Cache S3_VERSION_ID_ENCODING_TYPE env variable

Reading env variables is costly, so do it only once on startup.

Issue: ARSN-442

lib/versioning/VersionID.ts

@@ -21,6 +21,8 @@ const TEMPLATE_TS = new Array(LENGTH_TS + 1).join('0');
 const TEMPLATE_SEQ = new Array(LENGTH_SEQ + 1).join('0');
 const TEMPLATE_RG = new Array(LENGTH_RG + 1).join(' ');
 
+export let S3_VERSION_ID_ENCODING_TYPE = process.env.S3_VERSION_ID_ENCODING_TYPE;
+
 /**
  * Left-pad a string representation of a value with a given template.
  * For example: pad('foo', '00000') gives '00foo'.
@@ -121,7 +123,7 @@ export function generateVersionId(info: string, replicationGroupId: string): str
     lastTimestamp = ts;
 
     // if S3_VERSION_ID_ENCODING_TYPE is "hex", info is used.
-    if (process.env.S3_VERSION_ID_ENCODING_TYPE === 'hex' || !process.env.S3_VERSION_ID_ENCODING_TYPE) {
+    if (S3_VERSION_ID_HEX_ENCODING === 'hex' || !S3_VERSION_ID_ENCODING_TYPE) {
         // info field stays as is
     } else {
         info = ''; // eslint-disable-line

tests/unit/versioning/VersionID.spec.js

@@ -1,6 +1,5 @@
 const VID = require('../../../lib/versioning/VersionID');
 const assert = require('assert');
-const { env } = require('process');
 
 function randkey(length) {
     let key = '';
@@ -34,7 +33,7 @@ describe('test generating versionIds', () => {
         });
     });
     describe('legaxy hex encoding', () => {
-        env.S3_VERSION_ID_ENCODING_TYPE = 'hex';
+        VID.S3_VERSION_ID_ENCODING_TYPE = 'hex';
         const vids = generateRandomVIDs(count);
 
         it('sorted in reversed chronological and alphabetical order', () => {
@@ -69,7 +68,7 @@ describe('test generating versionIds', () => {
 
 
     describe('Short IDs', () => {
-        env.S3_VERSION_ID_ENCODING_TYPE = 'base62';
+        VID.S3_VERSION_ID_ENCODING_TYPE = 'base62';
         const vids = generateRandomVIDs(count);
 
         it('sorted in reversed chronological and alphabetical order', () => {