I want to create a Lambda function that runs through S3 files and if needed triggers other Lambda functions to parse the files in parallel.
Is this possible?
Yes it's possible. You would use the AWS SDK (which is included in the Lambda runtime environment for you) to invoke other Lambda functions, just like you would do in code running anywhere else.
You'll have to specify which language you are writing the Lambda function in if you want a more detailed answer.
If I understand your problem correctly you want one lambda that goes through a list of files in a S3-bucket. Some condition will decide whether a file should be parsed or not. For the files that should be parsed you want another 'file-parsing' lambda to parse those files.
To do this you will need two lambdas - one 'S3 reader' and one 'S3 file parser'.
For triggering the 'S3 file parser' lambda you have many few different options. Here are a two:
Trigger it using a SNS topic. (Here is an article on how to do that). If you have a very long list of files this might be an issue, as you most likely will surpass the number of instances of a lambda that can run in parallel.
Trigger it by invoking it with the AWS SDK. (See the article 'Leon' posted as comment to see how to do that.) What you need to consider here is that a long list of files might cause the 'S3 reader' lambda that controls the invocation to timeout since there is a 5 min runtime limit for a lambda.
Depending on the actual use case another potential solution is to just have one lambda that gets triggered when a file gets uploaded to the S3 bucket and let it decide whether it should get parsed or not and then parse it if needed. More info about how to do that can be found in this article and this tutorial.
Related
I have used many discord API wrappers, but as an experienced python developer, unfortunately I somehow still do not understand how a command gets called!
#client.command()
async demo(ctx):
channel = ctx.channel
await channel.send(f'Demonstration')
Above a command has been created (function) and it is placed after its decorator #client.command()
To my understanding, the decorator is in a way, a "check" performed before running the function (demo) but I do not understand how the discord.py library seemingly "calls" the demo function.....?? Is there some form of short/long polling system in the local imported discord.py library which polls the discord API and receives a list of jobs/messages and checks these against the functions the user has created?
I would love to know how this works as I dont understand what "calls" the functions that the user makes, and this would allow me to make my own wrapper for another similar social media platform! Many thanks in advance.
I am trying to work out how functions created by the user are seemingly "called" by the discord.py library. I have worked with the discord.py wrapper and other API wrappers before.
(See source code attached at the bottom of the answer)
The #bot.command() decorator adds a command to the internal lists/mappings of commands stored in the Bot instance.
Whenever a message is received, this runs through Bot.process_commands. It can then look through every command stored to check if the message starts with one of them (prefix is checked beforehand). If it finds a match, then it can invoke it (the underlying callback is stored in the Command instance).
If you've ever overridden an on_message event and your commands stopped working, then this is why: that method is no longer being called, so it no longer tries to look through your commands to find a match.
This uses a dictionary to make it far more efficient - instead of having to iterate over every single command & alias available, it only has to check if the first letters of the message match anything at all.
The commands.Command() decorator used in Cogs works slightly different. This turns your function into a Command instance, and when adding a cog (using Bot.add_cog()) the library checks every attribute to see if any of them are Command instances.
References to source code
GroupMixin.command() (called when you use #client.command()): https://github.com/Rapptz/discord.py/blob/24bdb44d54686448a336ea6d72b1bf8600ef7220/discord/ext/commands/core.py#L1493
As you can see, it calls add_command() internally to add it to the list of commands.
Adding commands (GroupMixin.add_command()): https://github.com/Rapptz/discord.py/blob/24bdb44d54686448a336ea6d72b1bf8600ef7220/discord/ext/commands/core.py#L1315
Bot.process_commands(): https://github.com/Rapptz/discord.py/blob/master/discord/ext/commands/bot.py#L1360
You'll have to follow the chain - most of the processing actually happens in get_context which tries to create a Context instance out of the message: https://github.com/Rapptz/discord.py/blob/24bdb44d54686448a336ea6d72b1bf8600ef7220/discord/ext/commands/bot.py#L1231
commands.Command(): https://github.com/Rapptz/discord.py/blob/master/discord/ext/commands/core.py#L1745
I am trying to find a clean way to access the regmap that is used with *RegisterNode for creating documentation and testing files. The TLRegisterNode has methods for generating the json through some Annotations. These are done in the regmap method by adding them to the ElaborationArtefacts object. Other protocols don't seem to have these annotations.
Is there anyway to iterate over the "regmap" Register Fields post elaboration or during?
I cannot just access the regmap as it's not really a val/var since it's a method. I can't quite figure out where this information is being stored. I don't really believe it's actually "storing" any information as much as it is simply creating the hardware to attach the specified logic to the RegisterNode based logic.
The JSON output is actually fine for me as I could just write a post processing script to convert JSON to my required formats, but I'm wondering if I can access this information OR if I could add a custom function call at the end. I cannot extend the case class *RegisterNode, but I'm not sure if it's possible to add custom functions to run at the end of the regmap method.
Here is something I threw together quickly:
//in *RegisterRouter.scala
def customregmap(customFunc: (RegField.Map*) => Unit, mapping: RegField.Map*) = {
regmap(mapping:_*)
customFunc(mapping:_*)
}
def regmap(mapping: RegField.Map*) = {
//normal stuff
}
A user could then create a custom function to run and pass it to the regmap or to the RegisterRouter
def myFunc(mapping: RegField.Map*): Unit = {
println("I'm doing my custom function for regmap!")
}
// ...
node.customregmap(myFunc,
0x0 -> coreControlRegFields,
0x4 -> fdControlRegFields,
0x8 -> fdControl2RegFields,
)
This is just a quick example I have. I believe what would be better, if something like this was possible, would be to have a Seq of functions that could be added to the RegisterNode that are ran at the end of the regmap method, similar to how TLRegisterNode currently works. So a user could add an arbitrary number and you still use the regmap call.
Background (not directly part of question):
I have a unified register script that I have built over the years in which I describe the registers for a particular IP. It works very similar to the RegField/node.regmap, except it obviously doesn't know about diplomacy and the like. It will generate the Verilog, but also a variety of files for DV (basic `defines for simple verilog simulations and more complex uvm_reg_block defines also with the ability to describe multiple of the IPs for a subsystem all the way up to an SoC level). It will also print out C Header files for SW and Sphinx reStructuredText for documentation.
Diplomacy actually solves one of the main issues I've been dealing with so I'm obviously trying to push most of my newer designs to Chisel/Diplo.
I ended up solving this by creating my own RegisterNode which is the same as the rocketchip RegisterNodes except that I use a different Elaboration Artifact to grab the info and store it for later.
I'm trying to deploy an app to production and getting a little confused by environment and application variables and what is happening at compile time vs runtime.
In my app, I have a genserver process that requires a token to operate. So I use config/releases.exs to set the token variable at runtime:
# config/releases.exs
import Config
config :my_app, :my_token, System.fetch_env!("MY_TOKEN")
Then I have a bit of code that looks a bit like this:
defmodule MyApp.SomeService do
use SomeBehaviour, token: Application.get_env(:my_app, :my_token),
other_config: :stuff
...
end
In production the genserver process (which does some http stuff) gives me 403 errors suggesting the token isn't there. So can I clarify, is the use keyword getting evaluated at compile time (in which case the application environment doest exist yet)?
If so, what is the correct way of getting runtime environment variables in to a service like this. Is it more correct to define the config in application.ex when starting the process? eg
children = [
{MyApp.SomeService, [
token: Application.get_env(:my_app, :my_token),
other_config: :stuff
]}
...
]
Supervisor.start_link(children, opts)
I may have answered my own questions here, but would be helpful to get someone who knows what they're doing confirm and point me in the right way. Thanks
elixir has two stages: compilation and runtime, both written in Elixir itself. To clearly understand what happens when one should figure out, that everything is macro and Elixir, during compilation stage, expands these macros until everything is expanded. That AST comes to runtime.
In your example, use SomeBehaviour, foo: :bar is implicitly calling SomeBehaviour.__using__/1 macro. To expand the AST, it requires the argument (keyword list) to be expanded as well. Hence, Application.get_env(:my_app, :my_token) call happens in compile time.
There are many possibilities to move it to runtime. If you are the owner of SomeBehaviour, make it accept the pair {:my_app, :my_token} and call Application.get_env/2 somewhere from inside it.
Or, as you suggested, pass it as a parameter to children; this code belongs to function body, meaning it won’t be attempted to expand during compilation stage, but would rather be passed as AST to the resulting BEAM to be executed in runtime.
I have an AWS CloudFormation template that creates an OpsWorks stack and deploys an application. To deploy the application, I am using a Lambda function and a custom resource which utilizes that function. My problem is: that Lambda function will only be executed one time during the creation of the stack, and then it will never be used again. Is there any way to delete the Lambda function by AWS CloudFormation at the end of the execution of the stack?
First, I should say Aditya is right, you shouldn't delete the backing Lambda as it's used throughout the lifecycle.
However, if you really really want to do it, one way is to simply have the function delete itself (and related resources, eg, role) after running.
that Lambda function will only be executed one time during the
creation of the stack, and then it will never be used again.
^^That's not the case. The backing Lambda function for a Lambda-backed custom resource will be invoked everytime the corresponding resource is touched (i.e. created, updated or deleted). AWS CloudFormation will pass RequestType parameter to that function everytime it sees that the resource is being touched, and pass it one of these values: Create, Update, Delete. Your Lambda function should perform the necessary action taking that param into account. Based on your question it appears that your Lambda function only caters to RequestType = Create?
Also, as per AWS docs, you won't be charged for creating a Lambda function, but only if you actually invoke it. So cost can't be deterring factor for keeping the function around.
On the contrary, if your concern is that you don't want extra clutter, you can try creating a common CloudFormation stack who's job will be to create shared resources, and you can then define that Lambda function over there? I'll have to know about your entire workflow to say for sure if that approach will work or not.
For what it's worth, I'd recommend not deleting the backing function of the Lambda-backed custom resource because it'll be a pain when someone touches the corresponding resource in the future, or wants to create another instance of the same resource type.
Some of your assumptions regarding custom resources are not true. In a Lambda backed custom resource, you implement your logic to support creation, update and deletion of the resource. These indications are sent from CloudFormation via the event and give you information about the stack process.
It’s important to understand the custom resource life cycle, to prevent your data from being deleted.
Create - that’s easy, when a resource is being created an event with request type Create is sent to your function.
Delete - this one is more tricky. When a resource is being deleted a Delete request type is sent. But there are more scenarios other than resource Delete. We will have to explain Update first.
Update - gets called if any of your custom resource properties were changed. For example, in our app we can modify the allowed callback urls, which will trigger the function with an Update request type
I welcome you to read more about best practices in creating custom resources in this blog post
Please correct me where I'm wrong (still learning Gulp, Streams, etc.) I'd like to create a custom reporter for my gulp-jscs results. For example, let's say I have 3 files in my gulp.src() stream. To my knowledge, each is piped one at a time through jscs, which attaches a .jscs object onto the file with its results, one such variable in that object is .errorCount.
What I'd like to do is have a variable I create, ie: maxErrors which I set to, say 5. Since we're processing 3 files, let's say the first file passes with 0 errors, but the next has 3 errors. I don't want to prematurely stop processing since the maxErrors tally has not been reached (3/5 currently). So it should continue to process the next file which lets say has 3 errors as well, putting us over our max, so that we interrupt jscs from continuing to process more files and instead fail out and then let our custom reporter function gain access to the files that have been processed so I can look at their .jscs objects and customize some output.
My problem here is that I don't understand the docs when they say: .pipe(jscs.reporter('name-of-reporter')) How does a string value invoke my reporter (which currently exists as a function I've imported called libs.reporters.myJSCSReporter. I know pipe() expects Stream objects, so I can't just put a function in the .pipe() call.
I hope I've explained myself well enough (please ask for clarifications otherwise).