graphile-worker
Advanced tools
Job queue for PostgreSQL running on Node.js - allows you to run jobs (e.g. sending emails, performing calculations, generating PDFs, etc) "in the background" so that your HTTP response/application code is not held up. Can be used with any PostgreSQL-backed application. Pairs beautifully with PostGraphile.
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In your existing Node.js project:
yarn add graphile-worker
# or: npm install --save graphile-worker
Create a tasks/ folder, and place in it JS files containing your task specs.
The names of these files will be the task identifiers, e.g. hello below:
// tasks/hello.js
module.exports = async ({ name }) => {
console.log(`Hello, ${name}`);
};
(Make sure you're in the folder that contains the tasks/ folder.)
npx graphile-worker -c "my_db"
# or, if you have a remote database, something like:
# npx graphile-worker -c "postgres://user:pass@host:port/db?ssl=1"
# or, if you prefer envvars
# DATABASE_URL="..." npx graphile-worker
(Note: npx runs the local copy of an npm module if it is installed, when
you're ready, switch to using the package.json "scripts" entry instead.)
Connect to your database and run the following SQL:
SELECT graphile_worker.add_job('hello', json_build_object('name', 'Bobby Tables'));
You should see the worker output Hello, Bobby Tables. Gosh, that was fast!
Instead of running graphile-worker via the CLI, you may use it directly in your Node.js code:
const { run } = require("graphile-worker");
async function main() {
const runner = await run({
connectionString: "postgres:///",
concurrency: 5,
pollInterval: 1000,
// you can set the taskList or taskDirectory but not both
taskList: {
testTask: async (payload, helpers) => {
console.log("working on task...");
},
},
// or:
// taskDirectory: `${__dirname}/tasks`,
});
}
main().catch(err => {
console.error(err);
process.exit(1);
});
You can then add jobs with the addJob method:
await runner.addJob("testTask", {
thisIsThePayload: true,
});
And stop the job runner with runner.stop().
Please support development of this project via sponsorship. With your support we can improve performance, usability and documentation at a greater rate, leading to reduced running and engineering costs for your organisation, leading to a net ROI.
Support contracts are also available; for more information see: https://www.graphile.org/support/
runTaskListOnce util)LISTEN/NOTIFY to be informed of jobs as they're inserted)SKIP LOCKED to find jobs to execute, resulting in faster fetches)Solid test suite testing internals, but external interfaces need tests to prevent regressions (get in touch if you'd like to help with this!). This specific codebase is young, but it's based on years of implementing similar job queues for Postgres. To give feedback please raise an issue or reach out on discord: http://discord.gg/graphile
PostgreSQL 10+* and Node 10+*.
If your database doesn't already include the pgcrypto and uuid-ossp
extensions we'll automatically install them into the public schema for you. If
you have them installed in a different schema (unlikely) you may face issues.
Making alias functions in the public schema, should solve this issue.
* Might work with older versions, but has not been tested.
yarn add graphile-worker
# or: npm install --save graphile-worker
graphile-worker manages it's own database schema (graphile_worker). Just
point graphile-worker at your database and we handle our own migrations:
npx graphile-worker -c "postgres://localhost/mydb"
(npx looks for the graphile-worker binary locally; it's often better to
use the "scripts" entry in package.json instead.)
The following CLI options are available:
Options:
--help Show help [boolean]
--version Show version number [boolean]
--connection, -c Database connection string, defaults to the 'DATABASE_URL'
envvar [string]
--once, -1 Run until there are no runnable jobs left, then exit
[boolean] [default: false]
--watch, -w [EXPERIMENTAL] Watch task files for changes, automatically
reloading the task code without restarting worker
[boolean] [default: false]
--jobs, -j number of jobs to run concurrently [default: 1]
--poll-interval how long to wait between polling for jobs in milliseconds
(for jobs scheduled in the future/retries)
[number] [default: 2000]
graphile-worker can be used as a library inside your Node.js application. It exposes the run(options) and runOnce(options) functions.
run(options) will run until either stopped by a signal event like SIGINT or by calling the stop() function on the object returned by run().
runOnce(options) is the equivalent of running the cli with the --once option. The function will run until there are no runnable jobs left.
The following options for both methods are available.
concurrency: The equivalent of the cli --jobs option with the same default value.pollInterval: The equivalent of the cli --poll-interval option with the same default value.connectionString: A PostgreSQL connection string to the database containing the job queue, orpgPool: A pg.Pool instance to usetaskDirectory: A path string to a directory containing the task handlers.taskList: An object with the task names as keys and a corresponding task handler functions as valuesExactly one of either taskDirectory or taskList must be provided. The same applies to connectionString and pgPool.
Example
const { Pool } = require("pg");
const { run } = require("graphile-worker");
const pgPool = new Pool({
connectionString: "postgres://postgres:postgres@localhost:5432/postgres",
});
async function main() {
const runner = await run({
pgPool,
// or: connectionString: process.env.DATABASE_URL,
concurrency: 1,
pollInterval: 2000,
taskList: {
testTask: async (payload, { debug }) => {
debug(`Received ${JSON.stringify(payload)}`);
},
},
// or: taskDirectory: `${__dirname}/tasks`,
});
// to clean up: runner.stop()
}
main().catch(err => {
console.error(err);
process.exit(1);
});
A task executor is a simple async JS function which receives as input the job payload and a collection of helpers. It does the work and then returns. If it returns then the job is deemed a success and is deleted from the queue. If it throws an error then the job is deemed a failure and the task is rescheduled using an exponential-backoff algorithm.
IMPORTANT: your jobs should wait for all asynchronous work to be completed before returning, otherwise we might mistakenly think they were successful.
IMPORTANT: we automatically retry the job if it fails, so it's often sensible to split large jobs into smaller jobs, this also allows them to run in parallel resulting in faster execution. This is particularly important for tasks that are not idempotent (i.e. running them a second time will have extra side effects) - for example sending emails.
Tasks are created in the tasks folder in the directory from which you run
graphile-worker; the name of the file (less the .js suffix) is used as
the task identifier. Currently only .js files that can be directly loaded
by Node.js are supported; if you are using Babel, TypeScript or similar you
will need to compile your tasks into the tasks folder.
current directory
├── package.json
├── node_modules
└── tasks
├── task_1.js
└── task_2.js
// tasks/task_1.js
module.exports = async payload => {
await doMyLogicWith(payload);
};
// tasks/task_2.js
module.exports = async (payload, { debug }) => {
// async is optional, but best practice
debug(`Received ${JSON.stringify(payload)}`);
};
Each task function is passed two arguments:
payload - the payload you passed when calling add_jobhelpers - an object containing:
debug - a helpful debug instance scoped to the name of the task (use the DEBUG envvar to expose)job - the whole job (including uuid, attempts, etc) - you shouldn't need thiswithPgClient - a helper to use to get a database clientaddJob - a helper to schedule a jobwithPgClient(callback)withPgClient gets a pgClient from the pool, calls await callback(pgClient), and finally releases the client and returns the result of
callback. This workflow makes testing your tasks easier.
Example:
const {
rows: [row],
} = await withPgClient(pgClient => pgClient.query("select 1 as one"));
addJob(identifier, payload?, options?)Schedules a job; arguments:
identifier: the name of the task to be executedpayload: an optional JSON-compatible object to give the task more context on what it is doingoptions: an optional object specifying:
queueName: the queue to run this task underrunAt: a Date to schedule this task to run in the futuremaxAttempts: how many retries should this task get? (Default: 25)Example:
await addJob("task_2", { foo: "bar" });
You can schedule jobs directly in the database, e.g. from a trigger or
function, or by calling SQL from your application code. You do this using the
graphile_worker.add_job function. (We'll add a JS helper for this soon...)
add_job accepts the following parameters (in this order):
identifier - the only required field, indicates the name of the task executor to run (omit the .js suffix!)payload - a JSON object with information to tell the task executor what to do (defaults to an empty object)queue_name - if you want certain tasks to run one at a time, add them to the same named queue (defaults to a random value)run_at - a timestamp after which to run the job; defaults to now.max_attempts - if this task fails, how many times should we retry it? Default: 25.Typically you'll want to set the identifier and payload:
SELECT graphile_worker.add_job(
'send_email',
json_build_object(
'to', 'someone@example.com',
'subject', 'graphile-worker test'
)
);
You can skip parameters you don't need by using PostgreSQL's named parameter support:
SELECT graphile_worker.add_job('reminder', run_at := NOW() + INTERVAL '2 days');
This snippet creates a trigger function which adds a job to execute
task_identifier_here when a new row is inserted into my_table.
CREATE FUNCTION my_table_created() RETURNS trigger AS $$
BEGIN
PERFORM graphile_worker.add_job('task_identifier_here', json_build_object('id', NEW.id));
RETURN NEW;
END;
$$ LANGUAGE plpgsql VOLATILE;
CREATE TRIGGER trigger_name AFTER INSERT ON my_table FOR EACH ROW EXECUTE PROCEDURE my_table_created();
If your tables are all defined with a single primary key named id then you
can define a more convenient dynamic trigger function which can be called from
multiple triggers for multiple tables to quickly schedule jobs.
CREATE FUNCTION trigger_job() RETURNS trigger AS $$
BEGIN
PERFORM graphile_worker.add_job(TG_ARGV[0], json_build_object(
'schema', TG_TABLE_SCHEMA,
'table', TG_TABLE_NAME,
'op', TG_OP,
'id', (CASE WHEN TG_OP = 'DELETE' THEN OLD.id ELSE NEW.id END)
));
RETURN NEW;
END;
$$ LANGUAGE plpgsql VOLATILE;
You might use this trigger like this:
CREATE TRIGGER send_verification_email
AFTER INSERT ON user_emails
FOR EACH ROW
WHEN (NEW.verified is false)
EXECUTE PROCEDURE trigger_job('send_verification_email');
CREATE TRIGGER user_changed
AFTER INSERT OR UPDATE OR DELETE ON users
FOR EACH ROW
EXECUTE PROCEDURE trigger_job('user_changed');
CREATE TRIGGER generate_pdf
AFTER INSERT ON pdfs
FOR EACH ROW
EXECUTE PROCEDURE trigger_job('generate_pdf');
CREATE TRIGGER generate_pdf_update
AFTER UPDATE ON pdfs
FOR EACH ROW
WHEN (NEW.title IS DISTINCT FROM OLD.title)
EXECUTE PROCEDURE trigger_job('generate_pdf');
To delete the worker code and all the tasks from your database, just run this one SQL statement:
DROP SCHEMA graphile_worker CASCADE;
graphile-worker is not intended to replace extremely high performance
dedicated job queues, it's intended to be a very easy way to get a job queue
up and running with Node.js and PostgreSQL. But this doesn't mean it's a
slouch by any means - it achieves an average latency from triggering a job in
one process to executing it in another of just 2ms, and each worker can
handle up to 731 jobs per second on modest hardware (2011 iMac).
graphile-worker is horizontally scalable. Each instance has a customisable
worker pool, this pool defaults to size 1 (only one job at a time on this
worker) but depending on the nature of your tasks (i.e. assuming they're not
compute-heavy) you will likely want to set this higher to benefit from
Node.js' concurrency. If your tasks are compute heavy you may still wish to
set it higher and then using Node's child_process (or Node v11's
worker_threads) to share the compute load over multiple cores without
significantly impacting the main worker's runloop.
To test performance you can run yarn perfTest. This reveals that on a 2011
iMac running both the worker and the database (and a bunch of other stuff)
starting the command, checking for jobs, and exiting takes about 0.40s and
running 20,000 trivial queued jobs across a
single worker pool of size 1 takes 27.35s (~731 jobs per second). Latencies
are also measured, from before the call to queue the job is fired until when
the job is actually executed. These latencies ranged from 1.39ms to 19.66ms
with an average of 1.90ms.
We currently use the formula exp(least(10, attempt)) to determine the
delays between attempts (the job must fail before the next attempt is
scheduled, so the total time elapsed may be greater depending on how long the
job runs for before it fails). This seems to handle temporary issues well,
after ~4 hours attempts will be made every ~6 hours until the maximum number
of attempts is achieved. The specific delays can be seen below:
select
attempt,
exp(least(10, attempt)) * interval '1 second' as delay,
sum(exp(least(10, attempt)) * interval '1 second') over (order by attempt asc) total_delay
from generate_series(1, 24) as attempt;
attempt | delay | total_delay
---------+-----------------+-----------------
1 | 00:00:02.718282 | 00:00:02.718282
2 | 00:00:07.389056 | 00:00:10.107338
3 | 00:00:20.085537 | 00:00:30.192875
4 | 00:00:54.598150 | 00:01:24.791025
5 | 00:02:28.413159 | 00:03:53.204184
6 | 00:06:43.428793 | 00:10:36.632977
7 | 00:18:16.633158 | 00:28:53.266135
8 | 00:49:40.957987 | 01:18:34.224122
9 | 02:15:03.083928 | 03:33:37.308050
10 | 06:07:06.465795 | 09:40:43.773845
11 | 06:07:06.465795 | 15:47:50.239640
12 | 06:07:06.465795 | 21:54:56.705435
13 | 06:07:06.465795 | 28:02:03.171230
14 | 06:07:06.465795 | 34:09:09.637025
15 | 06:07:06.465795 | 40:16:16.102820
16 | 06:07:06.465795 | 46:23:22.568615
17 | 06:07:06.465795 | 52:30:29.034410
18 | 06:07:06.465795 | 58:37:35.500205
19 | 06:07:06.465795 | 64:44:41.966000
20 | 06:07:06.465795 | 70:51:48.431795
21 | 06:07:06.465795 | 76:58:54.897590
22 | 06:07:06.465795 | 83:06:01.363385
23 | 06:07:06.465795 | 89:13:07.829180
24 | 06:07:06.465795 | 95:20:14.294975
yarn
yarn watch
In another terminal:
createdb graphile_worker_test
yarn test
FAQs
Job queue for PostgreSQL
The npm package graphile-worker receives a total of 33,447 weekly downloads. As such, graphile-worker popularity was classified as popular.
We found that graphile-worker demonstrated a healthy version release cadence and project activity because the last version was released less than a year ago. It has 1 open source maintainer collaborating on the project.
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