Counter

A thread-safe counter for tracking numeric values — message counts, totals, or any incrementing/decrementing metric. Obtained through metrics.getCounter().

Counters support method chaining for fluent updates.

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At a Glance

// Get or create a counter
const processed = metrics.getCounter('orders.processed');
const failed = metrics.getCounter('orders.failed');

// Increment
processed.increment();
processed.increment(5);

// Decrement
failed.decrement();

// Read value
stream.logInfo(`Processed: ${processed.count}`);

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Properties

Property	Type	Description
count	number	Current counter value

const counter = metrics.getCounter('my.counter');
stream.logInfo(counter.count);  // 0 (initially)

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Methods

increment(value?)

Increases the counter by 1 or the specified amount.

Parameter	Type	Description
value	number (optional)	Amount to add — defaults to 1

Returns: Counter (supports chaining)

const c = metrics.getCounter('events');

c.increment();       // +1
c.increment(5);      // +5
c.increment(2).increment(3);  // chained: +5 total

decrement(value?)

Decreases the counter by 1 or the specified amount.

Parameter	Type	Description
value	number (optional)	Amount to subtract — defaults to 1

Returns: Counter (supports chaining)

const c = metrics.getCounter('pending');

c.decrement();       // -1
c.decrement(3);      // -3
c.decrement(2).decrement(1);  // chained: -3 total

getCount()

Returns the current count. Same as reading count.

Returns: number

const total = counter.getCount();

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Complete Example

let OUTPUT_PORT;
let ERROR_PORT;

export function onInit() {
    OUTPUT_PORT = processor.getOutputPort('Output');
    ERROR_PORT  = processor.getOutputPort('Error');
}

export function onMessage() {
    const processed = metrics.getCounter('stream.records.processed');
    const errors    = metrics.getCounter('stream.records.errors');

    try {
        validateRecord(message);
        processed.increment();
        stream.emit(message, OUTPUT_PORT);
    } catch (err) {
        errors.increment();
        message.addStatus(Severity.ERROR, Status.create(VENDOR, 'VALIDATION_FAILED'));
        stream.emit(message, ERROR_PORT);
    }
}

export function onStreamEnd() {
    const processed = metrics.getCounter('stream.records.processed');
    const errors    = metrics.getCounter('stream.records.errors');

    stream.logInfo(`Stream complete: ${processed.count} processed, ${errors.count} errors`);
}

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See Also

• Metrics — Create and manage counters