Introduction

A Sequencer block for logging data with a message-based API. Compatible with the same Datastores as CDPLogger.

Glossary

This documentation refers to two kinds of events:

• CDP events - CDPEventManager events. For example, CDPAlarm Set, Clear and Acknowledge events. These are the events that are logged by CDP Logger, LogWriter and read by EventLogReader.
• Message events - the event inputs and outputs of sequencer blocks as defined by the IEC 61499 standard. In this document, also referred as event messages or just messages.

Usage

To set up a LogWriter, add it to a component. Next, select and add a Datastore (e.g. CDPCompactDatastore) into the LogWriter.

To write values, first send the WriteValueDefinition message to write the tags associated with the node providing values. Then send the WriteValue message to write the values. The WriteValue message event can be called multiple times for the same node. Finally, call the Flush message event to flush any internal buffers and commit the data to the datastore or wait until the AutoFlush triggers.

CDP events can be written in a similar way. First, call the WriteEventDefinition message to write the tags associated with the node emitting the CDP events. Then call the WriteEvent message to write an CDP event. As with values, either call Flush manually to make sure the data is committed to the datastore or wait until the AutoFlushTimeout triggers.

The following is a block diagram of the typical usage of the LogWriter block. See below for instructions on how to replicate the example.

Tips

• The LogWriter value inputs match the ValueLogReader outputs. This means that the LogWriter can be connected directly to the ValueLogReader and be used to extract either all or a subset of the logged data to a new datastore.
• Similarly, the LogWriter CDP event inputs match the EventLogReader outputs, so it can be used to extract CDP event data to a new datastore.
• The LogWriter CDP event inputs also match the CDPEventListener outputs. This can be used to log CDP events from a CDPEventListener to a datastore.

Configuration

See below for a list of configuration options specific to this block.

Datastore

Datastore is the backend used by LogWriter, usually some database. The default is CDPCompactDatastore.

For more information about datastores, see the Choosing a Datastore page.

Message Events

Writing Tags

The tags associated with a node can be written in two ways:

• Semicolon-separated tagname=value list in the Tags argument.
• Add each tag as a separate input argument with the tag name as the argument name and the tag value as the argument value. Note each user-added argument must be listed in the Data property of the message event.

This affects the WriteValue, WriteValueDefinition, WriteEvent and WriteEventDefinition message events.

Internal Message Events

When disabling the Hide Internal Items filter, some additional message events become visible. It is normally not necessary to access them.

Arguments

CDP Event Code Flags

Common event codes used in the CDP framework (note multiple flags can be set at the same time)): Common event codes used in the CDP framework (note that multiple flags can be set at the same time):

Properties

Accessing the Data

The data is written to the selected Datastore. Depending on the Datastore, the data can be accessed in different ways. For example, the CSVDatastore writes the data to a CSV file, which can be opened in a spreadsheet application. To access the written data with CDP tools, add a LogServer component and copy the Datastore configuration from the LogWriter. The LogServer component will then serve the data in the same way as the built-in server of CDP Logger.

There are several options to view logged data through the log server:

• Using CDP Studio Analyze mode Historic Data functionality which will detect a running CDP Logger or LogServer and connect to it. The Analyze mode can also be used to export the logged data to CSV format.
• Making your own GUI application that includes Database Graph Widget.
• Python code can query values from a running CDP Logger or LogServer using the PythonCDPLoggerClient.
• The ValueLogReader and EventLogReader sequencer blocks can be used to extract and process logged data.

The selected Datastore might provide other custom ways to view logged data. See the manual for the selected datastore to get specific information on that.

Examples

Here are some examples of using the LogWriter.

Logging CDPEventListener Events

Here is a minimal example using the LogWriter. The example uses a CDPEventListener and writes every CDP event it emits to a CSV file.

To run the example, just start the application. The extracted values will be written to a "log-events.csv" file in the application's working directory.

Here is how to replicate the example:

• Create a system.
• From the Resource tree, add
  • Sequencer.CDPEventListener - a block that listens to all CDP events in the system and emits an event message for each CDP event. In this minimal example, we have not set any filters, so the block will emit all CDP events.
  • CDPLogger.LogWriter - writes the received event messages to a new Datastore (CSVDatastore in this example).
• Add a CDPLogger.CSVDatastore into the LogWriter block to store extracted CDP events in a CSV file.
• Connect the blocks as shown in the image above.

Other Examples

See also some other examples containing the LogWriter:

• ValueLogReader and LogWriter - extract logged values from a CDP Logger datastore and write them to a new datastore.
• EventLogReader and LogWriter - extract logged events from a CDP Logger datastore and write them to a new datastore.