Policy Class

Command policy attributes used in all database commands.

Definition

Namespace: Aerospike.Client
Assembly: AerospikeClient (in AerospikeClient.dll) Version: 8.0.1+e35566e493546c0887ebb841c8e2a2c6a7cbde18
C#
public class Policy
Inheritance
Object    Policy
Derived

Constructors

Policy() Default constructor.
Policy(Policy) Copy constructor.

Properties

Txn Transaction identifier. If this field is populated, the corresponding command will be included in the transaction. This field is ignored for scan/query.

Default: null

Methods

Clone Creates a deep copy of this policy.
SetTimeout Create a single timeout by setting socketTimeout and totalTimeout to the same value.
SetTimeouts Set socketTimeout and totalTimeout. If totalTimeout defined and socketTimeout greater than totalTimeout, set socketTimeout to totalTimeout.

Fields

compress Use zlib compression on command buffers sent to the server and responses received from the server when the buffer size is greater than 128 bytes. This option will increase cpu and memory usage(for extra compressed buffers), but decrease the size of data sent over the network.

This compression feature requires the Enterprise Edition Server.

Default: false

failOnFilteredOut Throw exception if filterExp is defined and that filter evaluates to false (command ignored). The AerospikeException will contain result code .

This field is not applicable to batch, scan or query commands.

Default: false

filterExp Optional expression filter. If filterExp exists and evaluates to false, the command is ignored.

Default: null

maxRetries Maximum number of retries before aborting the current command. The initial attempt is not counted as a retry.

If maxRetries is exceeded, the command will abort with AerospikeException.Timeout.

WARNING: Database writes that are not idempotent (such as Add()) should not be retried because the write operation may be performed multiple times if the client timed out previous command attempts. It's important to use a distinct WritePolicy for non-idempotent writes which sets maxRetries = 0;

Default for write: 0 (no retries)

Default for read: 2 (initial attempt + 2 retries = 3 attempts)

Default for scan/query: 5 (6 attempts. See ScanPolicy() comments.)

readModeAP Read policy for AP (availability) namespaces.

Default: ONE

readModeSC Read policy for SC (strong consistency) namespaces.

Default: SESSION

readTouchTtlPercent Determine how record TTL (time to live) is affected on reads. When enabled, the server can efficiently operate as a read-based LRU cache where the least recently used records are expired. The value is expressed as a percentage of the TTL sent on the most recent write such that a read within this interval of the record�s end of life will generate a touch.

For example, if the most recent write had a TTL of 10 hours and read_touch_ttl_percent is set to 80, the next read within 8 hours of the record's end of life (equivalent to 2 hours after the most recent write) will result in a touch, resetting the TTL to another 10 hours.

Values:

  • 0 : Use server config default-read-touch-ttl-pct for the record's namespace/set.
  • -1 : Do not reset record TTL on reads.
  • 1 - 100 : Reset record TTL on reads when within this percentage of the most recent write TTL.

Default: 0

recordParser Alternate record parser.

Default: Use standard record parser.

replica Replica algorithm used to determine the target node for a partition derived from a key or requested in a scan/query.

Default: SEQUENCE

sendKey Send user defined key in addition to hash digest on both reads and writes. If the key is sent on a write, the key will be stored with the record on the server.

If the key is sent on a read, the server will generate the hash digest from the key and vildate that digest with the digest sent by the client. Unless this is the explicit intent of the developer, avoid sending the key on reads.

Default: false (do not send the user defined key)

sleepBetweenRetries Milliseconds to sleep between retries. Enter zero to skip sleep. This field is ignored when maxRetries is zero. This field is also ignored in async mode.

The sleep only occurs on connection errors and server timeouts which suggest a node is down and the cluster is reforming. The sleep does not occur when the client's socketTimeout expires.

Reads do not have to sleep when a node goes down because the cluster does not shut out reads during cluster reformation. The default for reads is zero.

The default for writes is also zero because writes are not retried by default. Writes need to wait for the cluster to reform when a node goes down. Immediate write retries on node failure have been shown to consistently result in errors. If maxRetries is greater than zero on a write, then sleepBetweenRetries should be set high enough to allow the cluster to reform (>= 3000ms).

Default: 0 (do not sleep between retries)

socketTimeout Socket idle timeout in milliseconds when processing a database command.

If socketTimeout is zero and totalTimeout is non-zero, then socketTimeout will be set to totalTimeout. If both socketTimeout and totalTimeout are non-zero and socketTimeout > totalTimeout, then socketTimeout will be set to totalTimeout. If both socketTimeout and totalTimeout are zero, then there will be no socket idle limit.

If socketTimeout is not zero and the socket has been idle for at least socketTimeout, both maxRetries and totalTimeout are checked. If maxRetries and totalTimeout are not exceeded, the command is retried.

For synchronous methods, socketTimeout is the socket SendTimeout and ReceiveTimeout. For asynchronous methods, the socketTimeout is implemented using the AsyncTimeoutQueue and socketTimeout is only used if totalTimeout is not defined.

Default: 30000ms

TimeoutDelay Delay milliseconds after socket read timeout in an attempt to recover the socket in the background. Processing continues on the original command and the user is still notified at the original command timeout.

When a command is stopped prematurely, the socket must be drained of all incoming data or closed to prevent unread socket data from corrupting the next command that would use that socket.

If a socket read timeout occurs and timeoutDelay is greater than zero, the socket will be drained until all data has been read or timeoutDelay is reached. If all data has been read, the socket will be placed back into the connection pool. If timeoutDelay is reached before the draining is complete, the socket will be closed.

Sync sockets are drained in the cluster tend thread at periodic intervals. timeoutDelay is not supported for async sockets.

Many cloud providers encounter performance problems when sockets are closed by the client when the server still has data left to write (results in socket RST packet). If the socket is fully drained before closing, the socket RST performance penalty can be avoided on these cloud providers.

The disadvantage of enabling timeoutDelay is that extra memory/processing is required to drain sockets and additional connections may still be needed for command retries.

If timeoutDelay were to be enabled, 3000ms would be a reasonable value.

Default: 0 (no delay, connection closed on timeout)

totalTimeout Total command timeout in milliseconds.

The totalTimeout is tracked on the client and sent to the server along with the command in the wire protocol. The client will most likely timeout first, but the server also has the capability to timeout the command.

If totalTimeout is not zero and totalTimeout is reached before the command completes, the command will abort with AerospikeException.Timeout.

If totalTimeout is zero, there will be no total time limit.

Default for scan/query: 0 (no time limit)

Default for all other commands: 1000ms

See Also