Updated Connections handling (#1127)

* Updated Connections handling

- The ConnectionPool.getConnection method now always returns a connection
- The ConnectionPool.update mehtod now cleans the dead list
- Deprecated the NoLivingConnectionsError

* Updated test

* Updated docs

* The NoLivingConnectionsError can still happen if the filter/selector returns no nodes

* Updated test

* Updated docs

* Catch undefined connections as well

* Updated test

* Updated ApiError type def

lib/Transport.js

@@ -123,10 +123,9 @@ class Transport {
     const makeRequest = () => {
       if (meta.aborted === true) return
       meta.connection = this.getConnection({ requestId: meta.request.id })
-      if (meta.connection === null) {
-        return callback(new NoLivingConnectionsError('There are no living connections'), result)
+      if (meta.connection == null) {
+        return callback(new NoLivingConnectionsError(), result)
       }
-
       // TODO: make this assignment FAST
       const headers = Object.assign({}, this.headers, options.headers)
 

lib/errors.js

@@ -51,7 +51,7 @@ class NoLivingConnectionsError extends ElasticsearchClientError {
     super(message)
     Error.captureStackTrace(this, NoLivingConnectionsError)
     this.name = 'NoLivingConnectionsError'
-    this.message = message || 'No Living Connections Error'
+    this.message = message || 'Given the configuration, the ConnectionPool was not able to find a usable Connection for this request.'
     this.meta = meta
   }
 }

lib/pool/ConnectionPool.js

@@ -50,13 +50,10 @@ class ConnectionPool extends BaseConnectionPool {
    * Marks a connection as 'alive'.
    * If needed removes the connection from the dead list
    * and then resets the `deadCount`.
-   * If sniffing is not enabled and there is only
-   * one node, this method is a noop.
    *
    * @param {object} connection
    */
   markAlive (connection) {
-    if (this._sniffEnabled === false && this.size === 1) return this
     const { id } = connection
     debug(`Marking as 'alive' connection '${id}'`)
     const index = this.dead.indexOf(id)
@@ -71,13 +68,10 @@ class ConnectionPool extends BaseConnectionPool {
    * Marks a connection as 'dead'.
    * If needed adds the connection to the dead list
    * and then increments the `deadCount`.
-   * If sniffing is not enabled and there is only
-   * one node, this method is a noop.
    *
    * @param {object} connection
    */
   markDead (connection) {
-    if (this._sniffEnabled === false && this.size === 1) return this
     const { id } = connection
     debug(`Marking as 'dead' connection '${id}'`)
     if (this.dead.indexOf(id) === -1) {
@@ -183,7 +177,7 @@ class ConnectionPool extends BaseConnectionPool {
 
   /**
    * Returns an alive connection if present,
-   * otherwise returns null.
+   * otherwise returns a dead connection.
    * By default it filters the `master` only nodes.
    * It uses the selector to choose which
    * connection return.
@@ -201,11 +195,13 @@ class ConnectionPool extends BaseConnectionPool {
       name: opts.name
     })
 
+    const noAliveConnections = this.size === this.dead.length
+
     // TODO: can we cache this?
     const connections = []
     for (var i = 0; i < this.size; i++) {
       const connection = this.connections[i]
-      if (connection.status === Connection.statuses.ALIVE) {
+      if (noAliveConnections || connection.status === Connection.statuses.ALIVE) {
         if (filter(connection) === true) {
           connections.push(connection)
         }
@@ -237,13 +233,7 @@ class ConnectionPool extends BaseConnectionPool {
    */
   update (connections) {
     super.update(connections)
-
-    for (var i = 0; i < this.dead.length; i++) {
-      if (this.connections.find(c => c.id === this.dead[i]) === undefined) {
-        this.dead.splice(i, 1)
-      }
-    }
-
+    this.dead = []
     return this
   }
 }

lib/pool/index.d.ts

@@ -103,7 +103,7 @@ declare class BaseConnectionPool {
   markDead(connection: Connection): this;
   /**
    * Returns an alive connection if present,
-   * otherwise returns null.
+   * otherwise returns a dead connection.
    * By default it filters the `master` only nodes.
    * It uses the selector to choose which
    * connection return.