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Fallback Provider

A FallbackProvider provides resilience, security and performance in a way that is customizable and configurable.

TYPES

<src>FallbackProviderOptions⇒ { cacheTimeout?: number , eventQuorum?: number , eventWorkers?: number , pollingInterval?: number , quorum?: number }

Additional options to configure a FallbackProvider.

class FallbackProvider

inherits from AbstractProvider, Provider

A FallbackProvider manages several Providers providing resilience by switching between slow or misbehaving nodes, security by requiring multiple backends to aggree and performance by allowing faster backends to respond earlier.

PROPERTIES

<src>fallbackProvider.providerConfigs⇒ Array< FallbackProviderState >read-only

<src>fallbackProvider.quorum⇒ numberread-only

The number of backends that must agree on a value before it is accpeted.

CREATING INSTANCES

<src>new FallbackProvider(providers: Array< AbstractProvider | FallbackProviderConfig >, network?: Networkish, options?: FallbackProviderOptions)

Creates a new FallbackProvider with providers connected to network.

If a Provider is included in providers, defaults are used for the configuration.

METHODS

<src>fallbackProvider._translatePerform(provider: AbstractProvider, req: PerformActionRequest)⇒ Promise< any >

Transforms a req into the correct method call on provider.

interface FallbackProviderConfig

A configuration entry for how to use a Provider.

PROPERTIES

<src>fallbackProviderConfig.priority⇒ number

The priority. Lower priority providers are dispatched first.

<src>fallbackProviderConfig.provider⇒ AbstractProvider

The provider.

<src>fallbackProviderConfig.stallTimeout⇒ number

The amount of time to wait before kicking off the next provider.

Any providers that have not responded can still respond and be counted, but this ensures new providers start.

<src>fallbackProviderConfig.weight⇒ number

The amount of weight a provider is given against the quorum.

interface FallbackProviderState

The statistics and state maintained for a Provider.

PROPERTIES

<src>fallbackProviderState.blockNumber⇒ number

The most recent blockNumber this provider has reported (-2 if none).

<src>fallbackProviderState.errorResponses⇒ number

The number of responses that errored.

<src>fallbackProviderState.lateResponses⇒ number

The number of responses that occured after the result resolved.

<src>fallbackProviderState.outOfSync⇒ number

How many times syncing was required to catch up the expected block.

<src>fallbackProviderState.requests⇒ number

The number of total requests ever sent to this provider.

<src>fallbackProviderState.rollingDuration⇒ number

A rolling average (5% current duration) for response time.

<src>fallbackProviderState.score⇒ number

The ratio of quorum-agreed results to total.

<src>fallbackProviderState.unsupportedEvents⇒ number

The number of requests which reported unsupported operation.