#
Other Providers

##
FallbackProvider inherits Provider
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The FallbackProvider is the most advanced Provider available in ethers.

It uses a quorum and connects to multiple Providers as backends, each configured with a priority and a weight .

When a request is made, the request is dispatched to multiple backends, randomly chosen (lower-value priority backends are always selected first) and the results from each are compared against the others. Only once the quorum has been reached will that result be accepted and returned to the caller.

By default the quorum requires 50% (rounded up) of the backends to agree. The weight can be used to give a backend Provider more influence.

new ethers.providers.FallbackProvider( providers [ , quorum ] )

Creates a new instance of a FallbackProvider connected to providers. If quorum is not specified, half of the total sum of the provider weights is used.

The providers can be either an array of Provider or FallbackProviderConfig. If a Provider is provided, the defaults are a priority of 1 and a weight of 1.

provider.providerConfigs ⇒ Array< FallbackProviderConfig >

The list of Provider Configurations that describe the backends.

provider.quorum ⇒ number

The quorum the backend responses must agree upon before a result will be resolved. By default this is half the sum of the weights.

###
FallbackProviderConfig

fallbackProviderConfig.provider ⇒ Provider

The provider for this configuration.

fallbackProviderConfig.priority ⇒ number

The priority used for the provider. Lower-value priorities are favoured over higher-value priorities. If multiple providers share the same priority, they are chosen at random.

fallbackProviderConfig.stallTimeout ⇒ number

The timeout (in ms) after which another Provider will be attempted. This does not affect the current Provider; if it returns a result it is counted as part of the quorum.

Lower values will result in more network traffic, but may reduce the response time of requests.

fallbackProviderConfig.weight ⇒ number

The weight a response from this provider provides. This can be used if a given Provider is more trusted, for example.

##
IpcProvider inherits JsonRpcProvider
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The IpcProvider allows the JSON-RPC API to be used over a local filename on the file system, exposed by Geth, Parity and other nodes.

This is only available in node.js (as it requires file system access, and may have additional complications due to file permissions. See any related notes on the documentation for the actual node implementation websites.

ipcProvider.path ⇒ string

The path this Provider is connected to.

##
UrlJsonRpcProvider inherits JsonRpcProvider
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This class is intended to be sub-classed and not used directly. It simplifies creating a Provider where a normal JsonRpcProvider would suffice, with a little extra effort needed to generate the JSON-RPC URL.

new ethers.providers.UrlJsonRpcProvider( [ network [ , apiKey ] ] )

Sub-classes do not need to override this. Instead they should override the static method `getUrl` and optionally `getApiKey`.

urlJsonRpcProvider.apiKey ⇒ any

The value of the apiKey that was returned from `InheritedClass.getApiKey`.

InheritingClass.getApiKey( apiKey ) ⇒ any

This function should examine the apiKey to ensure it is valid and return a (possible modified) value to use in `getUrl`.

InheritingClass.getUrl( network , apiKey ) ⇒ string

The URL to use for the JsonRpcProvider instance.

##
Web3Provider inherits JsonRpcProvider
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The Web3Provider is meant to ease moving from a web3.js based application to ethers by wrapping an existing Web3-compatible (such as a Web3HttpProvider, Web3IpcProvider or Web3WsProvider) and exposing it as an ethers.js Provider which can then be used with the rest of the library.

This may also be used to wrap a standard [EIP-1193 Provider](link-eip-1193].

new ethers.providers.Web3Provider( externalProvider [ , network ] )

Create a new Web3Provider, which wraps an EIP-1193 Provider or Web3Provider-compatible Provider.

web3Provider.provider ⇒ Web3CompatibleProvider

The provider used to create this instance.

###
ExternalProvider

An ExternalProvider can be either one for the above mentioned Web3 Providers (or otherwise compatible) or an EIP-1193 provider.

An ExternalProvider must offer one of the following signatures, and the first matching is used:

externalProvider.request( request ) ⇒ Promise< any >

This follows the EIP-1193 API signature.

The request should be a standard JSON-RPC payload, which should at a minimum specify the `method` and `params`.

The result should be the actual result, which differs from the Web3.js response, which is a wrapped JSON-RPC response.

externalProvider.sendAsync( request , callback ) ⇒ void

This follows the Web3.js Provider Signature.

The request should be a standard JSON-RPC payload, which should at a minimum specify the `method` and `params`.

The callback should use the error-first calling semantics, so `(error, result)` where the result is a JSON-RPC wrapped result.

externalProvider.send( request , callback ) ⇒ void

This is identical to `sendAsync`. Historically, this used a synchronous web request, but no current browsers support this, so its use this way was deprecated quite a long time ago

##
WebSocketProvider inherits JsonRpcProvider
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The WebSocketProvider connects to a JSON-RPC WebSocket-compatible backend which allows for a persistent connection, multiplexing requests and pub-sub events for a more immediate event dispatching.

The WebSocket API is newer, and if running your own infrastructure, note that WebSockets are much more intensive on your server resources, as they must manage and maintain the state for each client. For this reason, many services may also charge additional fees for using their WebSocket endpoints.

new ethers.providers.WebSocketProvider( [ url [ , network ] ] )

Returns a new WebSocketProvider connected to url as the network.

If url is unspecified, the default `"ws://localhost:8546"` will be used. If network is unspecified, it will be queried from the network.

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