azure function 404 not found when deployed from ARM, works fine when deployed from visual studio

Question

I have an azure function that works when manually deployed via visual studio. I then exported the ARM template from Azure portal and used this in a DevOps release pipeline. The release pipeline succeeds after creating storage a hosting plan the function app and deploying the code to the function app.

When trying to access the function app however it throws a 404 not found error. I've tried in postman and in the "code + test" section of the azure portal, but I get the same 404 error.

I assume the ARM template exported from azure portal is incorrect somehow but I cannot see how, as it deploys successfully.

Has anyone experienced this issue?

In case it is useful, below is the ARM template, almost as it was exported from the portal. I have changed function name and urls just to prevent any potential attacks.

{  
    "$schema": "https://schema.management.azure.com/schemas/2019-04-01/deploymentTemplate.json#",  
    "contentVersion": "1.0.0.0",  
    "parameters": {  
        "sites_myFuncName_name": {  
            "defaultValue": "myFuncName",  
            "type": "String"  
        },  
        "serverfarms_FuncsPlan_externalid": {  
            "defaultValue": "/subscriptions/xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxx/resourceGroups/myResourceGroup/providers/Microsoft.Web/serverfarms/hostingPlanName",  
            "type": "String"  
        }  
    },  
    "variables": {},  
    "resources": [  
        {  
            "type": "Microsoft.Web/sites",  
            "apiVersion": "2022-03-01",  
            "name": "[parameters('sites_myFuncName_name')]",  
            "location": "North Europe",  
            "kind": "functionapp",  
            "properties": {  
                "enabled": true,  
                "hostNameSslStates": [  
                    {  
                        "name": "myFuncName.azurewebsites.net",  
                        "sslState": "Disabled",  
                        "hostType": "Standard"  
                    },  
                    {  
                        "name": "myFuncName.scm.azurewebsites.net",  
                        "sslState": "Disabled",  
                        "hostType": "Repository"  
                    }  
                ],  
                "serverFarmId": "[parameters('serverfarms_FuncsPlan_externalid')]",  
                "reserved": false,  
                "isXenon": false,  
                "hyperV": false,  
                "vnetRouteAllEnabled": false,  
                "vnetImagePullEnabled": false,  
                "vnetContentShareEnabled": false,  
                "siteConfig": {  
                    "numberOfWorkers": 1,  
                    "acrUseManagedIdentityCreds": false,  
                    "alwaysOn": false,  
                    "http20Enabled": false,  
                    "functionAppScaleLimit": 200,  
                    "minimumElasticInstanceCount": 0  
                },  
                "scmSiteAlsoStopped": false,  
                "clientAffinityEnabled": false,  
                "clientCertEnabled": false,  
                "clientCertMode": "Required",  
                "hostNamesDisabled": false,  
                "customDomainVerificationId": "XXXXX",  
                "containerSize": 1536,  
                "dailyMemoryTimeQuota": 0,  
                "httpsOnly": true,  
                "redundancyMode": "None",  
                "storageAccountRequired": false,  
                "keyVaultReferenceIdentity": "SystemAssigned"  
            }  
        },  
        {  
            "type": "Microsoft.Web/sites/basicPublishingCredentialsPolicies",  
            "apiVersion": "2022-03-01",  
            "name": "[concat(parameters('sites_myFuncName_name'), '/ftp')]",  
            "location": "North Europe",  
            "dependsOn": [  
                "[resourceId('Microsoft.Web/sites', parameters('sites_myFuncName_name'))]"  
            ],  
            "properties": {  
                "allow": true  
            }  
        },  
        {  
            "type": "Microsoft.Web/sites/basicPublishingCredentialsPolicies",  
            "apiVersion": "2022-03-01",  
            "name": "[concat(parameters('sites_myFuncName_name'), '/scm')]",  
            "location": "North Europe",  
            "dependsOn": [  
                "[resourceId('Microsoft.Web/sites', parameters('sites_myFuncName_name'))]"  
            ],  
            "properties": {  
                "allow": true  
            }  
        },  
        {  
            "type": "Microsoft.Web/sites/config",  
            "apiVersion": "2022-03-01",  
            "name": "[concat(parameters('sites_myFuncName_name'), '/web')]",  
            "location": "North Europe",  
            "dependsOn": [  
                "[resourceId('Microsoft.Web/sites', parameters('sites_myFuncName_name'))]"  
            ],  
            "properties": {  
                "numberOfWorkers": 1,  
                "defaultDocuments": [  
                    "Default.htm",  
                    "Default.html",  
                    "Default.asp",  
                    "index.htm",  
                    "index.html",  
                    "iisstart.htm",  
                    "default.aspx",  
                    "index.php"  
                ],  
                "netFrameworkVersion": "v6.0",  
                "requestTracingEnabled": false,  
                "remoteDebuggingEnabled": false,  
                "remoteDebuggingVersion": "VS2019",  
                "httpLoggingEnabled": false,  
                "acrUseManagedIdentityCreds": false,  
                "logsDirectorySizeLimit": 35,  
                "detailedErrorLoggingEnabled": false,  
                "publishingUsername": "$myFuncName",  
                "scmType": "VSTSRM",  
                "use32BitWorkerProcess": true,  
                "webSocketsEnabled": false,  
                "alwaysOn": false,  
                "managedPipelineMode": "Integrated",  
                "virtualApplications": [  
                    {  
                        "virtualPath": "/",  
                        "physicalPath": "site\\wwwroot",  
                        "preloadEnabled": false  
                    }  
                ],  
                "loadBalancing": "LeastRequests",  
                "experiments": {  
                    "rampUpRules": []  
                },  
                "autoHealEnabled": false,  
                "vnetRouteAllEnabled": false,  
                "vnetPrivatePortsCount": 0,  
                "localMySqlEnabled": false,  
                "ipSecurityRestrictions": [  
                    {  
                        "ipAddress": "Any",  
                        "action": "Allow",  
                        "priority": 2147483647,  
                        "name": "Allow all",  
                        "description": "Allow all access"  
                    }  
                ],  
                "scmIpSecurityRestrictions": [  
                    {  
                        "ipAddress": "Any",  
                        "action": "Allow",  
                        "priority": 2147483647,  
                        "name": "Allow all",  
                        "description": "Allow all access"  
                    }  
                ],  
                "scmIpSecurityRestrictionsUseMain": false,  
                "http20Enabled": false,  
                "minTlsVersion": "1.2",  
                "scmMinTlsVersion": "1.2",  
                "ftpsState": "FtpsOnly",  
                "preWarmedInstanceCount": 0,  
                "functionAppScaleLimit": 200,  
                "functionsRuntimeScaleMonitoringEnabled": false,  
                "minimumElasticInstanceCount": 0,  
                "azureStorageAccounts": {}  
            }  
        },  
  
        {  
            "type": "Microsoft.Web/sites/functions",  
            "apiVersion": "2022-03-01",  
            "name": "[concat(parameters('sites_myFuncName_name'), '/FuncName')]",  
            "location": "North Europe",  
            "dependsOn": [  
                "[resourceId('Microsoft.Web/sites', parameters('sites_myFuncName_name'))]"  
            ],  
            "properties": {  
                "script_root_path_href": "https://myFuncName.scm.azurewebsites.net/api/vfs/site/wwwroot/FuncName/",  
                "script_href": "https://myFuncName.scm.azurewebsites.net/api/vfs/site/wwwroot/bin/MyFuncName.dll",  
                "config_href": "https://myFuncName.scm.azurewebsites.net/api/vfs/site/wwwroot/FuncName/function.json",  
                "test_data_href": "https://myFuncName.scm.azurewebsites.net/api/vfs/data/Functions/sampledata/FuncName.dat",  
                "href": "https://myFuncName.scm.azurewebsites.net/api/functions/FuncName",  
                "config": {},  
                "invoke_url_template": "https://myFuncName.azurewebsites.net/api/FuncName",  
                "language": "DotNetAssembly",  
                "isDisabled": false  
            }  
        },  
        {  
            "type": "Microsoft.Web/sites/hostNameBindings",  
            "apiVersion": "2022-03-01",  
            "name": "[concat(parameters('sites_myFuncName_name'), '/', parameters('sites_myFuncName_name'), '.azurewebsites.net')]",  
            "location": "North Europe",  
            "dependsOn": [  
                "[resourceId('Microsoft.Web/sites', parameters('sites_myFuncName_name'))]"  
            ],  
            "properties": {  
                "siteName": "myFuncName",  
                "hostNameType": "Verified"  
            }  
        }  
    ]  
}  

Answer 1

Hi.

In the end this turned out not to be a build issue for me.
The issue was the ARM template for the web app, exported from azure contained tons of extra stuff that was not required.
It had a resource for the service plan, and about a dozen storage resources and website resources.

As i was deploying storage and service plan separately via their own ARM templates i could remove these.
Then all the website resources could simply be deleted as they get created when i ran a zip deploy as part of the pipeline.