scan-hget

Containerized utility to scan Redis keys and hget a specified hashes field.

See lib/index.js that we use archetype https://github.com/evanx/redis-app

Use case

Sample data

redis-cli hset mytest:1001:h err some_error
redis-cli hset mytest:1002:h err other_error

where we might have the field err on some hashes keys.

We wish to perform a query on this specific field e.g. as follows using bash and redis-cli

for key in `redis-cli keys 'mytest:*:h'`
do
  echo $key `redis-cli hget $key err`
done

mytest:1001:h some_error
mytest:1002:h other_error

Usage

Use format=both to print the key and the field value:

pattern='mytest*' format=both field=err npm start

where we have specified the err field for the query.

mytest:1002:h other_error
mytest:1001:h some_error

where the hash key and the value of its err field have been printed.

Otherwise format=value will print only the field value:

pattern='mytest*' format=value field=err npm start

other_error
some_error

Config

See lib/spec.js

    pattern: {
        description: 'the matching pattern for Redis scan',
        example: '*'
    },
    field: {
        description: 'name of the hashes field to print'
    },
    limit: {
        description: 'the maximum number of keys to print',
        note: 'zero means unlimited',
        default: 30
    },
    format: {
        description: 'the output format',
        options: ['key', 'value', 'both', 'json'],
        default: 'key'
    }

Implementation

See lib/main.js

    let cursor;
    while (true) {
        const [result] = await multiExecAsync(client, multi => {
            multi.scan(cursor || 0, 'match', config.pattern);
        });
        cursor = parseInt(result[0]);
        const keys = result[1];
        if (config.format === 'key') {
            keys.forEach(key => {
                console.log(key);
                count++;
            });
        }
    }

Docker

Having audited the Dockerfile and code, you can build and run as follows:

docker build -t scan-hget https://github.com/evanx/scan-hget.git

where we tag the image as scan-hget

docker run --network=host -e pattern='*' -e field=role -e format=both scan-hget

where --network-host connects the container to your localhost bridge. The default redisHost of localhost works in that case.

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