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priam

4.0.1 • Public • Published

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priam

A simple Cassandra driver for NodeJS. It wraps the cassandra-driver modules with additional error/retry handling, external .cql file support, connection option resolution from an external source, and query composition, among other improvements.

The driver uses cassandra-driver over a binary-protocol connection. If a Thrift connection is desired, please use the latest 1.X release and simply specify the helenus driver option in config.

Priam is designed to be used as a single instance in order to preserve the connection pools. As an example, in an Express application, priam should be initialized at server startup and attached to the request object so that your controllers can access it.

Priam is actively developed and used by Go Daddy Website Builder to provide a high-availability and high-performance hosting platform based on the Cassandra database.

Example Usage

Check the example folder for a more complete example. Start by running: npm start followed by curl http://localhost:8080/ or curl http://localhost:8080/stream=true.

Using Known Connection Information

const path = require('path');
const db = require('priam')({
  config: {
    /* See https://docs.datastax.com/en/developer/nodejs-driver/4.3/api/type.ClientOptions/
 
       for full list of config options 
    */
    cqlVersion: '3.0.0', /* optional, defaults to '3.1.0' */
    socketOptions: {  /* optional, defaults as below */
      connectTimeout: 5000 /* optional, defaults to 4000 */
    },
    pooling: {  /* optional */
      coreConnectionsPerHost: {
        local: 2,
        remote: 1
      }
    },
    consistencyLevel: 'one', /* optional, defaults to one. Will throw if not a valid Cassandra consistency level*/
    numRetries: 3, /* optional, defaults to 0. Retries occur on connection failures. Deprecated, use retryOptions instead. */
    retryDelay: 100, /* optional, defaults to 100ms. Used on consistency fallback retry */
    retryOptions: { retries: 0 }, /* optional. See https://www.npmjs.com/package/retry for options */
    enableConsistencyFailover: true, /* optional, defaults to true */
    coerceDataStaxTypes: false, /* optional, defaults to true */
    queryDirectory: path.join(__dirname, 'path/to/your/cql/files'), /* optional, required to use #namedQuery() */
    credentials: {
      username: '<your_username>',
      password: '<your_password>'
    },
    keyspace: '<your_keyspace>', /* Default keyspace. Can be overwritten via options passed into #cql(), etc. */
    contactPoints: [ /* Ports are optional */
      '123.456.789.010:9042',
      '123.456.789.011:9042',
      '123.456.789.012:9042',
      '123.456.789.013:9042'
    ],
    localDataCenter: 'some_dc' /* required; used for selecting preferred nodes during load balancing */ 
  }
});

Executing CQL

The driver provides the #cql() method for executing CQL statements against Cassandra. It provides the following arguments:

  • cql: The CQL statement to execute. Parameters should be replaced with ? characters

  • dataParams: The parameters array. Should match the order of ? characters in the cql parameter

  • options: Optional. Additional options for the CQL call. See Query Options for the list of supported properties.

  • callback(err, data) or stream: Optional. See Query Return Options below.

dataParams will be normalized as necessary in order to be passed to Cassandra. In addition to primitives (Number/String), the driver supports JSON objects, Array and Buffer types. Object and Array types will be stringified prior to being sent to Cassandra, whereas Buffer types will be encoded.

hinted parameters are supported. Instead of the driver inferring the data type, it can be explicitly specified by using a specially formatted object. Similar to consistencies, data types are exposed via the <instance>.dataType object.

There is also a param(value [object], type [string]) helper method for creating hinted parameters, as shown below:

Example

const db = require('priam')({
  config: { /* ... options ... */ }
});
db.cql(
  'SELECT "myCol1", "myCol2" FROM "myColumnFamily" WHERE "keyCol1" = ? AND "keyCol2" = ?',
  [db.param('value_of_keyCol1', 'ascii'), db.param('value_of_keyCol2', 'ascii')],
  { consistency: db.consistencyLevel.one, queryName: 'myQuery', executeAsPrepared: true },
  function (err, data) {
    if (err) {
      console.log(`ERROR: ${err}`);
      return;
    }
    console.log('Returned data: ', data);
  }
);

Named Queries

The driver supports using named queries by calling the namedQuery method. This method behaves just like the cql method, only instead of passing the CQL as the first argument, you pass the name of a query. The query name must correspond to a file name preceding the .cql extension. For example, file myObjectSelect.cql would have a query name of myObjectSelect.

In order to use named queries, the queryDirectory option must be passed into the driver constructor.

Queries are loaded synchronously and cached when the driver is constructed.

Named queries will automatically provide the queryName and executeAsPrepared options when executing the CQL, though the caller can override these options by providing them in the options object.

Example

const db = require('priam')({
    config: { queryDirectory: path.join(__dirName, 'cql') }
}); /* 'cql' folder will be scanned and all .cql files loaded into memory synchronously */
db.namedQuery(
  'myColumnFamilySelect', /* name of .cql file with contents: 'SELECT "myCol1", "myCol2" FROM "myColumnFamily" WHERE "keyCol1" = ? AND "keyCol2" = ?' */
  ['value_of_keyCol1', 'value_of_keyCol2'],
  { consistency: db.consistencyLevel.ONE },
  function (err, data) {
    if (err) {
      console.log('ERROR: ', err);
      return;
    }
    console.log('Returned data: ', data);
  }
);

Query Return Options

For the cql and namedQuery methods, there are four ways to get back your data:

  • As a Promise - To get back a Promise, do not pass a callback argument. The Promise will resolve to an Array of rows.
  • Via a callback - If you supply a callback function as your last argument, it will be called with an error and data argument. If there was no error, data will be an Array.
  • Written to a Stream - If you pass a writable stream instead of a callback, the resulting rows will be written to this stream. Your stream will emit error events if an error occurs while executing the query.
  • As an async iterable - If you set the iterable option to true, then an async iterable is returned.

Fluent Syntax

The driver provides a fluent syntax that can be used to construct queries.

Calling #beginQuery() returns a Query object with the following chainable functions:

  • #query(cql [string]): Sets the cql for the query to execute.

  • #namedQuery(queryName [string]): Specifies the named query for the query to execute.

  • #param(value [object], hint [optional, string], isRoutingKey [optional, bool]): Adds a parameter to the query. Note: They are applied in the order added.

If isRoutingKey is provided and true, the given parameter will be used to determine the coordinator node to execute a query against, when using the datastax driver and a prepared statement.

  • #params(parameters [Array]): Adds the array of parameters to the query. Parameters should be created using db.param()

  • #options(optionsDictionary [object]): Extends the query options. See Query Options for the list of supported properties.

  • #consistency(consistencyLevelName [string]): Sets consistency level for the query. Alias for #options({ consistency: db.consistencyLevel[consistencyLevelName] }).

  • #all(): Default functionality. After calling execute will return array of any results found.

  • #first(): After calling execute will return first, if any of the results found.

  • #single(): Similar to first, will return first result however will yield an error if more than one record found.

  • #execute(callback [optional, function]): Executes the query. If a callback is not supplied, this will return a Promise.

  • #stream(): Executes the query and returns a readable Stream object.

  • #iterate(): Executes the query and returns an async iterable.

Fluent Syntax Examples

db
  .beginQuery()
  .query('SELECT "myCol1", "myCol2" FROM "myColumnFamily" WHERE "keyCol1" = ? AND "keyCol2" = ?')
  .param('value_of_keyCol1', 'ascii')
  .param('value_of_keyCol2', 'ascii')
  .consistency("one")
  .options({ queryName: 'myColumnFamilySelect' })
  .options({ executeAsPrepared: true })
  .execute(function (err, data) {
    if (err) {
      console.log('ERROR: ', err);
      return;
    }
    console.log('Returned data: ', data);
  });

Similarly, fluent syntax can be used for named queries.

db
  .beginQuery()
  .namedQuery('myColumnFamilySelect') /* name of .cql file with contents: 'SELECT "myCol1", "myCol2" FROM "myColumnFamily" WHERE "keyCol1" = ? AND "keyCol2" = ?' */
  .param('value_of_keyCol1', 'ascii')
  .param('value_of_keyCol2', 'ascii')
  .consistency('one')
  .execute(function (err, data) {
    if (err) {
      console.log('ERROR: ', err);
      return;
    }
    console.log('Returned data: ', data);
  });

The fluent syntax also supports promises, if a callback is not supplied to the #execute() function.

db
  .beginQuery()
  .namedQuery('myColumnFamilySelect') /* name of .cql file with contents: 'SELECT "myCol1", "myCol2" FROM "myColumnFamily" WHERE "keyCol1" = ? AND "keyCol2" = ?' */
  .param('value_of_keyCol1', 'ascii')
  .param('value_of_keyCol2', 'ascii')
  .consistency('one')
  .execute()
  .fail(function (err) {
    console.error('ERROR: ', err);
  })
  .done(function (data) {
    console.log('Returned data: ', JSON.stringify(data));
  });

For expected large data sets in a web application, it is a good idea to stream the data back.

const { Transform } = require('stream');
/* ... */
function (req, res, next) {
  db
    .beginQuery()
    .query('SELECT "myCol1", "myCol2" FROM "myColumnFamily" limit 1000000')
    .consistency("one")
    .options({ queryName: 'myColumnFamilySelect' })
    .options({ executeAsPrepared: true })
    .stream()
    .on('error', function (err) {
      res.statusCode(500).end(err.message);
    })
    .pipe(new Transform({
      writableObjectMode: true,
      readableObjectMode: false,
      transform(data, enc, next) {
        next(null, JSON.stringify(data)+'\n');
      }
    }))
    .pipe(res);
}

Batching Queries

Queries can be batched by using the fluent syntax to create a batch of queries. Standard CQL and named queries can be combined. If a consistency level for the batch is not supplied, the strictest consistency from the batched queries will be applied, if given. Similarly, if debug logs for one of the batched queries are suppressed, debug logs for the entire batch will be suppressed. queryName and executeAsPrepared for individual queries will be ignored.

Note: Batching prepared statements is currently not supported. If prepared statements are used in a batch, the entire CQL query will be sent over the wire.

IMPORTANT: Batching is only supported with INSERT, UPDATE and DELETE commands. If SELECT statements are added, the query will yield a runtime error.

For more information on batching, see the CQL 3.0 reference.

If using CQL 3.1, batches can be nested and timestamps will be applied at the query level instead of the batch level. If using CQL 3.0, only timestamps at the outermost batch level will be applied. Any others will be ignored.

Calling #beginBatch() returns a Query object with the following chainable functions:

  • #addQuery(query [Query]): Adds a query to the batch to execute. The query should be created by db.beginQuery().

  • #addBatch(batch [Batch]): Adds the queries contained within the batch parameter to the current batch.. The batch should be created by db.beginBatch().

  • #add(batchOrQuery [Batch or Query]): Allows null, Query, or Batch objects. See #addQuery() and #addBatch() above.

  • #options(optionsDictionary [object]): Extends the batch. See Query Options for the list of supported properties.

  • #timestamp(clientTimestamp [optional, long]): Specifies that USING TIMESTAMP <value> will be sent as part of the batch CQL. If clientTimestamp is not specified, the current time will be used.

  • #type(batchTypeName [string]): Specifies the type of batch that will be used. Available types are 'standard', 'counter' and 'unlogged'. Defaults to 'standard'. See CQL 3.1 reference for more details on batch types.

  • #consistency(consistencyLevelName [string]): Sets consistency level for the batch. Alias for #options({ consistency: db.consistencyLevel[consistencyLevelName] }).

  • #execute(callback [optional, function]): Executes the query. If a callback is not supplied, this will return a Promise.

Batch Syntax Example

db
  .beginBatch()
  .add(db.beginQuery(
    .query('UPDATE "myColumnFamily" SET "myCol1" = ?, "myCol2" = ? WHERE "keyCol1" = ? AND "keyCol2" = ?')
    .param('value_of_myCol1', 'ascii')
    .param('value_of_myCol2', 'ascii')
    .param('value_of_keyCol1', 'ascii')
    .param('value_of_keyCol2', 'ascii')
  )
  .add(db.beginQuery(
    .query('UPDATE "myOtherColumnFamily" SET "myCol" = ? WHERE "keyCol" = ?')
    .param('value_of_myCol', 'ascii')
    .param('value_of_keyCol', 'ascii')
  )
  .consistency('quorum')
  .type('counter')
  .timestamp()
  .execute()
  .fail(function (err) {
    console.log('ERROR: ', err);
  })
  .done(function (data) {
    console.log('Returned data: ', data);
  });

Query Options

All techniques for a query share the following set of options:

  • iterable - causes an async iterable to be returned
  • executeAsPrepared - informs the node-cassandra-cql driver to execute the given CQL as a prepared statement, which will boost performance if the query is executed multiple times.
  • queryName - allows metrics to be captured for the given query, assuming a metrics object was passed into the constructor. See the Monitoring / Instrumentation section for more information.
  • consistency - allows you to override any default consistency level that was specified in the driver's constructor.
  • resultHint - allows you to control how objects being returned by the underlying provider are treated. For example, a data type of objectAscii will result in JSON.parse() being called on the resulting value. Special data types of objectAscii and objectText are available for this purpose. If these data types are used in a parameter's hint field, they will be automatically mapped to the corresponding data type (e.g. ascii or `text) prior to executing the cql statement.
  • deserializeJsonStrings - informs Priam to inspect any string results coming back from the driver and calls JSON.parse() before returning the value back to you. This works similar to providing resultHint options for specific columns, but instead it applies to the entire set of columns. This was the default behavior prior to the 0.7.0 release.
  • coerceDataStaxTypes - informs Priam to convert any of the custom DataStax data types to standard JavaScript types (string, number). This is recommended if you are upgrading from a previous version of Priam and need to keep backwards-compatibility in your codebase with the previous version of the DataStax cassandra-driver module.
  • keyspace - allows you to specify another keyspace to execute a query against. This will override the default keyspace set in the connection information.
  • suppressDebugLog - allows you to disable debug logging of CQL for an individual query. This is useful for queries that may contain sensitive data that you do not wish to show up in debug logs.

Helper Functions

The driver also provides the following functions that wrap #cql(). They should be used in place of #cql() where possible, when not using named queries, as it will allow you to both use default consistency levels for different types of queries, and easily find references in your application to each query type.

  • select: calls #cql() with db.consistencyLevel.one

  • insert: calls #cql() with db.consistencyLevel.localQuorum

  • update: calls #cql() with db.consistencyLevel.localQuorum

  • delete: calls #cql() with db.consistencyLevel.localQuorum

Connection Management

Connection pools are automatically instantiated when the first query is run and kept alive for the lifetime of the driver. To manually initiate and/or close connections, you can use the following functions:

  • #connect(keyspace [string, optional], callback [Function]): Calls callback parameter after connection pool is initialized, or existing pool is retrieved. Can be used at application startup to immediately start the connection pool. You may also omit the callback parameter to receive a Promise instead.

  • #close(callback [Function]): Calls callback after all connection pools are closed. Returns a Promise if callback is not supplied. Useful for testing purposes.

Error Retries

The driver will automatically retry on network-related errors. In addition, other errors will be retried in the following conditions:

  • db.consistencyLevel.all will be retried at db.consistencyLevel.eachQuorum

  • db.consistencyLevel.quorum and db.consistencyLevel.eachQuorum will be retried at db.consistencyLevel.localQuorum

The following retry options are supported in the driver constructor:

  • enableConsistencyFailover: Optional. Defaults to true. If false, the failover described above will not take place.

  • numRetries: (Deprecated) Optional. Defaults to 0 (no retry). The number of retries to execute on network failure.

  • retryOptions: Optional. Defaults to { retries: 0 } (no retries). Retry logic in the event that a network failure happens. See the retry package for options. *Note: this will also affect the number of retries executed during consistency level fallback. For example, if the number of retries is 2 and a CQL query with db.consistencyLevel.all is submitted, it will be executed 3 times at db.consistencyLevel.all, 3 times at db.constistencyLevel.eachQuorum and 3 times at db.consistencyLevel.localQuorum before yielding an error back to the caller.

  • retryDelay: Optional. Defaults to 100. The number of milliseconds used for consistency level fallback.

Logging

The driver supports passing a winston logger inside of the options.

require('priam')({
  config: { /* connection information */ },
  logger: new (require('winston')).Logger({ /* logger options */ })
});

Debug logging of CQL can be turned off for an individual query by passing the suppressDebugLog = true option in the query options dictionary. This is useful for queries that may contain sensitive data that you do not wish to show up in debug logs.

Monitoring / Instrumentation

Instrumentation is supported via an optional metrics object passed into the driver constructor. The metrics object should have a method #measurement(queryName [string], duration [number], unit [string]).

const logger = new (require('winston')).Logger({ /* logger options */ })
const metrics = new MetricsClient();
require('priam')({
  config: { /* connection information */ },
  logger: logger,
  metrics: metrics
});

Events

Each priam instance is an EventEmitter. The following events are emitted:

EventParamsDescription
connectionRequested connectionRequestId A pooled connection has been requested. Expect a `connectionAvailable` event when this request has been fulfilled.
connectionResolving connectionResolutionId If a connection resolver is being used, emitted when the connection resolver is about to be invoked
connectionResolved connectionResolutionId If a connection resolver is being used, emitted when the connection resolver succeeds.
connectionResolvedError connectionResolutionId, err If a connection resolver is being used, emitted when the connection resolver fails.
connectionOpening connectionOpenRequestId Emitted when opening a new connection.
connectionOpened connectionOpenRequestId Emitted when the opening of a new connection has succeeded.
connectionFailed connectionOpenRequestId, err Emitted when the opening of a new connection has failed.
connectionAvailable connectionRequestId Emitted if a new or existing connection is ready to be used to execute a query.
connectionLogged logLevel, message, details Emitted when the underlying driver outputs log events.
connectionClosed Emitted when a connection closes.
queryStarted requestId Emitted when a query is about to be executed.
queryRetried requestId Emitted when a query is about to be retried.
queryCompleted requestId Emitted when a query has succeeded.
queryFailed requestId, err Emitted when a query has failed after exhausting any retries.

Using a Connection Resolver

If you are required to pull database credentials from a credential store (e.g. to support database failover or expiring old credentials), you should use the connectionResolver or connectionResolverPath options.

If used, the supplied connection resolver will be called before every CQL query is issued. It is up to the supplied connection resolver to follow whatever caching strategies are required for the environment.

The connectionResolver option allows you to pass in a connectionResolver object that has already been constructed.

const resolver = new MyConnectionResolver();
const db = require('priam')({
  config: {
    /* ... connection options ... */
  },
  connectionResolver: resolver
});

The connectionResolverPath will be loaded via a #require() call. Note: it is required from /lib/drivers/, so it is recommended to supply a resolver this way via a node module, as paths to source files should be relative to the internal path.

const db = require('priam')({
  config: {
    /* ... other connection options ... */
    connectionResolverPath: 'myResolverModule'
  }
});

Sample Connection Resolver Implementation

The supplied connection resolver should have the following method: #resolveConnection(config, callback).

config will be the priam configuration that was supplied to the constructor, so connection resolvers can access any custom configuration information specified when the driver was initialized.

callback(error, connectionInformation) should be called with the results from the connection resolver. If error is supplied, an error log message will be sent to the supplied logger. connectionInformation should always be supplied if known. If it is not supplied when an error is thrown, the error will be supplied to the #cql() callback.

connectionInformation should contain the following properties: username, password, contactPoints.

Your connection resolver may optionally be an EventEmitter. priam will listen to fetch and lazyfetch events and emit & log its own events in response to these. These events should emit two arguments, an Error for any fetch errors as the first and the resolved connection information as the second.

See example application for a concrete example using a connection resolver.

Port Mapping Options

If your connectionResolver connection information includes port, and is returning the port for a protocol you do not wish to use, (e.g. You want to use binary port 9042, but resolver is returning Thrift port 9160), you can use the connectionResolverPortMap option to perform the mapping.

const db = require('priam')({
  config: {
    /* ... other connection options, including Nimitz ... */
    connectionResolverPortMap = {
      from: '9160',
      to: '9042'
    }
  }
});

Release Notes

See the change log

Keywords

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