openzipkin/zipkin · error · NullPointerException

keys == null

Error message

keys == null

What it means

MySQLStorage.Builder.autocompleteKeys throws NullPointerException when passed a null list. The builder deliberately fails fast on null instead of storing it, because autocompleteKey tagging is optional but must be a well-formed list. Passing null is treated as a programming error, not an empty configuration.

Source

Thrown at zipkin-storage/mysql-v1/src/main/java/zipkin2/storage/mysql/v1/MySQLStorage.java:53

    boolean strictTraceId = true, searchEnabled = true;
    private DataSource datasource;
    private Settings settings = new Settings().withRenderSchema(false);
    private ExecuteListenerProvider listenerProvider;
    private Executor executor;
    List<String> autocompleteKeys = new ArrayList<>();

    @Override public Builder strictTraceId(boolean strictTraceId) {
      this.strictTraceId = strictTraceId;
      return this;
    }

    @Override public Builder searchEnabled(boolean searchEnabled) {
      this.searchEnabled = searchEnabled;
      return this;
    }

    @Override public Builder autocompleteKeys(List<String> keys) {
      if (keys == null) throw new NullPointerException("keys == null");
      this.autocompleteKeys = keys;
      return this;
    }

    public Builder datasource(DataSource datasource) {
      if (datasource == null) throw new NullPointerException("datasource == null");
      this.datasource = datasource;
      return this;
    }

    public Builder settings(Settings settings) {
      if (settings == null) throw new NullPointerException("settings == null");
      this.settings = settings;
      return this;
    }

    public Builder listenerProvider(@Nullable ExecuteListenerProvider listenerProvider) {
      this.listenerProvider = listenerProvider;

View on GitHub (pinned to 878ce2a1fa)

Solutions

1. Pass an empty list (List.of()) when no autocomplete keys are needed.
2. Default the config value before it reaches the builder, e.g. keys != null ? keys : List.of().
3. Fix the property source so the mapped value is never null (provide a default in application.yaml or the environment).

Example fix

// before
builder.autocompleteKeys(null);

// after
builder.autocompleteKeys(keys == null ? List.of() : keys);

builder.autocompleteKeys(keys == null ? List.of() : keys);

When it happens

Trigger: Calling builder.autocompleteKeys(null), or wiring the value from config/environment that resolves to null (e.g. a missing property mapped with @Value or a Map.get that returned null).

Common situations: Property-driven configuration where zipkin.storage.mysql.autocomplete-keys is absent, so the binding produces null; refactoring that removes the list initialization; copying from another storage module whose builder tolerated null.

Related errors

• datasource == null
• settings == null
• executor == null
• storage == null
• bootstrapServers == null

AI-assisted analysis of openzipkin/zipkin@878ce2a1fa (2026-08-14). Data as JSON: /api/errors/b28c4c15afcab17a. Report an issue: GitHub.