![]() ![]() Once exiftool gathers all information it throws BrokenPipeError and loop terminates (preventing from downloading any further chunks). Having the above we can construct the python loop that fetches consecutive bytes of the file and fills exiftool stdin in each iteration. Fortunately S3 provides ability to fetch only certain bytes of the file, via Range header. To retrieve the file itself, we will use S3 GETObject API call. However, since this property is provided by AWS S3 (via Content-Length header), I think this is acceptable. ![]() One thing to note, as presented above, we are missing file size (all other metadata headers are extracted). The exiftool will break the bash pipe and exit as soon as it gets all information. The code that builds a base Lambda image with all necessary build tools is put under Dockerfile.layer: In order to mimic the Lambda environment as close as possible, I decided to use a base Lambda docker image and perform any needed changes there. In our case, we need to zip exiftool and all its dependencies ( perl in this case). So for example, if we want to add new executable we could simply zip it as bin/executable and it should be available to run from Lambda code. Per default opt/bin is added to PATH environment variable and /opt/lib to LD_LIBRARY_PATH - reference. When Lambda is prepared to run, its contents are unzipped in /opt directory of the instance. Layer is simply a custom zip file that we create. The benefit over using Layer, is that we are not charged for initial duration of the “cold” phase. If we want to add additional binaries, we have a few options: create a custom docker image, use custom boot script or use Lambda Layer. They use Amazon Linux 2 (a fork of Red Hat Enterprise Linux) with addition of the language tool that is used for particular image (python, ruby, node, etc.). ![]() As a result, two consecutive runs of AWS Lambda will not last the same time (the second run will be faster - since it uses the “warm” phase).īecause of its purpose (event driven and ephemeral runs) the AWS Lambda are itself very limited environments. “Warm” on the other hand, re-uses the already running instance (as Lambda are not torn down momentary). “Cold” is simple a phase that instance needs to started from scratch. Unlike “standard” VPS its purpose is to run per defined event and then tear down.Īlthough managing the Lambda instances is Amazon internal implementation, we can distinguish “cold” and “warm” phases. Internally it is a virtual private server that allows us to define some of its computation resources (like RAM and - indirectly - CPU). The article describes code, which can be found here.ĪWS Lambda is Amazon serverless solution, that allows to run arbitrary code in few predefined languages. In this article I will present how to use it in disk and RAM limited environment like AWS Lambda. Internally, it is written in perl, which gives it some portability. The author of exiftool is quite responsive to questions posted there.Exiftool is file metadata parser and analyzer that handles majority of the formats. u/educational_s I'd suggest asking over on the exiftool forum with as much details as you can give as to what you are trying to do. The config file mentioned there is no longer needed as exiftool now has native support for these tags. If that is the case, then this exiftool forum post gives some details on how to embed the image. There's also the Google XMP-GDepth tags, which holds a separate embedded JPG/PNG file as a depth map. The first one is even more complex as it is a structure which contains multiple substructures, which includes the DeviceDepthMap structure.īut then, that might not be what the OP wants to write. The equivalent of a group of hashes/arrays in Perl or (I think) dictionaries/arrays in Python. These are Structured Data tags, which holds multiple pieces of data as a group. Instead, there's a DeviceDepthMap Structure, which is part of the definition of two other tags, the XMP-Device:Cameras tag and the XMP-Device:CameraDepthMap tag. There's no actual tag called DepthMap on that page. ![]()
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