Introduce neo4j.hasReachableServer API

packages/bolt-connection/src/connection-provider/connection-provider-direct.js

@@ -92,6 +92,13 @@ export default class DirectConnectionProvider extends PooledConnectionProvider {
     )
   }
 
+  getNegotiatedProtocolVersion () {
+    return new Promise((resolve, reject) => {
+      this._hasProtocolVersion(resolve)
+        .catch(reject)
+    })
+  }
+
   async supportsTransactionConfig () {
     return await this._hasProtocolVersion(
       version => version >= BOLT_PROTOCOL_V3

packages/bolt-connection/src/connection-provider/connection-provider-routing.js

@@ -244,6 +244,13 @@ export default class RoutingConnectionProvider extends PooledConnectionProvider
     )
   }
 
+  getNegotiatedProtocolVersion () {
+    return new Promise((resolve, reject) => {
+      this._hasProtocolVersion(resolve)
+        .catch(reject)
+    })
+  }
+
   async verifyConnectivityAndGetServerInfo ({ database, accessMode }) {
     const context = { database: database || DEFAULT_DB_NAME }
 

packages/core/src/connection-provider.ts

@@ -98,6 +98,18 @@ class ConnectionProvider {
     throw Error('Not implemented')
   }
 
+  /**
+   * Returns the protocol version negotiated via handshake.
+   *
+   * Note that this function call _always_ causes a round-trip to the server.
+   *
+   * @returns {Promise<number>} the protocol version negotiated via handshake.
+   * @throws {Error} When protocol negotiation fails
+   */
+  getNegotiatedProtocolVersion (): Promise<number> {
+    throw Error('Not Implemented')
+  }
+
   /**
    * Closes this connection provider along with its internals (connections, pools, etc.)
    *

packages/core/src/driver.ts

@@ -220,6 +220,19 @@ class Driver {
     return connectionProvider.supportsUserImpersonation()
   }
 
+  /**
+   * Returns the protocol version negotiated via handshake.
+   *
+   * Note that this function call _always_ causes a round-trip to the server.
+   *
+   * @returns {Promise<number>} the protocol version negotiated via handshake.
+   * @throws {Error} When protocol negotiation fails
+   */
+  getNegotiatedProtocolVersion (): Promise<number> {
+    const connectionProvider = this._getOrCreateConnectionProvider()
+    return connectionProvider.getNegotiatedProtocolVersion()
+  }
+
   /**
    * Returns boolean to indicate if driver has been configured with encryption enabled.
    *

packages/neo4j-driver-lite/src/index.ts

@@ -328,6 +328,26 @@ function driver (
   }
 }
 
+/**
+ * Verifies if the driver can reach a server at the given url.
+ *
+ * @experimental
+ * @since 5.0.0
+ * @param {string} url The URL for the Neo4j database, for instance "neo4j://localhost" and/or "bolt://localhost"
+ * @param {Pick<Config, 'logging'>} config Configuration object. See the {@link driver}
+ * @returns {true} When the server is reachable
+ * @throws {Error} When the server is not reachable or the url is invalid
+ */
+async function hasReachableServer (url: string, config?: Pick<Config, 'logging'>): Promise<true> {
+  const nonLoggedDriver = driver(url, { scheme: 'none', principal: '', credentials: '' }, config)
+  try {
+    await nonLoggedDriver.getNegotiatedProtocolVersion()
+    return true
+  } finally {
+    await nonLoggedDriver.close()
+  }
+}
+
 const USER_AGENT: string = 'neo4j-javascript/' + VERSION
 
 /**
@@ -393,6 +413,7 @@ const temporal = {
  */
 const forExport = {
   driver,
+  hasReachableServer,
   int,
   isInt,
   isPoint,
@@ -444,6 +465,7 @@ const forExport = {
 
 export {
   driver,
+  hasReachableServer,
   int,
   isInt,
   isPoint,

packages/neo4j-driver-lite/test/integration/driver.test.ts

@@ -45,4 +45,12 @@ describe('neo4j-driver-lite', () => {
     expect(result.records[0].length).toEqual(1)
     result.records[0].forEach(val => expect(val).toEqual(int(2)))
   })
+
+  test('hasReachableServer success', async () => {
+    await expect(neo4j.hasReachableServer(`${scheme}://${hostname}`)).resolves.toBe(true)
+  })
+
+  test('hasReachableServer failure', async () => {
+    await expect(neo4j.hasReachableServer(`${scheme}://${hostname}:9999`)).rejects.toBeInstanceOf(Error)
+  })
 })

packages/neo4j-driver-lite/test/unit/index.test.ts

@@ -222,7 +222,8 @@ describe('index', () => {
         supportsMultiDb: async () => true,
         supportsTransactionConfig: async () => true,
         supportsUserImpersonation: async () => true,
-        verifyConnectivityAndGetServerInfo: async () => new ServerInfo({})
+        verifyConnectivityAndGetServerInfo: async () => new ServerInfo({}),
+        getNegotiatedProtocolVersion: async () => 5.0
       }
     })
     expect(session).toBeDefined()

packages/neo4j-driver/src/index.js

@@ -305,6 +305,26 @@ function driver (url, authToken, config = {}) {
   }
 }
 
+/**
+ * Verifies if the driver can reach a server at the given url.
+ *
+ * @experimental
+ * @since 5.0.0
+ * @param {string} url The URL for the Neo4j database, for instance "neo4j://localhost" and/or "bolt://localhost"
+ * @param {object} config Configuration object. See the {@link driver}
+ * @returns {true} When the server is reachable
+ * @throws {Error} When the server is not reachable or the url is invalid
+ */
+async function hasReachableServer (url, config) {
+  const nonLoggedDriver = driver(url, { scheme: 'none', principal: '', credentials: '' }, config)
+  try {
+    await nonLoggedDriver.getNegotiatedProtocolVersion()
+    return true
+  } finally {
+    await nonLoggedDriver.close()
+  }
+}
+
 const USER_AGENT = 'neo4j-javascript/' + VERSION
 
 /**
@@ -385,6 +405,7 @@ const temporal = {
  */
 const forExport = {
   driver,
+  hasReachableServer,
   int,
   isInt,
   isPoint,
@@ -437,6 +458,7 @@ const forExport = {
 
 export {
   driver,
+  hasReachableServer,
   int,
   isInt,
   isPoint,

packages/neo4j-driver/test/driver.test.js

@@ -588,6 +588,16 @@ describe('#integration driver', () => {
     })
   })
 
+  it('hasReachableServer success', async () => {
+    await expectAsync(neo4j.hasReachableServer(`${sharedNeo4j.scheme}://${sharedNeo4j.hostname}`))
+      .toBeResolvedTo(true)
+  })
+
+  it('hasReachableServer failure', async () => {
+    await expectAsync(neo4j.hasReachableServer(`${sharedNeo4j.scheme}://${sharedNeo4j.hostname}:9999`))
+      .toBeRejected()
+  })
+
   const integersWithNativeNumberEquivalent = [
     [neo4j.int(0), 0],
     [neo4j.int(42), 42],

packages/neo4j-driver/types/index.d.ts

@@ -100,6 +100,11 @@ declare function driver (
   config?: Config
 ): Driver
 
+declare function hasReachableServer (
+  url: string,
+  config?: Pick<Config, 'logging'>
+): Promise<true>
+
 declare const types: {
   Node: typeof Node
   Relationship: typeof Relationship
@@ -158,6 +163,7 @@ declare const temporal: {
 
 declare const forExport: {
   driver: typeof driver
+  hasReachableServer: typeof hasReachableServer
   int: typeof int
   isInt: typeof isInt
   integer: typeof integer
@@ -218,6 +224,7 @@ declare const forExport: {
 
 export {
   driver,
+  hasReachableServer,
   int,
   isInt,
   integer,