Added support for multiple service instances

.gitignore

@@ -1,4 +1,5 @@
 node_modules
 
 config/*
-!config/*.example.js
+!config/*.example.js
+!config/setindent.js

README.md

@@ -1,5 +1,5 @@
 # ConsulWatcher
 
-This is a much simplified version of HashiCorp's Consul-Template, because what it accomplishes is awesome but I really dislike the Go template syntax. All configuration in this version are plain JavaScript.
+This is a much simplified version of HashiCorp's Consul-Template, because what it accomplishes is awesome but I really dislike the Go template syntax. All configuration in this version is plain JavaScript.
 
 It's main purpose is creating output files based on a Consul catalog, much like Consul-Template, but since the update handlers are just JavaScript functions you are free to do whatever you want, like calling a webservice or using a template library.

config/index.example.js

@@ -1,48 +1,49 @@
+const winston = require('winston');
+const setIndent = require('./setindent');
+
+
 const config = {
+  /*
+
+    Consul agent configuration
+      Determines the agent or server which will be queried and
+      monitored for the service catalog.
+
+      Recommended to be a local agent connected to the cluster.
+
+      Passed to the initialization of the Node Consul client.
+      For all options, see: https://github.com/silas/node-consul#init
+
+  */
+  consul: {
+    host: 'pc-mvrenswoude'
+  },
+
+
+  /*
+
+    Logging
+      See: https://github.com/winstonjs/winston#transports
+
+  */
+  logging: {
+    transports: [
+      new winston.transports.Console({
+        level: 'debug',
+        timestamp: true,
+        format: winston.format.combine(
+          winston.format.colorize(),
+          winston.format.simple()
+        )
+      })
+    ]
+  },
+
   onUpdate: [],
   afterUpdate: null
 };
 
 
-/*
-
-  Consul agent configuration
-    Determines the agent or server which will be queried and
-    monitored for the service catalog.
-
-    Recommended to be a local agent connected to the cluster.
-
-    Passed to the initialization of the Node Consul client.
-    For all options, see: https://github.com/silas/node-consul#init
-
-*/
-config.consul = {
-  host: 'localhost'
-}
-
-
-
-/*
-
-  Logging
-    See: https://github.com/winstonjs/winston#transports
-
-*/
-const winston = require('winston');
-
-config.logging = {
-  transports: [
-    new winston.transports.Console({
-      level: 'debug',
-      timestamp: true,
-      format: winston.format.combine(
-        winston.format.colorize(),
-        winston.format.simple()
-      )
-    })
-  ]
-};
-
 
 /*
 
@@ -65,26 +66,41 @@ config.logging = {
 const fs = require('fs').promises;
 
 
-config.onUpdate.push((catalog, logger) =>
+config.onUpdate.push(async (catalog, logger) =>
 {
   // Use catalog parameter to generate output
   let output = '';
 
   for (const service of catalog.services)
   {
-    output +=
-`Service: ${service.name}
-  Tags:    ${JSON.stringify(service.tags)}
-  Address: ${await service.getAddress()}
-  Port:    ${await service.getPort()}
+    let instances = '';
 
-`;
+    for (const instance of await service.getInstances())
+    {
+      instances += setIndent(2, `
+        Address: ${instance.address}
+        Port:    ${instance.port}
+
+        `);
+    }
+
+    output += setIndent(`
+      Service: ${service.name}
+        Tags:  ${JSON.stringify(service.tags)}
+
+      `);
+
+    output += instances + '\n';
   };
 
   await fs.writeFile('example-output.txt', output);
 });
 
 
+// Example on how to split the update handlers into a separate file
+config.onUpdate.push(require('./included.example'));
+
+
 /*
   afterUpdate handler
     This is a single handler which is called after all the onUpdate handlers

config/setindent.js

@@ -0,0 +1,49 @@
+// Inspired by dedent: https://github.com/dmnd/dedent
+function setIndent(indentOrValue, value = null)
+{
+  let indent;
+
+  if (typeof indentOrValue === 'number')
+    indent = indentOrValue;
+  else
+  {
+    indent = 0;
+    value = indentOrValue;
+  }
+
+
+
+  const lines = value.split('\n');
+  let minIndent = null;
+
+
+  // Determine minimum indent present in the value
+  for (const line of lines)
+  {
+    const whitespace = line.match(/^(\s+)/);
+    if (whitespace !== null)
+      minIndent = minIndent === null ? whitespace[1].length : Math.min(whitespace[1].length, minIndent);
+  }
+
+
+  // Calculate the difference to the requested indentation
+  const indentDelta = minIndent === null ? indent : minIndent - indent;
+  let result;
+
+  if (indentDelta < 0)
+  {
+    const add = ' '.repeat(-indentDelta);
+    result = lines.map(line => add + line).join('\n');
+  }
+  else
+    result = lines.map(line => line.slice(indentDelta)).join('\n');
+
+
+  // If the first or last line is empty, trim it (allows the template string to
+  // start at the next line to align properly). Similarly, if the last line is
+  // only whitespace, keep the newline but trim the spaces.
+  return result.replace(/^\n/g, '').replace(/[ \t]+$/g, '');
+}
+
+
+module.exports = setIndent;

index.js

@@ -1,9 +1,14 @@
+const options = require('minimist')(process.argv.slice(2));
+const winston = require('winston');
+
 const ConsulCatalog = require('./lib/consulcatalog');
-const logger = require('./lib/logger');
-const config = require('./config');
+const config = options.hasOwnProperty('config') ? require(options.config) : require('./config');
+
+const logger = winston.createLogger({
+  transports: config.logging.transports,
+});
+
 
 const catalog = new ConsulCatalog(logger, config);
 
 // TODO detect if the connection is down for too long, allow a custom notification to be sent
-
-// TODO provide a way to easily switch between configs, for multiple environments

lib/consulcatalog.js

@@ -68,7 +68,7 @@ class ConsulCatalog
 
   serviceByName(name)
   {
-    return this._services.find(service => service.name == name) || null;
+    return this._services.find(service => service.name === name) || null;
   }
 
 
@@ -97,7 +97,7 @@ class ConsulCatalog
     self._services = self._services.filter(service =>
     {
       const serviceIndex = serviceNames.indexOf(service.name);
-      if (serviceIndex == -1)
+      if (serviceIndex === -1)
       {
         // Previously detected service no longer appears in Consul, remove
         // any watches that may be present and remove it from the list
@@ -116,12 +116,12 @@ class ConsulCatalog
     });
 
     // All remaining entries in serviceNames are new
-    serviceNames.forEach(name =>
+    for (const name of serviceNames)
     {
       self._logger.debug(`Found new service: ${name}`)
       self._services.push(new ConsulService(self, name, data[name]));
       changed = true;
-    });
+    };
 
     return changed;
   }
@@ -139,7 +139,7 @@ class ConsulCatalog
     }
 
 
-    if (self._debouncedUpdate == null)
+    if (self._debouncedUpdate === null)
     {
       self._debouncedUpdate = debounce(() =>
       {
@@ -149,11 +149,11 @@ class ConsulCatalog
         self._logger.info('Running update handlers');
         const handlerPromises = [];
 
-        self._config.onUpdate.forEach(handler =>
+        for (const handler of self._config.onUpdate)
         {
           const handlerPromise = Promise.resolve(handler(self, self._logger));
           handlerPromises.push(handlerPromise);
-        });
+        };
 
         Promise.all(handlerPromises)
           .then(() =>
@@ -171,6 +171,11 @@ class ConsulCatalog
                   self._doUpdate();
                 }
               });
+          })
+          .catch(e =>
+          {
+            // TODO better exception handling
+            self._logger.error('Error while running update handlers: ', e);
           });
       }, 500);
     }
@@ -189,69 +194,22 @@ class ConsulService
     this._logger = catalog._logger;
 
     this._watch = null;
-    this._rawData = null;
-    this._rawDataPromise = null;
+    this._instances = null;
 
     this.name = name;
     this.tags = tags;
   }
 
 
-  async getAddress()
-  {
-    var rawData;
-    try
-    {
-      rawData = await this._getRawData();
-    }
-    catch(e)
-    {
-      // TODO better exception handling
-      this._logger.error('Error while retrieving service status', err);
-      return null;
-    }
-
-    if (rawData.length == 0)
-      return null;
-
-    if (rawData[0].Service.Address != '')
-      return rawData[0].Service.Address;
-
-    return rawData[0].Node.Address;
-  }
-
-
-  async getPort()
-  {
-    var rawData;
-    try
-    {
-      rawData = await this._getRawData();
-    }
-    catch(e)
-    {
-      // TODO better exception handling
-      this._logger.error('Error while retrieving service status', err);
-      return null;
-    }
-
-    return rawData.length > 0 ? rawData[0].Service.Port : null;
-  }
-
-
-  // TODO getHealth
-
-
-
-  _getRawData()
+  async getInstances()
   {
     const self = this;
 
-    if (self._rawDataPromise !== null)
-      return self._rawDataPromise;
+    if (self._instances !== null)
+      return Promise.resolve(self._instances);
 
     // Get status information for the service and start watching it
-    self._rawDataPromise = new Promise((resolve, reject) =>
+    return new Promise((resolve, reject) =>
     {
       let firstResponse = true;
 
@@ -269,7 +227,7 @@ class ConsulService
         if (firstResponse)
         {
           firstResponse = false;
-          resolve(self._rawData);
+          resolve(self._instances);
         }
       });
 
@@ -284,13 +242,8 @@ class ConsulService
           firstResponse = false;
           reject(err);
         }
-
-        // Try again the next time
-        self._rawDataPromise = null;
       });
     });
-
-    return self._rawDataPromise;
   }
 
 
@@ -317,16 +270,77 @@ class ConsulService
 
   _applyHealthData(data)
   {
-    if (data == this._rawData)
-      return false;
+    const self = this;
+    const isUpdate = self._instances !== null;
+
+    let changed = false;
+
+    // Remove instances that no longer exist
+    const instanceIds = {};
+    for (const dataInstance of data)
+      instanceIds[dataInstance.Service.ID] = dataInstance;
+
+
+    self._instances = (self._instances != null ? self._instances : []).filter(instance =>
+    {
+      if (instanceIds.hasOwnProperty(instance.id))
+      {
+        // Previously detected instance no longer appears in Consul,
+        // remove it from the list
+        changed = true;
+        return false;
+      }
+
+
+      if (instance._applyHealthData(instanceIds[instance.id]))
+        changed = true;
+
+      // Remove from instanceIds to indicate it has already been applied
+      delete instanceIds[instance.id];
+
+      return true;
+    });
+
+    // All remaining entries in instanceIds are new
+    for (const id of Object.keys(instanceIds))
+    {
+      self._logger.debug(`Found new service instance: ${id}`)
+      self._instances.push(new ConsulServiceInstance(id, instanceIds[id]));
+      changed = true;
+    };
 
-    const isUpdate = this._rawData != null;
-    this._rawData = data;
 
     // If this is the first time we've received data, it is guaranteed to be the result of
     // an update handler requesting this data and the handlers do not need to be called again.
-    return isUpdate;
+    return isUpdate && changed;
   }
 }
 
+
+class ConsulServiceInstance
+{
+  constructor(id, data)
+  {
+    this.id = id;
+    this.tags = [];
+    this.address = null;
+    this.port = null;
+    this.rawData = null;
+
+    this._applyHealthData(data);
+  }
+
+
+  _applyHealthData(data)
+  {
+    this.rawData = data;
+
+    this.id = data.Service.ID;
+    this.tags = data.Service.Tags;
+    this.address = data.Service.Address !== '' ? data.Service.Address : data.Node.Address;
+    this.port = data.Service.Port;
+  }
+}
+
+
 module.exports = ConsulCatalog;

lib/logger.js

@@ -1,9 +0,0 @@
-const winston = require('winston');
-const config = require('../config');
-
-// TODO make configurable
-let logger = winston.createLogger({
-  transports: config.logging.transports,
-});
-
-module.exports = logger;

package-lock.json

@@ -82,11 +82,6 @@
       "resolved": "https://registry.npmjs.org/debounce/-/debounce-1.2.0.tgz",
       "integrity": "sha512-mYtLl1xfZLi1m4RtQYlZgJUNQjl4ZxVnHzIR8nLLgi4q1YT8o/WM+MK/f8yfcc9s5Ir5zRaPZyZU6xs1Syoocg=="
     },
-    "dedent": {
-      "version": "0.7.0",
-      "resolved": "https://registry.npmjs.org/dedent/-/dedent-0.7.0.tgz",
-      "integrity": "sha1-JJXduvbrh0q7Dhvp3yLS5aVEMmw="
-    },
     "enabled": {
       "version": "2.0.0",
       "resolved": "https://registry.npmjs.org/enabled/-/enabled-2.0.0.tgz",
@@ -144,6 +139,11 @@
         "triple-beam": "^1.3.0"
       }
     },
+    "minimist": {
+      "version": "1.2.5",
+      "resolved": "https://registry.npmjs.org/minimist/-/minimist-1.2.5.tgz",
+      "integrity": "sha512-FM9nNUYrRBAELZQT3xeZQ7fmMOBg6nWNmJKTcgsJeaLstP/UODVpGsr5OhXhhXg6f+qtJ8uiZ+PUxkDWcgIXLw=="
+    },
     "ms": {
       "version": "2.1.2",
       "resolved": "https://registry.npmjs.org/ms/-/ms-2.1.2.tgz",

package.json

@@ -20,7 +20,7 @@
   "dependencies": {
     "consul": "^0.37.0",
     "debounce": "^1.2.0",
-    "dedent": "^0.7.0",
+    "minimist": "^1.2.5",
     "winston": "^3.3.3"
   },
   "devDependencies": {