Migrate Databricks workloads from classic compute to serverless compute. Use when migrating notebooks, jobs, pipelines, or Scala JARs (`spark_jar_task`) from classic clusters to serverless, checking if existing code is serverless-compatible, or writing new serverless-compatible code. Provides concrete fixes for the serverless Spark Connect architecture and guides the full migration. Not for classic DBR version upgrades or cluster configuration changes within classic compute.
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FIRST: Use the parent databricks-core skill for CLI basics, authentication, and profile selection.
Analyze existing Databricks code for serverless compute compatibility and guide migration from classic clusters. The skill follows a 4-step migration lifecycle: Ingest the workload → Analyze for compatibility → Test via A/B comparison → Validate and iterate.
This skill is published as an Agent Skill (agentskills.io) and runs in any compatible client:
databricks aitools install or follow the per-client docs./Workspace/Users/<you>/.assistant/skills/databricks-serverless-migration/ (per-user) or /Workspace/.assistant/skills/databricks-serverless-migration/ (workspace-wide, admin only). See Install in Databricks Genie Code for the three install methods and the important serverless-compute caveat (the Databricks CLI isn't pre-installed on serverless, so some deploy steps need adjustment).If you finish a migration analysis for a user who's currently running you from a laptop client, mention the Genie Code option once at the end — many users prefer iterating on migrations inside the workspace where the workload lives.
Migration blockers fall into three categories. Focus your effort on category 2 — that's where this skill helps most.
| Category | Description | Action |
|---|---|---|
| 1. Feature expanding | Databricks is actively expanding support (e.g., SparkML, custom JDBC) | Use the workaround now and revisit later |
| 2. Code/config change needed | Your code uses patterns that need updating for serverless (e.g., RDDs, DBFS, streaming triggers) | This skill helps here — it detects these patterns and provides fixes |
| 3. Classic-only | Workload requires capabilities not available on serverless (e.g., root OS access, R language) | Keep on classic compute |
Workload → Check language
├── R code → Category 3: keep on classic
├── Scala notebook cells → Category 2: port to PySpark/SQL, or compile as a JAR job task
├── Compiled Scala JAR (spark_jar_task, build.sbt/pom.xml/build.gradle) → see references/jar-migration.md
│ ├── Scala 2.12 build? → recompile against 2.13.16
│ ├── Bundles spark-core/spark-sql? → use databricks-connect % Provided
│ └── Bundles libs on the kernel classpath? → mark % Provided (see the classpath table in references/jar-migration.md)
├── Python / SQL → Continue
├── Uses RDD APIs? → Category 2: rewrite to DataFrame API (see fixes below)
├── Uses DBFS paths? → Category 2: migrate to UC Volumes
├── Uses Hive Metastore? → Category 2: migrate to Unity Catalog (or use HMS Federation)
├── Uses df.cache/persist? → Category 1: remove and materialize to Delta (native support coming soon)
├── Uses streaming?
│ ├── ProcessingTime trigger → Category 2: use AvailableNow or migrate to SDP
│ ├── Continuous trigger → Category 2: use SDP continuous mode
│ ├── No trigger specified → Category 2: add explicit .trigger(availableNow=True)
│ └── AvailableNow / Once → Ready ✓
├── Uses init scripts? → Category 2: use Environments
├── Uses VPC peering? → Category 2: use NCCs / Private Link
├── Uses unsupported Spark configs? → Category 2: remove (serverless auto-tunes)
├── Uses custom JDBC drivers? → Category 2: use Lakehouse Federation or built-in JDBC
├── Uses Docker containers? → Category 3: use Environments for libs, or keep on classic
└── All clear → Ready for serverless ✓Confirm the migration target is serverless compute. This skill is purpose-built for classic → serverless migrations. The checks, fixes, and workflow all target the serverless compute architecture (Spark Connect, Environments, NCCs). If the user wants to upgrade between classic DBR versions instead, this skill does not apply — classic DBR upgrades have a different compatibility surface and should follow the standard DBR upgrade guide.
Collect the full picture of what needs to migrate to serverless:
If the workload spans more than one user notebook (exclude _resources/ setup notebooks from the count), process them one at a time rather than all at once. The agent's context window is finite, and trying to hold the full source of an 8-notebook job in active context while doing analysis, fixes, and migration triggers autocompact thrashing (Claude Code) or equivalent context-overflow failures in other clients.
Procedure:
bundle_config.py (H4). If the source tree contains a bundle_config.py, parse it and follow any upstream-source declarations (git URLs, S3 paths, init_scripts, git_source, or custom upstream-repo declarations). Clone or fetch each referenced repo into a sibling location and include its notebooks in the enumeration. List "external sources" as a first-class artifact category in the migration plan. Without this step, multi-source demos (e.g., dbt-on-databricks references the upstream dbt-databricks-c360 repo) get mis-enumerated and the real task notebooks are missed.notebook_path (relative)detected_patterns[] (pattern IDs from this skill's catalog)blockers[] (Category-3 patterns this notebook hits, if any)migration_steps[] (concrete fixes ordered)unmigratable (bool — true if any blocker has no workaround)
d. If you have a writable scratch directory (~/.databricks-migration-skill/scratch/<run-id>/findings/), persist the summary as <notebook-basename>.json. This frees the source from context safely. If not, keep the summary compact in conversation history.detected_patterns array in the report aggregates across all notebooks; notebook_characteristics uses summed line counts and the union of language/streaming/ML flags.Threshold guidance: apply this procedure when the user notebook count is ≥ 3, or when individual notebooks exceed ~5KB of source. For 1–2 small notebooks the single-pass workflow in Steps 2–4 is fine.
Anti-pattern: do NOT attempt a "merge all notebooks into one big file" or "read all notebooks, then act in one mega-turn" strategy. Both defeat the purpose by reintroducing the original context-pressure problem.
Read notebooks before running them — do not rely on failed job runs to discover issues. A pre-run scan surfaces incompatibilities faster than iterating on error traces, and many serverless failures (hardcoded catalog references, init scripts, missing dependencies) are easy to spot statically but expensive to debug after a failed run.
Before creating or running any test job:
spark.table("main.schema.table"), spark.sql("... FROM main..."), catalog = "main")%pip install linesrequirements.txt or equivalent and resolve the full dependency setapt install, yum install) for conversion or escalationScan the code for patterns that are incompatible with the serverless compute architecture. These checks are serverless-specific — most of these patterns work fine on classic compute regardless of DBR version. For each issue found, report:
HIGH IMPACT. Before declaring a migrated notebook ready, run this lint pass on every output cell. Caused 3/7 demos to fail in the dbdemos E2E sweep (hls-readmission, fsi-fraud, retail-c360).
Detect: any cell that contains a # MAGIC %<word> line (e.g., # MAGIC %run, # MAGIC %sql, # MAGIC %md, # MAGIC %pip, # MAGIC %fs). Within that cell, every non-blank line must either start with # MAGIC or be a blank line. If a plain-Python comment (or any other Python code) precedes the # MAGIC %... directive in the same cell, the cell is corrupted: Databricks parses it as Python and %run falls back to IPython line magic, producing errors like File './00-global-setup-v2' not found.
Fix: never prepend plain-Python comments above a # MAGIC %... line within the same cell. Two valid options:
# MAGIC %md cell above (its own # COMMAND ---------- block).Example before (corrupted; %run fails with File not found):
# COMMAND ----------
# Migration: relative '%run ../../../_resources/00-global-setup-v2' may not
# resolve under serverless job tasks. Replaced with sibling reference.
# MAGIC %run ./00-global-setup-v2Example after (clean; %run fires as cell magic):
# COMMAND ----------
# MAGIC %md
# MAGIC Migration: relative %run path replaced with sibling reference.
# COMMAND ----------
# MAGIC %run ./00-global-setup-v2Category A: Unsupported APIs
| Pattern | Severity | Fix |
|---|---|---|
sc.parallelize(data) | Blocker | spark.createDataFrame([(x,) for x in data], ["value"]) |
rdd.map(fn) | Blocker | df.select(F.col("value") * 2) or df.withColumn(...) |
rdd.filter(fn) | Blocker | df.filter(F.col("value") > 3) |
rdd.reduce(fn) | Blocker | df.agg(F.sum("col")).collect()[0][0] |
rdd.flatMap(fn) | Blocker | df.select(F.explode(F.split(col, " "))) |
rdd.groupByKey() | Blocker | df.groupBy("key").agg(F.collect_list("value")) |
rdd.mapPartitions(fn) | Blocker | df.groupBy(F.spark_partition_id()).applyInPandas(fn, schema) |
sc.textFile(path) | Blocker | spark.read.text(path) |
sc.wholeTextFiles(path) | Blocker | spark.read.format("binaryFile").load(path) |
sc.broadcast(data) | Blocker | from pyspark.sql.functions import broadcast; df.join(broadcast(lookup_df), key) |
sc.accumulator(init) | Blocker | df.agg(F.sum("col")) or df.count() |
spark.sparkContext | Blocker | Use spark (SparkSession) directly |
SparkContext.getOrCreate() | Blocker | Not supported — raises RuntimeError: Only remote Spark sessions using Databricks Connect are supported. Replace with spark.createDataFrame() or spark.range() for data setup. |
sqlContext.sql(query) | Blocker | spark.sql(query) |
sc.hadoopConfiguration.set(...) | Blocker | Use UC external locations — no credential configs needed |
df.cache() / df.persist() | Warning | Remove caching calls. For expensive intermediate results, materialize to a Delta table. Native support coming soon. |
df.checkpoint() | Warning | Write to Delta table instead |
spark.catalog.cacheTable(t) / CACHE TABLE | Warning | Remove — not needed on serverless |
%scala cells in notebook | Blocker | Port to PySpark/SQL or compile as JAR for job tasks |
%r cells in notebook | Blocker | No serverless equivalent — keep on classic or port to PySpark |
Hive variable syntax ${var} | Warning | Use DECLARE VARIABLE / SET VARIABLE (SQL) or Python f-strings |
CREATE GLOBAL TEMPORARY VIEW | Blocker | Use CREATE OR REPLACE TEMPORARY VIEW — global_temp database doesn't exist on serverless |
global_temp. prefix in queries | Warning | Remove prefix — session-scoped temp views are accessible without qualifier |
Builtin max(..., key=) / min(..., key=) / sorted(..., key=) with from pyspark.sql.functions import * (A2) | Blocker | pyspark.sql.functions.max shadows the builtin and rejects key= (raises TypeError: max() got an unexpected keyword argument 'key'). Use sort+index: xs.sort(key=...); top = xs[0]. See MLflow on UC. |
from databricks import automl / automl.classify() / automl.regress() / automl.forecast() (A3) | Blocker | AutoML not available on serverless and the DBDemos.create_mockup_automl_run fallback hits PlanMetrics not JSON serializable on Spark Connect. Rewrite as inline scikit-learn Pipeline with mlflow.sklearn.log_model + mlflow.register_model + UC alias. See MLflow on UC. |
mlflow.pyfunc.spark_udf(...) followed by df.withColumn("prediction", loaded_model(struct(*features))) (A4) | Blocker on mlflow 2.19.0 | Closure bug on Spark Connect: batch_predict_fn captures loaded_model as a free variable; workers fail with NameError: cannot access free variable 'loaded_model'. Root cause is Spark Connect serialization. Preferred fix (portable, any mlflow), driver-side pandas inference: mlflow.pyfunc.load_model(uri).predict(df.toPandas()) then spark.createDataFrame(...). Fallback fix: pin mlflow>=2.20.0 in the environment spec. |
AutoCaptureConfigInput(enabled=...) in model-serving endpoint creation (A5) | Warning | Deprecated arg, breaks first-time endpoint deploy. Remove the auto_capture_config=AutoCaptureConfigInput(...) parameter entirely from EndpointCoreConfigInput(...). |
mlflow.<flavor>.log_model(..., registered_model_name=...) with mlflow.set_registry_uri("databricks-uc") in scope (M1) | Blocker | Under UC, registered_model_name= triggers an internal get_model_version_by_alias(..., 'Champion') call that raises RESOURCE_DOES_NOT_EXIST for brand-new models. Drop the kwarg from log_model; after the run, call mlflow.register_model(model_uri=f"runs:/{run.info.run_id}/model", name=<full_name>) and MlflowClient().set_registered_model_alias(...). See MLflow on UC. |
.latest_versions access on UC-registered models (e.g., client.get_registered_model(name).latest_versions) (M2) | Blocker | RegisteredModel.latest_versions is always None on UC; max(None, key=...) raises TypeError: 'NoneType' object is not iterable. Use client.search_model_versions(f"name='{name}'") + sort+index (per A2 above). See MLflow on UC. |
mlflow.<flavor>.log_model(...) without signature= kwarg, with mlflow.set_registry_uri("databricks-uc") in scope (M3) | Blocker | UC requires a model signature on every registered model. Without signature=, log_model raises MlflowException: Model signature is required for registering a model to Unity Catalog. Infer from a sample: signature = infer_signature(X_sample, model.predict(X_sample)) then pass as signature=signature to log_model. See MLflow on UC. |
Binary-classifier prediction column written as float64 (Double) when downstream Delta table expects Integer (M4) | Blocker on first write | sklearn binary classifiers (e.g. the AutoML → sklearn rewrite from A3) emit predict() results as float64. Writing to a Delta table whose prediction column is IntegerType fails with DELTA_FAILED_TO_MERGE_FIELDS: prediction (Double) vs prediction (Integer). Cast before writing: df.withColumn("prediction", col("prediction").cast("integer")). See MLflow on UC. |
Category B: Data Access
| Pattern | Severity | Fix |
|---|---|---|
dbfs:/ or /dbfs/ paths (persistent data) | Blocker | Replace with /Volumes/<your_catalog>/schema/volume/path |
dbfs:/tmp/, /dbfs/tmp/, paths with cache/scratch/temp | Warning | Use /tmp/ or /local_disk0/tmp/ (local driver disk) — do not use Volumes for temp files due to performance |
file:///dbfs/ FUSE mount paths | Warning | Replace persistent paths with /Volumes/...; replace temp paths with /local_disk0/tmp/ |
dbutils.fs.mount(...) | Blocker | Create UC external location + external volume |
hive_metastore.db.table | Warning | Migrate to UC or use HMS Federation: CREATE FOREIGN CATALOG ... USING CONNECTION hms_connection |
CREATE DATABASE/CREATE SCHEMA without USE CATALOG or 3-level name | Blocker | Prepend spark.sql("USE CATALOG <your_catalog>") at notebook start before any CREATE statements. Detect target catalog from existing table references, or ask the user. |
| IAM instance profile references | Warning | Use UC external locations + storage credentials |
| Hive SerDe tables | Blocker | Migrate to Delta tables in UC |
Bare catalog = "<value>" / schema = "<value>" assignment in config.py, config/__init__.py, _config*.py, or any Python file referenced via %run (B1) | Blocker | Catalog rewrite must scan all config files, not just notebook bodies that contain spark.table(...). Replace literals like "main", "main__build", "hive_metastore" with the user's target catalog (typically home_<user>). Post-rewrite, grep the entire migrated tree for residual literal catalog refs. |
spark.sql("CREATE CATALOG IF NOT EXISTS ...") (B2) | Blocker | Privilege check fires before IF NOT EXISTS short-circuits, so non-admin users hit PERMISSION_DENIED: User does not have CREATE CATALOG on Metastore even when the catalog already exists. Guard with SHOW CATALOGS LIKE '...' probe first; only emit CREATE CATALOG if the probe returns empty. Apply recursively across the entire migrated tree, including _resources/00-global-setup-v2.py and config* files. Same pattern applies to CREATE SCHEMA IF NOT EXISTS and CREATE VOLUME IF NOT EXISTS in catalogs the user doesn't own. |
Category C: Streaming
| Pattern | Severity | Fix |
|---|---|---|
.trigger(processingTime=...) | Blocker | .trigger(availableNow=True) + set maxFilesPerTrigger or maxBytesPerTrigger to prevent OOM |
.trigger(continuous=...) | Blocker | Migrate to SDP continuous mode |
No .trigger() call on writeStream | Blocker | Must add .trigger(availableNow=True) — Spark defaults to ProcessingTime("0 seconds") which is not supported |
| Kafka source | Info | Works with AvailableNow; use maxOffsetsPerTrigger to control batch size |
| Auto Loader | Info | Works; use cloudFiles.maxFilesPerTrigger (note the cloudFiles. prefix) |
Category D: Configuration
| Pattern | Severity | Fix |
|---|---|---|
Unsupported spark.conf.set(...) | Warning | Remove — only 6 configs supported: spark.sql.shuffle.partitions, spark.sql.session.timeZone, spark.sql.ansi.enabled, spark.sql.files.maxPartitionBytes, spark.sql.legacy.timeParserPolicy, spark.databricks.execution.timeout. Serverless auto-tunes everything else. |
| Init scripts | Blocker | Use Environments: add dependencies via notebook Environment panel or requirements.txt. Pin specific versions. |
| Cluster policies | Info | Use budget policies for cost attribution |
| Docker containers | Blocker | Use Environments for library management. Keep on classic only if Docker is needed for OS-level customization. |
%run ./relative/path or %run ../path | Warning | Relative %run paths may not resolve correctly in serverless job tasks. Fix: (1) Inline the referenced notebook's code if <500 lines (preferred), (2) Convert to dbutils.notebook.run("<absolute_workspace_path>", timeout) with absolute path. Found in ~19% of repos. |
os.environ["VAR"] (system/custom env vars) | Warning | Use os.environ.get() with fallback, spark.version for Spark info, or dbutils.widgets for custom vars |
SET hivevar: / ${hivevar:...} (Hive variable substitution) | Blocker | Use SQL session variables: DECLARE OR REPLACE VARIABLE name = value (DBR 14.1+) |
| Environment variables (in init scripts) | Warning | Use dbutils.widgets or job parameters |
| Explicit executor count/memory configs | Info | Remove — serverless auto-scales and auto-tunes |
Retired Foundation Model endpoint references, e.g., databricks-meta-llama-3-1-405b-instruct and similar (D1) | Blocker | Detect by content scan across every migrated file (not by filename pattern). Common refs in ai_query(endpoint => '...'), ChatDatabricks(endpoint=...), model-serving config, and Genie/AI-Functions SQL. Replace with the current default databricks-meta-llama-3-3-70b-instruct. Verify the replacement endpoint exists in the target workspace before final deploy. |
Category E: Libraries
| Pattern | Severity | Fix |
|---|---|---|
| JAR libraries in notebooks | Blocker | Compile as JAR job task (Scala 2.13, JDK 17, env version 4+) |
| Compiled Scala JAR migration (version + dependency conflicts) | Blocker | Recompile against Scala 2.13.16; depend on databricks-connect % Provided; mark kernel-bundled deps % Provided. Full procedure + env-4 classpath in JAR Migration |
| Maven coordinates | Blocker | Replace with PyPI packages in Environments |
%pip install without version pins | Warning | Pin versions: %pip install numpy==2.2.2 pandas==2.2.3 |
| Custom Spark data sources (v1/v2 JARs) | Blocker | Use Lakehouse Federation, Lakeflow Connect, or PySpark custom data sources |
| LZO format files | Blocker | Convert to Parquet or Delta |
AutoML-trained model loaded via mlflow.pyfunc.spark_udf(..., env_manager='local') inside an SDP .py library file (E1) | Blocker | The SDP serverless image does not ship databricks-automl-runtime; cloudpickle.load raises ModuleNotFoundError: No module named 'databricks.automl_runtime'. Auto-emit %pip install -q databricks-automl-runtime as the first non-comment line of the SDP .py library file. %pip install is supported in SDP .py library files and runs once per update before SQL flows are planned. Same fix works for non-SDP notebooks loading AutoML-trained models. |
| AutoML → sklearn rewrite (A3) with pre-existing model-serving endpoint (E2) | Blocker on first redeploy | The rewrite changes model signature (e.g., drops id from inputs). A pre-existing endpoint pinned to the old AutoML signature fails create/update with HTTP 400 Failed to enforce schema of data ... Model is missing inputs ['id']. In the downstream serving notebook for the migrated test endpoint (not a live production endpoint serving real traffic), flip force_update = False → force_update = True so the endpoint re-binds to the current prod (or Champion) alias. Before flipping, confirm the endpoint name matches the migrated copy. |
Category F: Networking
| Pattern | Severity | Fix |
|---|---|---|
| VPC peering configuration | Blocker | Create NCCs, get stable IPs, allowlist on resource firewalls. S3 same-region access works without changes. |
| Direct S3/ADLS access without UC | Warning | Use UC external locations |
Category G: Sizing & Debugging
| Pattern | Severity | Fix |
|---|---|---|
| Large driver memory configs | Info | Serverless REPL default is 8GB (high-memory option for 16GB+ via Environments) |
| Spark UI references | Info | Use Query Profile instead: click "See performance" under cell output |
Category H: Job-level config (dbt_task, SDP, multi-source, deploy preconditions)
These checks operate on the job/pipeline spec JSON and on deploy preconditions, not on notebook bodies. Apply them alongside the per-notebook checks in Categories A–G.
| Pattern | Severity | Fix |
|---|---|---|
dbt_task block in job spec (H1) | Blocker for dbt workloads | Three sub-checks: (1) warehouse_id: swap known-busy or non-serverless warehouses to a Stable/dedicated DBSQL serverless warehouse. (2) project_directory: rewrite to the migrated workspace location (e.g., /Workspace/Users/<me>/<demo>-skill-migrated/...). (3) libraries[]: replace classic-only Python wheels with pinned serverless-compatible versions; flag dbt-databricks < 1.7.x. |
SDP pipeline spec deployed alongside the original demo with the same schema (H2) | Blocker | UC rejects parallel deploy with Table is already managed by pipeline <orig-id>. When the target path includes a migration suffix (e.g., -skill-migrated/), automatically suffix the pipeline's target schema (e.g., dbdemos_retail_c360 → dbdemos_retail_c360_skill_migrated). Apply the same rewrite to any LIVE / STREAMING TABLE references in transformation files that hard-code the schema. Lint the pipeline spec before deploy: if any target table already exists and belongs to another pipeline, fail with a clear message. |
Workspace import 10 MB cap (H3) | Advisory (foreseeable) | Pre-deploy precondition: walk the migrated tree before databricks workspace import and flag any file > 10 MB. Reroute large files (sample CSVs, dbt seed data, sample datasets, etc.) to UC Volumes (databricks fs cp) instead of workspace import. Emit a UC Volumes upload command alongside the workspace import command, with a manifest of what went where. Not blocking in most workloads but blocks any demo using dbt seed or large sample CSVs. |
Multi-source workloads with bundle_config.py declaring upstream git URLs (H4) | Diagnostic | Without this, the skill mis-enumerates user notebooks. Parse bundle_config.py and follow any upstream-source declarations (git URLs, S3 paths). Clone or fetch the referenced repos before per-notebook enumeration. List "external sources" as a first-class artifact category in the migration plan. See Multi-source enumeration. Concrete example: dbt-on-databricks's bundle_config.py references the upstream dbt-databricks-c360 repo; the real task notebooks live there, not in the local dbdemos-notebooks/ tree. |
The migration output MUST include a Serverless Environment specification alongside migrated code. Generate this by:
import statements and %pip install lines to detect required packagespip install commands from the job configurationenvironments field:{
"environment_key": "Default",
"spec": {
"client": "2",
"dependencies": ["mlflow==2.12.1", "scikit-learn==1.3.0", "xgboost==2.0.3"]
}
}Important: ML runtime libraries (mlflow, scikit-learn, hyperopt, xgboost, tensorflow, torch, etc.) are NOT pre-installed on serverless compute. They MUST be listed explicitly in the environment spec dependencies. ML runtime is NOT available on serverless — always use Serverless Environments with explicit package dependencies instead.
Use separate branches for testing and production to keep test-only workarounds out of the code that ships. The test branch is a safe sandbox for experimentation; the production branch contains only changes that production actually needs.
| Aspect | Test branch | Production branch |
|---|---|---|
| Name pattern | serverless-test-{job_name}-{timestamp} | serverless-prod-{job_name} |
| Base branch | Any working branch | Must be master |
| Purpose | Verify serverless compatibility | Deploy to production |
| Test-only workarounds | Yes (catalog overrides, sampled data, date limits) | No |
| Compatibility fixes | Yes (discover them here) | Yes (apply the validated ones) |
| Job config changes | Yes (for the test job) | Yes (for the prod job) |
| Catalog | Test catalog | Production catalog |
| PR required | No | Yes |
| Merged to master | No | Yes |
Test branch (serverless-test-{job_name}-{timestamp}): Temporary, no PR needed.
Production branch (serverless-prod-{job_name}): PR required, created from master.
When the job reads from production tables, do not point the test job at production data. Instead, create sampled copies of upstream tables in a dedicated test catalog and run the test job against those.
The recommended pattern:
CREATE TABLE IF NOT EXISTS <test_catalog>.<schema>.<table> AS SELECT * FROM <prod_catalog>.<schema>.<table> LIMIT N (typical N: 10–1000 rows)CREATE TABLE permission on the test catalogWith schema names preserved, the same notebook code runs in both environments — only the catalog widget value changes.
| Change type | Production? | Reason |
|---|---|---|
| Remove incompatible Spark configs | Yes | Serverless compatibility fix |
| Update library versions | Yes | Serverless compatibility fix |
| Replace DBFS paths with UC Volumes | Yes | Serverless compatibility fix |
| Remove init scripts, add Environments | Yes | Serverless compatibility fix |
| Fix hardcoded cluster settings | Yes | Serverless compatibility fix |
| Catalog override to test catalog | No | Test workaround only |
| Empty DataFrame handling for missing test data | No | Test workaround only |
| Date range limiting for faster tests | No | Test workaround only |
Simple test: Would production fail without this change on serverless? If yes → include. If no → test branch only.
After both branches are ready, compare outputs:
# Compare outputs between classic and serverless runs
classic_df = spark.read.table("main.output.classic_results")
serverless_df = spark.read.table("main.output.serverless_results")
assert classic_df.count() == serverless_df.count(), "Row count mismatch"
assert classic_df.schema == serverless_df.schema, "Schema mismatch"
diff = classic_df.exceptAll(serverless_df)
assert diff.count() == 0, f"Found {diff.count()} differing rows"Temporary bridge configs: If the serverless run fails, you may temporarily set supported Spark configs (like spark.sql.shuffle.partitions) to bridge gaps. Mark these as temporary — remove once the workload stabilizes.
Once the A/B comparison passes:
system.billing.usage) and budget policiesAt the end of a successful migration run, surface these artifacts so the user can verify the work and inspect the results:
| Deliverable | What it is | Why it matters |
|---|---|---|
| Test branch name/URL | The serverless-test-{job_name}-{timestamp} branch with all compatibility fixes and test workarounds | Lets the user see what changed during experimentation, including test-only adjustments |
| Production branch name/URL | The serverless-prod-{job_name} branch containing only the validated compatibility fixes | This is what ships — the user reviews and merges the PR from here |
| Test job ID and run URL | The serverless test job that validated the migration | Proves the notebook runs successfully on serverless against sampled data |
| Classic vs serverless comparison | A/B result summary (row counts, schema check, row-level diff) | Confidence that serverless output matches classic output |
| Serverless environment spec | The environments JSON block (client version + pinned dependencies) | Ready to paste into the production job config |
| Change summary | List of what went to production vs test-only (with reasons) | Audit trail for the PR reviewer |
If any deliverable is missing, the migration is incomplete — do not mark it as done.
Do not attempt workarounds for these — surface them to the user and stop:
# BEFORE (classic)
df = spark.read.csv("dbfs:/mnt/datalake/sales/data.csv", header=True)
df.write.parquet("dbfs:/mnt/output/results")
# AFTER (serverless)
df = spark.read.csv("/Volumes/main/sales/raw_data/data.csv", header=True)
df.write.parquet("/Volumes/main/analytics/output/results")
# Replace mounts with external volumes (SQL):
# CREATE EXTERNAL VOLUME main.data.raw_files LOCATION 's3://my-bucket/data/';
# Then use: /Volumes/main/data/raw_files/
# Pandas paths too:
# BEFORE: pd.read_csv("/dbfs/mnt/data/file.csv")
# AFTER: pd.read_csv("/Volumes/main/data/volume/file.csv")from pyspark.sql import functions as F
# parallelize + map
# BEFORE:
rdd = sc.parallelize([1, 2, 3])
result = rdd.map(lambda x: x * 2).collect()
# AFTER:
df = spark.createDataFrame([(1,), (2,), (3,)], ["value"])
result = df.select((F.col("value") * 2).alias("value")).collect()
# flatMap (word splitting)
# BEFORE:
words = sc.parallelize(["hello world"]).flatMap(lambda l: l.split(" ")).collect()
# AFTER:
df = spark.createDataFrame([("hello world",)], ["line"])
words = df.select(F.explode(F.split("line", " ")).alias("word")).collect()
# groupByKey
# BEFORE:
rdd = sc.parallelize([("a", 1), ("b", 2), ("a", 3)])
grouped = rdd.groupByKey().mapValues(list).collect()
# AFTER:
df = spark.createDataFrame([("a", 1), ("b", 2), ("a", 3)], ["key", "value"])
grouped = df.groupBy("key").agg(F.collect_list("value").alias("values")).collect()
# mapPartitions → applyInPandas
# BEFORE:
def process_partition(iterator):
yield sum(iterator)
result = sc.parallelize(range(100), 4).mapPartitions(process_partition).collect()
# AFTER:
import pandas as pd
def process_group(pdf: pd.DataFrame) -> pd.DataFrame:
return pd.DataFrame({"total": [pdf["id"].sum()]})
result = (spark.range(100).repartition(4)
.groupBy(F.spark_partition_id())
.applyInPandas(process_group, schema="total long")
.collect())
# textFile
# BEFORE: rdd = sc.textFile("/mnt/data/file.txt")
# AFTER: df = spark.read.text("/Volumes/catalog/schema/volume/file.txt")
# wholeTextFiles
# BEFORE: rdd = sc.wholeTextFiles("/mnt/data/dir/")
# AFTER: df = spark.read.format("binaryFile").load("/Volumes/catalog/schema/volume/dir/")# CRITICAL: Omitting .trigger() defaults to ProcessingTime(0) — not supported on serverless
# BEFORE (fails on serverless — no trigger = ProcessingTime default):
query = df.writeStream.format("delta").outputMode("append").start(path)
# BEFORE (fails — explicit ProcessingTime):
query = df.writeStream.trigger(processingTime="10 seconds").start(path)
# AFTER (serverless compatible):
query = (df.writeStream
.format("delta")
.outputMode("append")
.trigger(availableNow=True)
.option("checkpointLocation", "/Volumes/main/data/checkpoints/stream1")
.start("/Volumes/main/data/output/stream1"))
query.awaitTermination()
# With OOM prevention (recommended for large sources):
query = (spark.readStream.format("delta")
.option("maxFilesPerTrigger", 100) # Delta/Parquet sources
.option("maxBytesPerTrigger", "10g") # Limit data per micro-batch
.load(input_path)
.writeStream
.trigger(availableNow=True)
.option("checkpointLocation", checkpoint_path)
.start(output_path))
# Kafka: use maxOffsetsPerTrigger
query = (spark.readStream.format("kafka")
.option("kafka.bootstrap.servers", "broker:9092")
.option("subscribe", "topic1")
.option("maxOffsetsPerTrigger", 100000) # Kafka-specific
.load()
.writeStream.trigger(availableNow=True).start(output_path))
# Auto Loader: use cloudFiles.maxFilesPerTrigger (note the prefix)
query = (spark.readStream.format("cloudFiles")
.option("cloudFiles.format", "json")
.option("cloudFiles.maxFilesPerTrigger", 1000) # cloudFiles. prefix
.load(landing_path)
.writeStream.trigger(availableNow=True).start(output_path))# BEFORE (classic):
df = spark.read.parquet(path)
df.cache()
df.count() # materialize cache
result1 = df.filter("status = 'active'")
result2 = df.groupBy("region").agg(F.sum("revenue"))
# AFTER (serverless — remove .cache(); native support coming soon):
df = spark.read.parquet(path)
result1 = df.filter("status = 'active'")
result2 = df.groupBy("region").agg(F.sum("revenue"))
# For truly expensive intermediate results, materialize to Delta:
expensive_df.write.format("delta").mode("overwrite").saveAsTable("main.scratch.intermediate")
result = spark.table("main.scratch.intermediate")
# SQL equivalent:
# BEFORE: CACHE TABLE my_table
# AFTER: (just remove the CACHE TABLE statement)| Pattern | Fix | Full example |
|---|---|---|
sc.broadcast / sc.accumulator / sqlContext.sql | Use SparkSession equivalents: broadcast() join, df.agg(), spark.sql() | Code Patterns |
| Init scripts | Move to Environment panel or requirements.txt. Do NOT install PySpark. Pin versions. | Code Patterns |
| Hive Metastore tables | Use HMS Federation as bridge (CREATE FOREIGN CATALOG) or migrate directly (CREATE TABLE ... AS SELECT) | Code Patterns |
| Custom JDBC JARs | Use Lakehouse Federation (CREATE CONNECTION ... TYPE POSTGRESQL) or built-in JDBC (works on serverless) | Code Patterns |
| Spark UI debugging | Use Query Profile: click "See performance" under cell output, or df.explain(True) | Code Patterns |
import os
is_serverless = os.getenv("IS_SERVERLESS", "").lower() == "true"Remove job_clusters/new_cluster, add environments with serverless spec, replace job_cluster_key with environment_key, remove init_scripts. See Configuration Guide for full before/after JSON and environment version mapping.
Environment version mapping (match to the DBR version the workload was on):
| Classic DBR | Serverless spec.client | Python |
|---|---|---|
| 13.x, 14.x | "1" | 3.10 |
| 15.x | "2" | 3.11 |
| 16.x+ | "3" | 3.12 |
When migrating a job, the job configuration JSON must be transformed alongside notebook code. The agent should perform all of the following:
Init scripts to Serverless Environments: Detect init_scripts in the job JSON. Extract all pip install commands and convert them to Environment dependencies. For OS-level packages (apt install/yum install) that have pip equivalents (e.g., apt install python3-opencv becomes opencv-python), convert them. Flag OS-level packages without pip equivalents as serverless-incompatible (Category 3).
Cluster libraries (Maven/JAR) to Environment or Volumes: Maven coordinates for Python-wrapping JARs should be replaced with their PyPI equivalent in the Environment spec. Custom JARs on DBFS need to be moved to /Volumes/<your_catalog>/schema/volume/ and referenced there. Custom Spark data source JARs (v1/v2) are a Category 3 blocker — flag them for classic retention.
job_clusters to serverless compute: Remove job_clusters / new_cluster blocks entirely. Add an environments array with the serverless spec. Replace job_cluster_key in each task with environment_key. Remove init_scripts, num_workers, node_type_id, spark_version. See Configuration Guide for a complete before/after example.
spark_conf migration: Scan all spark.conf.set(...) calls in the notebook and spark_conf entries in the job JSON. For each:
spark.sql.shuffle.partitions, spark.sql.session.timeZone, spark.sql.ansi.enabled, spark.sql.files.maxPartitionBytes, spark.sql.legacy.timeParserPolicy, spark.databricks.execution.timeoutfs.s3a.*, fs.azure.* — replaced by UC external locations# Removed: auto-tuned on serverless or # Removed: use UC external locations insteaddbutils.widgets.text("catalog", "main") # Default to production
catalog = dbutils.widgets.get("catalog")
df = spark.table(f"{catalog}.sales.orders")
# Pass catalog="test_catalog" as a job parameter during testingSee Configuration Guide for mock table catalog mapping and test job creation patterns.
Always get the actual error with w.jobs.get_run_output(run_id=...) before guessing. Common errors:
| Error | Fix |
|---|---|
INFINITE_STREAMING_TRIGGER_NOT_SUPPORTED | Add .trigger(availableNow=True) |
UNRESOLVED_COLUMN | Temp view name collision — use unique names |
TABLE_OR_VIEW_NOT_FOUND | DBFS/HMS table not accessible — migrate to UC |
Py4JError: ... is not available | SparkContext/RDD used — rewrite to DataFrame |
| Package installation timeout | Pin versions; do NOT install PySpark as a dependency |
ModuleNotFoundError: No module named 'mlflow' | Add to environment spec dependencies — ML runtime is NOT available on serverless |
SparkContext.getOrCreate() is NOT supported / RuntimeError: Only remote Spark sessions | Replace with spark.createDataFrame() or spark.range() |
UC_FILE_SCHEME_FOR_TABLE_CREATION_NOT_SUPPORTED | Use managed tables or /Volumes/... paths |
PERMISSION_DENIED: CREATE SCHEMA on Catalog 'main' | Add spark.sql("USE CATALOG <your_catalog>") before CREATE statements |
DATA_SOURCE_NOT_FOUND: Failed to find data source | Category 3 blocker — custom JAR data source needs classic compute |
NoSuchMethodError: scala.Predef$.wrapRefArray / NoClassDefFoundError: scala/Serializable on a JAR run | Scala version mismatch — JAR compiled against 2.12; serverless is 2.13.16. Recompile against 2.13.16. See JAR Migration |
NoClassDefFoundError for org/apache/spark/... on a JAR run | Spark bundled instead of provided. Mark databricks-connect % Provided (and rewrite any SparkContext/RDD source). See JAR Migration |
SyntaxError after migration | Ensure comments are inside MAGIC blocks, not straddling cell delimiters |
File './<name>' not found from %run (or %run fires as IPython line magic) | A1: a plain-Python comment is preceding # MAGIC %run in the same cell. Move the comment to its own # MAGIC %md cell above. |
TypeError: max() got an unexpected keyword argument 'key' | A2: from pyspark.sql.functions import * shadowed builtin max. Use sort+index instead of max(..., key=). |
TypeError: Object of type PlanMetrics is not JSON serializable | A3: automl.classify/regress/forecast not supported; the DBDemos.create_mockup_automl_run fallback hits this on Spark Connect. Rewrite as inline sklearn Pipeline. |
NameError: cannot access free variable 'loaded_model' | A4: mlflow 2.19.0 pyfunc.spark_udf closure bug on Spark Connect. Use driver-side pyfunc.load_model + toPandas() + spark.createDataFrame, or pin mlflow>=2.20.0. |
ModuleNotFoundError: No module named 'databricks.automl_runtime' | E1: SDP image missing databricks-automl-runtime. Emit %pip install -q databricks-automl-runtime at top of the SDP .py library file. |
HTTP 400: Failed to enforce schema of data ... Model is missing inputs ['id'] | E2: AutoML → sklearn rewrite changed model signature; flip downstream force_update = False → True. |
RESOURCE_DOES_NOT_EXIST from get_model_version_by_alias(..., 'Champion') during log_model | M1: drop registered_model_name= from log_model under UC; call mlflow.register_model(...) after the run. |
TypeError: 'NoneType' object is not iterable from .latest_versions | M2: RegisteredModel.latest_versions is always None on UC. Use client.search_model_versions(...) + sort+index. |
MlflowException: Model signature is required for registering a model to Unity Catalog | M3: UC requires signature= on log_model. Infer via infer_signature(X_sample, model.predict(X_sample)) and pass to log_model(..., signature=signature). See MLflow on UC. |
404 on ai_query(endpoint => 'databricks-meta-llama-3-1-405b-instruct') | D1: retired Foundation Model endpoint. Replace with databricks-meta-llama-3-3-70b-instruct via content scan across all migrated files. |
PERMISSION_DENIED: User does not have CREATE CATALOG on Metastore (even when catalog exists) | B2: priv check fires before IF NOT EXISTS short-circuits. Guard with SHOW CATALOGS LIKE '...' probe. Apply recursively, including _resources/ and config* files. |
Table is already managed by pipeline <pipeline-id> on SDP parallel deploy | H2: suffix the migrated pipeline's target schema (e.g., <orig>_skill_migrated). |
DELTA_FAILED_TO_MERGE_FIELDS: prediction (Double) vs prediction (Integer) | M4: AutoML → sklearn rewrite emits float64 predictions; cast to IntegerType for binary classifiers before writing. See MLflow on UC. |
See Configuration Guide for the full error reference and SDK code examples.
| Criteria | Performance-Optimized | Standard |
|---|---|---|
| Startup time | <50 seconds | 4-6 minutes |
| Cost | Higher | Significantly lower |
| Available for | Notebooks, Jobs, SDP | Jobs and SDP only |
| Best for | Interactive work, dev, time-sensitive | Batch ETL, scheduled pipelines |
| Default | Yes (UI and API) | Must be explicitly selected |
Standard mode is NOT available for notebooks. Notebooks always use Performance-Optimized.
| Setting | Value |
|---|---|
| REPL VM memory | 8GB default (high-memory option available) |
| Max executors | 32 (Premium), 64 (Enterprise) — raise via support |
| Supported Spark configs | 6 only (see Category D above) |
| Debugging | Query Profile (no Spark UI) |
| ANSI SQL | Enabled by default (configurable) |
When migration fails or hits an unmigratable pattern, generate a structured failure report and offer the user a one-step path to file it as a GitHub issue. This feedback loop is how the skill learns — without it, gaps go undiscovered.
See Failure Reporting for the full redaction checklist, URL-encoding recipe, and example pre-filled link.
Offer to file a GitHub issue any time the workload cannot be fully migrated to serverless as-is. Reports from "known" patterns (R, Scala, custom JAR data sources, JVM access, third-party connectors) are just as valuable as reports from unknown patterns — they tell maintainers which gaps users hit most often, which drives prioritization.
Concretely, ALWAYS offer if any of these is true:
retry_count >= max_retries (typically 5) and final status is FAILED/migration-reportDo NOT offer to file only when:
Write a JSON file to ~/.databricks-migration-skill/reports/failure-<ISO-timestamp>.json. Create the directory if it doesn't exist.
Schema (strictly follow — no free-text code or identifiers):
{
"report_version": "1.1",
"report_id": "<uuid-v4>",
"skill_version": "<from SKILL.md frontmatter metadata.version>",
"timestamp": "<ISO 8601 UTC>",
"failure_phase": "analyze | migrate | test | validate",
"detected_patterns": [
{"category": "A", "pattern_id": "rdd_parallelize", "count": 3}
],
"attempted_fixes": [
{"pattern_id": "rdd_parallelize", "fix_applied": "<fix_id>", "attempt_number": 1, "outcome": "failed"}
],
"final_error_category": "unknown_api | missing_library | data_access | permission | custom_data_source | jvm_access | unsupported_language | other",
"final_error_signature": "<SHA256 of top 3 stack frames, NOT the frames themselves>",
"retry_count": 5,
"total_duration_seconds": 245,
"notebook_characteristics": {
"lines_of_code": 180,
"language": "python | sql | scala | r",
"uses_streaming": false,
"uses_ml_libraries": true,
"databricks_runtime_source": "<DBR version only, no cluster identifiers>"
}
}Hard requirement — the report must be safe to share publicly on GitHub Issues:
rdd_parallelize), never code snippets, function bodies, or even single-line examplesgo/ links, Confluence page IDs, Google Doc IDs, Slack user or channel IDs (U…, C…), PROD-* / SEV-* / SC-* ticket numbersnotebook_characteristics fieldsBefore writing the report, scan every string field against this pattern checklist. If any pattern matches, drop the offending field (do not redact partially — empty string is safer than risking leakage):
| Pattern | What to scrub |
|---|---|
[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Za-z]{2,} | Email addresses |
dbfs:/, /dbfs/, s3://, abfss://, gs://, wasbs:// | Cloud storage paths |
https?://[a-z0-9-]+\.cloud\.databricks\.com, https?://adb-\d+\.\d+\.azuredatabricks\.net | Workspace URLs |
U[A-Z0-9]{8,}, C[A-Z0-9]{8,} | Slack user / channel IDs |
\bgo/[a-z0-9-]+\b | go/ links |
| `\b(PROD | SEV |
[0-9a-f]{20,} (heuristic) | Likely doc/file/workspace IDs |
| Catalog/schema/table name literals from the analyzed notebook | Drop and replace with "<redacted>" |
The notebook_characteristics fields are the only safe surface for workload metadata. Do not add new fields without expanding this checklist.
The redaction above happens at generation time and depends on the model applying every rule. That is not enough on a path that ends in a public GitHub issue. After serializing the report to JSON:
gh issue create command. Print the local file path, list the patterns that matched, and tell the user to redact the file manually before sharing.This deterministic check is non-negotiable; do not skip it even when you are confident the generation-time redaction was applied.
When the decision tree above says "offer to file", the default output is local-only. The pre-filled URL and gh command are shown only after the user has acknowledged the local file and the post-serialization scrub (see above) is clean.
Default response — always include:
~/.databricks-migration-skill/reports/failure-<timestamp>.json, with <timestamp> filled in).Only after the user explicitly confirms (e.g. "share it", "file the issue", "looks good") AND the deterministic post-serialization scrub above returned clean, then produce:
https://github.com/databricks/databricks-agent-skills/issues/new?template=migration-feedback.md&title=<…>&body=<…> URL, both parameters URL-encoded.gh issue create --repo databricks/databricks-agent-skills … command, body-file pointing at the local report.Do not produce the URL or gh command in the same turn as the file write. Two turns: write + offer review, then publish after explicit confirmation.
Use this exact wrap-up template, replacing <…> placeholders:
Migration could not complete. A failure report has been generated at:
~/.databricks-migration-skill/reports/failure-<timestamp>.json
The report contains anonymized diagnostic data (detected pattern IDs, error
category, retry count, notebook characteristics) and no code content or PII.
Submission is optional and opt-in.
To help improve this skill, file the report as a GitHub issue:
Option A — One-click in browser (pre-filled):
<PREFILLED_ISSUE_URL>
Option B — From the terminal (if you have the GitHub CLI installed):
gh issue create \
--repo databricks/databricks-agent-skills \
--title "<TITLE>" \
--body-file ~/.databricks-migration-skill/reports/failure-<timestamp>.json \
--label migration-skill
Before submitting, please open the JSON and confirm nothing sensitive
slipped through. We never transmit reports automatically.Build <PREFILLED_ISSUE_URL> like this:
[migration-skill] <final_error_category> in <failure_phase> phase
Example: [migration-skill] custom_data_source in migrate phase```json) with the report JSON inlined.%20 for spaces, %23 for #, %0A for newline, etc.).https://github.com/databricks/databricks-agent-skills/issues/new?template=migration-feedback.md&title=<URL-encoded title>&body=<URL-encoded body>If your runtime cannot actually write the file (sandboxed, no filesystem write), still show the path the file WOULD be at and produce Options A and B. The user can write the JSON to disk themselves.
The full recipe with a worked example is in Failure Reporting.
Never transmit the report automatically. The user owns their data and must review before sharing. If the user declines, do not press them — log the local report path and move on.
When migration succeeds, generate a per-workload report with the same structure as the failure report (minus the redaction-to-publish step), listing the patterns detected and the fixes applied for each workload. Write to ~/.databricks-migration-skill/reports/success-<timestamp>.json and tell the user the file path.
When several independent workloads are in scope, migrate them in parallel (e.g. one subagent per workload). Keep the per-notebook steps within a single workload sequential, as in Step 1.5.
For detailed workarounds and code examples beyond the quick fixes above:
latest_versions replacement, spark_udf closure-bug fix, prediction-column dtype alignmentbundle_config.py and fetching upstream git sources before per-notebook analysisea6452e
If you maintain this skill, you can claim it as your own. Once claimed, you can manage eval scenarios, bundle related skills, attach documentation or rules, and ensure cross-agent compatibility.