Handler Function

Handler function is a function that will be invoked by AWS Lambda when the trigger is activated.

/**
 * The main function
 * @param {object} event Event from system
 * @returns 
 */
export const handler = async (event) => {
    // Return the output
    return { statusCode: 200, body: 'Success' };
};

Loading Global Variables

// Load environment variables
try {
    dotenv.config({ path: '/var/task/.env' });
} catch (err) {
    console.error('Error loading .env file:', err);
    return { statusCode: 500 };
}

Creating the CSV File Storage

// Setup logging before executing the rest of the code
if (!fs.existsSync(process.env.S3_CSV_FOLDER)) {
    fs.mkdirSync(process.env.S3_CSV_FOLDER, { recursive: true });
}

Checking Execution Lock

// Check execution
const executingQueryChk = `SELECT is_executing, started_at, finished_at
    FROM indices.s3_execution
    WHERE is_executing = true
    LIMIT 1`;
const resultEx = await execQuery(executingQueryChk);
if (resultEx.rows.length > 0) {
    const startedAt = convertDateStringToDate(resultEx.rows[0]['started_at']);
    const finishedAt = convertDateStringToDate(resultEx.rows[0]['finished_at'])
    const currentTime = new Date();
    // Convert ms to minutes
    const timeDifferenceInMinutes = Math.floor((currentTime - startedAt) / (1000 * 60));
    if (startedAt > finishedAt && Math.abs(timeDifferenceInMinutes) < process.env.AFTER_FAILED_IGNORING_MINUTES) {
        return processEnding(false);
    }
}

Finding Import Date

// Find importing date
const findDateQuery = `SELECT date_hns 
    FROM indices.s3_date_hns 
    WHERE is_imported = false
    ORDER BY date_hns ASC
    LIMIT 1`;
const result = await execQuery(findDateQuery);
const now = result.rows[0]['date_hns'];

Updating Execution Info

// Update execution info
const updateStartQuery = `UPDATE indices.s3_execution
    SET is_executing = true, started_at = $1, last_executed_date_hns = $2, last_error = null`;
await execQuery(updateStartQuery, [
    getTimestamp(),
    formatDateForPostgres(now),
]);

Updating Import Date Info

// Update importing date
const updateStartedAtQuery = `UPDATE indices.s3_date_hns
    SET is_imported = false, started_at = $1
    WHERE date_hns = $2`;
await execQuery(updateStartedAtQuery, [
    getTimestamp(),
    formatDateForPostgres(now),
]);