# Logging

### Overview <a href="#overview" id="overview"></a>

zeknd has built-in configurable logging. The user can configure the log level and the log destination.

### #zeknd SDK Logging <a href="#loom-sdk-logging" id="loom-sdk-logging"></a>

#### #Configuring the log level <a href="#configuring-the-log-level" id="configuring-the-log-level"></a>

The zeknd SDK provides two types of logs:

* blockchain logs (blockchain transactions and consensus events).
* zeknd SDK logs (generated by the SDK itself, i.e emitted events).

As an example, add the following to your zeknd`.yaml` to set logging levels:

```
zekndLogLevel: debug # sets the log level for events emitted from the zeknd SDK
BlockchainLogLevel: error # sets the log level for the blockchain logs.
```

> Defaults for the zeknd`LogLevel` and `BlockchainLogLevel` are `info` and `error` respectively.

#### #Configuring the log destination <a href="#configuring-the-log-destination" id="configuring-the-log-destination"></a>

Currently, a file target is supported for the zeknd logs:

```
LogDestination: "file://zeknd.log" # zeknd.log is also the default target.
```

To log to stderr, specify the destination as `file://-`

### #Contract logging <a href="#contract-logging" id="contract-logging"></a>

Configurations like log level and destination are separate for contracts. These are set using environment variables.

Example: `CONTRACT_LOG_LEVEL=debug CONTRACT_LOG_DESTINATION="file://-" $`zeknd`_EXE run`

This will set the contract log level to `debug` and the destination to stderr.

The default for log level and destination are `info` and `file://contract.log` respectively.

#### #Logging from the contract <a href="#logging-from-the-contract" id="logging-from-the-contract"></a>

The contract context has a pre-configured logger that can be used for structured logging. Let's look at an example:

```
ctx.Logger().Info("Created account", "owner", owner, "address", addr)
```

will generate a log line like:

```
ts=2018-05-13T02:06:49.817229589Z module=zeknd level=info _msg="Created account" owner=godbole4 address="\ufffd8\ufffd\ufffd\ufffd\ufffd\ufffd$Y+H\ufffd\u0012\u000c]\u001a\ufffd\ufffd\ufffd\ufffd"
```

Available methods on the context logger are `Error`, `Warn`, `Info`, and `Debug`.

<br>

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