class Client
Represents a database client that maintains multiple connections to the cluster nodes, providing methods to execute CQL statements.
The Client
uses policies
to decide which nodes to connect to, which node
to use per each query execution, when it should retry failed or timed-out executions and how reconnection to down
nodes should be made.
- Global
- This class is global
Augments
Events
hostAdd
Emitted when a new host is added to the cluster.
-
Host
The host being added.
hostDown
Emitted when a host in the cluster changed status from up to down.
-
host
The host that changed the status.
hostRemove
Emitted when a host is removed from the cluster
-
Host
The host being removed.
hostUp
Emitted when a host in the cluster changed status from down to up.
-
host
The host that changed the status.
Members
HostMap
hosts
Gets an associative array of cluster hosts.
String
keyspace
Gets the name of the active keyspace.
Metadata
metadata
Gets the schema and cluster metadata information.
ClientMetrics
metrics
The ClientMetrics
instance used to expose measurements of its internal
behavior and of the server as seen from the driver side.
By default, a DefaultMetrics
instance is used.
Constructor
Client
(ClientOptions
options)
Creates a new instance of Client
.
Methods
batch
(Array
<string
> or Array
<{query, params}> queries, [QueryOptions
options], [ResultCallback
callback])
Executes batch of queries on an available connection to a host.
It returns a Promise
when a callback
is not provided.
connect
([function
callback])
Attempts to connect to one of the contactPoints
and discovers the rest the nodes of the
cluster.
When the Client
is already connected, it resolves immediately.
It returns a Promise
when a callback
is not provided.
eachRow
(String
query, [Array
or Object
params], [QueryOptions
options], function
rowCallback, [function
callback])
Executes the query and calls rowCallback
for each row as soon as they are received. Calls the final
callback
after all rows have been sent, or when there is an error.
The query can be prepared (recommended) or not depending on the prepare
flag.
execute
(String
query, [Array
or Object
params], [QueryOptions
options], [ResultCallback
callback])
Executes a query on an available connection.
The query can be prepared (recommended) or not depending on the prepare
flag.
Some execution failures can be handled transparently by the driver, according to the
RetryPolicy
or the
SpeculativeExecutionPolicy
used.
It returns a Promise
when a callback
is not provided.
executeGraph
(String
query, [Object
or null
parameters], [GraphQueryOptions
or null
options], [function
callback])
Executes a graph query.
It returns a Promise
when a callback
is not provided.
Gets the host that are replicas of a given token.
getState
()Gets a snapshot containing information on the connections pools held by this Client at the current time.
The information provided in the returned object only represents the state at the moment this method was called and it’s not maintained in sync with the driver metadata.
shutdown
([function
callback])
Closes all connections to all hosts.
It returns a Promise
when a callback
is not provided.
Executes the query and pushes the rows to the result stream as soon as they received.
The stream is a ReadableStream
object
that emits rows.
It can be piped downstream and provides automatic pause/resume logic (it buffers when not read).
The query can be prepared (recommended) or not depending on QueryOptions
.prepare flag. Retries on multiple
hosts if needed.