fix(stac-validate): cache json schema objects to reduce network failu…

…res TDE-1212 (#1029)

#### Motivation

_What does this change aim to achieve?_

We are seeing quite a few network related failures when validating JSON
schema objects

#### Modification

Cache JSON schema objects locally when the docker container is built

_Why is this change being made? What implications or other
considerations are there?_

#### Checklist

_If not applicable, provide explanation of why._

- [ ] Tests updated
- [ ] Docs updated
- [ ] Issue linked in Title

.gitignore

@@ -1,2 +1,3 @@
 node_modules
-build
+build
+json-schema-cache

Dockerfile

@@ -18,4 +18,7 @@ ADD package.json package-lock.json /app/
 RUN npm install --omit=dev
 ADD build/src /app/
 
+# Cache of copy of the STAC JSON schemas by triggering a validation run
+RUN node /app/index.js stac-validate https://nz-imagery.s3-ap-southeast-2.amazonaws.com/new-zealand/new-zealand_2020-2021_10m/rgb/2193/collection.json
+
 ENTRYPOINT ["node", "/app/index.js"]

src/commands/stac-validate/stac.validate.ts

@@ -2,6 +2,7 @@ import { fsa } from '@chunkd/fs';
 import Ajv, { DefinedError, SchemaObject, ValidateFunction } from 'ajv';
 import { fastFormats } from 'ajv-formats/dist/formats.js';
 import { boolean, command, flag, number, option, restPositionals, string } from 'cmd-ts';
+import { createHash } from 'crypto';
 import { dirname, join } from 'path';
 import { performance } from 'perf_hooks';
 import * as st from 'stac-ts';
@@ -13,6 +14,27 @@ import { hashStream } from '../../utils/hash.js';
 import { Sha256Prefix } from '../../utils/hash.js';
 import { config, registerCli, verbose } from '../common.js';
 
+/**
+ * Store a local copy of JSON schemas into a cache directory
+ *
+ * This is to prevent overloading the remote hosts as stac validation can trigger lots of schema requests
+ *
+ * @param url JSON schema to load
+ * @returns object from the cache if it exists or directly from the uri
+ */
+async function readSchema(url: string): Promise<object> {
+  const cacheId = createHash('sha256').update(url).digest('hex');
+  const cachePath = `./json-schema-cache/${cacheId}.json`;
+  try {
+    return await fsa.readJson<object>(cachePath);
+  } catch (e) {
+    return fsa.readJson<object>(url).then(async (obj) => {
+      await fsa.write(cachePath, JSON.stringify(obj));
+      return obj;
+    });
+  }
+}
+
 export const commandStacValidate = command({
   name: 'stac-validate',
   description: 'Validate STAC files',
@@ -78,8 +100,9 @@ export const commandStacValidate = command({
       strict: args.strict,
       loadSchema: (uri: string): Promise<SchemaObject> => {
         let existing = Schemas.get(uri);
+
         if (existing == null) {
-          existing = fsa.readJson(uri);
+          existing = readSchema(uri);
           Schemas.set(uri, existing);
         }
         return existing;
@@ -99,7 +122,7 @@ export const commandStacValidate = command({
       if (schema != null) return schema;
       let existing = ajvSchema.get(uri);
       if (existing == null) {
-        existing = fsa.readJson<object>(uri).then((json) => ajv.compileAsync(json));
+        existing = readSchema(uri).then((json) => ajv.compileAsync(json));
         ajvSchema.set(uri, existing);
       }
       return existing;