Log server (#433)

* Start on log file server.
* Support for delete, get, head, and post; with passing tests!

Author: jgfoster

extras/log_file_server/.gitignore

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+# https://dart.dev/guides/libraries/private-files
+# Created by `dart pub`
+.dart_tool/

extras/log_file_server/analysis_options.yaml

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+# This file configures the static analysis results for your project (errors,
+# warnings, and lints).
+#
+# This enables the 'recommended' set of lints from `package:lints`.
+# This set helps identify many issues that may lead to problems when running
+# or consuming Dart code, and enforces writing Dart using a single, idiomatic
+# style and format.
+#
+# If you want a smaller set of lints you can change this to specify
+# 'package:lints/core.yaml'. These are just the most critical lints
+# (the recommended set includes the core lints).
+# The core lints are also what is used by pub.dev for scoring packages.
+
+include: package:lints/recommended.yaml
+
+# Uncomment the following section to specify additional rules.
+
+# linter:
+#   rules:
+#     - camel_case_types
+
+# analyzer:
+#   exclude:
+#     - path/to/excluded/files/**
+
+# For more information about the core and recommended set of lints, see
+# https://dart.dev/go/core-lints
+
+# For additional information about configuring this file, see
+# https://dart.dev/guides/language/analysis-options

extras/log_file_server/bin/server.dart

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+import 'dart:async' show Future;
+import 'dart:io';
+
+import 'package:shelf/shelf.dart';
+import 'package:shelf/shelf_io.dart';
+import 'package:shelf_router/shelf_router.dart';
+
+const rootDir = '/var/opt/oap/logs';
+
+// Configure routes.
+final _router = Router()
+  ..delete('/logs/deleteMe.log', _delete)
+  ..get('/logs/<path>', _get)
+  ..head('/logs/<path>', _head)
+  ..post('/logs/<path>', _post);
+
+Future<Response> _delete(Request req) async {
+  var file = File('$rootDir/deleteMe.log');
+  if (file.existsSync()) {
+    await file.delete();
+  }
+  return Response.ok(null);
+}
+
+Future<Response> _get(Request req, String path) async {
+  var file = File('$rootDir/$path');
+  if (!file.existsSync()) {
+    return Response.notFound(null);
+  }
+  var body = file.readAsStringSync();
+  return Response.ok(body);
+}
+
+Future<Response> _head(Request req, String path) async {
+  var file = File('$rootDir/$path');
+  if (!file.existsSync()) {
+    return Response.notFound(null);
+  }
+  var length = file.lengthSync();
+  return Response.ok(null, headers: {'content-length': '$length'});
+}
+
+Future<Response> _post(Request req, String path) async {
+  // validate received data
+  var mimeType = req.mimeType;
+  if (mimeType != 'text/plain') {
+    return Response.badRequest(body: 'Content-Type must be text/plain!');
+  }
+  if (req.isEmpty) {
+    return Response.badRequest(body: 'Body must not be empty!');
+  }
+
+  // get body
+  var length = req.contentLength;
+  var body = await req.readAsString();
+  if (length != body.length) {
+    return Response.badRequest(
+        body: 'Content-Length of $length '
+            'did not match body.length of ${body.length}!');
+  }
+
+  // // get remote address
+  // var connectionInfo =
+  //     req.context['shelf.io.connection_info'] as HttpConnectionInfo;
+  // var remoteAddress = connectionInfo.remoteAddress.address;
+  // print('remoteAddress = "$remoteAddress" (${remoteAddress.runtimeType})');
+
+  var file = File('$rootDir/$path');
+  file.createSync(exclusive: false);
+  file.writeAsStringSync(
+    body,
+    mode: FileMode.writeOnlyAppend,
+  );
+  return Response.ok(null);
+}
+
+void main(List<String> args) async {
+  Directory(rootDir).create(recursive: true);
+
+  // Use any available host or container IP (usually `0.0.0.0`).
+  final ip = InternetAddress.anyIPv4;
+
+  // Configure a pipeline that logs requests.
+  final handler = Pipeline().addMiddleware(logRequests()).addHandler(_router);
+
+  // For running in containers, we respect the PORT environment variable.
+  final port = int.parse(Platform.environment['PORT'] ?? '8080');
+  final server = await serve(handler, ip, port);
+  print('Server listening on port ${server.port}');
+}