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Java Client Best Practices

Enable Client Log

Each AerospikeClient instance runs a background cluster tend thread that periodically polls all nodes for cluster status. This background thread generates log messages that reflect node additions/removal and any errors when retrieving node status, peers, partition maps and racks. It's critical that user applications enable this log to receive these important messages.

See Enable Log.

Share Client Instance

Each AerospikeClient instance spawns a maintenance thread that periodically makes info requests to all server nodes for cluster status. Multiple client instances create additional load on the server. Use only one client instance per cluster in an application and share that instance among multiple threads. AerospikeClient is thread-safe.

Set Maximum Connections

Set ClientPolicy.maxConnsPerNode and/or ClientPolicy.asyncMaxConnsPerNode to the maximum number of connections allowed (default 300) per server node. Sync and async connections are tracked separately. The number of connections used per node depends on concurrent commands in progress plus sub-commands used for parallel multi-node commands (batch, scan, and query). One connection will be used for each command. A transaction will fail if the maximum number of connections would be exceeded.

User-Defined Key

By default, the user-defined key is not stored on the server. It is converted to a hash digest which is used to identify a record. If the user-defined key must persist on the server, use one of the following methods:

  • Set WritePolicy.sendKey to true. The key is sent to the server for storage on writes, and retrieved on multi-record scans and queries.
  • Explicitly store and retrieve the user-defined key in a bin.

Avoid Value/Bin Generic Object Constructors

Do not use Value or Bin constructors that take in an object. These constructors are slower than hard-coded constructors because the object must be queried (using instanceof) for its real type. They also use the default Java serializer, which is the slowest of all serialization implementations. Instead, serialize the object with a better serializer and use the byte[] constructor.


Use AerospikeClient.operate() to batch multiple operations (add/get) on the same record in a single call.

Replace Mode

In cases where all record bins are created or updated in a transaction, enable Replace mode on the transaction to increase performance. The server then does not have to read the old record before updating. Do not use Replace mode when updating a subset of bins.

WritePolicy policy = new WritePolicy();
policy.recordExistsAction = RecordExistsAction.REPLACE;
client.put(policy, key, bins);


Each database command takes in a policy as the first argument. If the policy is identical for a group of commands, reuse them instead of instantiating policies for each command.

Also, set policy defaults in ClientPolicy and pass in a null policy on each command.

ClientPolicy policy = new ClientPolicy();
policy.readPolicyDefault.socketTimeout = 50;
policy.readPolicyDefault.totalTimeout = 110;
policy.readPolicyDefault.sleepBetweenRetries = 10;
policy.writePolicyDefault.socketTimeout = 200;
policy.writePolicyDefault.totalTimeout = 450;
policy.writePolicyDefault.sleepBetweenRetries = 50;

AerospikeClient client = new AerospikeClient(policy, "hostname", 3000);
client.put(null, new Key("test", "set", 1), new Bin("bin", 5));

If a policy needs to change from the default (such as setting an expected generation), instantiate that policy on-the-fly:

public void putIfGeneration(Key key, int generation, Bin... bins) {
WritePolicy policy = new WritePolicy(client.writePolicyDefault);
policy.generationPolicy = GenerationPolicy.EXPECT_GEN_EQUAL;
policy.generation = generation;
client.put(policy, key, bins);

Circuit Breaker

Employ a circuit breaker that activates when a maximum error count is reached for a node and rejects transactions to that node until the specified error window expires. The following ClientPolicy fields can create a circuit breaker.


Maximum number of errors allowed per node per errorRateWindow. Errors include connection errors, timeouts and device overload. If maximum errors are reached, further transactions to that node are retried to another node depending on replica policy. If maxRetries are exhausted, a backoff exception AerospikeException.Backoff is thrown with error code ResultCode.MAX_ERROR_RATE.


The number of cluster tend iterations that defines the window for maxErrorRate. One tend iteration is defined as the tend interval (default 1 second) plus the time to tend all nodes. At the end of the window, the error count is reset to zero and backoff state is removed on all nodes.

The user application could optionally use a fallback cluster to handle traffic when the circuit breaker is employed.