feat: register service.

src/app-config.model.ts

@@ -0,0 +1,5 @@
+import { IOptions } from "etcd3";
+
+export class AppConfig {
+  etcd!: Pick<IOptions, "auth" | "hosts">;
+}

src/config-loader.ts

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+import { AppConfig } from "./app-config.model";
+import { debug } from "console";
+import { Etcd3 } from "etcd3";
+import { load } from "js-yaml";
+import { hostname } from "os";
+import { getEtcdInstance } from "./etcd-connection";
+
+class ConfigLoader {
+  private etcd: Etcd3;
+
+  private readonly currHost = hostname();
+  private readonly configKeyPrefix = "share/config";
+
+  constructor(config: AppConfig) {
+    this.etcd = getEtcdInstance(config);
+  }
+
+  async loadConfig(configKey: string): Promise<any> {
+    const str = await this.etcd
+      .get(`${this.configKeyPrefix}/${this.currHost}/${configKey}`)
+      .string();
+
+    if (!str) {
+      debug("config-loader", `No config found for ${configKey}`);
+      return null;
+    }
+    return load(str);
+  }
+}

src/etcd-connection.ts

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+import { Etcd3 } from "etcd3";
+import { AppConfig } from "./app-config.model";
+function connectEtcd(config: AppConfig) {
+  return new Etcd3({
+    ...config.etcd,
+  });
+}
+
+let instance: Etcd3;
+
+export function getEtcdInstance(config: AppConfig) {
+  if (!instance) {
+    instance = connectEtcd(config);
+  }
+  return instance;
+}

src/index.ts

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+export * from "./app-config.model";
+export * from "./config-loader";
+export * from "./etcd-connection";
+export * from "./service-register";

src/service-register.ts

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+import { AppConfig } from "./app-config.model";
+import { Etcd3 } from "etcd3";
+import { hostname } from "os";
+import { getEtcdInstance } from "./etcd-connection";
+import debug from "debug";
+
+export class ServiceRegister {
+  private etcd: Etcd3;
+
+  private readonly currHost = hostname();
+  private readonly hostKeyPrefix = "share/gateway/hosts";
+
+  private readonly logger = debug("fennec:config:register");
+
+  constructor(config: AppConfig) {
+    this.etcd = getEtcdInstance(config);
+  }
+
+  async register(key: string, upstream: string) {
+    const fullKey = `${this.hostKeyPrefix}/${this.currHost}/${key}`;
+    this.logger(`Registering ${key} with upstream ${upstream}`);
+    this.logger(`full key:  ${fullKey}`);
+
+    try {
+      await this.etcd.put(fullKey).value(upstream).exec();
+      this.logger(`registered!`);
+    } catch (error) {
+      this.logger(`register failed!`);
+      this.logger(error);
+      throw error;
+    }
+  }
+}