gatewayd-plugin-cache

The gatewayd-plugin-cache is a GatewayD plugin for caching query results in Redis and this is how it works:

  1. The plugin listens for incoming queries from the client(s).
  2. When a new client connects to GatewayD, the plugin detects the client’s selected database from the client’s startup message. The client’s database is cached in Redis.
  3. If the query is a SELECT query, the plugin checks whether the query results are cached in Redis or not. If they are, the plugin returns the cached results to the client. Otherwise, the plugin executes the query and caches the results in Redis.
  4. Any query that updates the cached data triggers the plugin to invalidate the cached data in Redis.
  5. Expiry time can be set on cached data to prevent stale data from being returned to the client.
  6. If a client is abruptly disconnected, stale keys might be left behind in Redis. A periodic cache invalidator runs every minute (configurable) to invalidate those stale keys.

Features

  • Basic caching of database responses to client queries
  • Invalidate cached responses by parsing incoming queries (table-based):
    • DML: INSERT, UPDATE and DELETE
    • Multi-statements: UNION, INTERSECT and EXCEPT
    • DDL: TRUNCATE, DROP and ALTER
    • WITH clause
    • Multiple queries (delimited by semicolon)
  • Periodic cache invalidation for invalidating stale client keys
  • Support for setting expiry time on cached data
  • Support for caching responses from multiple databases on multiple servers
  • Detect client’s chosen database from the client’s startup message
  • Prometheus metrics for quantifying cache hits, misses, gets, sets, deletes and scans
  • Prometheus metrics for counting total RPC method calls
  • Logging
  • Configurable via environment variables

Installation

It is assumed that you have already installed PostgreSQL, Redis and GatewayD.

The plugin is compatible with Linux, Windows and macOS.

Automatic installation

The latest version of the plugin can be installed automatically by running the following command. This command downloads and installs the latest version of the plugin from GitHub releases to the plugins directory in the current directory. The command will then enable the plugin automatically by copying the default configuration to gatewayd_plugins.yaml from the project’s GitHub repository.

gatewayd plugin install github.com/gatewayd-io/gatewayd-plugin-cache@latest

Manual installation

  1. Download and install the latest version of gatewayd-plugin-cache by copying the binary to a directory that is in your PATH or accessible to GatewayD.
  2. Copy the configuration to gatewayd_plugins.yaml.
  3. Make sure that the configuration parameters and environment variables are correct, particularly the localPath, checksum and the REDIS_URL.

After installing the plugin using any of the above methods, you can start GatewayD and test the plugin by querying the database via GatewayD.

Configuration

The plugin can be configured via environment variables or command-line arguments. For more information about other configuration parameters, see plugins configuration.

plugins:
  - name: gatewayd-plugin-cache
    enabled: True
    localPath: ../gatewayd-plugin-cache/gatewayd-plugin-cache
    url: github.com/gatewayd-io/gatewayd-plugin-cache@latest
    args: ["--log-level", "info"]
    env:
      - MAGIC_COOKIE_KEY=GATEWAYD_PLUGIN
      - MAGIC_COOKIE_VALUE=5712b87aa5d7e9f9e9ab643e6603181c5b796015cb1c09d6f5ada882bf2a1872
      - REDIS_URL=redis://localhost:6379/0
      - EXPIRY=1h
      # - DEFAULT_DB_NAME=postgres
      - METRICS_ENABLED=True
      - METRICS_UNIX_DOMAIN_SOCKET=/tmp/gatewayd-plugin-cache.sock
      - METRICS_PATH=/metrics
      - API_GRPC_ADDRESS=localhost:19090
      - PERIODIC_INVALIDATOR_ENABLED=True
      - PERIODIC_INVALIDATOR_INTERVAL=1m
      - PERIODIC_INVALIDATOR_START_DELAY=1m
      - EXIT_ON_STARTUP_ERROR=False
      - SENTRY_DSN=https://70eb1abcd32e41acbdfc17bc3407a543@o4504550475038720.ingest.sentry.io/4505342961123328
      - CACHE_CHANNEL_BUFFER_SIZE=100
    checksum: 3988e10aefce2cd9b30888eddd2ec93a431c9018a695aea1cea0dac46ba91cae

Environment variables

Name Description Default
MAGIC_COOKIE_KEY The key for the magic cookie. GATEWAYD_PLUGIN
MAGIC_COOKIE_VALUE The value for the magic cookie. 5712b87aa5d7e9f9e9ab643e6603181c5b796015cb1c09d6f5ada882bf2a1872
REDIS_URL The URL of the Redis server. redis://localhost:6379/0
EXPIRY The expiry time for cached data. 1h
DEFAULT_DB_NAME The default database name, in case you have a single database on your database server. postgres
METRICS_ENABLED Whether to enable metrics. True
METRICS_UNIX_DOMAIN_SOCKET The path to the Unix domain socket for exposing metrics. This must be accessible to GatewayD. /tmp/gatewayd-plugin-cache.sock
METRICS_PATH The path for exposing metrics. /metrics
API_GRPC_ADDRESS The address for the GatewayD gRPC API server. localhost:19090
PERIODIC_INVALIDATOR_ENABLED Whether to enable periodic cache invalidation. This runs every PERIODIC_INVALIDATOR_INTERVAL and removes stale client keys, not cached values. True
PERIODIC_INVALIDATOR_INTERVAL The interval for periodic cache invalidation. 1m
PERIODIC_INVALIDATOR_START_DELAY The delay before starting periodic cache invalidation. 1m
EXIT_ON_STARTUP_ERROR Whether to exit the plugin if there is an error during startup. False
SENTRY_DSN Sentry DSN. Set to empty string to disable Sentry. https://70eb1abcd32e41acbdfc17bc3407a543@o4504550475038720.ingest.sentry.io/4505342961123328
CACHE_CHANNEL_BUFFER_SIZE The buffer size for the cache channel. 100

Command-line arguments

Name Description Default
--log-level The log level. info

Build for testing

To build the plugin for development and testing, run the following command in the project’s root directory after cloning the repository.

git clone [email protected]:gatewayd-io/gatewayd-plugin-cache.git
cd gatewayd-plugin-cache
make build-dev

Running the above commands clones the repository, changes the current directory and runs the go mod tidy and go build commands to compile and generate the plugin binary.