# Error Handling
source: https://docs.chalk.ai/docs/query-errors

## Run resolvers in the presence of upstream failures.

Chalk returns an error channel in addition the requested feature values.

There are several types of errors one could expect:

### Error categories

### Request error

Request errors are raised before execution of your resolver code.
They may occur due to invalid feature names in the
input or a request that cannot be satisfied by the resolvers you
have defined.

### Field error

Field errors are raised while running a feature resolver
for a particular field.
For this type of error, you'll find a feature and resolver
attribute in the error type.

When a feature resolver crashes, you will receive null value
in the response.
To differentiate from a resolver returning a null value and
a failure in the resolver, you need to check the error schema.

### Network error

Network errors are thrown outside your resolvers.
For example, your request was unauthenticated,
connection failed, or an error occurred within Chalk.

### Error schema

The online query interface for resolvers returns the following schema:

### Response Schema

The outputs features and any query metadata (discussed in detail at
Query Basics.)

Errors encountered while running the resolvers. Each element in the list is a
ChalkError. If no errors were encountered, this field is empty.

### ChalkError

The type of error, matching one of the error codes.

The category of the error, given in the type field for the
error codes. This will be one of
"REQUEST", "NETWORK", and
"FIELD".

A readable description of the error message.

The exception that caused the failure, if applicable.

The name of the class of the exception.

The message taken from the exception.

The stacktrace produced by the code.

The fully qualified name of the failing feature, eg.
user.identity.has_voip_phone.

The fully qualified name of the failing resolver, eg.
my.project.get_fraud_score.

### Error code

The query contained features that do not exist.

A resolver was required as part of running the dependency graph that could not be found.

The query is invalid. All supplied features need to be rooted in the same top-level entity.

A feature value did not match the expected schema (eg. incompatible type "int"; expected "str")

The resolver for a feature errored.

The resolver for a feature timed out.

A crash in a resolver that was to produce an input for the resolver crashed, and so the resolver
could not run crashed, and so the resolver could not run.

The request was submitted with an invalid authentication header.

The request has credentials that do not provide the required authorization to execute an operation.

An unspecified error occurred.