---
eip: 801
title: Canary Standard
author: ligi <ligi@ligi.de>
type: Standards Track
category: ERC
status: Stagnant
created: 2017-12-16
---

## Simple Summary

A standard interface for canary contracts.

## Abstract

The following standard allows the implementation of canaries within contracts.
This standard provides basic functionality to check if a canary is alive, keeping the canary alive and optionally manage feeders.

## Motivation

The canary can e.g. be used as a [warrant canary](https://en.wikipedia.org/wiki/Warrant_canary).
A standard interface allows other applications to easily interface with canaries on Ethereum - e.g. for visualizing the state, automated alarms, applications to feed the canary or contracts (e.g. insurance) that use the state.

## Specification

### Methods

#### isAlive()

Returns if the canary was fed properly to signal e.g. that no warrant was received.

``` js
function isAlive() constant returns (bool alive)
```

#### getBlockOfDeath()

Returns the block the canary died.
Throws if the canary is alive.

``` js
function getBlockOfDeath() constant returns (uint256 block)
```

#### getType()

Returns the type of the canary:

* `1` = Simple (just the pure interface as defined in this ERC)
* `2` = Single feeder (as defined in ERC-TBD)
* `3` = Single feeder with bad food (as defined in ERC-TBD)
* `4` = Multiple feeders (as defined in ERC-TBD)
* `5` = Multiple mandatory feeders (as defined in ERC-TBD)
* `6` = IOT (as defined in ERC-TBD)

`1` might also be used for a special purpose contract that does not need a special type but still wants to expose the functions and provide events as defined in this ERC.

``` js
function getType() constant returns (uint8 type)
```

### Events

#### RIP

MUST trigger when the contract is called the first time after the canary died.

``` js
event RIP()
```

## Implementation

TODO

## Copyright
Copyright and related rights waived via [CC0](../LICENSE.md).