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Refactor optimistic locking loop into an abstract base class #26

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Oct 31, 2023
Merged

Refactor optimistic locking loop into an abstract base class #26

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120 changes: 66 additions & 54 deletions src/index.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -28,6 +28,38 @@
dangerously?: boolean
}

abstract class BaseDynamoDBAutoIncrement {
constructor(readonly props: DynamoDBAutoIncrementProps) {}

protected abstract next(
item: Record<string, NativeAttributeValue>
): Promise<{ puts: PutCommandInput[]; nextCounter: number }>

async put(item: Record<string, NativeAttributeValue>) {
for (;;) {
const { puts, nextCounter } = await this.next(item)

if (this.props.dangerously) {
await Promise.all(puts.map((obj) => this.props.doc.put(obj)))
} else {
try {
await this.props.doc.transactWrite({
TransactItems: puts.map((Put) => ({ Put })),
})
} catch (e) {
if (e instanceof TransactionCanceledException) {
continue
} else {
throw e

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}
}
}

return nextCounter
}
}
}

/**
* Update an auto-incrementing partition key in DynamoDB.
*
Expand Down Expand Up @@ -55,9 +87,7 @@
* })
* ```
*/
export class DynamoDBAutoIncrement {
constructor(readonly props: DynamoDBAutoIncrementProps) {}

export class DynamoDBAutoIncrement extends BaseDynamoDBAutoIncrement {
async #getLast(): Promise<number | undefined> {
return (
(
Expand All @@ -70,62 +100,44 @@
)
}

async put(item: Record<string, NativeAttributeValue>) {
for (;;) {
const counter = await this.#getLast()
protected async next(item: Record<string, NativeAttributeValue>) {
const counter = await this.#getLast()

let nextCounter, ConditionExpression, ExpressionAttributeValues
if (counter === undefined) {
nextCounter = this.props.initialValue
ConditionExpression = 'attribute_not_exists(#counter)'
} else {
nextCounter = counter + 1
ConditionExpression = '#counter = :counter'
ExpressionAttributeValues = {
':counter': counter,
}
let nextCounter, ConditionExpression, ExpressionAttributeValues
if (counter === undefined) {
nextCounter = this.props.initialValue
ConditionExpression = 'attribute_not_exists(#counter)'
} else {
nextCounter = counter + 1
ConditionExpression = '#counter = :counter'
ExpressionAttributeValues = {
':counter': counter,
}
}

const puts: PutCommandInput[] = [
{
ConditionExpression,
ExpressionAttributeNames: {
'#counter': this.props.counterTableAttributeName,
},
ExpressionAttributeValues,
Item: {
...this.props.counterTableKey,
[this.props.counterTableAttributeName]: nextCounter,
},
TableName: this.props.counterTableName,
const puts: PutCommandInput[] = [
{
ConditionExpression,
ExpressionAttributeNames: {
'#counter': this.props.counterTableAttributeName,
},
{
ConditionExpression: 'attribute_not_exists(#counter)',
ExpressionAttributeNames: {
'#counter': this.props.tableAttributeName,
},
Item: { [this.props.tableAttributeName]: nextCounter, ...item },
TableName: this.props.tableName,
ExpressionAttributeValues,
Item: {
...this.props.counterTableKey,
[this.props.counterTableAttributeName]: nextCounter,
},
]

if (this.props.dangerously) {
await Promise.all(puts.map((obj) => this.props.doc.put(obj)))
} else {
try {
await this.props.doc.transactWrite({
TransactItems: puts.map((Put) => ({ Put })),
})
} catch (e) {
if (e instanceof TransactionCanceledException) {
continue
} else {
throw e
}
}
}
TableName: this.props.counterTableName,
},
{
ConditionExpression: 'attribute_not_exists(#counter)',
ExpressionAttributeNames: {
'#counter': this.props.tableAttributeName,
},
Item: { [this.props.tableAttributeName]: nextCounter, ...item },
TableName: this.props.tableName,
},
]

return nextCounter
}
return { puts, nextCounter }
}
}
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