Optimise Ajv cache usage (#1062)

* Add cache usage

* fix tests

* change comment

* Update src/middlewares/openapi.request.validator.ts

Co-authored-by: Roberto Bruggemann <[email protected]>

---------

Co-authored-by: Roberto Bruggemann <[email protected]>

Author: 0bex0

src/middlewares/openapi.request.validator.ts

@@ -21,6 +21,7 @@ import {
   ContentType,
   ajvErrorsToValidatorError,
   augmentAjvErrors,
+  useAjvCache,
 } from './util';
 
 type OperationObject = OpenAPIV3.OperationObject;
@@ -29,7 +30,6 @@ type ReferenceObject = OpenAPIV3.ReferenceObject;
 type SecurityRequirementObject = OpenAPIV3.SecurityRequirementObject;
 type SecuritySchemeObject = OpenAPIV3.SecuritySchemeObject;
 type ApiKeySecurityScheme = OpenAPIV3.ApiKeySecurityScheme;
-
 export class RequestValidator {
   private middlewareCache: { [key: string]: RequestHandler } = {};
   private apiDoc: OpenAPIV3.DocumentV3 | OpenAPIV3.DocumentV3_1;
@@ -80,7 +80,7 @@ export class RequestValidator {
     const key = `${req.method}-${path}-${contentTypeKey}`;
 
     if (!this.middlewareCache[key]) {
-      const middleware = this.buildMiddleware(path, reqSchema, contentType);
+      const middleware = this.buildMiddleware(path, reqSchema, contentType, key);
       this.middlewareCache[key] = middleware;
     }
     return this.middlewareCache[key](req, res, next);
@@ -104,6 +104,7 @@ export class RequestValidator {
     path: string,
     reqSchema: OperationObject,
     contentType: ContentType,
+    ajvCacheKey: string
   ): RequestHandler {
     const apiDoc = this.apiDoc;
     const schemaParser = new ParametersSchemaParser(this.ajv, apiDoc);
@@ -113,7 +114,7 @@ export class RequestValidator {
     const validator = new Validator(this.apiDoc, parameters, body, {
       general: this.ajv,
       body: this.ajvBody,
-    });
+    }, ajvCacheKey);
 
     const allowUnknownQueryParameters = !!(
       reqSchema['x-eov-allow-unknown-query-parameters'] ??
@@ -330,6 +331,7 @@ class Validator {
       general: Ajv;
       body: Ajv;
     },
+    ajvCacheKey: string
   ) {
     this.apiDoc = apiDoc;
     this.schemaGeneral = this._schemaGeneral(parametersSchema);
@@ -338,8 +340,8 @@ class Validator {
       ...(<any>this.schemaGeneral).properties, // query, header, params props
       body: (<any>this.schemaBody).properties.body, // body props
     };
-    this.validatorGeneral = ajv.general.compile(this.schemaGeneral);
-    this.validatorBody = ajv.body.compile(this.schemaBody);
+    this.validatorGeneral = useAjvCache(ajv.general, this.schemaGeneral, ajvCacheKey);
+    this.validatorBody = useAjvCache(ajv.body, this.schemaBody, ajvCacheKey);
   }
 
   private _schemaGeneral(parameters: ParametersSchema): object {

src/middlewares/openapi.response.validator.ts

@@ -6,7 +6,7 @@ import {
   augmentAjvErrors,
   ContentType,
   ajvErrorsToValidatorError,
-  findResponseContent,
+  findResponseContent, useAjvCache,
 } from './util';
 import {
   OpenAPIV3,
@@ -109,7 +109,7 @@ export class ResponseValidator {
 
     let validators = this.validatorsCache[key];
     if (!validators) {
-      validators = this.buildValidators(responses);
+      validators = this.buildValidators(responses, key);
       this.validatorsCache[key] = validators;
     }
     return validators;
@@ -212,7 +212,7 @@ export class ResponseValidator {
    * @param responses
    * @returns a map of validators
    */
-  private buildValidators(responses: OpenAPIV3.ResponsesObject): {
+  private buildValidators(responses: OpenAPIV3.ResponsesObject, ajvCacheKey: string): {
     [key: string]: ValidateFunction;
   } {
     const validationTypes = (response) => {
@@ -295,9 +295,10 @@ export class ResponseValidator {
         const schema = contentTypeSchemas[contentType];
         schema.paths = this.spec.paths; // add paths for resolution with multi-file
         schema.components = this.spec.components; // add components for resolution w/ multi-file
+        const validator = useAjvCache(this.ajvBody, <object>schema, `${ajvCacheKey}-${code}-${contentType}`)
         validators[code] = {
           ...validators[code],
-          [contentType]: this.ajvBody.compile(<object>schema),
+          [contentType]: validator,
         };
       }
     }

src/middlewares/util.ts

@@ -1,6 +1,6 @@
 import type { ErrorObject } from 'ajv-draft-04';
 import { Request } from 'express';
-import { ValidationError } from '../framework/types';
+import { AjvInstance, ValidationError } from '../framework/types';
 
 export class ContentType {
   public readonly mediaType: string = null;
@@ -174,3 +174,20 @@ export const zipObject = (keys, values) =>
     return acc
   }, {})
 
+/**
+ * Tries to fetch a schema from ajv instance by the provided key otherwise adds (and
+ * compiles) the schema under provided key. We provide a key to avoid ajv library
+ * using the whole schema as a cache key, leading to a lot of unnecessary memory
+ * usage - this is not recommended by the library either:
+ * https://ajv.js.org/guide/managing-schemas.html#cache-key-schema-vs-key-vs-id
+ *
+ * @param ajvCacheKey - Key which will be used for ajv cache
+ */
+export function useAjvCache(ajv: AjvInstance, schema: object, ajvCacheKey: string) {
+  let validator = ajv.getSchema(ajvCacheKey);
+  if (!validator) {
+    ajv.addSchema(schema, ajvCacheKey);
+    validator = ajv.getSchema(ajvCacheKey);
+  }
+  return validator
+}