Tags

Everything in the library is exposed via a flexible system of events, each providing complete context. Tags extend such context for tasks and transactions, so they can be easily tracked and logged with complete details. Module pg-monitor makes the best use of tags and other details reported by pg-promise events.

A tag can be set either explicitly, as an option for the corresponding method, or implicitly, with a named callback function. The explicit declaration has the priority and overrides the implicit one.

Explicit direct tagging

An explicit tag can be passed in directly, when it is a simple string or number:

db.task('my-task', t => {

});

db.tx('my-transaction', t => {

});

db.txIf('my-task-or-transaction', t => {

});

Explicit property tagging

The tag can be set explicitly as an option for the method:

db.task({tag: 'my-task'}, t => {

});

db.tx({tag: 'my-transaction'}, t => {

});

db.txIf({tag: 'my-task-or-transaction'}, t => {

});

Implicit tagging

Name of the callback function implicitly sets the tag name:

db.task(function myTask(t) {

});

db.tx(function myTransaction(t) {

});

db.txIf(function myTaskOrTransaction(t) {

});

When handling events task, transact, query and receive you are given the complete context, including the tag, to allow detailed, context-linked logging.

Example

// Initialization Options;
const options = {
    query(e) {
        if (e.ctx) {
            // e.ctx.tag - is the tag set;
            // the query is part of a task or transaction;
            if (e.ctx.isTX) {
                // log the transaction details;
            } else {
                // log the task details;
            }
        }
        console.log('QUERY:', e.query);
    },
    task(e) {
        if (e.ctx.finish) {
            console.log('Task/Finish:', e.ctx.tag);
        } else {
            console.log('Task/Start:', e.ctx.tag);
        }
    },
    transact(e) {
        if (e.ctx.finish) {
            console.log('TX/Finish:', e.ctx.tag);
        } else {
            console.log('TX/Start:', e.ctx.tag);
        }
    }
};

In most cases for your tag you would use a text string for logging, but the tag can be of any type, the library doesn't care what the tag really is.

And if you want to use a custom tag object, while allowing pg-monitor to log it as a text string, add toString function to the object to return the tag's name for logging.

Handling and formatting all query-related events can be a daunting task, and therefore it is recommended that you use pg-monitor for that.