Merge pull request Jigsaw-Code#251 from Jigsaw-Code/fortuna-refactor

Separate shared metrics code

coreos.txt

@@ -0,0 +1,52 @@
+-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----
+

key.txt

@@ -0,0 +1,51 @@
+-----BEGIN RSA PRIVATE KEY-----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=
+-----END RSA PRIVATE KEY-----

src/shadowbox/infrastructure/json_config.ts

@@ -0,0 +1,112 @@
+// Copyright 2018 The Outline Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//      http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+import * as fs from 'fs';
+
+import * as file_read from './file_read';
+import * as logging from './logging';
+
+export interface JsonConfig<T> {
+  // Returns a reference (*not* a copy) to the json object backing the config.
+  data(): T;
+  // Writes the config to the backing storage.
+  write();
+}
+
+export function loadFileConfig<T>(filename: string): JsonConfig<T> {
+  const text = file_read.readFileIfExists(filename);
+  let dataJson = {} as T;
+  if (text) {
+    dataJson = JSON.parse(text) as T;
+  }
+  return new FileConfig<T>(filename, dataJson);
+}
+
+// FileConfig is a JsonConfig backed by a filesystem file.
+export class FileConfig<T> implements JsonConfig<T> {
+  constructor(private filename: string, private dataJson: T) {}
+
+  data(): T {
+    return this.dataJson;
+  }
+
+  write() {
+    // Write to temporary file, then move that temporary file to the
+    // persistent location, to avoid accidentally breaking the metrics file.
+    // Use *Sync calls for atomic operations, to guard against corrupting
+    // these files.
+    const tempFilename = `${this.filename}.${Date.now()}`;
+    try {
+      fs.writeFileSync(tempFilename, JSON.stringify(this.dataJson), {encoding: 'utf8'});
+      fs.renameSync(tempFilename, this.filename);
+    } catch (error) {
+      // TODO: Stop swalling the exception and handle it in the callers.
+      logging.error(`Error writing config ${this.filename} ${error}`);
+    }
+  }
+}
+
+// ChildConfig is a JsonConfig backed by another config.
+export class ChildConfig<T> implements JsonConfig<T> {
+  constructor(private parentConfig: JsonConfig<{}>, private dataJson: T) {}
+
+  data(): T {
+    return this.dataJson;
+  }
+
+  write() {
+    this.parentConfig.write();
+  }
+}
+
+// DelayedConfig is a JsonConfig that only writes the data in a periodic time interval.
+// Calls to write() will mark the data as "dirty" for the next inverval.
+export class DelayedConfig<T> implements JsonConfig<T> {
+  private dirty = false;
+  constructor(private config: JsonConfig<T>, writePeriodMs: number) {
+    // This repeated call will never be cancelled until the execution is terminated.
+    setInterval(() => {
+      if (!this.dirty) {
+        return;
+      }
+      this.config.write();
+      this.dirty = false;
+    }, writePeriodMs);
+  }
+
+  data(): T {
+    return this.config.data();
+  }
+
+  write() {
+    this.dirty = true;
+  }
+}
+
+// InMemoryConfig is a JsonConfig backed by an internal member variable. Useful for testing.
+export class InMemoryConfig<T> implements JsonConfig<T> {
+  // Holds the data JSON as it was when `write()` was called.
+  public mostRecentWrite: T;
+  constructor(private dataJson: T) {
+    this.mostRecentWrite = this.dataJson;
+  }
+
+  data(): T {
+    return this.dataJson;
+  }
+
+  write() {
+    this.mostRecentWrite = JSON.parse(JSON.stringify(this.dataJson));
+  }
+}

src/shadowbox/model/metrics.ts

@@ -15,34 +15,15 @@
 import {AccessKeyId} from './access_key';
 
 export type LastHourMetricsReadyCallback =
-    (startDatetime: Date, endDatetime: Date, lastHourUserStats: Map<AccessKeyId, PerUserStats>) =>
-        void;
+    (startDatetime: Date, endDatetime: Date,
+     lastHourUserMetrics: Map<AccessKeyId, PerUserMetrics>) => void;
 
-// TODO: replace "user" with "access key" in metrics.  This may also require changing
-// - the metrics server
-// - the metrics bigquery tables
-// - the persisted metrics format (JSON file).
-export interface Stats {
-  // Record the number of bytes transferred for a user, and include known
-  // client IP addresses that are connected for that user.  If there are >1
-  // IP addresses, numBytes is the sum of bytes transferred across all of those
-  // clients - we do not know the breakdown of how many bytes were transferred
-  // per IP address, due to limitations of the ss-server.  ipAddresses are only
-  // used for recording which countries clients are connecting from.
-  recordBytesTransferred(
-      userId: AccessKeyId, metricsUserId: AccessKeyId, numBytes: number, ipAddresses: string[]);
-  // Get 30 day data usage, broken down by userId.
-  get30DayByteTransfer(): DataUsageByUser;
-  // Register callback for hourly metrics report.
-  onLastHourMetricsReady(callback: LastHourMetricsReadyCallback): void;
-}
-
-export interface PerUserStats {
+export interface PerUserMetrics {
   bytesTransferred: number;
   anonymizedIpAddresses: Set<string>;
 }
 
-// Byte transfer stats for the past 30 days, including both inbound and outbound.
+// Byte transfer metrics for the past 30 days, including both inbound and outbound.
 // TODO: this is copied at src/model/server.ts.  Both copies should
 // be kept in sync, until we can find a way to share code between the web_app
 // and shadowbox.

src/shadowbox/model/shadowsocks_server.ts

@@ -16,7 +16,7 @@ import * as dgram from 'dgram';
 
 export interface ShadowsocksServer {
   startInstance(
-      portNumber: number, password: string, statsSocket: dgram.Socket,
+      portNumber: number, password: string, metricsSocket: dgram.Socket,
       encryptionMethod?: string): Promise<ShadowsocksInstance>;
 }
 

src/shadowbox/server/libev_shadowsocks_server.ts

@@ -30,17 +30,17 @@ export class LibevShadowsocksServer implements ShadowsocksServer {
   constructor(private publicAddress: string, private verbose: boolean) {}
 
   public startInstance(
-      portNumber: number, password: string, statsSocket: dgram.Socket,
+      portNumber: number, password: string, metricsSocket: dgram.Socket,
       encryptionMethod = this.DEFAULT_METHOD): Promise<ShadowsocksInstance> {
     logging.info(`Starting server on port ${portNumber}`);
 
-    const statsAddress = statsSocket.address();
+    const metricsAddress = metricsSocket.address();
     const commandArguments = [
       '-m', encryptionMethod,  // Encryption method
       '-u',                    // Allow UDP
       '--fast-open',           // Allow TCP fast open
       '-p', portNumber.toString(), '-k', password, '--manager-address',
-      `${statsAddress.address}:${statsAddress.port}`
+      `${metricsAddress.address}:${metricsAddress.port}`
     ];
     logging.info('starting ss-server with args: ' + commandArguments.join(' '));
     // Add the system DNS servers.
@@ -77,7 +77,7 @@ export class LibevShadowsocksServer implements ShadowsocksServer {
     }));
 
     return Promise.resolve(new LibevShadowsocksServerInstance(
-        childProcess, portNumber, password, encryptionMethod, accessUrl, statsSocket));
+        childProcess, portNumber, password, encryptionMethod, accessUrl, metricsSocket));
   }
 }
 
@@ -88,7 +88,7 @@ class LibevShadowsocksServerInstance implements ShadowsocksInstance {
   constructor(
       private childProcess: child_process.ChildProcess, public portNumber: number, public password,
       public encryptionMethod: string, public accessUrl: string,
-      private statsSocket: dgram.Socket) {}
+      private metricsSocket: dgram.Socket) {}
 
   public stop() {
     logging.info(`Stopping server on port ${this.portNumber}`);
@@ -106,30 +106,30 @@ class LibevShadowsocksServerInstance implements ShadowsocksInstance {
   // https://github.com/shadowsocks/shadowsocks-libev/blob/a16826b83e73af386806d1b51149f8321820835e/src/server.c#L172
   public onInboundBytes(callback: (bytes: number, ipAddresses: string[]) => void) {
     if (this.eventEmitter.listenerCount(this.INBOUND_BYTES_EVENT) === 0) {
-      this.createStatsListener();
+      this.createMetricsListener();
     }
     this.eventEmitter.on(this.INBOUND_BYTES_EVENT, callback);
   }
 
-  private createStatsListener() {
+  private createMetricsListener() {
     let lastInboundBytes = 0;
-    this.statsSocket.on('message', (buf: Buffer) => {
-      let statsMessage;
+    this.metricsSocket.on('message', (buf: Buffer) => {
+      let metricsMessage;
       try {
-        statsMessage = parseStatsMessage(buf);
+        metricsMessage = parseMetricsMessage(buf);
       } catch (err) {
-        logging.error('error parsing stats: ' + buf + ', ' + err);
+        logging.error('error parsing metrics: ' + buf + ', ' + err);
         return;
       }
-      if (statsMessage.portNumber !== this.portNumber) {
-        // Ignore stats for other ss-servers, which post to the same statsSocket.
+      if (metricsMessage.portNumber !== this.portNumber) {
+        // Ignore metrics for other ss-servers, which post to the same metricsSocket.
         return;
       }
-      const delta = statsMessage.totalInboundBytes - lastInboundBytes;
+      const delta = metricsMessage.totalInboundBytes - lastInboundBytes;
       if (delta > 0) {
         this.getConnectedClientIPAddresses()
             .then((ipAddresses: string[]) => {
-              lastInboundBytes = statsMessage.totalInboundBytes;
+              lastInboundBytes = metricsMessage.totalInboundBytes;
               this.eventEmitter.emit(this.INBOUND_BYTES_EVENT, delta, ipAddresses);
             })
             .catch((err) => {
@@ -165,12 +165,12 @@ class LibevShadowsocksServerInstance implements ShadowsocksInstance {
   }
 }
 
-interface StatsMessage {
+interface MetricsMessage {
   portNumber: number;
   totalInboundBytes: number;
 }
 
-function parseStatsMessage(buf): StatsMessage {
+function parseMetricsMessage(buf): MetricsMessage {
   const jsonString = buf.toString()
                          .substr('stat: '.length)  // remove leading "stat: "
                          .replace(/\0/g, '');      // remove trailing null terminator