How to Access Object From Amazon s3 using getSignedUrl Operation
I`m able to generate Signed url using getSignedUrl method.
var url = s3.getSignedUrl('getObject', paramsurl);
using this url can i access full object from s3? i make http request but its only return 1000 as xml response. how to find next set of Objects and push to new array?
Your questions appears to be related to how many S3 objects are returned in a single ListObjects call.
If so, when you call the underlying APIs that list AWS resources, the API will typically return, by default, 1000 items. It will also return a 'next token' that you can use in a subsequent call to the same API to return the next batch of items.
Sometimes, you can also specify a 'max items' or 'max keys' in your request to allow you to override the default of 1000.
PS if you use the AWS SDKs then this batching of results is typically hidden from you.
Related
I am going through the documentation of ListObjects function in AWS' go SDK.
(the same holds more or less for the actual API endpoint)
So the docs write:
Returns some or all (up to 1,000) of the objects in a bucket.
What does this mean? If my bucket has 200.000 objects this API call will not work?
This example uses ListObjectsPages (which calls ListObjects under the hood) and claims to list all objects.
What is the actual case here?
I am going through the documentation of ListObjects function in AWS' go SDK.
Use ListObjectsV2. It behaves more or less the same, but it's an updated version of ListObjects. It's not super common for AWS to update APIs, and when they do, it's usually for a good reason. They're great about backwards compatibility which is why ListObjects still exists.
This example uses ListObjectsPages (which calls ListObjects under the hood) and claims to list all objects.
ListObjectsPages is a paginated equivalent of ListObjects, and ditto for the V2 versions which I'll describe below.
Many AWS API responses are paginated. AWS uses Cursor Pagination; this means request responses include a cursor - ContinuationToken in the case of ListObjectsV2 . If more objects exist (IsTruncated in the response), a subsequent ListObjectsV2 request content can provide the ContinuationToken to continue the listing where the first response left off.
ListObjectsV2Pages handles the iterative ListObjectsV2 requests for you so you don't have to handle the logic of ContinuationToken and IsTruncated. Instead, you provide a function that will be invoked for each "page" in the response.
So it's accurate to say ListObjectsV2Pages will list "all" the objects, but it's because it makes multiple ListObjectsV2 calls in the backend that it will list more than one page of responses.
Thus, ...Pages functions can be considered convenience functions. You should always use them when appropriate - they take away the pain of pagination, and pagination is critical to make potentially high volume api responses operable. In AWS, if pagination is supported, assume you need it - in typical cases, the first page of results is not guaranteed to contain any results, even if subsequent pages do.
The AWS Go SDK V2 gives us paginator types to help us manage S3's per-query item limits. ListObjectsV2Pages is gone. In its place we get ListObjectsV2Paginator, which deals with the pagination details that #Daniel_Farrell mentioned.
The constructor accepts the same params as the list objects query (type ListObjectsV2Input). The paginator exposes 2 methods: HasMorePages: bool and NextPage: (*ListObjectsV2Output, error).
var items []Item
for p.HasMorePages() {
batch, err := p.NextPage(ctx)
// etc...
item = append(items, newItems...)
}
In the scenario of listing all versions of an object using its key as a prefix:
import boto3
bucket = 'bucket name'
key = 'key'
s3 = boto3.resource('s3')
versions = s3.Bucket(bucket).object_versions.filter(Prefix=key)
for version in versions:
obj = version.get()
print(obj.get('VersionId'), obj.get('ContentLength'), obj.get('LastModified'))
Do I get charged only for listing the objects that are matching the prefix?
If so, is each object/version listed treated as a separate list request?
No, each object/version listed is not treated as a separate list request. You're only paying for the API requests to S3 (at something like $0.005 per 1000 API requests). A single API request will return many (up to 1000) objects/versions that match the indicated prefix. The prefix filtering itself happens server-side in S3.
The way to get a handle on this is to understand that AWS SDK calls ultimately result in API requests to AWS service endpoints e.g. S3 APIs. What you need to do is work out how your SDK client requests map to the underlying API requests to determine what is likely happening.
If your request is a simple 'list objects in my bucket' case, the boto3 SDK is going to make one or more ListObjectsV2 API calls. I say "or more" because the SDK may need to make more than one API request because API requests typically yield a maximum number of results (e.g. 1000 objects in a ListObjectsV2 response). If there are 2500 objects in the bucket, for example, then three ListObjectsV2 requests would need to be made to the S3 API.
If your request is 'list objects in my bucket with a given prefix', then you need to know what capabilities are present on the ListObjectsV2 API call. Importantly, prefix is one of the parameters. This is how you know that S3 itself is doing the filtering on your supplied prefix (where you have indicated .filter(Prefix=key) in your code). If this were not a feature of the underlying S3 API, then your SDK (boto3 etc.) would be the one doing the filtering on prefix and that would be a much more expensive and vastly slower operation, because the SDK would have to list all objects, potentially resulting in many more LIST requests, and filter them client-side. Note: the ListObjectVersions API is similar to ListObjectsV2 in this regard and both support prefix.
Also, note that VersionId, Size, and LastModifed are all attributes that appear in the ListObjectVersions response, so no further API requests are needed to fetch this information.
So, in your case, assuming that there are fewer than 1000 object versions that match your indicated prefix, I believe that this equates to one S3 API request to ListObjectVersions (and this is considered a LIST request rather than a GET request for billing afaik, even though it is a GET HTTP request to https://mybucket.s3.amazonaws.com/?versions under the covers).
Is there a simple way to retrieve all items from a DynamoDB table using a mapping template in an API Gateway endpoint? I usually use a lambda to process the data before returning it but this is such a simple task that a Lambda seems like an overkill.
I have a table that contains data with the following format:
roleAttributeName roleHierarchyLevel roleIsActive roleName
"admin" 99 true "Admin"
"director" 90 true "Director"
"areaManager" 80 false "Area Manager"
I'm happy with getting the data, doesn't matter the representation as I can later transform it further down in my code.
I've been looking around but all tutorials explain how to get specific bits of data through queries and params like roles/{roleAttributeName} but I just want to hit roles/ and get all items.
All you need to do is
create a resource (without curly braces since we dont need a particular item)
create a get method
use Scan instead of Query in Action while configuring the integration request.
Configurations as follows :
enter image description here
now try test...you should get the response.
to try it out on postman deploy the api first and then use the provided link into postman followed by your resource name.
API Gateway allows you to Proxy DynamoDB as a service. Here you have an interesting tutorial on how to do it (you can ignore the part related to index to make it work).
To retrieve all the items from a table, you can use Scan as the action in API Gateway. Keep in mind that DynamoDB limits the query sizes to 1MB either for Scan and Query actions.
You can also limit your own query before it is automatically done by using the Limit parameter.
AWS DynamoDB Scan Reference
Specifically, in an origin response triggered function (EX. With 404 Status), how can I read an HTML file stored in S3 and use its content for the response body?
(I would like to manually return a custom error page just as CloudFront does, but choosing it based on cookies).
NOTE: The HTML file in S3 is stored in the same bucket of my website. OAI Enabled.
Thank you very much!
Lambda#Edge functions don't currently¹ have direct access to any body content from the origin.
You will need to grant your Lambda Execution Role the necessary privileges to read from the bucket, and then use s3.getObject() from the JavaScript SDK to fetch the object from the bucket, then use its body.
The SDK is already in the environment,² so you don't need to bundle it with your code. You can just require it, and create the S3 client globally, outside the handler, which saves time on subsequent invocations.
'use strict';
const AWS = require('aws-sdk');
const s3 = new AWS.S3({ region: 'us-east-2' }); // use the correct region for your bucket
exports.handler ...
Note that one of the perceived hassles of updating a Lambda#Edge function is that the Lambda console gives the impression that redeploying it is annoyingly complicated... but you don't have to use the Lambda console to do this. The wording of the "enable trigger and replicate" checkbox gives you the impression that it's doing something important, but it turns out... it isn't. Changing the version number in the CloudFront configurarion and saving changes accomplishes the same purpose.
After you create a new version of the function, you can simply go to the Cache Behavior in the CloudFront console and edit the trigger ARN to use the new version number, then save changes.
¹currently but I have submitted this as a feature request; this could potentially allow a response trigger to receive a copy of the response body and rewrite it. It would necessarily be limited to the maximum size of the Lambda API (or smaller, as generated responses are currently limited), and might not be applicable in this case, since I assume you may be fetching a language-specific response.
²already in the environment. If I remember right, long ago, Lambda#Edge didn't include the SDK, but it is always there, now.
I'm using Amazon API Gateway to execute a Lambda function when the API endpoint is called. In my Lambda function I'm updating a DynamoDB table.
Whenever I call the API with caching disabled using Chrome Developer Tools, the DynamoDB table is updated.
When I have caching enabled, the first request from my API updates the table, every subsequent request is much faster but doesn't update the table.
I'm assuming that CloudFront is caching the responses so as to not have to call the Lambda function each time.
Is there any way to force the Lambda function to be executed with each request?
Few possible solutions:
CloudFront should be used only when u want caching. In this case you don't need it; so call API endpoint directly from browser instead of calling CF end point. This will also save your cloudfront cost.
With each request add a timestamp.
If you have to use CF; you can configure it very easily as to what requests should ALWAYS go to API end points ( which serves dynamic content) while which one should be cached.
Probably you are calling CF as a GET request; just make it POST which is NEVER cached. Ideally, as you are updating table it should be a POST request. This should be simplistic solution with minimal and right changes.