A PostgreSQL extension that enables asynchronous (non-blocking) HTTP/HTTPS requests with SQL.
Requires libcurl >= 7.83. Compatible with PostgreSQL > = 12.
Documentation: https://supabase.github.io/pg_net
- Introduction
- Technical Explanation
- Installation
- Configuration
- Requests API
- Monitoring requests
- GET requests
- POST requests
- DELETE requests
- Practical Examples
- Syncing data with an external data source using triggers
- Calling a serverless function every minute with PG_CRON
- Retrying failed requests
- Contributing
The PG_NET extension enables PostgreSQL to make asynchronous HTTP/HTTPS requests in SQL. It eliminates the need for servers to continuously poll for database changes and instead allows the database to proactively notify external resources about significant events. It seamlessly integrates with triggers, cron jobs (e.g., PG_CRON), and procedures, unlocking numerous possibilities. Notably, PG_NET powers Supabase's Webhook functionality, highlighting its robustness and reliability.
Common use cases for the PG_NET extension include:
- Calling external APIs
- Syncing data with outside resources
- Calling a serverless function when an event, such as an insert, occurred
However, it is important to note that the extension has a few limitations. Currently, it only supports three types of asynchronous requests:
- async http GET requests
- async http POST requests with a JSON payload
- async http DELETE requests
Ultimately, though, PG_NET offers developers more flexibility in how they monitor and connect their database with external resources.
The extension introduces a new net schema, which contains two unlogged tables, a type of table in PostgreSQL that offers performance improvements at the expense of durability. You can read more about unlogged tables here. The two tables are:
-
http_request_queue: This table serves as a queue for requests waiting to be executed. Upon successful execution of a request, the corresponding data is removed from the queue.The SQL statement to create this table is:
CREATE UNLOGGED TABLE net.http_request_queue ( id bigint NOT NULL DEFAULT nextval('net.http_request_queue_id_seq'::regclass), method text NOT NULL, url text NOT NULL, headers jsonb NOT NULL, body bytea NULL, timeout_milliseconds integer NOT NULL ) -
_http_response: This table holds the responses of each executed request.The SQL statement to create this table is:
CREATE UNLOGGED TABLE net._http_response ( id bigint NULL, status_code integer NULL, content_type text NULL, headers jsonb NULL, content text NULL, timed_out boolean NULL, error_msg text NULL, created timestamp with time zone NOT NULL DEFAULT now() )
When any of the three request functions (http_get, http_post, http_delete) are invoked, they create an entry in the net.http_request_queue table.
The extension employs C's libCurl library within a PostgreSQL background worker to manage HTTP requests. This background worker regularly checks the http_request_queue table and executes the requests it finds there.
Once a response is received, it gets stored in the _http_response table. By monitoring this table, you can keep track of response statuses and messages.
You can activate the pg_net extension via Supabase's dashboard by following these steps:
- Navigate to the 'Database' page.
- Select 'Extensions' from the sidebar.
- Search for "pg_net" and enable the extension.
Clone this repo and run
make && make installTo make the extension available to the database add on postgresql.conf:
shared_preload_libraries = 'pg_net'
By default, pg_net is available on the postgres database. To use pg_net on a different database, you can add the following on postgresql.conf:
pg_net.database_name = '<dbname>';
Using pg_net on multiple databases in a cluster is not supported.
To activate the extension in PostgreSQL, run the create extension command. The extension creates its own schema named net to avoid naming conflicts.
create extension pg_net;
the extension creates 3 configurable variables:
- pg_net.batch_size (default: 200): An integer that limits the max number of rows that the extension will process from
net.http_request_queueduring each read - pg_net.ttl (default: 6 hours): An interval that defines the max time a row in the
net.http_responsewill live before being deleted - pg_net.database_name (default: 'postgres'): A string that defines which database the extension is applied to
- pg_net.username (default: NULL): A string that defines which user will the background worker be connected with. If not set (
NULL), it will assume the bootstrap user.
All these variables can be viewed with the following commands:
show pg_net.batch_size;
show pg_net.ttl;
show pg_net.database_name;
show pg_net.username;You can change these by editing the postgresql.conf file (find it with SHOW config_file;) or with ALTER SYSTEM:
alter system set pg_net.ttl to '1 hour'
alter system set pg_net.batch_size to 500;
Then, reload the settings and restart the pg_net background worker with:
select net.worker_restart();
Note that doing ALTER SYSTEM requires SUPERUSER but on PostgreSQL >= 15, you can do:
grant alter system on parameter pg_net.ttl to <role>;
grant alter system on parameter pg_net.batch_size to <role>;
To allow regular users to update pg_net settings.
net.http_get(
-- url for the request
url text,
-- key/value pairs to be url encoded and appended to the `url`
params jsonb default '{}'::jsonb,
-- key/values to be included in request headers
headers jsonb default '{}'::jsonb,
-- the maximum number of milliseconds the request may take before being cancelled
timeout_milliseconds int default 1000
)
-- request_id reference
returns bigint
strict
volatile
parallel safe
language plpgsqlThe following examples use the Postman Echo API.
SELECT net.http_get (
'https://postman-echo.com/get?foo1=bar1&foo2=bar2'
) AS request_id;NOTE: You can view the response with the following query:
SELECT * FROM net._http_response;
SELECT net.http_get(
'https://postman-echo.com/get',
-- Equivalent to calling https://postman-echo.com/get?foo1=bar1&foo2=bar2&encoded=%21
-- The "!" is url-encoded as %21
'{"foo1": "bar1", "foo2": "bar2", "encoded": "!"}'::JSONB
) AS request_id;SELECT net.http_get(
'https://postman-echo.com/get?foo1=bar1&foo2=bar2',
headers := '{"API-KEY-HEADER": "<API KEY>"}'::JSONB
) AS request_id;net.http_post(
-- url for the request
url text,
-- body of the POST request
body jsonb default '{}'::jsonb,
-- key/value pairs to be url encoded and appended to the `url`
params jsonb default '{}'::jsonb,
-- key/values to be included in request headers
headers jsonb default '{"Content-Type": "application/json"}'::jsonb,
-- the maximum number of milliseconds the request may take before being cancelled
timeout_milliseconds int default 1000
)
-- request_id reference
returns bigint
volatile
parallel safe
language plpgsqlThe following examples post to the Postman Echo API.
SELECT net.http_post(
'https://postman-echo.com/post',
'{"key": "value", "key": 5}'::JSONB,
headers := '{"API-KEY-HEADER": "<API KEY>"}'::JSONB
) AS request_id;NOTE: If multiple rows are sent using this method, each row will be sent as a separate request.
WITH selected_row AS (
SELECT
*
FROM target_table
LIMIT 1
)
SELECT
net.http_post(
'https://postman-echo.com/post',
to_jsonb(selected_row.*),
headers := '{"API-KEY-HEADER": "<API KEY>"}'::JSONB
) AS request_id
FROM selected_row;WARNING: when sending multiple rows, be careful to limit your payload size.
WITH selected_rows AS (
SELECT
-- Converts all the rows into a JSONB array
jsonb_agg(to_jsonb(target_table)) AS JSON_payload
FROM target_table
-- Generally good practice to LIMIT the max amount of rows
)
SELECT
net.http_post(
'https://postman-echo.com/post'::TEXT,
JSON_payload,
headers := '{"API-KEY-HEADER": "<API KEY>"}'::JSONB
) AS request_id
FROM selected_rows;net.http_delete(
-- url for the request
url text,
-- key/value pairs to be url encoded and appended to the `url`
params jsonb default '{}'::jsonb,
-- key/values to be included in request headers
headers jsonb default '{}'::jsonb,
-- the maximum number of milliseconds the request may take before being cancelled
timeout_milliseconds int default 2000
)
-- request_id reference
returns bigint
strict
volatile
parallel safe
language plpgsql
security definerThe following examples use the Dummy Rest API.
SELECT net.http_delete(
'https://dummy.restapiexample.com/api/v1/delete/2'
) AS request_id;WITH selected_id AS (
SELECT
id
FROM target_table
LIMIT 1 -- if not limited, it will make a delete request for each returned row
)
SELECT
net.http_delete(
'https://dummy.restapiexample.com/api/v1/delete/'::TEXT,
format('{"id": "%s"}', id)::JSONB
) AS request_id
FROM selected_id;WITH selected_id AS (
SELECT
id
FROM target_table
LIMIT 1 -- if not limited, it will make a delete request for each returned row
)
SELECT
net.http_delete(
'https://dummy.restapiexample.com/api/v1/delete/' || id
) AS request_id
FROM selected_rowThe following example comes from Typesense's Supabase Sync guide
-- Create the function to delete the record from Typesense
CREATE OR REPLACE FUNCTION delete_record()
RETURNS TRIGGER
LANGUAGE plpgSQL
AS $$
BEGIN
SELECT net.http_delete(
url := format('<TYPESENSE URL>/collections/products/documents/%s', OLD.id),
headers := '{"X-Typesense-API-KEY": "<Typesense_API_KEY>"}'
)
RETURN OLD;
END $$;
-- Create the trigger that calls the function when a record is deleted from the products table
CREATE TRIGGER delete_products_trigger
AFTER DELETE ON public.products
FOR EACH ROW
EXECUTE FUNCTION delete_products();The PG_CRON extension enables PostgreSQL to become its own cron server. With it you can schedule regular calls to activate serverless functions.
Useful links:
SELECT cron.schedule(
'cron-job-name',
'* * * * *', -- Executes every minute (cron syntax)
$$
-- SQL query
SELECT net.http_get(
-- URL of Edge function
url:='https://<reference id>.functions.Supabase.co/example',
headers:='{
"Content-Type": "application/json",
"Authorization": "Bearer <TOKEN>"
}'::JSONB
) as request_id;
$$
);Every request made is logged within the net._http_response table. To identify failed requests, you can execute a query on the table, filtering for requests where the status code is 500 or higher.
SELECT
*
FROM net._http_response
WHERE status_code >= 500;While the net._http_response table logs each request, it doesn't store all the necessary information to retry failed requests. To facilitate this, we need to create a request tracking table and a wrapper function around the PG_NET request functions. This will help us store the required details for each request.
CREATE TABLE request_tracker(
method TEXT,
url TEXT,
params JSONB,
body JSONB,
headers JSONB,
request_id BIGINT
)Below is a function called request_wrapper, which wraps around the PG_NET request functions. This function records every request's details in the request_tracker table, facilitating future retries if needed.
CREATE OR REPLACE FUNCTION request_wrapper(
method TEXT,
url TEXT,
params JSONB DEFAULT '{}'::JSONB,
body JSONB DEFAULT '{}'::JSONB,
headers JSONB DEFAULT '{}'::JSONB
)
RETURNS BIGINT
AS $$
DECLARE
request_id BIGINT;
BEGIN
IF method = 'DELETE' THEN
SELECT net.http_delete(
url:=url,
params:=params,
headers:=headers
) INTO request_id;
ELSIF method = 'POST' THEN
SELECT net.http_post(
url:=url,
body:=body,
params:=params,
headers:=headers
) INTO request_id;
ELSIF method = 'GET' THEN
SELECT net.http_get(
url:=url,
params:=params,
headers:=headers
) INTO request_id;
ELSE
RAISE EXCEPTION 'Method must be DELETE, POST, or GET';
END IF;
INSERT INTO request_tracker (method, url, params, body, headers, request_id)
VALUES (method, url, params, body, headers, request_id);
RETURN request_id;
END;
$$
LANGUAGE plpgsql;To retry a failed request recorded via the wrapper function, use the following query. This will select failed requests, retry them, and then remove the original request data from both the net._http_response and request_tracker tables.
WITH retry_request AS (
SELECT
request_tracker.method,
request_tracker.url,
request_tracker.params,
request_tracker.body,
request_tracker.headers,
request_tracker.request_id
FROM request_tracker
INNER JOIN net._http_response ON net._http_response.id = request_tracker.request_id
WHERE net._http_response.status_code >= 500
LIMIT 3
),
retry AS (
SELECT
request_wrapper(retry_request.method, retry_request.url, retry_request.params, retry_request.body, retry_request.headers)
FROM retry_request
),
delete_http_response AS (
DELETE FROM net._http_response
WHERE id IN (SELECT request_id FROM retry_request)
RETURNING *
)
DELETE FROM request_tracker
WHERE request_id IN (SELECT request_id FROM retry_request)
RETURNING *;The above function can be called using cron jobs or manually to retry failed requests. It may also be beneficial to clean the request_tracker table in the process.
Checkout the Contributing page to learn more about adding to the project.