Invoke Oracle Functions using the OCI Go SDK

This example demonstrates how to invoke a function on Oracle Functions using (preview version of) the Oracle Cloud Infrastructure Go SDK.

Introduction

To be specifc, it shows how you can invoke a function by its name given that you also provide the application name (to which the function belongs), the OCI compartment (for which your Oracle Functions service is configured) and the OCID of your tenancy

OCI SDK exposes two endpoints for Oracle Functions

• functions.FunctionsManagementClient - for CRUD operations e.g. creating applications, listing functions etc.
• functions.FunctionsInvokeClient - only required for invoking a function

along with a number of wrapper structs like functions.FunctionSummary, functions.ApplicationSummary, and identity.Compartment.

The invokeFunction function in struct FunctionsUtil (functions-util.go) takes a functions.FunctionSummary for a given function, the desired payload, and uses functions.FunctionsInvokeClient to actually invoke the function. This seems relatively straightforward but obtaining a functions.FunctionSummary requires navigating from the OCI compartment, to the application, to the function. This involves multiple lookups (API calls).

To illustrate the steps, the FunctionsUtils struct provides a number of methods that capture the steps required to navigate the OCI object model

• getCompartment(compartmentName) returns a Compartment with a given name using ListCompartments function in identity.IdentityClient - it looks for compartments in the tenancy with the provided name
• getApplication(appName, compartment) searches in the specified compartment for the named application using the ListApplications function exposed by functions.FunctionsManagementClient
• getFunction(funcName, application) searches in the specified application for the named function using ListFunctions in functions.FunctionsManagementClient. The result is a functions.FunctionSummary object which provides the function ID, name, and invoke endpoint

The key thing to note here is that the function ID and its invoke endpoint will not change unless you delete the function (or the application it's a part of). As a result you do not need to repeat the above mentioned flow of API calls - the funtion ID and its invoke endpoint can be derived once and then cached in-memory (e.g. in a map) or an external data store

Once we have a functions.FunctionSummary (containing function OCID and invoke enpdoint) at our disposal we can use the invokeFunction(function,payload) function in FunctionsUtils which:

• builds functions.InvokeFunctionRequest with the function OCID and the (optional) payload which we want to send to our function
• sets functionsInvokeClient.Host to the value of the invoke endpoint
• andn finally calls invokeFunction function in functions.FunctionsInvokeClient with the functions.InvokeFunctionRequest returning the String response from the resulting functions.InvokeFunctionResponse object

Authentication

The client program needs to authenticate to OCI before being able to make service calls. The standard OCI authenitcation is used, which accepts the following inputs (details below) - tenant OCID, user OCID, fingerprint, private key and passphrase (optional). These details are required to instantiate a common.ConfigurationProvider using common.NewRawConfigurationProvider method and subsequently used by the service client objects (functions.FunctionsInvokeClient, functions.FunctionsManagementClient, identity.IdentityClient)

This example does not assume the presence of an OCI config file on the machine from where this is being executed. However, if you have one present as per the standard OCI practices i.e. a config file in your home directory, you can use common.DefaultConfigProvider for convenience

Pre-requisites

1. Install latest Fn CLI -

curl -LSs https://raw.githubusercontent.com/fnproject/cli/master/install | sh

2. Create a function to invoke

Create a function using Go Hello World Function

Install preview OCI Go SDK

You need to add the OCI Go SDK to your GOPATH

Set GOPATH environment variable

export GOPATH=<YOUR_GOPATH>

1. Back up your existing installation of OCI Go SDK and remove it from your GOPATH

2. Download and unzip the preview version of the OCI Go SDK

    unzip oci-go-sdk-preview@35505cb3d6a.zip
   

3. Copy the preview SDK to your GOPATH

    cp -R oci-go-sdk-preview@35505cb3d6a/ $GOPATH/src/github.com/oracle/oci-go-sdk
   

Set environment variables

export TENANT_OCID=<OCID of your tenancy>
export USER_OCID=<OCID of the OCI user>
export PUBLIC_KEY_FINGERPRINT=<public key fingerprint>
export PRIVATE_KEY_LOCATION=<location of the private key on your machine>

please note that PASSPHRASE is optional i.e. only required if your private key has one

export PASSPHRASE=<private key passphrase>

e.g.

export TENANT_OCID=ocid1.tenancy.oc1..aaaaaaaaydrjd77otncda2xn7qrv7l3hqnd3zxn2u4siwdhniibwfv4wwhtz
export USER_OCID=ocid1.user.oc1..aaaaaaaavz5efd7jwjjipbvm536plgylg7rfr53obvtghpi2vbg3qyrnrtfa
export PUBLIC_KEY_FINGERPRINT=42:42:5f:42:ca:a1:2e:58:d2:63:6a:af:42:d5:3d:42
export PRIVATE_KEY_LOCATION=/Users/foobar/oci_api_key.pem

and only if your private key has a passphrase:

export PASSPHRASE=4242

You can now invoke your function!

Clone this repository -

git clone https://github.com/abhirockzz/fn-go-sdk-invoke

Change to the correct directory where you cloned the example:

go run src/*.go --compartmentName=<compartmentName> --appName=<appName> --funcName=<funcName> --invokePayload=<(optional) invokePayload>

Payload is optional. If your function doesn't expect any input parameters, you can omit --invokePayload argument

e.g. with payload:

go run src/*.go --compartmentName=mycompartment --appName=helloworld-app --funcName=helloworld-go --invokePayload={\"name\":\"foobar\"}

e.g. without payload:

go run src/*.go --compartmentName=mycompartments --appName=helloworld-app --funcName=helloworld-go

What if my function needs input in binary form ?

This example demonstrates how to invoke a boilerplate function which accepts (an optional) string payload (JSON data). But, it is possible to send binary payload as well.

You can use this Tensorflow based function as an example to explore the possibility of invoking a function using binary content - https://github.com/abhirockzz/fn-hello-tensorflow. This function expects the image data (in binary form) as an input and returns what object that image resembles along with the percentage accuracy

If you were to deploy the above function and invoke it using Fn CLI, the command would something like this - cat /home/foo/cat.jpeg | fn invoke fn-tensorflow-app classify. In this case, the cat.jpeg image is being passed as an input to the function. The programmatic (using Go SDK) equivalent of this would look something like the below snippet, where the function invocation request (functions.InvokeFunctionRequest) is being built along with the binary input (image file content)

functionPayload, _ := os.Open("/home/foo/cat.jpeg") //error handling ignored for brevity
defer functionPayload.Close()
invokeFunctionReq := functions.InvokeFunctionRequest{FunctionId: functionID, InvokeFunctionBody: functionPayload}

Pay attention to the following line functionPayload, _ := os.Open("/home/foo/cat.jpeg"). The InvokeFunctionBody accepts an io.ReadCloser - as a result, it is possible to use os.File (or any other compatible type) as a function payload

Troubleshooting

If you fail to set the required environment variables like TENANT_OCID etc.

You will see the following error - panic: Please set the environment variable TENANT_OCID

If you do not provide required arguments i.e. compartment name etc.

You will see the following error - panic: Please set mandatory flag compartmentName

If you provide an invalid value for function name etc.

You will see something similar to - panic: Could not find function myfunc in application myapp

If you provide an incorrect TENANT_OCID or USER_OCID or PUBLIC_KEY_FINGERPRINT

You will get this error - Service error:NotAuthenticated. The required information to complete authentication was not provided or was incorrect.. http status code: 401. Opc request id: 4d7d76463a4f437361a1eb47815015d9/450D86C860C0592949AFF344C6DB17F0/84F3CCC7542175C08646CD4E213A2CEF

If your key has a passphrase but you fail to set the environment variable PASSPHRASE or provid an incorrect value

You will get this error - panic: Could not instantiate Identity client - can not create client, bad configuration: x509: decryption password incorrect