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.
Note:
All applied filters are lost after Broker restart and have to be applied again.
This document covers the following topics:
This section provides an introduction to command logging in EntireX and offers examples of how command logging is implemented. It covers the following topics:
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:
| Attribute | Description |
|---|---|
CMDLOG |
Set this to "N" if command logging is not needed. |
CMDLOG-FILE-SIZE |
A numeric value indicating the maximum size of command log file in KB. |
NUM-CMDLOG-FILTER |
The maximum number of filters that can be set. |
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.
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 Linux and Windows, the startup options
-y and -z are evaluated
by executable etbnuc. These options are used to
specify the command log file names. Startup script/service assign these files
by default.
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.
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.
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.
Note:
Programmatic command logging ignores any filters set in the kernel.
The examples assume that Broker has been started with the attribute
CMDLOG=Y.
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.
| Command | Description |
|---|---|
etbcmd
-blocalhost:1970:TCP -cSET-CMDLOG-FILTER -dBROKER -xuser
-nACLASS/ASERVER/ASERVICE |
This command sets
filters on ACLASS/ASERVER/ASERVICE. All ACI calls issued
by all users to this service will be logged.
|
etbcmd
-blocalhost:1970:TCP -cSET-CMDLOG-FILTER -dBROKER -xuser
-nACLASS/ASERVER/ASERVICE -Usaguser1 |
This command set
filters on ACLASS/ASERVER/ASERVICE and user ID
saguser1. All ACI calls to this service as well as those
issued by saguser1 will be logged.
|
Note:
If more than one service is set as a filter, all ACI calls
sent to any of these services will be logged. Identical filters
cannot be set. Attempts to set a second filter that matches an existing filter
will be rejected. Similarly, the maximum number of filters that can be added is
defined in NUM-CMDLOG-FILTER. If the maximum
number of filters is already being used, delete an existing filter to
make room for a new filter.
The following provides an example of how to delete an existing filter on a service.
To delete a filter
Enter the following command.
etbcmd -d BROKER -b localhost:1970:TCP -c CLEAR-CMDLOG-FILTER -nACLASS/ASERVER/ASERVICE -U saguser1
If the filter does not exist, the command will return an error.
Filters can be set and still be disabled (made inactive).
To disable a filter
Enter the following command.
etbcmd -blocalhost:1970:TCP -cDISABLE-CMDLOG-FILTER -dBROKER -xuser -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 -blocalhost:1970:TCP -cENABLE-CMDLOG-FILTER -dBROKER -xuser -nACLASS/ASERVER/ASERVICE -Usaguser1
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.
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 file names and paths - one for each of the two command log files.
The sample startup script installed with the product uses file names
CMDLOG1 and CMDLOG2 as the 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 -blocalhost:1970:TCP -cSWITCH-CMDLOG -dBROKER -xuser
The command above will close the currently open file and open the one that has been dormant.