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import { DecodedLogArgs, LogWithDecodedArgs } from 'ethereum-types';
const NUM_BLOCKS_PER_QUERY = 10000; // Number of blocks to query for events at a time.
const NUM_RETRIES = 3; // Number of retries if a request fails or times out.
export type GetEventsFunc<ArgsType extends DecodedLogArgs> = (
fromBlock: number,
toBlock: number,
) => Promise<Array<LogWithDecodedArgs<ArgsType>>>;
/**
* Gets all events between the given startBlock and endBlock by querying for
* NUM_BLOCKS_PER_QUERY at a time. Accepts a getter function in order to
* maximize code re-use and allow for getting different types of events for
* different contracts. If the getter function throws with a retryable error,
* it will automatically be retried up to NUM_RETRIES times.
* @param getEventsAsync A getter function which will be called for each step during pagination.
* @param startBlock The start of the entire block range to get events for.
* @param endBlock The end of the entire block range to get events for.
*/
export async function getEventsWithPaginationAsync<ArgsType extends DecodedLogArgs>(
getEventsAsync: GetEventsFunc<ArgsType>,
startBlock: number,
endBlock: number,
): Promise<Array<LogWithDecodedArgs<ArgsType>>> {
let events: Array<LogWithDecodedArgs<ArgsType>> = [];
for (let fromBlock = startBlock; fromBlock <= endBlock; fromBlock += NUM_BLOCKS_PER_QUERY) {
const toBlock = Math.min(fromBlock + NUM_BLOCKS_PER_QUERY - 1, endBlock);
const eventsInRange = await _getEventsWithRetriesAsync(getEventsAsync, NUM_RETRIES, fromBlock, toBlock);
events = events.concat(eventsInRange);
}
return events;
}
/**
* Calls the getEventsAsync function and retries up to numRetries times if it
* throws with an error that is considered retryable.
* @param getEventsAsync a function that will be called on each iteration.
* @param numRetries the maximum number times to retry getEventsAsync if it fails with a retryable error.
* @param fromBlock the start of the sub-range of blocks we are getting events for.
* @param toBlock the end of the sub-range of blocks we are getting events for.
*/
export async function _getEventsWithRetriesAsync<ArgsType extends DecodedLogArgs>(
getEventsAsync: GetEventsFunc<ArgsType>,
numRetries: number,
fromBlock: number,
toBlock: number,
): Promise<Array<LogWithDecodedArgs<ArgsType>>> {
let eventsInRange: Array<LogWithDecodedArgs<ArgsType>> = [];
for (let i = 0; i <= numRetries; i++) {
try {
eventsInRange = await getEventsAsync(fromBlock, toBlock);
} catch (err) {
if (isErrorRetryable(err) && i < numRetries) {
continue;
} else {
throw err;
}
}
break;
}
return eventsInRange;
}
function isErrorRetryable(err: Error): boolean {
return err.message.includes('network timeout');
}
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