1 files changed, 412 insertions, 0 deletions
diff --git a/frontend-old/node_modules/@grpc/grpc-js/src/resolver-dns.ts b/frontend-old/node_modules/@grpc/grpc-js/src/resolver-dns.ts
new file mode 100644
index 0000000..31e0d0b
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+++ b/frontend-old/node_modules/@grpc/grpc-js/src/resolver-dns.ts
@@ -0,0 +1,412 @@
+/*
+ * Copyright 2019 gRPC 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 {
+  Resolver,
+  ResolverListener,
+  registerResolver,
+  registerDefaultScheme,
+} from './resolver';
+import * as dns from 'dns';
+import * as util from 'util';
+import { extractAndSelectServiceConfig, ServiceConfig } from './service-config';
+import { Status } from './constants';
+import { StatusObject } from './call-interface';
+import { Metadata } from './metadata';
+import * as logging from './logging';
+import { LogVerbosity } from './constants';
+import { SubchannelAddress, TcpSubchannelAddress } from './subchannel-address';
+import { GrpcUri, uriToString, splitHostPort } from './uri-parser';
+import { isIPv6, isIPv4 } from 'net';
+import { ChannelOptions } from './channel-options';
+import { BackoffOptions, BackoffTimeout } from './backoff-timeout';
+
+const TRACER_NAME = 'dns_resolver';
+
+function trace(text: string): void {
+  logging.trace(LogVerbosity.DEBUG, TRACER_NAME, text);
+}
+
+/**
+ * The default TCP port to connect to if not explicitly specified in the target.
+ */
+export const DEFAULT_PORT = 443;
+
+const DEFAULT_MIN_TIME_BETWEEN_RESOLUTIONS_MS = 30_000;
+
+const resolveTxtPromise = util.promisify(dns.resolveTxt);
+const dnsLookupPromise = util.promisify(dns.lookup);
+
+/**
+ * Merge any number of arrays into a single alternating array
+ * @param arrays
+ */
+function mergeArrays<T>(...arrays: T[][]): T[] {
+  const result: T[] = [];
+  for (
+    let i = 0;
+    i <
+    Math.max.apply(
+      null,
+      arrays.map(array => array.length)
+    );
+    i++
+  ) {
+    for (const array of arrays) {
+      if (i < array.length) {
+        result.push(array[i]);
+      }
+    }
+  }
+  return result;
+}
+
+/**
+ * Resolver implementation that handles DNS names and IP addresses.
+ */
+class DnsResolver implements Resolver {
+  private readonly ipResult: SubchannelAddress[] | null;
+  private readonly dnsHostname: string | null;
+  private readonly port: number | null;
+  /**
+   * Minimum time between resolutions, measured as the time between starting
+   * successive resolution requests. Only applies to successful resolutions.
+   * Failures are handled by the backoff timer.
+   */
+  private readonly minTimeBetweenResolutionsMs: number;
+  private pendingLookupPromise: Promise<dns.LookupAddress[]> | null = null;
+  private pendingTxtPromise: Promise<string[][]> | null = null;
+  private latestLookupResult: TcpSubchannelAddress[] | null = null;
+  private latestServiceConfig: ServiceConfig | null = null;
+  private latestServiceConfigError: StatusObject | null = null;
+  private percentage: number;
+  private defaultResolutionError: StatusObject;
+  private backoff: BackoffTimeout;
+  private continueResolving = false;
+  private nextResolutionTimer: NodeJS.Timeout;
+  private isNextResolutionTimerRunning = false;
+  private isServiceConfigEnabled = true;
+  private returnedIpResult = false;
+  constructor(
+    private target: GrpcUri,
+    private listener: ResolverListener,
+    channelOptions: ChannelOptions
+  ) {
+    trace('Resolver constructed for target ' + uriToString(target));
+    const hostPort = splitHostPort(target.path);
+    if (hostPort === null) {
+      this.ipResult = null;
+      this.dnsHostname = null;
+      this.port = null;
+    } else {
+      if (isIPv4(hostPort.host) || isIPv6(hostPort.host)) {
+        this.ipResult = [
+          {
+            host: hostPort.host,
+            port: hostPort.port ?? DEFAULT_PORT,
+          },
+        ];
+        this.dnsHostname = null;
+        this.port = null;
+      } else {
+        this.ipResult = null;
+        this.dnsHostname = hostPort.host;
+        this.port = hostPort.port ?? DEFAULT_PORT;
+      }
+    }
+    this.percentage = Math.random() * 100;
+
+    if (channelOptions['grpc.service_config_disable_resolution'] === 1) {
+      this.isServiceConfigEnabled = false;
+    }
+
+    this.defaultResolutionError = {
+      code: Status.UNAVAILABLE,
+      details: `Name resolution failed for target ${uriToString(this.target)}`,
+      metadata: new Metadata(),
+    };
+
+    const backoffOptions: BackoffOptions = {
+      initialDelay: channelOptions['grpc.initial_reconnect_backoff_ms'],
+      maxDelay: channelOptions['grpc.max_reconnect_backoff_ms'],
+    };
+
+    this.backoff = new BackoffTimeout(() => {
+      if (this.continueResolving) {
+        this.startResolutionWithBackoff();
+      }
+    }, backoffOptions);
+    this.backoff.unref();
+
+    this.minTimeBetweenResolutionsMs =
+      channelOptions['grpc.dns_min_time_between_resolutions_ms'] ??
+      DEFAULT_MIN_TIME_BETWEEN_RESOLUTIONS_MS;
+    this.nextResolutionTimer = setTimeout(() => {}, 0);
+    clearTimeout(this.nextResolutionTimer);
+  }
+
+  /**
+   * If the target is an IP address, just provide that address as a result.
+   * Otherwise, initiate A, AAAA, and TXT lookups
+   */
+  private startResolution() {
+    if (this.ipResult !== null) {
+      if (!this.returnedIpResult) {
+        trace('Returning IP address for target ' + uriToString(this.target));
+        setImmediate(() => {
+          this.listener.onSuccessfulResolution(
+            this.ipResult!,
+            null,
+            null,
+            null,
+            {}
+          );
+        });
+        this.returnedIpResult = true;
+      }
+      this.backoff.stop();
+      this.backoff.reset();
+      this.stopNextResolutionTimer();
+      return;
+    }
+    if (this.dnsHostname === null) {
+      trace('Failed to parse DNS address ' + uriToString(this.target));
+      setImmediate(() => {
+        this.listener.onError({
+          code: Status.UNAVAILABLE,
+          details: `Failed to parse DNS address ${uriToString(this.target)}`,
+          metadata: new Metadata(),
+        });
+      });
+      this.stopNextResolutionTimer();
+    } else {
+      if (this.pendingLookupPromise !== null) {
+        return;
+      }
+      trace('Looking up DNS hostname ' + this.dnsHostname);
+      /* We clear out latestLookupResult here to ensure that it contains the
+       * latest result since the last time we started resolving. That way, the
+       * TXT resolution handler can use it, but only if it finishes second. We
+       * don't clear out any previous service config results because it's
+       * better to use a service config that's slightly out of date than to
+       * revert to an effectively blank one. */
+      this.latestLookupResult = null;
+      const hostname: string = this.dnsHostname;
+      /* We lookup both address families here and then split them up later
+       * because when looking up a single family, dns.lookup outputs an error
+       * if the name exists but there are no records for that family, and that
+       * error is indistinguishable from other kinds of errors */
+      this.pendingLookupPromise = dnsLookupPromise(hostname, { all: true });
+      this.pendingLookupPromise.then(
+        addressList => {
+          if (this.pendingLookupPromise === null) {
+            return;
+          }
+          this.pendingLookupPromise = null;
+          this.backoff.reset();
+          this.backoff.stop();
+          const ip4Addresses: dns.LookupAddress[] = addressList.filter(
+            addr => addr.family === 4
+          );
+          const ip6Addresses: dns.LookupAddress[] = addressList.filter(
+            addr => addr.family === 6
+          );
+          this.latestLookupResult = mergeArrays(ip6Addresses, ip4Addresses).map(
+            addr => ({ host: addr.address, port: +this.port! })
+          );
+          const allAddressesString: string =
+            '[' +
+            this.latestLookupResult
+              .map(addr => addr.host + ':' + addr.port)
+              .join(',') +
+            ']';
+          trace(
+            'Resolved addresses for target ' +
+              uriToString(this.target) +
+              ': ' +
+              allAddressesString
+          );
+          if (this.latestLookupResult.length === 0) {
+            this.listener.onError(this.defaultResolutionError);
+            return;
+          }
+          /* If the TXT lookup has not yet finished, both of the last two
+           * arguments will be null, which is the equivalent of getting an
+           * empty TXT response. When the TXT lookup does finish, its handler
+           * can update the service config by using the same address list */
+          this.listener.onSuccessfulResolution(
+            this.latestLookupResult,
+            this.latestServiceConfig,
+            this.latestServiceConfigError,
+            null,
+            {}
+          );
+        },
+        err => {
+          if (this.pendingLookupPromise === null) {
+            return;
+          }
+          trace(
+            'Resolution error for target ' +
+              uriToString(this.target) +
+              ': ' +
+              (err as Error).message
+          );
+          this.pendingLookupPromise = null;
+          this.stopNextResolutionTimer();
+          this.listener.onError(this.defaultResolutionError);
+        }
+      );
+      /* If there already is a still-pending TXT resolution, we can just use
+       * that result when it comes in */
+      if (this.isServiceConfigEnabled && this.pendingTxtPromise === null) {
+        /* We handle the TXT query promise differently than the others because
+         * the name resolution attempt as a whole is a success even if the TXT
+         * lookup fails */
+        this.pendingTxtPromise = resolveTxtPromise(hostname);
+        this.pendingTxtPromise.then(
+          txtRecord => {
+            if (this.pendingTxtPromise === null) {
+              return;
+            }
+            this.pendingTxtPromise = null;
+            try {
+              this.latestServiceConfig = extractAndSelectServiceConfig(
+                txtRecord,
+                this.percentage
+              );
+            } catch (err) {
+              this.latestServiceConfigError = {
+                code: Status.UNAVAILABLE,
+                details: `Parsing service config failed with error ${
+                  (err as Error).message
+                }`,
+                metadata: new Metadata(),
+              };
+            }
+            if (this.latestLookupResult !== null) {
+              /* We rely here on the assumption that calling this function with
+               * identical parameters will be essentialy idempotent, and calling
+               * it with the same address list and a different service config
+               * should result in a fast and seamless switchover. */
+              this.listener.onSuccessfulResolution(
+                this.latestLookupResult,
+                this.latestServiceConfig,
+                this.latestServiceConfigError,
+                null,
+                {}
+              );
+            }
+          },
+          err => {
+            /* If TXT lookup fails we should do nothing, which means that we
+             * continue to use the result of the most recent successful lookup,
+             * or the default null config object if there has never been a
+             * successful lookup. We do not set the latestServiceConfigError
+             * here because that is specifically used for response validation
+             * errors. We still need to handle this error so that it does not
+             * bubble up as an unhandled promise rejection. */
+          }
+        );
+      }
+    }
+  }
+
+  private startNextResolutionTimer() {
+    clearTimeout(this.nextResolutionTimer);
+    this.nextResolutionTimer = setTimeout(() => {
+      this.stopNextResolutionTimer();
+      if (this.continueResolving) {
+        this.startResolutionWithBackoff();
+      }
+    }, this.minTimeBetweenResolutionsMs).unref?.();
+    this.isNextResolutionTimerRunning = true;
+  }
+
+  private stopNextResolutionTimer() {
+    clearTimeout(this.nextResolutionTimer);
+    this.isNextResolutionTimerRunning = false;
+  }
+
+  private startResolutionWithBackoff() {
+    if (this.pendingLookupPromise === null) {
+      this.continueResolving = false;
+      this.backoff.runOnce();
+      this.startNextResolutionTimer();
+      this.startResolution();
+    }
+  }
+
+  updateResolution() {
+    /* If there is a pending lookup, just let it finish. Otherwise, if the
+     * nextResolutionTimer or backoff timer is running, set the
+     * continueResolving flag to resolve when whichever of those timers
+     * fires. Otherwise, start resolving immediately. */
+    if (this.pendingLookupPromise === null) {
+      if (this.isNextResolutionTimerRunning || this.backoff.isRunning()) {
+        if (this.isNextResolutionTimerRunning) {
+          trace('resolution update delayed by "min time between resolutions" rate limit');
+        } else {
+          trace('resolution update delayed by backoff timer until ' + this.backoff.getEndTime().toISOString());
+        }
+        this.continueResolving = true;
+      } else {
+        this.startResolutionWithBackoff();
+      }
+    }
+  }
+
+  /**
+   * Reset the resolver to the same state it had when it was created. In-flight
+   * DNS requests cannot be cancelled, but they are discarded and their results
+   * will be ignored.
+   */
+  destroy() {
+    this.continueResolving = false;
+    this.backoff.reset();
+    this.backoff.stop();
+    this.stopNextResolutionTimer();
+    this.pendingLookupPromise = null;
+    this.pendingTxtPromise = null;
+    this.latestLookupResult = null;
+    this.latestServiceConfig = null;
+    this.latestServiceConfigError = null;
+    this.returnedIpResult = false;
+  }
+
+  /**
+   * Get the default authority for the given target. For IP targets, that is
+   * the IP address. For DNS targets, it is the hostname.
+   * @param target
+   */
+  static getDefaultAuthority(target: GrpcUri): string {
+    return target.path;
+  }
+}
+
+/**
+ * Set up the DNS resolver class by registering it as the handler for the
+ * "dns:" prefix and as the default resolver.
+ */
+export function setup(): void {
+  registerResolver('dns', DnsResolver);
+  registerDefaultScheme('dns');
+}
+
+export interface DnsUrl {
+  host: string;
+  port?: string;
+}