IPLAYER-45548: Replace cache key package version with schema version (#…

…42)

README.md

@@ -116,6 +116,12 @@ Both `maxage` and `staleIfError` accept an options object.
 |`connectionCircuitBreakerOptions`|object|maxAge,staleIfError| When present an instance of [Levee](https://github.com/krakenjs/levee) will be created with these configuration options to use on connection to cache.|
 |`includeCacheStatusInCtx`|boolean|maxAge,staleIfError| When present, a `cacheStatus` array - recording all cache events, will be set in `context` for use by other plugins. `includeCacheStatusInCtx` is `false` by default.|
 
+## Cache version
+
+The cache verison is stored in the `config.json`, this is distinct from the library version in the `package.json`. The cache version is used in the cache key and is intended to reduce cache fragmentation in a scenario where multiple different versions of this library might be in use across a single estate.
+
+The cache version **must** be incremented if a change is made to the data stored in the cache that would be incompatible with the existing version. Otherwise it should not be changed.
+
 ## Cache Key Structure
 
 The cache uses `catbox` to provide a simple pluggable interface, this supports segmenting the cache as well as IDs, thus the following segments are used:

config.json

@@ -0,0 +1,5 @@
+{
+  "cache": {
+    "version": "4.3.1"
+  }
+}

lib/cache.js

@@ -3,11 +3,12 @@
 const _ = require('lodash');
 const bluebird = require('bluebird');
 const events = require('./events');
-const VERSION = require('../package').version;
+const VERSION = require('../config').cache.version;
 
 const TimeoutError = bluebird.TimeoutError;
 
 function createCacheKey(segment, ctx, opts) {
+  /** The `VERSION` should be manually incremented in the config if there are changes to the data */
   const versionedSegment = `http-transport:${VERSION}:${segment}`;
   const requiredIdPart = `${ctx.req.getMethod()}:${ctx.req.getUrl()}`;
   const varyOn = _.get(opts, 'varyOn');

test/cache.js

@@ -11,7 +11,7 @@ const { events } = require('../');
 
 const sandbox = sinon.createSandbox();
 const SEGMENT = 'body';
-const VERSION = require('../package').version;
+const VERSION = require('../config').cache.version;
 const bodySegment = {
   segment: `http-transport:${VERSION}:body`,
   id: 'GET:http://www.example.com/'

test/index.js

@@ -7,7 +7,7 @@ const Catbox = require('@hapi/catbox');
 const Memory = require('@hapi/catbox-memory').Engine;
 const bluebird = require('bluebird');
 
-const VERSION = require('../package').version;
+const VERSION = require('../config').cache.version;
 const httpTransportCache = require('../');
 
 const bodySegment = {

test/maxAge.js

@@ -14,7 +14,7 @@ const { events } = cache;
 
 const api = nock('http://www.example.com');
 
-const VERSION = require('../package').version;
+const VERSION = require('../config').cache.version;
 
 const defaultHeaders = {
   'cache-control': 'max-age=60'

test/staleIfError.js

@@ -14,7 +14,7 @@ const toError = require('@bbc/http-transport-to-error');
 const cache = require('../');
 const events = require('../').events;
 
-const VERSION = require('../package').version;
+const VERSION = require('../config').cache.version;
 const api = nock('http://www.example.com');
 
 const sandbox = sinon.createSandbox();