feat(stac-db): Provide sensible defaults for pgSTAC db parameters

lib/database/index.ts

@@ -6,6 +6,8 @@ import {
 import { Construct } from "constructs";
 import { BootstrapPgStac, BootstrapPgStacProps } from "../bootstrapper";
 
+const instanceSizes: Record<string, number> = require("./instance-memory.json");
+
 /**
  * An RDS instance with pgSTAC installed. This is a wrapper around the
  * `rds.DatabaseInstance` higher-level construct making use
@@ -18,12 +20,22 @@ export class PgStacDatabase extends Construct {
   constructor(scope: Construct, id: string, props: PgStacDatabaseProps) {
     super(scope, id);
 
+    const defaultParameters = this.getParameters(
+      props.instanceType?.toString() || "m5.large",
+      props.parameters
+    );
     const parameterGroup = new rds.ParameterGroup(this, "parameterGroup", {
       engine: props.engine,
       parameters: {
-        max_locks_per_transaction: "1024",
-        work_mem: "64000",
-        temp_buffers: "32000",
+        shared_buffers: defaultParameters.sharedBuffers,
+        effective_cache_size: defaultParameters.effectiveCacheSize,
+        work_mem: defaultParameters.workMem,
+        maintenance_work_mem: defaultParameters.maintenanceWorkMem,
+        max_locks_per_transaction: defaultParameters.maxLocksPerTransaction,
+        temp_buffers: defaultParameters.tempBuffers,
+        seq_page_cost: defaultParameters.seqPageCost,
+        random_page_cost: defaultParameters.randomPageCost,
+        ...props.parameters,
       },
     });
 
@@ -45,6 +57,45 @@ export class PgStacDatabase extends Construct {
 
     this.pgstacSecret = bootstrap.secret;
   }
+
+  public getParameters(
+    instanceType: string,
+    parameters: PgStacDatabaseProps["parameters"]
+  ): DatabaseParameters {
+    // https://github.com/aws/aws-cli/issues/1279#issuecomment-909318236
+    const memory_in_kb = instanceSizes[instanceType] * 1024;
+
+    // It's only necessary to consider passed in parameters for any value that used to
+    // derive subsequent values. Values that don't have dependencies will be overriden
+    // when we unpack the passed-in user parameters
+    const maxConnections = parameters?.maxConnections
+      ? Number.parseInt(parameters.maxConnections)
+      : // https://docs.aws.amazon.com/AmazonRDS/latest/UserGuide/CHAP_Limits.html#RDS_Limits.MaxConnections
+        Math.min(Math.round((memory_in_kb * 1024) / 9531392), 5000);
+    const sharedBuffers = parameters?.sharedBufers
+      ? Number.parseInt(parameters.sharedBufers)
+      : Math.round(0.25 * memory_in_kb);
+
+    const effectiveCacheSize = Math.round(0.75 * memory_in_kb);
+    const workMem = Math.floor(sharedBuffers / maxConnections);
+    const maintenanceWorkMem = Math.round(0.25 * sharedBuffers);
+
+    const tempBuffers = 128 * 1024;
+    const seqPageCost = 1;
+    const randomPageCost = 1.1;
+
+    return {
+      maxConnections: `${maxConnections}`,
+      sharedBuffers: `${sharedBuffers}`,
+      effectiveCacheSize: `${effectiveCacheSize}`,
+      workMem: `${workMem}`,
+      maintenanceWorkMem: `${maintenanceWorkMem}`,
+      maxLocksPerTransaction: "1024",
+      tempBuffers: `${tempBuffers}`,
+      seqPageCost: `${seqPageCost}`,
+      randomPageCost: `${randomPageCost}`,
+    };
+  }
 }
 
 export interface PgStacDatabaseProps extends rds.DatabaseInstanceProps {
@@ -53,3 +104,50 @@ export interface PgStacDatabaseProps extends rds.DatabaseInstanceProps {
   readonly pgstacUsername?: BootstrapPgStacProps["pgstacUsername"];
   readonly secretsPrefix?: BootstrapPgStacProps["secretsPrefix"];
 }
+
+export interface DatabaseParameters {
+  /**
+   * @default - LEAST({DBInstanceClassMemory/9531392}, 5000)
+   */
+  readonly maxConnections: string;
+
+  /**
+   * @default - 25% of instance memory
+   */
+  readonly sharedBuffers: string;
+
+  /**
+   * @default - 75% of instance memory
+   */
+  readonly effectiveCacheSize: string;
+
+  /**
+   * @default - shared buffers divided by max connections
+   */
+  readonly workMem: string;
+
+  /**
+   * @default - 25% of shared buffers
+   */
+  readonly maintenanceWorkMem: string;
+
+  /**
+   * @default 1024
+   */
+  readonly maxLocksPerTransaction: string;
+
+  /**
+   * @default 131172 (128 * 1024)
+   */
+  readonly tempBuffers: string;
+
+  /**
+   * @default 1
+   */
+  readonly seqPageCost: string;
+
+  /**
+   * @default 1.1
+   */
+  readonly randomPageCost: string;
+}