I'm currently implementing a C++ backend server using azure-storage-cpp to download blob files locally. Azure Storage Cpp works on top of cpprestsdk (casablanca), which provides parallel tasking.
The simple example from the documentation allows me to start a blob download. Fine. Now I'd like to know how can I cancel the download/task on demand?
I'm using this method to download into a file.
This method returns a pplx::task<void>. So my guess was I could use this to properly stop the download.
But the documentation for pplx::task constructor says:
The version of the constructor that takes a cancellation token creates a task that can be canceled using the <c>cancellation_token_source</c> the token was obtained from. Tasks created without a cancellation token are not cancelable.
Window Azure Storage Cpp creates the task for us when calling download_to_file_async. So is there a way to cancel/stop a pplx:task created by azure storage cpp?
If not, I think I'm going to use the REST api with libcurl.
Related
Im a little confused since AWS has a lot of features and I do not know what to use.
So, I was creating a Lambda function that does a lot of stuff with a remote web, process could last at least a minute.
So my idea was creating an API that calls this lambda, have lambda create an unique ID and return a response right away to the client with a token., save this token to a DB.
Then have lambda process all this stuff with a remote web and, when it finishes, save the results to the DB and a bucket (a file), so this result is ready to deliver when the client makes another call to another API that makes a query to the DB to know the status of this process.
Thing is, it seems that if a response is sent from the handler, lambda terminates the execution, Im afraid the processing with the remote web will never finish.
I have read that step functions is the way to go, but I cant figure out which service will take the processing, ¿maybe another lambda?
Is there another service that is more suitable for this type of work?, this process involves scrapping a page and downloading files, is written in python.
I have read that step functions is the way to go, but I cant figure
out which service will take the processing, ¿maybe another lambda?
Yes, another Lambda function would do the background processing. You could also just have the first Lambda invoke a second Lambda directly, without using Step Functions. Or the first Lambda could place the task info in an SQS queue that another Lambda polls.
Is there another service that is more suitable for this type of work?
Lambda functions are fine for this. You just need to split your task into multiple functions somehow, either by one Lambda calling the other directly, or by using Step Functions, or an SQS queue or something.
I am trying write an application to continuously upload large data (multipart uploads) to Amazon's S3 Storage. However, my application needs to be able to shut down mid-transfer and pick up from where it left off the next time it's restarted.
From playing around a little bit with the C++ SDK, the TransferManager class provides a RetryUpload function that requires a shared pointer to the TransferHandle object that is returned upon issuing an initial UploadFile call. However, the transfer handle object will no longer be in existence if the application crashes or has to shut down mid-operation.
In such a case, is it possible to resume a multipart upload using the TransferManager class? In effect, this probably requires the reconstruction of the transfer handle object, which I am not quite sure how to do. It seems that the TransferManager class is just a nice wrapper around the S3Client, which seems to be more clearer on how to resume the operation but also seems to be more painful to use for general multipart uploading
Can a COMPLETED process be modified using cockpit in enterprise version of Camunda such that it is brought back to its last stage (stage just before completion)?
Note that community version is being evaluated using REST API and condition is that the processInstanceId should not change.
The reason for asking this question is after Camunda has successfully finished processing as per work-flow and now is responding to the caller using REST API and suddenly there is a network outage, so in this special case, Camunda and the caller's respository shall be out of sync.
The closest you can get to this is the POST /process-definition/{id}/restart API. However, it does not restore the process instance with the same id.
Links:
https://docs.camunda.org/manual/7.7/reference/rest/process-definition/post-restart-process-instance-sync/
https://docs.camunda.org/manual/7.7/user-guide/process-engine/process-instance-restart
I registered my task app in Spring Cloud Data Flow, created a definition for it and the status shows 'unknown'. I created the stream and trying to launch the task through task-sink and I get an error:
java.lang.IllegalStateException: failed to resolve MavenResource:
How to launch a task from the task-sink? Am I missing something? Any help is appreciated. Another question I have is how do I access the payload sent via TaskLaunchRequest in my task?
S1 http | step1: transformer-rabbit | log
S2 :S1.step1 > filter --expression=payload.contains('CUSTADDRMODRQ_V15') | task-processor | task-sink
task-sink is launching the task provided by the uri in the TaskLaunchRequest. It is looking for the resource as shown in the log
OUT Using manager EnhancedLocalRepositoryManager with priority 10.0 for /home/vcap/.m2/repository
OUT Using transporter HttpTransporter with priority 5.0 for https://repo.spring.io/libs-snapshot and finally failing.
The task is deployed in our repository and as mentioned I registered and created the definition for it as well.
This one is in cf environment and I am using SCDF server 1.0.0.M4.
In the application.properties for the task-sink i am providing maven.remote.repositories.snapshots.url=**
task create fis-ifx-event-task --definition "fis-event-task"
My goal is launching the task from the stream.
Thanks for the information. I am in fact using the BUILD-SNAPSHOT as I am unable to enable taks in 1.0.0M4 version. Here is the one I am using spring-cloud-dataflow-server-cloudfoundry-1.0.0.BUILD-20160808.144306-116. I am able to register and create task definitions. The status of the task definition is showing as 'unknown' even when I am using the sample task module provided by your team. But when I initiate the flow of the stream and when task-sink tries to launch the task, it is unable to find the maven resource. When I create the task definition, does the task module gets deployed? I don't see any app in Pivotal Apps Manager. As mentioned earlier, I provided maven.remote.repositories.snapshot.url in the application.properties file for the task-sink application. Another thing I observed is when I launch the task manually from dataflow shell it gives an error CF-UnprocessableEntity(10008): The request is semantically invalid: Unknown field(s): 'staging_disk_in_mb', 'staging_memory_in_mb' and also a message saying 'Source is empty'. Presently the task is supposed to print the timestamp and is not dependent on any input.
TaskProcessor code:
#EnableBinding(Processor.class)
#EnableConfigurationProperties(TaskProcessorProperties.class)
public class TaskProcessor {
#Autowired
private TaskProcessorProperties processorProperties;
public TaskProcessor() {
}
#Transformer(inputChannel = Processor.INPUT, outputChannel = Processor.OUTPUT)
#ELI(level = "info", eventType = ELIEventType.INBOUND)
public Object setupRequest(String message) {
Map<String, String> properties = new HashMap<String, String>();
properties.put("payload", message);
TaskLaunchRequest request = new TaskLaunchRequest(processorProperties.getUri(), null, properties, null);
return new GenericMessage<>(request);
}
}
TaskSink code:
#SpringBootApplication
#EnableTaskLauncher
#EnableBinding(Sink.class)
#EnableConfigurationProperties(TaskSinkProperties.class)
public class FisIfxEventTaskSinkApplication {
public static void main(String[] args) {
SpringApplication.run(FisIfxEventTaskSinkApplication.class, args);
}
}
I provided the stream I am using earlier in the post. Sink is receiving the TaskLaunchRequest with uri and payload as you can see here and unable to launch the task.
OUT registering [40, java.io.File] with serializer org.springframework.integration.codec.kryo.FileSerializer
2016-08-10T16:08:55.02-0600 [APP/0]
OUT Launching Task for the following resource TaskLaunchRequest{uri='maven://com.xxx:fis.ifx.event-task:jar:1.0-SNAPSHOT', commandlineArguments=[], environmentProperties={payload={"statusCode":0,"fisT
opic":"CustomerDataUpdated","payloadId":"CUSTADDRMODR``Q_V15","customerIds":[1597304]}}, deploymentProperties={}}
Before I begin, you have a number of questions here. In the future, it's better to break them up into multiple questions so that they are easier to find by other users and easier to answer. That being said:
A little context on the current state of things
In order to understand how things will work, it's important to understand the current state of things. The current releases of the software involved are:
Pivotal Cloud Foundry (PCF) - 1.7.12. This version is required for any task support.
Spring Cloud Task (SCT) - 1.0.2.RELEASE
Spring Cloud Data Flow CF (SCDF) - 1.0.0.BUILD-SNAPSHOT (current as of the date of this post).
Currently PCF 1.7.12+ has all the capabilities to run tasks. You can create v3 applications (the type of application used to launch a task), run it as a task, etc. However, the tooling around that functionality is not currently complete. There is no support for v3 applications in Apps Manager or the CLI. There is a plugin for the CLI that is more of a dev tool that can be used to help with some functions (it will show you logs, etc), but it is not fully functional and requires a specific version of the CLI to work [1]. This is one of the reasons that the task functionality within PCF is still considered experimental.
Spring Cloud Task is currently GA and supports all the functionality needed to effectively run tasks on CF. However, it's important to note that SCT doesn't handle orchestration so the actual launching of tasks on CF is the responsibility of either the user, or Spring Cloud Data Flow (the easier route).
Spring Cloud Data Flow's Cloud Foundry server implementation currently has functionality to launch tasks on PCF in the latest snapshots. We have validated this against 1.7.12 as well as the development branch of 1.8.
The task workflow within SCDF
Tasks are fundamentally different from stream applications within the context of SCDF. When you create a stream definition, you are given the option to deploy it. What this does is it actually downloads the Spring Boot über jars and deploys them to PCF as long running processes. If they go down, PCF, will relaunch them as expected, etc.
Tasks on the other hand, are not deployed. They are launched. The difference is that while you create a task definition, there is nothing deployed until you click launch. And when the task completes, the software is shut down and cleaned up. So while a stream definition may have states, it's really a one to one relationship between the definition and the deployed software. Where with a task, you can launch a task definition as many times as you want.
Your issues
Reading through your post, I see a few things that you are struggling with. Let me see if I can help:
Task Definitions within SCDF and launching them via a stream - When launching a task from a stream, the task registry within SCDF is not used. The sink expects the URL for the resource to be within the TaskLauchRequest.
Apps Manager and tasks - As mentioned above, there is no support for v3 applications in Apps Manager yet so you won't be able to see your tasks there.
Viewing the logs - In order to debug what's going wrong with launching your task on CF, you're going to want to view the logs. To do so, use the v3 CLI plugin mentioned above to view them. It's important to note that you can only tail live logs with the plugin, not view logs that have previously been rendered. Because of that, when testing, you'll want to tail the logs as soon as the app is created, before it's launched.
Error in SCDF Shell - The error you received from the SCDF shell (CF-UnprocessableEntity(10008):...) leads me to wonder if you have both the correct version of PCF (1.7.12+) and the correct version of the following other libraries:
spring-cloud-deployer-cloudfoundry - The latest snapshots
cf-java-client - 2.0.0.M10+
reactor-core - 3.0.0.RC1+
I hope this helps!
[1] https://github.com/cloudfoundry/v3-cli-plugin
Task support is not available in 1.0.0.M4 release of SCDF's CF-server. In this release, the task commands/REST-APIs should be disabled - see here. And for that reason, you wouldn't see any docs related to Tasks in the 1.0.0.M4 reference guide.
That said, the Task support is available/enabled in the BUILD-SNAPSHOT release. If you're locally building the CF-server and upon pushing it to CF, you could take advantage the task commands in the shell to create and launch task definitions.
I am trying to execute following flow:
user hits AWS Gateway (REST),
it triggers AWS Lambda,
that uses Tinkerpop/Gremlin connects to
TitanDB on EC2, that uses
AWS DynamoDB in cloud (not on EC2) as backend.
Right now I have managed to crete fully working TitanDB instance on EC2, that stores data in DynamoDB in cloud.
I am also able to connect from AWS Lambda to EC2 through Tinkerpop/Gremlin BUT only this way:
Cluster.build()
.addContactPoint("10.x.x.x") // ip of EC2
.create()
.connect()
.submit("here I type my query as string and it will work");
And this works, however I strongly prefer to use "Criteria API" (GremlinPipeline) instead of plain Gremlin language.
In other words, I need ORM or something like that.
I know, that Tinkerpop includes it.
I have realized, that what I need is object of class Graph.
This is what I have tried:
Graph graph = TitanFactory
.build()
.set("storage.hostname", "10.x.x.x")
.set("storage.backend", "com.amazon.titan.diskstorage.dynamodb.DynamoDBStoreManager")
.set("storage.dynamodb.client.credentials.class-name", "com.amazonaws.auth.DefaultAWSCredentialsProviderChain")
.set("storage.dynamodb.client.credentials.constructor-args", "")
.set("storage.dynamodb.client.endpoint", "https://dynamodb.ap-southeast-2.amazonaws.com")
.open();
However, it throws "Could not find implementation class: com.amazon.titan.diskstorage.dynamodb.DynamoDBStoreManager".
Of course, computer is correct, as IntelliJ IDEA also cannot find it.
My dependencies:
//
// aws
compile 'com.amazonaws:aws-lambda-java-core:+'
compile 'com.amazonaws:aws-lambda-java-events:+'
compile 'com.amazonaws:aws-lambda-java-log4j:+'
compile 'com.amazonaws:aws-java-sdk-dynamodb:1.10.5.1'
compile 'com.amazonaws:aws-java-sdk-ec2:+'
//
// database
// titan 1.0.0 is compatible with gremlin 3.0.2-incubating, but not yet with 3.2.0
compile 'com.thinkaurelius.titan:titan-core:1.0.0'
compile 'org.apache.tinkerpop:gremlin-core:3.0.2-incubating'
compile 'org.apache.tinkerpop:gremlin-driver:3.0.2-incubating'
What is my goal: have fully working Graph object
What is my problem: I don't have DynamoDBStoreManager class, and I do not know what dependency I have to add.
My additional question is: why connecting through Cluster class requires only IP and works, but TitanFactory requires properties like those I have used on gremlin-server on EC2?
I do not want to create second server, I just want to connect as client to it and take Graph object.
EDIT:
After adding resolver, it builds, in output I get multiple:
13689 [TitanID(0)(4)[0]] WARN com.thinkaurelius.titan.diskstorage.idmanagement.ConsistentKeyIDAuthority - Temporary storage exception while acquiring id block - retrying in PT2.4S: com.thinkaurelius.titan.diskstorage.TemporaryBackendException: Wrote claim for id block [1, 51) in PT0.342S => too slow, threshold is: PT0.3S
and execution hangs on open() method, so does not allow me to execute any queries.
For the DynamoDBStoreManager class, you would need this dependency:
compile 'com.amazonaws:dynamodb-titan100-storage-backend:1.0.0'
Then for the DynamoDBLocal issue, try adding this resolver:
resolvers += "AWS DynamoDB Local Release Repository" at "http://dynamodb-local.s3-website-us-west-2.amazonaws.com/release"
I'm not entirely clear on what this means -- "Criteria API" instead of plain Gremlin language. I'm guessing that you mean that you want to interact with the graph using Java rather than passing Gremlin as a string over to a running Titan/Gremlin Server? If this is the case, then you don't need to start a Titan/Gremlin Server at all (step 4 above). Write an AWS Lambda program (step 2-3 above) that creates a direct Titan client connection via TitanFactory, where all of the Titan configuration properties are for your DynamoDB instance (step 5 above).