> ## Documentation Index
> Fetch the complete documentation index at: https://docs.sqd.dev/llms.txt
> Use this file to discover all available pages before exploring further.

<AgentInstructions>

## Submitting Feedback

If you encounter incorrect, outdated, or confusing documentation on this page, submit feedback:

POST https://docs.sqd.dev/feedback

```json
{
  "path": "/en/sdk/squid-sdk/reference/logger",
  "feedback": "Description of the issue"
}
```

Only submit feedback when you have something specific and actionable to report.

</AgentInstructions>

# Squid SDK Logger

> Native logger module of Squid SDK — pino-based structured logging with log levels, JSON output, and integration with batch processor lifecycle.

A [`Logger`](https://github.com/subsquid/squid/tree/master/util/logger) interface is injected into the [handler context](/en/sdk/squid-sdk/reference/processors/architecture#batch-context) with `ctx.log`. It is bound to the namespace `sqd:processor:mapping`. The context logger is a recommended way of logging for squid processors.

`Logger` exposes the following logging levels, in order of increasing severity:

* `TRACE`
* `DEBUG`
* `INFO`
* `WARN`
* `ERROR`
* `FATAL`

By default, the logging level is set to `INFO`.

And here is an example:

```typescript theme={"system"}
processor.run(new TypeormDatabase(), async (ctx) => {
  ctx.log.trace("Trace Log example");
  ctx.log.debug("Debug Log example");
  ctx.log.info("Info Log example");
  ctx.log.warn("Warn Log example");
  ctx.log.error("Error Log example");
  ctx.log.fatal("Fatal Log example")
});
```

## Overriding the log level

The log level can be overridden by setting a matching namespace selector to one of the `SQD_TRACE`, ..., `SQD_FATAL` env variables. In particular, to set the handler logs level to `DEBUG` set the environment variable `SQD_DEBUG` to `sqd:processor:mapping`:

```bash theme={"system"}
SQD_DEBUG=sqd:processor:mapping
```

The namespace selector supports wildcards, so one can also enable internal debug logs of `@subsquid/substrate-processor` with

```
SQD_DEBUG=sqd:processor*
```

since all processor context loggers inherit the processor-level namespace `sqd:processor`.

## Accessing logs of a deployed Squid

Processor logs can be inspected once the squid is deployed to Cloud:

```bash theme={"system"}
sqd logs -n <name> -s <slot> -f --level=<level>
```

or

```bash theme={"system"}
sqd logs -n <name> -t <tag> -f --level=<level>
```

<Accordion title="For older version-based deployments...">
  ...the slot string is `v${version}`, so use

  ```bash theme={"system"}
  sqd logs -n <name> -s v<version> -f --level=<level>
  ```

  Check out the [Slots and tags guide](/en/cloud/resources/slots-and-tags) to learn more.
</Accordion>

The available levels are:

* `info`
* `warning`
* `debug`
* `error` - will fetch messages emitted by
  * `ctx.log.error`
  * `ctx.log.fatal`
  * `ctx.log.trace`

See [CLI Reference](/en/sdk/squid-sdk/squid-cli/logs) or `sqd logs --help` for a full list of log options supported by SQD Cloud.