.events.SomeLog.topic ],
    extrinsic: true
  })
  .setFields({
    event: \{\},
    call: {
      origin: true,
      success: true,
      error: true
    },
    extrinsic: {
      hash: true,
      fee: true,
      tip: true
    }
  })

Step 5

Finally, update the batch handler to use the new batch context. The main change here is that now block.items is split into three separate iterables: block.calls, block.events and block.extrinsics. There are two ways to migrate:

If you’re in a hurry, use the orderItems(block: Block) function from this snippet:

src/main.ts

// ...
// paste the gist here

processor.run(db, async ctx => {
  // ...
  for (let block of ctx.blocks) {
    for (let item of orderItems(block)) {
      // item processing code should work unchanged
    }
  }
  // ...
})

Alternatively, rewrite your batch handler using the new batch context interface.

See Block data for Substrate for the documentation on Substrate-specific part of batch context.

Step 6

Rewrite your typegen.json in the new style. Here is an example:

{
  "outDir": "src/types",
  "specVersions": "https://v2.archive.subsquid.io/metadata/kusama",
  "pallets": {
    "Balances": {
      "events": [
        "Transfer"
      ],
      "calls": [],
      "storage": [],
      "constants": []
    }
  }
}

Note the changes:

Archive URL as "specVersions" is replaced with an URL of our new metadata service ("https://v2.archive.subsquid.io/metadata/kusama")
Requests for data wrappers are now made on a per-pallet basis.

Check out the updated Substrate typegen documentation page. If you used any storage calls, consult this documentation page for guidance. Once you’re done migrating typegen.json, regenerate the wrapper classes with

npx squid-substrate-typegen typegen.json

Step 7

Iteratively reconcile any type errors arising when building your squid (e.g. with npm run build). If you need to specify the field selection generic type argument explicitly, get it as a typeof of the setFields argument value:

import \{Block\} from '@subsquid/substrate-processor'

const fieldSelection = {
  event: \{\},
  call: {
    origin: true,
    success: true,
    error: true
  },
  extrinsic: {
    hash: true,
    fee: true,
    tip: true
  }
} as const

type MyBlock = Block<typeof fieldSelection>
// ...

At this point your squid should be able to work with the ArrowSquid tooling. If it doesn’t, read on.

Troubleshooting

If these instructions did not work for you, please let us know at the SquidDevs Telegram chat.

​Migrate to ArrowSquid (Substrate)

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​Troubleshooting

Migrate to ArrowSquid (Substrate)

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Troubleshooting