host.json (v2)

The schema for host.json has changed enough in Azure Functions v2+ that the functions host will throw an exception if the file is missing the "version": "2.0" property. Please note that this requires the value as a string and "version":2.0 will not work. "version": "2.0" is still the valid schema for Azure Functions v3.

This page provides a migration guide for the sections that have changed. For full definitions of those sections, see https://docs.microsoft.com/en-us/azure/azure-functions/functions-host-json. The official documentation will be updated with the v2 schema soon.

All application-level extension settings now live under "extensions"

This means that the following settings that were in the root of the json object in v1, now live under extensions in v2:

{
  "extensions": {
    "cosmosDB": { },
    "eventHubs": { },
    "http": { },
    "queues": { },
    "sendGrid": { },
    "serviceBus": { },
    "durableTask": { }
  }
}

All logging settings now live under "logging"

This means that the "tracing" and "logger" have been removed.

{
  "logging": {
    "fileLoggingMode": { },
    "applicationInsights": { }
  }
}

Log category filtering follows .NET Core layout

Filtering now follows the same pattern as documented by the JSON settings here: https://docs.microsoft.com/en-us/aspnet/core/fundamentals/logging/?view=aspnetcore-2.1#log-filtering.

For example, the following will disable all logging except the logs coming from the function named 'MyFunction'

{
  "logging": {
    "logLevel": {
      "Function.MyFunction": "Information",
      "default": "None"
    }
  }
}

Sample host.json

{
    "version": "2.0",
    "watchDirectories": [ "Shared", "Test" ],
    "healthMonitor": {
        "enabled": true,
        "healthCheckInterval": "00:00:10",
        "healthCheckWindow": "00:02:00",
        "healthCheckThreshold": 6,
        "counterThreshold": 0.80
    },
    "functionTimeout": "00:05:00",
    "logging": {
        "fileLoggingMode": "debugOnly"
    },
    "extensions": {
        "cosmosDB": {
            "connectionMode": "Gateway",
            "protocol": "Https",
            "leaseOptions": {
                "leasePrefix": "prefix1"
            }
        },
        "sendGrid": {
            "from": "Azure Functions <[email protected]>"
        },
        "http": {
            "routePrefix": "api",
            "maxConcurrentRequests": 5,
            "maxOutstandingRequests": 30
        },
        "queues": {
            "visibilityTimeout": "00:00:10",
            "maxPollingInterval": "00:00:15",
            "maxDequeueCount": 3
        },
        "eventHubs": {
            "batchCheckpointFrequency": 5,
            "eventProcessorOptions": {
                "maxBatchSize": 256,
                "prefetchCount": 512
            }
        },
        "serviceBus": {
            "prefetchCount": 100,
            "messageHandlerOptions": {
                "maxConcurrentCalls": 32,
                "maxAutoRenewDuration": "00:55:00"
            }
        }
    }
}