# Hydra Processor

Hydra processor is a client-side 'sink' tool used to fetch substrate events from a Hydra indexer. It sequentially applies the event handlers one by one in the order the events have been emitted.

## Commands

* [`hydra-processor help [COMMAND]`](/hydra/hydra-processor.md#hydra-processor-help-command)
* [`hydra-processor migrate`](/hydra/hydra-processor.md#hydra-processor-migrate)
* [`hydra-processor run`](/hydra/hydra-processor.md#hydra-processor-run)

## `hydra-processor help [COMMAND]`

display help for hydra-processor

```
display help for <%= config.bin %>

USAGE
  $ hydra-processor help [COMMAND]

ARGUMENTS
  COMMAND  command to show help for

OPTIONS
  --all  see all commands in CLI
```

*See code:* [*@oclif/plugin-help*](https://github.com/oclif/plugin-help/blob/v2.2.3/src/commands/help.ts)

## `hydra-processor migrate`

```
undefined

USAGE
  $ hydra-processor migrate

OPTIONS
  -e, --env=env  Path to a file with environment variables
```

## `hydra-processor run`

```
undefined

USAGE
  $ hydra-processor run

OPTIONS
  -e, --env=env            Path to a file with environment variables
  -m, --manifest=manifest  Manifest file
  --id=id                  ID of the processor (useful for multi-processor setups)
  --indexer=indexer        Indexer URL to source events
```

## Qickstart

Before the first run, the processor should set up auxiliary database tables required for its work:

```
hydra-processor migrate
```

Then `hydra-processor` can be run against the manifest file (by default, it looks up `manifest.yml` in the current folder)

```
hydra-processor run -m <path/to/manifest> -e <path to a file with env variables>
```

## Environment variables

Hydra processor requires a manifest file and certain environment variables to be set.

| Variable               |       Default      | Required |                                                       Description |
| ---------------------- | :----------------: | -------: | ----------------------------------------------------------------: |
| INDEXER\_ENDPOINT\_URL |          -         |  **Yes** | Hydra indexer endpoint to source the raw event and extrinsic data |
| MANIFEST\_PATH         |    manifest.yml    |   **No** |                                         Path to the manifest file |
| DB\_NAME               |          -         |  **Yes** |                                                     Database name |
| DB\_PORT               |          -         |  **Yes** |                                                     Database port |
| DB\_HOST               |          -         |  **Yes** |                                                     Database host |
| DB\_USER               |          -         |  **Yes** |                                                     Database user |
| DB\_PASS               |          -         |  **Yes** |                                                 Database password |
| PROMETHEUS\_PORT       |        3000        |   **No** |             A prometheus metrics endpoint is started at this port |
| POLL\_INTERVAL\_MS     | 1 sec (60000 msec) |   **No** |          How often the processor polls the indexer for new blocks |

The required variables can either be set externally or loaded from a file using the `-e` flag, e.g.:

```
hydra-processor migrate -e .env
```

## Manifest file

The manifest file describes which and how the events and extrinsics should be processed. Here is an example for Kusama blockchain:

```
version: '0.1'
description: Test manifest
repository: https://github.com/
## currently only these settings for the datasouce section are accepted
dataSource:
  kind: substrate 
  chain: kusama
  indexerVersion: '0.0.4'
# compiled model classes generated by hydra-cli codegen from the input schema 
entities:
  - mappings/lib/generated/**/*.model.js
mappings:
  hydraCommonVersion: '0.0.3'
  # process only blocks with height >= 1M 
  blockInterval: '[1000000,]'
  # js module that exports the handler functions 
  mappingsModule: mappings/lib/mappings
  # additinal libraries the processor loads
  # typically it is a module with event and extrinsic types generated by hydra-typegen 
  imports:
    - mappings/lib/mappings/generated/types
  eventHandlers:
  # event name
    - event: balances.Transfer 
  # function handler name with the argument types
      handler: balancesTransfer(DatabaseManager, Balances.TransferEvent)
  extrinsicHandlers:
    # infer defaults here
    #- extrinsic: Balances.Transfer 
    #- extrinsic: Sudo.batchCall 
    #  handler: handleSudoCall(DatabaseManager,SubstrateEvent)
  preBlockHooks:
  postBlockHooks:
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://dzhelezov.gitbook.io/hydra/hydra-processor.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.