aws runtime_error ai_generated true

SnapStart classpath error: Failed to load class from snapshot due to classpath mismatch

ID: aws/lambda-snapstart-classpath-error

Also available as: JSON · Markdown · 中文
78%Fix Rate
82%Confidence
1Evidence
2024-01-10First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
Lambda SnapStart (Java 11) active — — —
AWS SDK for Java 2.21.0 active — — —

Root Cause

Lambda SnapStart snapshot was taken with a different classpath than the runtime environment, often caused by mutable classpath dependencies or environment variable changes after snapshot creation.

generic

中文

Lambda SnapStart快照是在与运行时环境不同的类路径下拍摄的，通常是由于在快照创建后修改了类路径依赖项或环境变量。

Official Documentation

https://docs.aws.amazon.com/lambda/latest/dg/snapstart-troubleshooting.html

Workarounds

  1. 80% success Ensure all dependencies are immutable and not downloaded at runtime. Use a layer or bundle all JARs in the deployment package: # Example: build a fat JAR with Maven Shade Plugin mvn clean package shade:shade aws lambda update-function-code --function-name my-function --zip-file fileb://target/my-function.jar 
    Ensure all dependencies are immutable and not downloaded at runtime. Use a layer or bundle all JARs in the deployment package:
# Example: build a fat JAR with Maven Shade Plugin
mvn clean package shade:shade
aws lambda update-function-code --function-name my-function --zip-file fileb://target/my-function.jar
  2. 75% success Set environment variables in the function configuration before taking the snapshot, and never change them after: aws lambda update-function-configuration --function-name my-function --environment Variables={KEY=VALUE} --snap-start ApplyOn=PublishedVersions 
    Set environment variables in the function configuration before taking the snapshot, and never change them after:
aws lambda update-function-configuration --function-name my-function --environment Variables={KEY=VALUE} --snap-start ApplyOn=PublishedVersions
  3. 85% success Publish a new version after fixing dependencies to take a fresh snapshot: aws lambda publish-version --function-name my-function 
    Publish a new version after fixing dependencies to take a fresh snapshot:
aws lambda publish-version --function-name my-function

中文步骤

  1. 确保所有依赖项都是不可变的，并且不在运行时下载。使用层或将所有JAR打包到部署包中：
# 示例：使用Maven Shade Plugin构建胖JAR
mvn clean package shade:shade
aws lambda update-function-code --function-name my-function --zip-file fileb://target/my-function.jar
  2. 在拍摄快照之前，在函数配置中设置环境变量，之后永远不要更改：
aws lambda update-function-configuration --function-name my-function --environment Variables={KEY=VALUE} --snap-start ApplyOn=PublishedVersions
  3. 修复依赖项后发布新版本以拍摄新快照：
aws lambda publish-version --function-name my-function

Dead Ends

Common approaches that don't work:

  1. Rebuild and redeploy the Lambda function without changing anything else 90% fail

    The root cause is classpath mismatch; simply rebuilding without fixing the mutable dependency issue won't help.

  2. Disable SnapStart and re-enable it 85% fail

    Disabling and re-enabling SnapStart without addressing the classpath mismatch will reproduce the same error.

  3. Increase Lambda memory or timeout 95% fail

    Classpath errors are not related to memory or timeout; these settings don't affect class loading.