Command Logging in EntireX

Command logging is a feature to assist in debugging Broker ACI applications. A command in this context represents one user request sent to the Broker and the related response of Broker.

Command logging is a feature that writes the user requests and responses to file in a way it is already known with Broker trace and TRACE-LEVEL=1. But command logging works completely independent from trace, and data is written to a file only if defined command trace filters detect a match.

Broker stub applications send commands or requests to the Broker kernel, and the Broker kernel returns a response to the requesting application. Developers who need to resolve problems in an application need access to those request and response strings inside the Broker kernel. That's where command logging comes in. With command logging, request and response strings from or to an application are written to a file that is separate from the Broker trace file. Command logging works based on defined filters. Nothing is logged if there are no filters. If filters are defined and if there is a match, this user request is logged.

This document covers the following topics:

• Introduction to Command Logging

• Command Log Filtering using Command-line Interface ETBCMD

• ACI-driven Command Logging

• Dual Command Log Files

Introduction to Command Logging

This section provides an introduction to command logging in EntireX and offers examples of how command logging is implemented. It covers the following topics:

• Overview

• Command Log Files

• Defining Filters

• Programmatically Turning on Command Logging

Overview

Command logging is similar to a Broker trace that is generated when the Broker attribute TRACE-LEVEL is set to 1. Broker trace and command logging are independent of each other, and therefore the configuration of command logging is separate from Broker tracing.

The following Broker attributes are involved in command logging:

In addition to CMDLOG=YES, the Broker needs the assignment of the dual command logging files during startup. If these assignments are missing, Broker will set CMDLOG=NO. See also Broker Attributes.

Command Log Files

The Broker keeps a record of commands (request and response strings) in a command log file.

At Broker startup, you will need to supply two command log file names and paths. Only one file is open at a time, however, and the Broker writes commands (requests and responses) to this file.

Under z/OS, the file requirements are two equally sized, physical sequential files defined with a record length of 121 bytes, i.e.
DCB=(LRECL=121,RECFM=FB,BLKSIZE=nnnn). We recommend you allocate files with a single (primary) extent only. For example SPACE=(CYL,(30,0)). The minimum file size is approximately 3 cylinders of 3390 device. Alternatively, the dual command log files can be allowed in USS HFS file system.

• If the value of CMDLOG-FILE-SIZE is lower than the capacity of the CMDLOG data set, CMDLOG-FILE-SIZE is used.

• If the value of CMDLOG-FILE-SIZE is greater than the capacity of the CMDLOG data set, CMDLOG-FILE-SIZE is adjusted to the capacity of the data set.

• If no CMDLOG-FILE-SIZE was defined, it is set to the capacity of the CMDLOG data set.

When the size of the active command log file reaches the KB limit set by CMDLOG-FILE-SIZE, the file is closed and the second file is opened and becomes active. When the second file also reaches the KB limit set by CMDLOG-FILE-SIZE, the first file is opened and second file is closed. Existing log data in a newly opened file will be lost.

Defining Filters

In command logging, a filter is used to store and identify a class, server, or service, as well as a user ID.

Use the command-line tool etbcmd to define a filter. During processing, the Broker evaluates the class, server, service, and user ID associated with each incoming request and compares them with the same parameters specified in the filters. If there is a match, the request string and response string of the request is printed out to the command log file.

Programmatically Turning on Command Logging

Applications using ACI version 9 or above have access to the new field LOG-COMMAND in the ACI control block.

If this field is set, the accompanying request and the Broker's response to this request is logged to the command log file.

Command Log Filtering using Command-line Interface ETBCMD

The examples assume that Broker has been started with the attribute CMDLOG=Y.

• Setting Filters

• Deleting Filters

• Disabling and Enabling a Filter

Setting Filters

Filters need to be set before running the stub applications whose commands are to be logged. Filter for class, server, service may contain fully qualified names (ACLASS/ASERVER/ASERVICE) or asterisk for any (e.g. ACLASS/*/ASERVICE). Partially qualified filter names (ACLA*/ASERVER/ASERV*) are not supported.

//ETBCMD  EXEC PGM=ETBCMD,
// PARM=('/-blocalhost:1970:TCP -cSET-CMDLOG-FILTER -xuser ',
//       '-dBROKER -nACLASS/ASERVER/ASERVICE')

//ETBCMD  EXEC PGM=ETBCMD,
// PARM=('/-blocalhost:1970:TCP -cSET-CMDLOG-FILTER -xuser ',
//       '-dBROKER -nACLASS/ASERVER/ASERVICE -Usaguser1')

Deleting Filters

The following provides an example of how to delete an existing filter on a service.

To delete a filter

• Enter the following command.

  //ETBCMD  EXEC PGM=ETBCMD,
  // PARM=('/-blocalhost:1970:TCP -cCLEAR-CMDLOG-FILTER -xuser ',
  //       '-dBROKER -nACLASS/ASERVER/ASERVICE')

  If the filter does not exist, the command will return an error.

Disabling and Enabling a Filter

Filters can be set and still be disabled (made inactive).

To disable a filter

• Enter the following command.

  //ETBCMD  EXEC PGM=ETBCMD,
  // PARM=('/-blocalhost:1970:TCP -cDISABLE-CMDLOG-FILTER -xuser ',
  //       '-dBROKER -nACLASS/ASERVER/ASERVICE -Usaguser1')

  Note:
  A disabled filter will not bring down the count of filters in use.

To enable a filter

• Enter the following command to enable the disabled filter.

  //ETBCMD  EXEC PGM=ETBCMD,
  // PARM=('/-blocalhost:1970:TCP -cENABLE-CMDLOG-FILTER -xuser ',
  //       '-dBROKER -nACLASS/ASERVER/ASERVICE -Usaguser1')

ACI-driven Command Logging

EntireX components that communicate with Broker can trigger command logging by setting the field LOG-COMMAND in the ACI control block.

When handling ACI functions with command log turned on, Broker will not evaluate any filters. Application developers must remember to reset the LOG-COMMAND field if subsequent requests are not required to be logged.

Dual Command Log Files

Broker's use of two command log files prevents any one command log file from becoming too large.

When starting a Broker with command log support, you must therefore specify two data sets and DD names - one for each of the two command log files. The sample started task EXBSTART delivered with the EXX107.JOBS data set uses DDCLOGR1 and DDCLOGR2 as default command log file names.

At startup, Broker initializes both files and keeps one of them open. Command log statements are printed to the open file until the size of this file reaches the value specified in the Broker attribute CMDLOG-FILE-SIZE. This value must be specified in KB.

When the size of the open file exceeds the value specified in the Broker attribute CMDLOG-FILE-SIZE, Broker closes this file and opens the other, dormant file. Because the Broker closes a log file only when unable to print out a complete log line, the size of a full file may be smaller than CMDLOG-FILE-SIZE.

To switch log files on demand, using ETBCMD

• An open command log file can be forcibly closed even before the size limit is reached. Enter the following command.

  //ETBCMD  EXEC PGM=ETBCMD,
  // PARM=('/-blocalhost:1970:TCP -cSWITCH-CMDLOG -xuser ',
  //       '-dBROKER')

  The command above will close the currently open file and open the one that has been dormant.