Table of Contents |
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Checklist
- User Stories Documented
- User Stories Reviewed
- Design Reviewed
- APIs reviewed
- Release priorities assigned
- Test cases reviewed
- Blog post
Introduction
what is the motivation for this exercise
An error message is text that is displayed to describe a problem that has occurred that is preventing the user or the system from completing a task. The problem could result in data corruption or loss. Other message types include confirmations, warnings, and notifications. The guidelines in this topic are intended to help you write clear error messages that are easy to localize and useful for customers.
Goals
The goals of this wiki page is to provide guideline on writing better error messages and also improve error message in Dataprep, Plugins and CDAP platform.
Guidelines for Error Messages
1. Make error messages more contextual.
Contextual error messages provide specific information particular to error situation. Error messages without any context are very hard to interpret by users. Contextual information may include information such as why the error happened, what is the error value, what is the expected value, how user can fix the error etc.
For example, if there is a mismatch in data type of a field, providing more contextual information to user in error message would help user understand the problem and fix it if needed.
No Format |
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Error Message:
Data type mismatch for field 'X'.
Better Error Message:
Field 'X' is of data type 'int' in the schema. However, provided data type is 'string'. |
2. Do not include implementation details in user facing error messages.
Exposing implementation details to end users can be confusing and users may not be able to take any action to solve error situation. Thats why user facing error messages should not include implementation details. Below are some of the cases where we can avoid exposing implementation details:
Avoid using class hashes in error messages. For example:
No Format Error Message: co.cask.directives.language.SetCharset@781ecbac : Invalid type 'java.lang.String' of column 'body'. Should be of type String. Better Error Message: Error executing 'set-charset' directive: The 'body' column was expected to be a byte array or ByteBuffer, but is of type 'String'.
Avoid using exception class names in user facing error messages. For example:
No Format Error Message: java.lang.IllegalArgumentException: Database driver 'cloudsql-postgresql' not found. Better Error Message: Database driver 'cloudsql-postgresql' not found. Please make sure correct database driver is deployed.
Avoid using technical implementation details in user facing error messages. For example:
No Format Error Message: Failed to configure pipeline: valueOf operation on abc failed. Better Error Message: Failed to configure pipeline: Expected type of field 'X' is either int/double but found 'abc'.
3. Error message should provide direction to user if action is needed from user.
An error message has 3 parts, problem identification, cause details if helpful, and a solution if possible. Whenever error situation occurs, users would like to fix it immediately. The error message should have enough information to guide the user in right direction.
4. Provide complete concise error message to user and avoid ambiguity.
An error message should be a complete sentence which provides clear message. User should be able to understand the problem by reading the error message. For example:
No Format |
---|
Error Message:
io.cdap.directives.transformation.Decode@c2e00f5 : Failed to decode hex value.
Better Error Message:
Error while decoding field 'X' as hex value. Please make sure the provided field is encoded as hex. |
4. Always prefer error message specific to the error situation instead of generic error messages
Whenever possible, use specific error message instead of generic error message. For example:
No Format |
---|
Error Message:
Failed to decode hex value.
Better Error Message:
Error while decoding field 'X' as hex value. Please make sure the provided field is encoded as hex. |
5. Validation Errors
Validate for empty string/ null string before using the text in error message
6. Configuration parameters
Bug Fixes
Approach
Approach #1
Approach #2
API changes
New Programmatic APIs
New Java APIs introduced (both user facing and internal)
Deprecated Programmatic APIs
New REST APIs
200 - On success
404 - When application is not available
500 - Any internal errors
Deprecated REST API
Path | Method | Description |
---|---|---|
/v3/apps/<app-id> | GET | Returns the application spec for a given application |
CLI Impact or Changes
- Impact #1
- Impact #2
- Impact #3
UI Impact or Changes
- Impact #1
- Impact #2
- Impact #3
Security Impact
What's the impact on Authorization and how does the design take care of this aspect
Impact on Infrastructure Outages
System behavior (if applicable - document impact on downstream [ YARN, HBase etc ] component failures) and how does the design take care of these aspect
Test Scenarios
Releases
Release 6.1.0
Related Work
Contextual error messages provides meaningful information to CDAP users which can help them move forward in error situations. However, sometimes error messages can be vague and without context which can lead to an unpleasant user experience. Providing meaningful error messages to the users is a challenge. In many error situations, for the same type of error, the error message format is different. This inconsistency can confuse the users. Having a central repository of errors would help developers reuse the same error messages as well as formulate error messages in a consistent way.
When user is encountered with an error situation, error message can point users to appropriate actions. Sometimes the remedy would require users to follow a certain steps. For example, in wrangler, when a deployed database driver does not contain the driver class, users would need to repackage the jar and redeploy the jar. In this case, having a catalog of errors would help users to quickly find the steps to follow to fix the underlying issue. One approach to solve this challenge is to surface error codes to users along with error messages. Error codes would help users search the catalog with an error code and find the remedial steps.
Goals
There are three goals which needs to be achieved to improve error handling:
- Provide a guideline to write better error messages: General best practices on formulating a meaningful Error Message
- Add a framework to add error codes to the error messages so that users can browse the catalog to figure out remedial steps.
- Add a framework to standardized error messages and put them at central location for better visibility.
Scenarios
Scenario 1: Errors in Wrangler
Scenario 1.1
Alice wants to wrangle data using CDAP's Wrangler tool. As part of that, Alice wants to connect to Database Source using Wrangler Connection. While attempting to do that, Alice is seeing a cryptic error message while testing the connection that she does not know how to resolve just by looking at the error message. In order figure out cause of the issue and recommended action, Alice will like to browse error code catalog with the error code displayed along with the error message.
Scenario 1.2
Alice is applying transformations to the data on the fly using CDAP's Wrangler tool. However, while applying transformations, Alice sees an error message that does not suggest recommended action to fix the issue. She wants to browse the error code catalog to figure out recommended actions to resolve the issue.
Scenario 1.3
Alice wants to wrangle data using CDAP's Wrangler tool. While applying transformations to the connected source data on the fly, Alice tries to parse boolean column as csv. However, Alice observes that built-in directives to parse boolean data as csv and avro returns different error messages. Alice would like to see standard error message from both the directives when column type is incompatible.
Scenario 1.4
Alice wants to wrangle data using CDAP's Wrangler tool. While connecting to the source Alice uses user name and password stored in secure store. However, the secure store keys are not resolved. Alice wants to look at the error code and share it with the CDAP developer to figure out the underlying root cause.
Scenario 2: Errors in Pipeline
Scenario 2.1
Alice is a pipeline developer who has built a pipeline using CDAP data pipeline studio. While running the pipeline, it failed with no meaningful error message in logs.To debug this issue further, Alice wants to share error code from the logs with Bob, the data pipeline app developer to figure out what is the cause of the error.
Scenario 2.2
As a data pipeline developer, Alice is trying to get schema from the database source. While attempting to do that from CDAP data pipeline studio, Alice sees an error message. In order to figure out the cause and action for the error message, Alice will like to search the error code in the error catalog.
Scenario 2.3
As a data pipeline developer, Alice is trying to validate the pipeline. While attempting to validate it, Alice saw an error message that requires fixing the plugin property. Alice want to have an error code along with the error message so that she can search the probable cause on error catalog.
Scenario 2.4
As a data pipeline developer, Alice is using secure macros in the pipeline, however, the secure macros are not resolved. Alice wants to use the error code and share it with CDAP developer to figure out the root cause.
Scenario 3: Errors in CDAP
Scenario 3.1
As a CDAP user, Alice wants to upload a plugin to CDAP. However, Alice is not deploy a plugin and gets an error. Alice wants to use the error code to browse the catalog to figure out the cause and recommended action.
Scenario 3.2
As a CDAP user, Alice wants to enable Wrangler to wrangle data. However, Wrangler service is not starting up.Alice wants to use the error code so that it can be shared with the support engineer for further debugging.
Scenario 3.3
As a CDAP user, Alice wants to enable Wrangler to wrangle data. However, Wrangler service is not starting up.Alice wants to use the error code so that it can be shared with CDAP developer to figure out the root cause.
Design Discussions
Code Block |
---|
/**
* Represents error codes.
*/
@Beta
public enum ErrorCode {
// 11 prefix for directive errors
UNSUPPORTED_ENCODING_TYPE("WRA-111001"),
// 12 prefix for handler errors
DRIVER_CLASS_NOT_FOUND("WRA-121001"),
INVALID_MACRO_ERROR("WRA-121102");
.....
// 13 prefix for storage
....
private String code;
ErrorCode(String code) {
this.code = code;
}
/**
* Returns the code for this error.
*/
public String getCode() {
return this.code;
}
} |
Code Block | ||||
---|---|---|---|---|
| ||||
/**
* Error information provider.
*/
@Beta
public interface ErrorInfoProvider {
/**
* Returns error code associated with the error.
* NOTE: this interface returns special error code for backwards compatibility.
*/
default ErrorCode getErrorCode() {
return ErrorCode.UNDEFINED_CODE;
}
/**
* Returns an array of arguments to formulate error messages.
*/
default Object[] getErrorArgs() {
return null;
}
} |
Look up in the exception vs highest level (Handler and Wrangler Transform)
- should be done in the exception - What if for some reason resolution fails?
Code Block | ||||
---|---|---|---|---|
| ||||
/**
* Class description here.
*/
public class DirectiveLoadException extends Exception implements ErrorInfoProvider {
private static final MessageLookup LOOKUP = new MessageLookup();
private ErrorCode errorCode;
private Object[] errorArgs;
...
public DirectiveLoadException(ErrorCode errorCode, Object... args) {
super(LOOKUP.get(errorCode.name(), args));
this.errorCode = errorCode;
this.errorArgs = args;
}
@Override
public ErrorCode getErrorCode() {
return errorCode;
}
@Override
public Object[] getErrorArgs() {
return errorArgs;
}
} |
Impact on UI
Test Scenarios
Test ID | Test Description | Expected Results |
---|---|---|
Bug Fixes
Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-14378 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-15040 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-15499 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-15593 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-14797 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-15426 Jira Legacy server Cask Community Issue Tracker columns key,summary,type,created,updated,due,assignee,reporter,priority,status,resolution serverId 45b48dee-c8d6-34f0-9990-e6367dc2fe4b key CDAP-15581
Releases
Release 6.1.0