0 - Common Layer on Apache Dubbo

0-1 - Thread Pool Resource Exhaustion

Mon, 01 Jan 0001 00:00:00 +0000

The server’s thread resources have been exhausted.
By default, there are 200 business threads on the Dubbo server. If the number of concurrent requests exceeds 200, new requests will be rejected, and this error will be thrown.

Possible Causes

The consumer’s concurrent request volume is too high, causing the number of threads created on the provider side to exceed the limit.
The provider side may have blocking threads due to business calls to external application interfaces while executing the business.

Troubleshooting and Resolution Steps

Enable Dubbo’s access log feature to check for a large number of RPC service calls in a short period.
Use jps and jstack commands to check the status of various threads in the thread pool to see if there are blocking issues caused by business calls to external application interfaces.
If the consumer’s concurrent request volume is too high, adjust the provider side’s dubbo.provider.threads parameter to increase the number of Dubbo’s thread pool.
If the QPS of the provider’s business is indeed too high and the current number of servers cannot handle it, increase the number of provider servers to share the load.

This error code FAQ page references Kongming’s “Common Dubbo Errors and Solutions”.
The cited article is licensed under CC-BY-4.0, granting rights for compilation. Special thanks to the original author.

0-2 - Illegal Property Value

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

This prompt indicates that the value configured by the user does not match the data type required by the attribute itself. For example, the dubbo.consumer.threads property can only accept numeric values, but the value entered by the user includes letters.

Troubleshooting and Resolution Steps

Refer to the Configuration Item Reference Manual to find the erroneous configuration item, check the specified type of that item, and verify if there is any type inconsistency.

0-3 - Unable to access cache path

Mon, 01 Jan 0001 00:00:00 +0000

Other modules reuse the file-based caching mechanism from the Common layer (currently the metadata module), while the file cache mechanism in the Common layer cannot access its specified directory.

2022-08-29 00:35:00,189 ERROR [org.apache.dubbo.common.cache.FileCacheStoreFactory:?] - [DUBBO] Cache store path can't be created: , dubbo version: , current host: 10.0.1.1, error code: 0-3. This may be caused by inaccessible of cache path, go to https://dubbo.apache.org/faq/0/3 to find instructions. 
java.nio.file.FileAlreadyExistsException: [Path]
	at java.base/sun.nio.fs.WindowsException.translateToIOException(WindowsException.java:87)
	at java.base/sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:103)
	at java.base/sun.nio.fs.WindowsException.rethrowAsIOException(WindowsException.java:108)
	at java.base/sun.nio.fs.WindowsFileSystemProvider.createDirectory(WindowsFileSystemProvider.java:521)
	at java.base/java.nio.file.Files.createDirectory(Files.java:700)
	at java.base/java.nio.file.Files.createAndCheckIsDirectory(Files.java:807)
	at java.base/java.nio.file.Files.createDirectories(Files.java:753)
	at org.apache.dubbo.common.cache.FileCacheStoreFactory.getInstance(FileCacheStoreFactory.java:90)
	...

Possible Causes

Multiple Dubbo processes (or other Java processes) are using the same cache file.
Read and write failures due to file system permission issues in the directory containing the cache file.

Diagnosis and Resolution Steps

Find the inaccessible directory from the actual exception shown below and determine its file access permissions.
Check if there are other Dubbo instances accessing this path.
Try configuring Java System Properties (Java system properties configured with -D) dubbo.meta.cache.filePath and dubbo.mapping.cache.filePath, specifying a directory that the current user can fully control.

0-4 - Cache Entry Limit Exceeded

Mon, 01 Jan 0001 00:00:00 +0000

Other modules reuse the file-based caching mechanism of the Common layer (currently the metadata module), and the Common layer’s file cache mechanism has “detected” that the entry limit has been exceeded.

Possible Reasons

Users have irrationally configured the Java System Property (configured with -D) dubbo.mapping.cache.entrySize or dubbo.meta.cache.entrySize.

Default Values

dubbo.mapping.cache.entrySize	dubbo.meta.cache.entrySize
10000	100

Troubleshooting and Resolution Steps

Try reconfiguring the above Java System Property (configured with -D).
If these System Properties are not configured at all, please issue a report on the GitHub Issue Tracker.

0-5 - Cache file size exceeded

Mon, 01 Jan 0001 00:00:00 +0000

Other modules reuse the file-based caching mechanism of the Common layer (currently the metadata module), and the file caching mechanism of the Common layer has “detected” that the file size has exceeded the limit.

Possible Causes

The user has improperly configured the Java System Property (configured with -D) dubbo.mapping.cache.maxFileSize or dubbo.meta.cache.maxFileSize.
The cache file has been corrupted due to a file system or disk error.

dubbo.mapping.cache.maxFileSize and dubbo.meta.cache.maxFileSize do not have explicitly stated default values, while the maximum file size default value found based on the logic of org.apache.dubbo.common.cache.FileCacheStore.LimitedLengthBufferedWriter is: Long.MAX_VALUE (2⁶³-1) .

0-6 - Thread Interruption Exception

Mon, 01 Jan 0001 00:00:00 +0000

Possible Reasons

A running thread is explicitly interrupted by calling interrupt() while it is in wait, sleep, or join states.

Troubleshooting and Resolution Steps

When a normally running thread calls the interrupt() method, it sets the current thread’s interrupt status to true, but the thread’s execution will not be affected. You can take action based on the actual situation or check if the business code has been misused.

0-7 - Reflection class not found

Mon, 01 Jan 0001 00:00:00 +0000

Possible Reasons

Generally, this occurs when Class.forName(className) is executed and the current class className cannot be found.
The business logic explicitly excludes the current className class, resulting in it not being found during loading.

Troubleshooting and Resolution Steps

Check if className exists in Class.forName(className).
Investigate the business logic to see if any configuration or scanned annotations use exclude to exclude certain classes or packages.

0-8 - Reflection Failure

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

When reflecting to call a method, the current method is not set with the correct parameter type values, meaning the parameter types do not match.

Troubleshooting and Resolution Steps

Check if there are any parameter type values that are not correctly set to match.

0-9 - Notification event failure

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The custom listener encountered a runtime exception during processing.

Troubleshooting and Resolution Steps

Check the business class that implements the org.apache.dubbo.rpc.ExporterListener interface, as there may be a logical error in the implementation methods.

0-10 - Current call is not supported

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The method currently being called may have been deprecated or marked with @Deprecated, which does not affect the execution result.

Troubleshooting and Resolution Steps

Please use other alternative API methods.

0-11 - Service Stopping Failed

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

Connections are not closed in a timely manner, or insufficient memory may cause some exceptions when the service stops.

Troubleshooting and Resolution Steps

Close the connection after the response content is completed.

0-12 - Unknown Exception

Mon, 01 Jan 0001 00:00:00 +0000

Unknown exceptions are generally caused by API usage or configuration issues.

Possible Causes

Encoding exceptions, unsupported encryption and decryption methods, etc.

Troubleshooting and Resolution Steps

You can locate the lines of business code based on the stack trace information.

0-13 - An exception occurs in the metrics collector

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

Errors occurred during the push of metric data, the server being pushed is unreachable or there are some configuration errors, currently supporting Prometheus.

Troubleshooting and Resolution Steps

Please refer to the configuration item reference manual Configuration Item Reference Manual.

0-14 - Monitoring Exceptions

Mon, 01 Jan 0001 00:00:00 +0000

Used to count the number of RPC calls and the duration of calls, the extension interface is MonitorFactory, and the corresponding implementation class is DubboMonitorFactory.

Possible Causes

Users can implement the MonitorFactory extension interface at this layer to achieve custom monitoring statistics strategies. In the implementation class of the custom monitoring statistics strategy, a runtime business exception has occurred.

Troubleshooting and Resolution Steps

Check the business class of the org.apache.dubbo.monitor.MonitorFactory interface; the implementation method may contain logical errors in the code.

0-15 - Exception Occurred When Loading Extension Class

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The clazz class does not implement the interface class of the current extension point.
The extension name may be an interface or does not exist.

Troubleshooting and Resolution Steps

Check the declaration of the extension class and ensure there is a matching extension implementation class.
The extension implementation class must implement the extension point interface class and methods.

0-16 - No available executor

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The internal executor is unavailable and thus returns null.

Troubleshooting and Resolution Steps

No intervention is needed; Dubbo will internally execute the createExecutorIfAbsent method to construct a new executor.

0-17 - An unknown exception occurs when the executor is shutting down

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

A custom executor may have been used, and an exception was raised when writing the destroy method.

Troubleshooting and Resolution Steps

Check whether a custom implementation of org.apache.dubbo.common.threadpool.manager.ExecutorRepository is used and inspect the custom shutdown method.

0-18 - Thread pool executor is misused

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The number of threads is customized, and an unknown exception occurs within the system.

Troubleshooting and Resolution Steps

You can analyze the stack information using some third-party tools or jstack [PID] > jstack.log to locate the issue.

0-19 - Exception Occurred While Processing Task

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

Improper handling of custom business logic.

Troubleshooting and Resolution Steps

You can analyze the stack information using some third-party tools or jstack [PID] > jstack.log to locate the issue.

0-20 - Exception occurs when storing stack information

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The JVM has set the parameter -XX:+DisableAttachMechanism
The specified stack dump path does not exist; in this case, the system will attempt to create it, and a SecurityException may occur during creation, possibly due to lack of permissions.

Troubleshooting and Resolution Steps

Check if the JVM has set the above parameter.
Check if the account running the service has permissions to create folders.

0-21 - Too many instances are built

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

It generally refers to too many instances created by org.apache.dubbo.common.timer.HashedWheelTimer.

Troubleshooting and Resolution Steps

It does not affect the construction of instances, but there may be a risk of memory leaks.

0-22 - Input and Output Stream Exception

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

Reading a local file that is no longer available.
Attempting to read/write a file without permission.
Attempting to write to a file but no disk space is available.

Troubleshooting and Resolution Steps

Check if the local file exists.
Check file permissions.
Check disk space.

You can analyze the stack trace information with some third-party tools or by using jstack [PID] > jstack.log for diagnosis.

0-23 - Serialization data conversion exception

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

There are circular references in the data to be serialized, leading to a stack overflow.
The referenced jar package version is low or has compatibility issues.

Troubleshooting and Resolution Steps

If using FastJson, remove SerializerFeature.DisableCircularReferenceDetect
Check or upgrade the version for testing.

You can analyze stack information using some third-party tools or by running jstack [PID] > jstack.log for troubleshooting.

0-24 - Exception of Overriding Field Values

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The entity class does not have setter/getter methods set.
There may be nested properties.

Troubleshooting and Resolution Steps

Check the entity class and set the setter/getter methods.
Check if nested annotations are used based on the stack trace information.

0-25 - Load Mapping Error

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

Insufficient file access permissions

Troubleshooting and Resolution Steps

Check file permissions. You can use some third-party tools or jstack [PID] > jstack.log to analyze the stack information for diagnosis.

0-26 - Warning message when publishing metadata service

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The metadata prompts warning messages when storing the mapping relationship between the interface and the application.

Troubleshooting and Resolution Steps

Generally, you can analyze based on the stack information, or you may choose not to handle it.

0-27 - Thread Pool Isolation Configuration Exception

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The application’s thread pool isolation capability is not enabled, but isolation thread pool information is configured in ServiceConfig.

Troubleshooting and Resolution Steps

Enable the application’s thread pool isolation capability: dubbo.application.executor-management-mode=isolation

0-28 - Actions that may cause dangerous behavior

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

You have performed one of the following actions:

Attempted to or have adjusted the output location of accesslog

Troubleshooting and Resolution Steps

Please check if the accesslog.fixed.path=true switch in the application configuration is turned on; if it is not on, it can be ignored. If it is currently on, please confirm whether the action of switching the accesslog path was executed by a trusted person to avoid potential security risks.

0-29 - Tracer dependency not found

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

You have enabled tracing in the configuration file, but the Tracer dependency was not found.

Currently, there are two supported Tracers, OpenTelemetry and Brave.

Troubleshooting and Resolution Steps

Choose one Tracer dependency for your project:


<dependency>
 <groupId>io.micrometer</groupId>
 <artifactId>micrometer-tracing-bridge-otel</artifactId>
 <optional>true</optional>
</dependency>


<dependency>
 <groupId>io.micrometer</groupId>
 <artifactId>micrometer-tracing-bridge-brave</artifactId>
 <optional>true</optional>
</dependency>

0-99 - Called a Deprecated Method

Mon, 01 Jan 0001 00:00:00 +0000

Possible Causes

The user has called a deprecated method.

Troubleshooting and Resolution Steps

Check the user’s code for any methods that are marked as @Deprecated in the current version being used. If found, replace them with the corresponding methods; if not, you can ignore this.