Svc::ActiveLogger Component

1. Introduction

The Svc::ActiveLogger component processes events from other components. The events are put in packets and sent to an external user like a ground system. The component provides event filtering and writing event logs to a file.

2. Requirements

The requirements for Svc::ActiveLogger are as follows:

Requirement	Description	Verification Method
AL-001	The `Svc::ActiveLogger` component shall store events.	Inspection; Unit Test
AL-002	The `Svc::ActiveLogger` component shall store a configurable circular buffer of events by severity.	Unit Test
AL-003	The `Svc::ActiveLogger` component shall write the circular buffers to a file upon command	Unit Test
AL-004	The `Svc::ActiveLogger` component shall have commands to filter events based on event severity.	Unit Test
AL-005	The `Svc::ActiveLogger` component shall filter events on receipt of the event on the caller's thread but before being placed in the event buffer.	Unit Test
AL-006	The `Svc::ActiveLogger` component shall filter events on the thread of the component before sending them as packets, but after they have been stored in the circular buffers	Unit Test
AL-007	The `Svc::ActiveLogger` component shall filter events based on the event ID.	Unit Test

3. Design

3.1 Context

3.1.1 Component Diagram

The Svc::ActiveLogger component has the following component diagram:

`Svc::ActiveLogger` Diagram

3.1.2 Ports

The Svc::ActiveLogger component uses the following port types:

Port Data Type	Name	Direction	Kind	Usage
`Fw::Log`	LogRecv	Input	Synchronous	Receive events from components
`Fw::Com`	PktSend	Output	n/a	Send event packets to external user
`Svc::FatalEvent`	FatalAnnounce	Output	n/a	Send FATAL event (to health)

3.2 Functional Description

The Svc::ActiveLogger component provides an event logging function for the software. The framework autocoder allows developers to specify a set of events in the component XML (see User's Guide). For those components, the autocoder will add an Fw::Log output port to send events in serialized form. The ActiveLogger filters the events and sends them as packets to other components that send them out of the system.

NOTE: Event ID value 0 is reserved for the logger.

3.2.1 Filtering

The Svc::ActiveLogger LogRecv input port handler filters events on the thread of the caller to lessen the CPU load caused by sending events via IPC to the component thread. The filters can be set by severity. By default, the DIAGNOSTIC events are filtered since the number can be the highest and are typically only used for development and debugging. This input filter is modified by the SET_EVENT_REPORT_FILTER command.

The thread of the component retrieves the log events from the message queue and stores them in a circular buffer by event severity. There is a second filter that determines whether or not the the event will be converted to a packet and sent via the PktSend port. This allows more events to be stored in the circular buffers than are sent, so that in the event more diagnostic data is needed the event buffers can be dumped. This input filter is modified by the SET_EVENT_SEND_FILTER command.

The component also allows filtering events by event ID. There is a configuration parameter that sets the number of IDs that can be filtered. This allows operators to mute a particular event that might be flooding the event queue. This filter can be set on either receipt of the event or prior to sending the event. In most cases, it is desirable to filter on receipt so a flooding event does not overwhelm the message queue. These filters is modified by the SET_EVENT_ID_REPORT_FILTER and SET_EVENT_ID_SEND_FILTER command.

3.2.2 Log Buffers

The component has a set of circular buffers that store a history of events. The depth of the filters is configurable. The set of events stored in the buffers are those that pass the input filters and are queued for the component thread. The intent is that the larger set of events than those sent can be stored in the buffers and dumped to a file if needed. The DUMP_EVENT_LOG command will dump the contents of a log to a file.

3.2.3 Fatal Announce

When the ActiveLogger component receives a FATAL event, it calls the FatalAnnounce port. Another component that has a system response to FATALs (such as reset) can connect to the port to be informed when a FATAL has occurred.