fix(pushgateway): keep Content-Encoding for pushes after delete()

CHANGELOG.md

@@ -26,6 +26,7 @@ project adheres to [Semantic Versioning](http://semver.org/).
 - fix: Non-nullish, non-string label values are coerced to strings when a combination is first stored, so exposition escapes them; the store also keeps its own copy, so mutating the caller's object after recording no longer changes the stored series
 - fix: Label-less summaries report `labels: {}` in `getMetricsAsJSON()`, like other metrics (Fixes [#838](https://github.com/prometheus/client_js/issues/838))
 - chore: update benchmark baseline to v0.16.1
+- fix: `Pushgateway#delete()` no longer removes `Content-Encoding` from the shared request headers, so gzip stays on for later `push()`/`pushAdd()` calls
 
 ### Added
 

lib/pushgateway.js

@@ -75,11 +75,15 @@ async function useGateway(method, job, groupings) {
 
 	const httpModule = requestParams.protocol === 'https:' ? https : http;
 	const options = { ...this.requestOptions, method };
+	if (method === 'DELETE' && options.headers) {
+		// DELETE has no body, so drop Content-Encoding from a copy of the
+		// headers. Deleting it from the shared object would stop later
+		// push()/pushAdd() calls from sending it.
+		options.headers = { ...options.headers };
+		delete options.headers['Content-Encoding'];
+	}
 
 	return new Promise((resolve, reject) => {
-		if (method === 'DELETE' && options.headers) {
-			delete options.headers['Content-Encoding'];
-		}
 		const req = httpModule.request(requestParams, options, resp => {
 			let body = '';
 			resp.setEncoding('utf8');

test/pushgatewayTest.js

@@ -301,6 +301,35 @@ describe.each([
 				expect(mockHttp.isDone());
 			});
 		});
+
+		it('should keep the gzip header for pushes after a delete', async () => {
+			const headers = { 'Content-Encoding': 'gzip' };
+			const deleteMock = nock('http://192.168.99.100:9091', {
+				badheaders: ['Content-Encoding'],
+			})
+				.delete('/metrics/job/testJob')
+				.reply(200);
+			const pushMock = nock('http://192.168.99.100:9091', {
+				reqheaders: {
+					'Content-Encoding': 'gzip',
+				},
+			})
+				.post('/metrics/job/testJob', gzipSync(body))
+				.reply(200);
+
+			instance = new Pushgateway(
+				'http://192.168.99.100:9091',
+				{ headers },
+				registry,
+			);
+
+			await instance.delete({ jobName: 'testJob' });
+			await instance.pushAdd({ jobName: 'testJob' });
+
+			expect(deleteMock.isDone()).toBe(true);
+			expect(pushMock.isDone()).toBe(true);
+			expect(headers).toEqual({ 'Content-Encoding': 'gzip' });
+		});
 	};
 
 	describe('global registry', () => {