Retry http 502, 503, 504 status codes (#39)

* Retry http 502, 503, 504 status codes

* Implement requested changes

* Fix types, +1's and add unit test (commented)

* Fix nit missing semi colon

* Add unit tests for retries

* Up version to 0.10.2

* Enable unit tests

Author: janpieterz

make.js

@@ -162,8 +162,7 @@ target.units = function () {
 target.test = function () {
     target.build();
 
-    console.log("-------Unit Tests-------");
-    run('tsc -p ./test/units --outDir ' + unitPath, true);
+    target.units();
 
     console.log("-------Other Tests-------");
     run('tsc -p ./test/tests --outDir ' + testPath, true);

package-lock.json

@@ -1,6 +1,6 @@
 {
   "name": "azure-pipelines-tool-lib",
-  "version": "0.10.1",
+  "version": "0.10.2",
   "description": "Azure Pipelines Tool Installer Lib for CI/CD Tasks",
   "main": "tool.js",
   "scripts": {

package.json

@@ -428,4 +428,48 @@ describe('Tool Tests', function () {
             }
         });
     });
+
+    it("works with a 502 temporary failure", async function() {
+        this.timeout(5000);
+        nock('http://microsoft.com')
+            .get('/temp502')
+            .twice()
+            .reply(502, undefined);
+        nock('http://microsoft.com')
+            .get('/temp502')
+            .reply(200, undefined);
+
+        return new Promise<void>(async (resolve, reject) => {
+            try {
+                let statusCodeUrl: string = "http://microsoft.com/temp502";
+                let downPath: string = await toolLib.downloadTool(statusCodeUrl);
+
+                resolve();
+            } catch (err) {
+                reject(err);
+            }
+        });
+    });
+
+    it("doesn't retry 502s more than 3 times", async function() {
+        this.timeout(5000);
+        nock('http://microsoft.com')
+            .get('/perm502')
+            .times(3)
+            .reply(502, undefined);
+
+        return new Promise<void>(async (resolve, reject) => {
+            try {
+                let statusCodeUrl: string = "http://microsoft.com/perm502";
+                let downPath: string = await toolLib.downloadTool(statusCodeUrl);
+
+                reject('Shouldnt have succeeded');
+            } catch (err) {
+                if (err['httpStatusCode'] && err['httpStatusCode'] == 502) {
+                    resolve();
+                }
+                reject(err);
+            }
+        });
+    });
 });

test/units/toolTests.ts

@@ -45,6 +45,10 @@ export function prependPath(toolPath: string) {
     console.log('##vso[task.prependpath]' + toolPath);
 }
 
+function delay(ms: number) {
+    return new Promise(resolve => setTimeout(resolve, ms));
+}
+
 //-----------------------------
 // Version Functions
 //-----------------------------
@@ -217,10 +221,21 @@ export async function downloadTool(url: string, fileName?: string): Promise<stri
             if (fs.existsSync(destPath)) {
                 throw new Error("Destination file path already exists");
             }
-
-            // TODO: retries
+            
             tl.debug('downloading');
+            const statusCodesToRetry = [httpm.HttpCodes.BadGateway, httpm.HttpCodes.ServiceUnavailable, httpm.HttpCodes.GatewayTimeout];
+            let retryCount: number = 1;
+            const maxRetries: number = 3;
             let response: httpm.HttpClientResponse = await http.get(url);
+
+            while(retryCount < maxRetries && statusCodesToRetry.indexOf(response.message.statusCode) > -1) {
+                tl.debug(`Download attempt "${retryCount}" of "${maxRetries}" failed with status code "${response.message.statusCode}".`);
+                retryCount += 1;
+                await delay(1000);
+                tl.debug(`Downloading attempt "${retryCount}" of "${maxRetries}"`);
+                response = await http.get(url);
+            }
+            
             if (response.message.statusCode != 200) {
                 let err: Error = new Error('Unexpected HTTP response: ' + response.message.statusCode);
                 err['httpStatusCode'] = response.message.statusCode;