Cyber Timer

[Reuquen Boyett]

every module contains and communicates through the node. A module can have different types of communication by defining read/write and/or service/client in a node. WarningDuplicate name is not allowed in topo objects, such as node, reader/writer, service/clinet in the topo.

Base Class for Reader Reader is identified by one apollo::cyber::proto::RoleAttribute, it contains the channel_name, channel_id that we subscribe, and host_name, process_id and node that we are located, and qos that describes our transportation quality.

If you want to set a key-value, and hope other nodes to get the value, Routing, sensor internal/external references are set by Parameter Service ParameterServer can set a parameter, and then you can get/list paramter(s) by start a ParameterClient to send responding request WarningYou should only have one ParameterServer works

Wrapper for a glog Logger which asynchronously writes log messages. This class starts a new thread responsible for forwarding the messages to the logger, and performs double buffering. Writers append to the current buffer and then wake up the logger thread. The logger swaps in a new buffer and writes any accumulated messages to the wrapped Logger.

This double-buffering design dramatically improves performance, especially for logging messages which require flushing the underlying file (i.e WARNING and above for default). The flush can take a couple of milliseconds, and in some cases can even block for hundreds of milliseconds or more. With the double-buffered approach, threads can proceed with useful work while the IO thread blocks.

WarningThe logger limits the total amount of buffer space, so if the underlying log blocks for too long, eventually the threads generating the log messages will block as well. This prevents runaway memory usage.

Flush() and Write() must not be called after this. NOTE: this is currently only used in tests: in real life, we enable async logging once when the program starts and then never disable it. REQUIRES: Start() must have been called.

I got handed a piece of existing javascript and asked to modify it by my boss - trouble is, I barely know my way around javascript at all - our back end developer quit unexpectedly, and I'm just trying to help out.

I need to make it so this countdown timer always displays double digits (01 instead of 1). I've searched here and tried some of the similar question solutions, but they're all rather specific to the individual question and I'm not having any luck at all making changes using if else if statements (partly because my js understanding and syntax is not good.) Hopefully it's a easy fix for someone who knows what they're doing! Thanks in advance.

A watchdog timer (WDT, or simply a watchdog), sometimes called a computer operating properly timer (COP timer),[1] is an electronic or software timer that is used to detect and recover from computer malfunctions. Watchdog timers are widely used in computers to facilitate automatic correction of temporary hardware faults, and to prevent errant or malevolent software from disrupting system operation.

During normal operation, the computer regularly restarts the watchdog timer to prevent it from elapsing, or "timing out". If, due to a hardware fault or program error, the computer fails to restart the watchdog, the timer will elapse and generate a timeout signal. The timeout signal is used to initiate corrective actions. The corrective actions typically include placing the computer and associated hardware in a safe state and invoking a computer reboot.

Microcontrollers often include an integrated, on-chip watchdog. In other computers the watchdog may reside in a nearby chip that connects directly to the CPU, or it may be located on an external expansion card in the computer's chassis.

Watchdog timers are commonly found in embedded systems and other computer-controlled equipment where humans cannot easily access the equipment or would be unable to react to faults in a timely manner. In such systems, the computer cannot depend on a human to invoke a reboot if it hangs; it must be self-reliant. For example, remote embedded systems such as space probes are not physically accessible to human operators; these could become permanently disabled if they were unable to autonomously recover from faults. In robots and other automated machines, a fault in the control computer could cause equipment damage or injuries before a human could react, even if the computer is easily accessed. A watchdog timer is usually employed in cases like these.

Watchdog timers are also used to monitor and limit software execution time on a normally functioning computer. For example, a watchdog timer may be used when running untrusted code in a sandbox, to limit the CPU time available to the code and thus prevent some types of denial-of-service attacks.[2] In real-time operating systems, a watchdog timer may be used to monitor a time-critical task to ensure it completes within its maximum allotted time and, if it fails to do so, to terminate the task and report the failure.

The act of restarting a watchdog timer is commonly referred to as kicking[a] the watchdog.[3][4] Kicking is typically done by writing to a watchdog control port or by setting a particular bit in a register. Alternatively, some tightly coupled[b] watchdog timers are kicked by executing a special machine language instruction. An example of this is the CLRWDT (clear watchdog timer) instruction found in the instruction set of some PIC microcontrollers.

In computers that are running operating systems, watchdog restarts are usually invoked through a device driver. For example, in the Linux operating system, a user space program will kick the watchdog by interacting with the watchdog device driver, typically by writing a zero character to .mw-parser-output .monospacedfont-family:monospace,monospace/dev/watchdog or by calling a KEEPALIVE ioctl.[5] The device driver, which serves to abstract the watchdog hardware from user space programs, may also be used to configure the time-out period and start and stop the timer.

Some watchdog timers will only allow kicks during a specific time window. The window timing is usually relative to the previous kick or, if the watchdog has not yet been kicked, to the moment the watchdog was enabled. The window begins after a delay following the previous kick, and ends after a further delay. If the computer attempts to kick the watchdog before or after the window, the watchdog will not be restarted, and in some implementations this will be treated as a fault and trigger corrective action.

A watchdog timer is said to be enabled when operating and disabled when idle. Upon power-up, a watchdog may be unconditionally enabled or it may be initially disabled and require an external signal to enable it. In the latter case, the enabling signal may be automatically generated by hardware or it may be generated under software control.

Watchdog timers come in many configurations, and many allow their configurations to be altered. For example, the watchdog and CPU may share a common clock signal as shown in the block diagram below, or they may have independent clock signals. A basic watchdog timer has a single timer stage which, upon timeout, typically will reset the CPU:

Two or more timers are sometimes cascaded to form a multistage watchdog timer, where each timer is referred to as a timer stage, or simply a stage. For example, the block diagram below shows a three-stage watchdog. In a multistage watchdog, only the first stage is kicked by the processor. Upon first stage timeout, a corrective action is initiated and the next stage in the cascade is started. As each subsequent stage times out, it triggers a corrective action and starts the next stage. Upon final stage timeout, a corrective action is initiated, but no other stage is started because the end of the cascade has been reached. Typically, single-stage watchdog timers are used to simply restart the computer, whereas multistage watchdog timers will sequentially trigger a series of corrective actions, with the final stage triggering a computer restart.[4]

Watchdog timers may have either fixed or programmable time intervals. Some watchdog timers allow the time interval to be programmed by selecting from among a few selectable, discrete values. In others, the interval can be programmed to arbitrary values. Typically, watchdog time intervals range from ten milliseconds to a minute or more. In a multistage watchdog, each timer may have its own, unique time interval.

A watchdog timer may initiate any of several types of corrective action, including maskable interrupt, non-maskable interrupt, hardware reset, fail-safe state activation, power cycling, or combinations of these. Depending on its architecture, the type of corrective action or actions that a watchdog can trigger may be fixed or programmable. Some computers (e.g., PC compatibles) require a pulsed signal to invoke a hardware reset. In such cases, the watchdog typically triggers a hardware reset by activating an internal or external pulse generator, which in turn creates the required reset pulses.[4]

In embedded systems and control systems, watchdog timers are often used to activate fail-safe circuitry. When activated, the fail-safe circuitry forces all control outputs to safe states (e.g., turns off motors, heaters, and high-voltages) to prevent injuries and equipment damage while the fault persists. In a two-stage watchdog, the first timer is often used to activate fail-safe outputs and start the second timer stage; the second stage will reset the computer if the fault cannot be corrected before the timer elapses.

For example, the above diagram shows a likely configuration for a two-stage watchdog timer. During normal operation the computer regularly kicks Stage1 to prevent a timeout. If the computer fails to kick Stage1 (e.g., due to a hardware fault or programming error), Stage1 will eventually timeout. This event will start the Stage2 timer and, simultaneously, notify the computer (by means of a non-maskable interrupt) that a reset is imminent. Until Stage2 times out, the computer may attempt to record state information, debug information, or both. As a last resort, the computer will be reset upon Stage2 timeout.

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