Adjust read capacity by wanted time #2
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added 3 commits
November 27, 2017 11:04
New option to use strongly consistent reads
lib/dynamo-backup.js
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| ddb.describeTable({ TableName: tableName }, function (err, data) { | ||
| if (err) { | ||
| return callback(err); | ||
| } | ||
| var descTime = new Date().getTime() - startDescTime - 0.3; |
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time is in milliseconds, 0.3ms is the during time to parse response result (average)
lib/dynamo-backup.js
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| this.consistentRead = !!options.consistentRead; // strongly consistent | ||
| this.consistentRatio = this.consistentRead ? 1 : 0.5; // eventually consistent consumes 1/2 of a read capacity unit. | ||
| this.singleCapacitySize = 4096 / this.consistentRatio; // 4KB for consistent, 8KB for eventually consistent | ||
| this.maxSingleScanReadCapacity = 1048576 / this.singleCapacitySize; // 1MB per scan page |
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4096 and 1048576could be stored in constants to be more explicit
lib/dynamo-backup.js
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| var averageItemSize = Math.ceil(Table.TableSizeBytes / Table.ItemCount); | ||
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| var minimumNbScans = Math.ceil(Table.TableSizeBytes / 1048576); // 1 scan can't return more than 1MB of data | ||
| var estimatedWriteTime = minimumNbScans * 0.035 * self.tablesToBackup.length; // ~35ms for 1MB response (estimation) with tables concurrency |
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1048576 and 0.035 in constants
lib/dynamo-backup.js
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| return; | ||
| } | ||
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| var estimatedFetchRatio = speed / 16384 ; // estimation ratio: if >1: faster, <1: slower. (16KB = highWaterMark of stream) |
lib/dynamo-backup.js
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| var ddb = new AWS.DynamoDB(); | ||
| ddb.updateTable(params, function(err, data) { |
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=>
`ddb.updateTable(params, callback);
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Fix SSE option: add variable to use AES256 or aws:kms
Apply fix from markitx#63
New option to create backup in specified during time.
New option to use strongly consistent reads