Author: | Dag Haavi Finstad |
---|---|
Date: | 2023-10-13 |
Version: | 1.0.2 |
Manual section: | 3 |
import vsthrottle;
A Varnish vmod for rate-limiting traffic on a single Varnish server. Offers a simple interface for throttling traffic on a per-key basis to a specific request rate.
Keys can be specified from any VCL string, e.g. based on client.ip, a specific cookie value, an API token, etc.
The request rate is specified as the number of requests permitted over a period. To keep things simple, this is passed as two separate parameters, 'limit' and 'period'.
This VMOD implements a token-bucket algorithm. State associated with the token bucket for each key is stored in-memory using BSD's red-black tree implementation.
Memory usage is around 100 bytes per key tracked.
- Prototype
is_denied(STRING key, INT limit, DURATION period)
- Arguments
key: A unique identifier to define what is being throttled - more examples below
limit: How many requests in the specified period
period: The time period
- Return value
- BOOL
- Description
- Can be used to rate limit the traffic for a specific key to a maximum of 'limit' requests per 'period' time. A token bucket is uniquely identified by the triplet of its key, limit and period, so using the same key multiple places with different rules will create multiple token buckets.
- Example
sub vcl_recv { if (vsthrottle.is_denied(client.identity, 15, 10s)) { # Client has exceeded 15 reqs per 10s return (synth(429, "Too Many Requests")); } # ... }
The source tree is based on autotools to configure the building, and does also have the necessary bits in place to do functional unit tests using the varnishtest tool.
This VMOD is written for Varnish Cache 4.1.
Pre-installation configuration:
./autogen.sh ./configure
If you have installed Varnish to a non-standard directory, call
autogen.sh
and configure
with PKG_CONFIG_PATH
pointing to
the appropriate path. For example, when varnishd configure was called
with --prefix=$PREFIX
, use
PKG_CONFIG_PATH=${PREFIX}/lib/pkgconfig export PKG_CONFIG_PATH
Make and install the vmod:
make # builds the vmod make install # installs your vmod in `VMODDIR` make check # runs the unit tests in ``src/tests/*.vtc``
The libvmod-vsthrottle vmod will now be available in your VMODDIR and can be copied to other systems as required.
In your VCL you can now use this vmod along the following lines:
import vsthrottle; sub vcl_recv { if (vsthrottle.is_denied(client.identity, 15, 10s)) { # Client has exceeded 15 reqs per 10s return (synth(429, "Too Many Requests")); } }