デバッグ後、私はUnprocessedItems
応答要素に気付きました。調べた後、UnprocessedItems
in the docs私はもっと詳しく読んだはずです。以下のコードは、遅延(指数バックオフ)を伴う再試行ループを実行します:
var clearEventTable = function (tableName, client, cleared) {
var exclusiveStartKey = null;
var retryCount = 0;
var read = function(query, callback) {
client.scan(query, function (err, page) {
if(err) {
console.log(err);
return callback(err);
}
retryCount = 0;
exclusiveStartKey = page.LastEvaluatedKey || null;
if(page.Count == 0) {
return callback(null, {});
}
if(page.Count < 25 && exclusiveStartKey) {
console.log("read capacity limit reached: " + JSON.stringify(page, null, 2));
}
var keys = _.map(page.Items, function(n) {
return { DeleteRequest: { Key: n } };
});
var batch = {
RequestItems: {},
ReturnConsumedCapacity: "INDEXES",
ReturnItemCollectionMetrics: "SIZE"
};
batch.RequestItems[tableName] = keys;
callback(null, batch);
});
};
var write = function(batch, callback) {
if(batch && batch.RequestItems){
client.batchWriteItem(batch, function(err, result) {
if(err) {
console.log(err);
return callback(err);
}
if(Object.keys(result.UnprocessedItems).length !== 0) {
console.log("Retry batchWriteItem: " + JSON.stringify(result, null, 2));
retryCount++;
var retry = {
RequestItems: result.UnprocessedItems,
ReturnConsumedCapacity: "INDEXES",
ReturnItemCollectionMetrics: "SIZE"
};
// retry with exponential backoff
var delay = retryCount > 0 ? (50 * Math.pow(2, retryCount - 1)) : 0;
setTimeout(write(retry, callback), delay);
return;
}
callback(null, result);
});
} else {
callback(null);
}
};
var params = {
TableName: tableName,
ProjectionExpression: "aggregateId,id",
Limit: 25, // max 25 per batchWriteItem
ConsistentRead: false,
ReturnConsumedCapacity: "TOTAL"
};
async.doWhilst(function (next) {
// retrieve entities
if (exclusiveStartKey)
params.ExclusiveStartKey = exclusiveStartKey;
async.compose(write, read)(params, function (err, result) {
if (err) next(err);
else next(null, result);
});
}, function() {
// test if we need to load more
return exclusiveStartKey !== null;
}, function (err, r) {
// return results
if (err) {
console.log(err);
return cleared(err);
}
return cleared(null);;
});
};