Note: Descriptions are shown in the official language in which they were submitted.
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Description
Method and arrangement for monitoring a program
The invention relates to a method and an arrangement
for monitoring a program.
A program is normally monitored by means of specific
brake points at which a programmer can view debugging
information and, if necessary, can deduce that there is
a malfunction in the program. This manual measure is
extremely tedious and time-consuming in the case of a
sufficiently large program with numerous subroutines.
Furthermore, the debugging information is mostly
evaluated offline, that is to say not during the time
in which the program is running. If the program is part
of a distributed system, it is no longer feasible to
coordinate clear, manual monitoring.
European Patent Application EP 0 470 322 Al discloses a
message-based debugger, in which an object program
interacts with a monitor program via message queues,
and checks the correctness of the code of program
sections.
The object of the invention is to specify a method and
an arrangement for monitoring a program, which allow
efficient monitoring even when the program is running,
particularly in a distributed system. The present
invention allows such monitoring to be carried out even
for a large number of programs.
This object is achieved by the features in the
independent patent claims. Developments of the
invention are described in the dependent claims.
AMENDED SHEET
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In order to achieve the object, a method for monitoring
a program is specified, in which the program has an
instrumentation part added to it. The instrumentation
part generates a message, and transmits this message to
a monitoring process. The monitoring process initiates
a predetermined action.
AMENDED SHEET
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An instrumentation part is a program part or a
(program) code (fragment) which is linked to the
program to be monitored. This link can be produced by
embedding the instrumentation part in the program
itself, or in a function associated with the program.
By way of example, the program can itself be
instrumented at a number of points, each of which then
sends messages to the monitoring process when specific
events occur. At the same time, an output routine in
the program could be instrumented so that, in addition
to the normal (that is to say without any
instrumentation) output from the program, further
outputs are passed to the monitoring process
(instrumentation of the input/output interface of the
program).
The monitoring process preferably coordinates the
messages which are sent (possibly by numerous
distributed) programs. Furthermore, the monitoring
process may have a number of different actions which it
can initiate or start as a consequence of the messages:
~ For example, the messages can be displayed. The
messages are preferably displayed as a function of
time, for example in the form of a message sequence
chart (MSC). Displays in the form of a tree structure
or in the form of lists are also feasible.
~ Furthermore, it is possible to intervene in the
running of the program. For example, the
instrumentation part could cause the program to wait
for a response from the monitoring process before
itself being continued. This response can be produced
by a user/programmer, or can be produced
automatically as a function of specific presets (IF-
THEN-ELSE structure). The automated
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running can be carried out as a dedicated subroutine,
coordinated by the monitoring process.
~ It is also possible for the action to correspond to
an open or closed-loop control task. One example of
this would be switching a unit in a technical system
on or off as soon as specific presets are satisfied
or have been signaled to the monitoring process.
The advantages of the method proposed here include the
capability to monitor the program while it is running.
The instrumentation ensures that specific events are
signaled, even while the program is running, in the
form of messages to the monitoring process, where these
messages are collected and processed in a suitable
manner. In particular, the monitoring process can use a
filter function to ensure that the only messages which
are displayed or taken into account are those which
actually correspond to the filtered presets.
Furthermore, the capability for use in a distributed
system is a major advantage. The complex interaction
between a large number of different programs in a
distributed system makes fault tracing difficult. The
transmission of messages to the monitoring process from
each instrumented (also distributed) program when there
are a large number of different programs which do not
all run on the same computer platform allow - after
suitable filtering and/or processing, for example on
the basis of a message sequence chart - the
preservation of an overview, thus making it
considerably simpler to trace a specific action in the
distributed system, and hence considerably simplify the
fault tracing process associated with this.
In this case, it should be noted that a program as
described above may invariably also in each case be a
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part of a cohesive program or a function linked to
(associated with) the program.
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It is particularly advantageous for middleware which is
associated with the program to be monitored to be
instrumented. In this case, a functionality which is
controlled by the program can be instrumented
centrally. This is actually a major advantage since,
for example, there is no need to instrument all the
input/output routines in the program in this way, with
only the one associated routine being instrumented in
the middleware, instead of this. This actually
corresponds to instrumentation of all the input/output
routines in the program to be monitored. The actual
addition at the one point in the middleware is
extremely economic, since there is no need to search
through the entire program to be monitored for said
routines. The instrumentation can be changed centrally,
at one point, for all the affected routines (interface
encapsulation). Furthermore, this type of
instrumentation is highly flexible and can be added to.
If the program to be monitored changes, the
instrumentation is already prepared, in terms of the
affected routines (in this case, the input/output
routines by way of example) for the next program to be
monitored.
In particular, in a distributed system, that is to say
in a system which has a number of computers which are
linked to one another by a network, the following
mechanisms are monitored in the program:
~ Message transmission (message passing, task to task):
A receiver (program or process) waits for a message.
It cannot continue until the message has been
transmitted by a transmitter.
~ Remote procedure call (RPC)
By way of example, a process tries to start a program
on another computer (remote). The
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process waits until the remote computer has completed
the processing. Normally, the process is informed
whether the processing has been successful or
unsuccessful.
~ Task join:
A process is added to another process. The added
process does not exist any longer from then on.
If the system is distributed and has a number of
computers, then each system is intrinsically autonomous
and has, for example, its own system clock. In order to
ensure semantic correctness, it is important to check
the plausibility, for example the time stamp, of the
respective messages. Each message that is sent is, in
particular, given a time stamp which can be used for
synchronization. For example, the transmission of a
message may require a specific time period, and the
time sequence must be clarified when displaying a
number of messages in the monitoring process. If the
system clocks in the individual systems become
desynchronized (which must generally be assumed to be
the case), then the monitoring process defines the
correct time sequence of the transmitted messages. This
is done, in particular, by means of a heuristic, which
checks whether an assumption is or is not correct. If
this is the case, the most recently transmitted time
sequence is adopted, and if not, a next assumption is
checked. The check is based on message semantics: for
example, a response cannot occur before a question.
This makes it possible to deduce the relationships
between the two system clocks involved. A time offset
is defined, which satisfies plausibility of the system
clocks . The offset can be adapted as soon as a further
system clock with a reference to at least one of the
two specific system clocks needs to be taken into
account.
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The method described above can preferably be used for
testing, controlling and maintaining the program, or a
technical system associated with the program.
In order to achieve the object, an arrangement for
monitoring a program is also specified, in which a
processor unit is provided, which is set up in such a
manner that
a) the program can have an instrumentation part added
to it;
b) the instrumentation part generates a message and
transmits it to a monitoring process;
c) the monitoring process initiates an action.
This arrangement is particularly suitable for carrying
out the method according to the invention, or one of
its developments explained above.
Exemplary embodiments of the invention will be
explained and described in the following text with
reference to the drawing, in which:
Figure 1 shows a block diagram with logic components
for monitoring a program;
Figure 2 shows various illustrations of mechanisms to
be monitored in a distributed system;
Figure 3 shows a processor unit.
Figure 1 shows a block diagram with logic components
for monitoring a program. The program 101 to be
monitored is provided with a filter functionality 102
and instrumentation 103. The monitoring process
mentioned widely above has blocks comprising an event
generator 104,
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an event manager 109 and the various display options
115 to 120 (views).
The event generator 104 contains a parser 105, two
message interfaces 106, 107 and a file 108. The event
manager 109 comprises a merger 110, an event list 111
(trace event list), a filter unit 112 and a filtered
list 113. The respective entry within the filtered list
113 is selected via a navigation unit 114 (stepper).
The filter functionality 102 is provided for selecting
specific instrumentation parts of the instrumentation
103 which are of interest for the respective
application. The result of the instrumentation, the
messages, are transmitted to a communication interface
(socket) 107, or are written to a file 108. The
incoming messages are processed in the parser 105, and
are transmitted to the merger 110, where the entries of
the messages received from the parser 105 are stored in
a list 111. In particular, the semantic check of the
time stamps attached to the messages is also carried
out here. Optionally, in block 112, all the messages
stored by the merger 110 in the list 111 are filtered
on the basis of specific presets. This results in the
filtered list 113, whose entries can be selected by
means of the stepper 114.
The stepper 114 is used as the interaction medium for
the user. Input can be entered there, and are passed on
via the socket 106 of the event generator 104 to the
instrumented program part 103. In particular, this
interaction allows an interplay between the program and
the instrumentation.
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The interaction can take place by means of a user input
or, alternatively, via a rule on the basis of "if ...
then ...". Furthermore, an action 121 can be carried
out which, against the background of the monitoring
process, leads to external control or some other
external intervention.
The filtered list 113 can be processed in various
representations 115 to 120. The data in the filtered
list 113 can be displayed as:
~ list (block 115),
~ hierarchically sorted view (for example on the basis
of computers or the structure of programs and
processes, block 116),
~ message sequence chart (MSC, block 117), in which
case it is possible to take account of predetermined
grouping,
~ detailed view (each message has an associated range
of information relating to a transmitter, receiver,
time stamp, message content, etc; block 118),
~ list of the user inputs (block 119),
~ test report (block 120).
Figure 2 shows various representations of mechanisms to
be monitored in a distributed system. To this end,
Figure 2 is subdivided into Figures 2A, 2B and 2C. The
horizontal line in each case represents the time
axis t.
Figure 2A shows the message transmission. A transmitter
201 sends a message at a time tl, and this is received
by a receiver 202 at a time t2. The receiver 203 has
already started to wait for this message at a time t3.
It waits until the time t2, before the receiver 202
continues with its task.
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. Figure 2B shows the remote procedure call (RPC)
mechanism. A process 203 sends a "CLIENT BEGIN(Call
object.method(...)" message to an addressee 204 at a
time t4. This message arrives at the addressee 204 at a
time t5, the addressee 205 preferably being a specific
computer, remote from the computer on which the process
203 is running. The addressee 204 initiates the
execution of the transmitted command at this time t5 by
means of the "SERVER BEGIN" command. The execution in
the addressee 204 is completed at a time t6, the task
is stopped ("SERVER END") and the result "res" is sent
back to the process 203 ("Return res=obj.meth(...)").
The result arrives at process 203 at a time t7, and the
RPC is ended by the "CLIENT END" command. The process
has waited from t4 to t7 and now continues using the
result "res" determined in the addressee 204, for its
processing.
Figure 2C shows an example of a control flow. In this
case, the intention is to join two processes to one
another ("Task Join"). A process Taskl 205 sends a
"JOIN REQUEST" command to a process Task2 206 at a time
t8. When it arrives there, at a time t9, a "JOIN START"
command results in the process of joining the Task2 206
process to the Task 1 205 process, which lasts until a
time t10. At the time t10, the "JOIN DONE" command
results in a return to the process Taskl 205, which
resumes its task with a "JOIN END" command at a time
tll. The process Taskl 205 waited from t8 to tll, and
the process Task2 206 is ended after t10.
Figures 2A, 2B and 2C show various mechanisms which can
be monitored in a distributed system in order to obtain
an overview of the interaction between programs and
processes running in a distributed manner. Particularly
for fault tracing or during maintenance work, it is an
inestimable advantage to be able to trace actions at
the interface between the processes.
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Figure 3 shows a processor unit PRZE. The processor
unit PRZE has a processor CPU, a memory SPE and an
input/output interface IOS, which is used in various
ways via an interface IFC: a graphics interface allows
an output to be seen on a monitor MON and/or to be
output on a printer PRT. Inputs are entered via a mouse
MAS or a keyboard TAST. The processor unit PRZE also
has a databus BUS, which provides the connection from a
memory MEM, the processor CPU and the input/output
interface IOS. Furthermore, additional components can
be connected to the databus BUS, such as additional
memory, a data memory (hard disk) or a scanner.
