provider.fallback

Documentation for eth_defi.provider.fallback Python module.

JSON-RPC provider fallback and redundancy mechanisms.

Functions

get_fallback_provider(web3)

Get the fallback provider of a Wen3 instance.

Classes

FallbackProvider

Fault-tolerance for JSON-RPC requests with multiple providers.

FallbackStrategy

Different supported fallback strategies.

Exceptions

ExtraValueError

A ValueError that is used to signal that the RPC response was not valid.
exception ExtraValueError

Bases: ValueError

A ValueError that is used to signal that the RPC response was not valid.

Add extra debugging.

__init__(*args, **kwargs)
__new__(**kwargs)
add_note()

Exception.add_note(note) – add a note to the exception

with_traceback()

Exception.with_traceback(tb) – set self.__traceback__ to tb and return self.

class FallbackStrategy

Bases: enum.Enum

Different supported fallback strategies.

cycle_on_error = 'cycle_on_error'

Automatically switch to the next provider on an error

class FallbackProvider

Bases: eth_defi.provider.named.BaseNamedProvider

Fault-tolerance for JSON-RPC requests with multiple providers.

Fall back to the next provider on the list if a JSON-RPC request fails. Contains build-in retry logic in round-robin manner. We will also recover from situations when we suspect the node does not have the block data we are asking yet (but should have shorty).

See also

  • eth_defi.middlware.exception_retry_middleware()

  • eth_defi.middlware.ProbablyNodeHasNoBlock()

Note

FallbackProvider does not call any middlewares installed on the providers themselves.

Parameters

  • providers – List of provider we cycle through.

  • strategy –

    What is the strategy to deal with errors.

    Currently on cycling supported.

  • retryable_exceptions – List of exceptions we can retry.

  • retryable_status_codes – List of HTTP status codes we can retry.

  • retryable_rpc_error_codes – List of GoEthereum error codes we can retry.

  • sleep – Seconds between retries.

  • backoff – Multiplier to increase sleep.

  • retries – How many retries we attempt before giving up.

  • switchover_noisiness – How loud we are about switchover issues.

  • state_missing_switch_over_delay –

    If we encounter state missing condition at node, what is the minimum time (seconds) we wait before trying to switch to next node.

    See code comments for details.

__init__(providers, strategy=FallbackStrategy.cycle_on_error, retryable_exceptions=(<class 'requests.exceptions.ConnectionError'>, <class 'requests.exceptions.HTTPError'>, <class 'requests.exceptions.Timeout'>, <class 'requests.exceptions.TooManyRedirects'>, <class 'web3.exceptions.BlockNotFound'>, <class 'requests.exceptions.ChunkedEncodingError'>, <class 'http.client.RemoteDisconnected'>, <class 'eth_defi.middleware.SomeCrappyRPCProviderException'>, <class 'requests.exceptions.ContentDecodingError'>), retryable_status_codes=(429, 500, 502, 503, 504, 525, 520, 410, 403, 400), retryable_rpc_error_codes=(-32003, -32043, -32005, -32701, 42903, -32002, -32603, -32052, -32601), sleep=5.0, backoff=1.6, retries=6, state_missing_switch_over_delay=12.0, switchover_noisiness=30)
Parameters

  • providers (list[eth_defi.provider.named.BaseNamedProvider | web3.providers.rpc.rpc.HTTPProvider]) – List of provider we cycle through.

  • strategy –

    What is the strategy to deal with errors.

    Currently on cycling supported.

  • retryable_exceptions – List of exceptions we can retry.

  • retryable_status_codes – List of HTTP status codes we can retry.

  • retryable_rpc_error_codes – List of GoEthereum error codes we can retry.

  • sleep (float) – Seconds between retries.

  • backoff (float) – Multiplier to increase sleep.

  • retries (int) – How many retries we attempt before giving up.

  • switchover_noisiness – How loud we are about switchover issues.

  • state_missing_switch_over_delay (float) –

    If we encounter state missing condition at node, what is the minimum time (seconds) we wait before trying to switch to next node.

    See code comments for details.

currently_active_provider

Currently active provider

api_retry_counts

provider number-> api method name -> retry counts dict

property endpoint_uri

Return the active node URI endpoint.

For HTTPProvider compatibility.

has_multiple_providers()

Have we configured multiple providers

Return type

bool

reset_switch()

Reset the provider switch to the first provider.

  • Assume we have main provider and more expensive backup providers

  • Try to switch back to the main provider if we have switched away due to a temporary error

  • Used in batch scan tasks

switch_provider(log_level=None, randomise=False, cause='<not specified>')

Switch to next available provider.

Parameters

  • log_level (int) – Logging level to be verbose about the switch over

  • random – If set switch to a random provider instead of cycling.

  • cause (str) –

get_active_provider()

Get currently active provider.

If this provider fails, we are automatically recycled to the next one.

Return type

eth_defi.provider.named.BaseNamedProvider | web3.providers.rpc.rpc.HTTPProvider

get_total_api_call_counts()

Get API call coubst across all providers

Return type

dict[str, int]

make_request(method, params)

Make a request.

  • By default use the current active provider

  • If there are errors try cycle through providers and sleep between cycles until one provider works

  • Use a special “ignore_error” parameter to skip retries, if given in eth_call payload.

Parameters

  • method (web3.types.RPCEndpoint) –

  • params (Any) –

Return type

web3.types.RPCResponse

property call_endpoint_uri: str

Return the active node URI where call JSON-RPCs go.

Warning

Endpoint URIs often contain API keys. They should be never publicly displayed as is.

request_func(w3, middleware_onion)

@param w3 is the web3 instance @param middleware_onion is an iterable of middleware,

ordered by first to execute

@returns a function that calls all the middleware and

eventually self.make_request()

Parameters

  • w3 (Web3) –

  • middleware_onion (web3.datastructures.NamedElementOnion[str, Type[web3.middleware.base.Web3Middleware]]) –

Return type

Callable[[…], web3.types.RPCResponse]

get_fallback_provider(web3)

Get the fallback provider of a Wen3 instance.

Can be nested in eth_defi.provider.mev_block.MEVBlockerProvider.

Parameters

web3 (web3.main.Web3) – Web3 instance

Raises

AssertionError – If there is no fallback provider available

Return type

eth_defi.provider.fallback.FallbackProvider