Logging from the Contract code

Output

Logging output goes to stdout; as this is a docker container by default, this is easily captured using standard docker tools.

The following levels are used.

• CRITICAL
• ERROR
• WARNING
• DEBUG
• INFO

Enabling Logging

In the docker-compose.yml environment variables of the peer

CORE_CHAINCODE_LOGGING_LEVEL=[CRITICAL|ERROR|WARNING|DEBUG|INFO]

In a transaction function in the contract

    async setLogLevel(ctx,loglevel) {

        ctx.logging.setLevel(loglevel);

        const logger = ctx.logging.getLogger("a name of your choice");
        // or
        const logger = ctx.logging.getLogger(); // defaults to contract name

        logger.info('Updated the log level to ',loglevel);

    }

Getting the Log level

In a transaction function in the contract

    let loglevel = process.env.CORE_CHAINCODE_LOGGING_LEVEL;

APIs that can be used in the contract

The ‘logger’ object that is returned is a Winston Logger object.