Automatic Job Retry upon Failure

Availability

This feature is available since MogDB 1.1.0.

Introduction

If an error occurs in batch processing jobs due to network exceptions or deadlocks, failed jobs are automatically retried.

Benefits

In common fault scenarios, such as network exception and deadlock, queries retry automatically in case of failure to improve database usability.

Description

MogDB provides the job retry mechanism: gsql Retry.

• The gsql retry mechanism uses a unique error code (SQL STATE) to identify an error that requires a retry. The function of the client tool gsql is enhanced. The error code configuration file retry_errcodes.conf is used to configure the list of errors that require a retry. The file is stored in the installation directory at the same level as gsql. gsql provides the \set RETRY [number] command to enable or disable the retry function. The number of retry times ranges from 5 to 10, and the default value is 5. When this function is enabled, gsql reads the preceding configuration file. The error retry controller records the error code list through the container. If an error occurs in the configuration file after the function is enabled, the controller sends the cached query statement to the server for retry until the query is successful or an error is reported when the number of retry times exceeds the maximum.

Enhancements

None

Constraints

• Functionality constraints:

  • Retrying increases execution success rate but does not guarantee success.

• Error type constraints:

  Only the error types in Table 1 are supported.

  Table 1 Supported error types

  Error Type	Error Code	Remarks
  CONNECTION_RESET_BY_PEER	YY001	TCP communication error. Print information: “Connection reset by peer”
  STREAM_CONNECTION_RESET_BY_PEER	YY002	TCP communication error. Print information: “Stream connection reset by peer” (communication between DNs)
  LOCK_WAIT_TIMEOUT	YY003	Lock wait timeout. Print information: “Lock wait timeout”
  CONNECTION_TIMED_OUT	YY004	TCP communication error. Print information: “Connection timed out”
  SET_QUERY_ERROR	YY005	Failed to deliver the SET command. Print information: “Set query error”
  OUT_OF_LOGICAL_MEMORY	YY006	Failed to apply for memory. Print information: “Out of logical memory”
  SCTP_MEMORY_ALLOC	YY007	SCTP communication error. Print information: “Memory allocate error”
  SCTP_NO_DATA_IN_BUFFER	YY008	SCTP communication error. Print information: “SCTP no data in buffer”
  SCTP_RELEASE_MEMORY_CLOSE	YY009	SCTP communication error. Print information: “Release memory close”
  SCTP_TCP_DISCONNECT	YY010	SCTP and TCP communication error. Print information: “SCTP, TCP disconnect”
  SCTP_DISCONNECT	YY011	SCTP communication error. Print information: “SCTP disconnect”
  SCTP_REMOTE_CLOSE	YY012	SCTP communication error. Print information: “Stream closed by remote”
  SCTP_WAIT_POLL_UNKNOW	YY013	Waiting for an unknown poll. Print information: “SCTP wait poll unknow”
  SNAPSHOT_INVALID	YY014	Invalid snapshot. Print information: “Snapshot invalid”
  ERRCODE_CONNECTION_RECEIVE_WRONG	YY015	Failed to receive a connection. Print information: “Connection receive wrong”
  OUT_OF_MEMORY	53200	Out of memory. Print information: “Out of memory”
  CONNECTION_EXCEPTION	08000	Failed to communicate with DNs due to connection errors. Print information: “Connection exception”
  ADMIN_SHUTDOWN	57P01	System shutdown by the administrator. Print information: “Admin shutdown”
  STREAM_REMOTE_CLOSE_SOCKET	XX003	Remote socket disabled. Print information: “Stream remote close socket”
  ERRCODE_STREAM_DUPLICATE_QUERY_ID	XX009	Duplicate query. Print information: “Duplicate query id”
  ERRCODE_STREAM_CONCURRENT_UPDATE	YY016	Concurrent stream query and update. Print information: “Stream concurrent update”

• Statement type constraints:

  Support single-statement stored procedures, functions, and anonymous blocks. Statements in transaction blocks are not supported.

• Statement constraints of a stored procedure:

  • If an error occurs during the execution of a stored procedure containing EXCEPTION (including statement block execution and statement execution in EXCEPTION), the stored procedure can be retried. If the error is captured by EXCEPTION, the stored procedure cannot be retried.
  • Advanced packages that use global variables are not supported.
  • DBE_TASK is not supported.
  • PKG_UTIL file operation is not supported.

• Data import constraints:

  • The COPY FROM STDIN statement is not supported.
  • The gsql \copy from metacommand is not supported.
  • Data cannot be imported using JDBC CopyManager copyIn.

Dependencies

Valid only if the gsql tool works normally and the error list is correctly configured.

Related Pages

gsql