mlflow

Logs the parameters, metrics, and model file from each training run, then tracks that model's versions through a shared registry as it moves from staging to production.

WHEN TO USE

SCOPE

USE FOR

Log the learning rate, batch size, and resulting accuracy for every training run automatically.
Compare several past experiment runs side by side to see which settings worked best.
Promote a specific model version from staging to production through a shared registry.
Load a named model straight from the registry's production stage to run predictions.
Serve a trained model locally or deploy it to a cloud endpoint with one command.

This is a saved copy of the skill's SKILL.md instructions. It may differ from the upstream file or the version you install.

In this document (14)

MLflow: ML Lifecycle Management Platform

When to Use This Skill

Use MLflow when you need to:

Track ML experiments with parameters, metrics, and artifacts
Manage model registry with versioning and stage transitions
Deploy models to various platforms (local, cloud, serving)
Reproduce experiments with project configurations
Compare model versions and performance metrics
Collaborate on ML projects with team workflows
Integrate with any ML framework (framework-agnostic)

Users: 20,000+ organizations | GitHub Stars: 23k+ | License: Apache 2.0

Installation

# Install MLflow
pip install mlflow

# Install with extras
pip install mlflow[extras]  # Includes SQLAlchemy, boto3, etc.

# Start MLflow UI
mlflow ui

# Access at http://localhost:5000

Quick Start

Basic Tracking

import mlflow

# Start a run
with mlflow.start_run():
    # Log parameters
    mlflow.log_param("learning_rate", 0.001)
    mlflow.log_param("batch_size", 32)

    # Your training code
    model = train_model()

    # Log metrics
    mlflow.log_metric("train_loss", 0.15)
    mlflow.log_metric("val_accuracy", 0.92)

    # Log model
    mlflow.sklearn.log_model(model, "model")

Autologging (Automatic Tracking)

import mlflow
from sklearn.ensemble import RandomForestClassifier

# Enable autologging
mlflow.autolog()

# Train (automatically logged)
model = RandomForestClassifier(n_estimators=100, max_depth=5)
model.fit(X_train, y_train)

# Metrics, parameters, and model logged automatically!

Core Concepts

1. Experiments and Runs

Experiment: Logical container for related runs Run: Single execution of ML code (parameters, metrics, artifacts)

import mlflow

# Create/set experiment
mlflow.set_experiment("my-experiment")

# Start a run
with mlflow.start_run(run_name="baseline-model"):
    # Log params
    mlflow.log_param("model", "ResNet50")
    mlflow.log_param("epochs", 10)

    # Train
    model = train()

    # Log metrics
    mlflow.log_metric("accuracy", 0.95)

    # Log model
    mlflow.pytorch.log_model(model, "model")

# Run ID is automatically generated
print(f"Run ID: {mlflow.active_run().info.run_id}")

2. Logging Parameters

with mlflow.start_run():
    # Single parameter
    mlflow.log_param("learning_rate", 0.001)

    # Multiple parameters
    mlflow.log_params({
        "batch_size": 32,
        "epochs": 50,
        "optimizer": "Adam",
        "dropout": 0.2
    })

    # Nested parameters (as dict)
    config = {
        "model": {
            "architecture": "ResNet50",
            "pretrained": True
        },
        "training": {
            "lr": 0.001,
            "weight_decay": 1e-4
        }
    }

    # Log as JSON string or individual params
    for key, value in config.items():
        mlflow.log_param(key, str(value))

3. Logging Metrics

with mlflow.start_run():
    # Training loop
    for epoch in range(NUM_EPOCHS):
        train_loss = train_epoch()
        val_loss = validate()

        # Log metrics at each step
        mlflow.log_metric("train_loss", train_loss, step=epoch)
        mlflow.log_metric("val_loss", val_loss, step=epoch)

        # Log multiple metrics
        mlflow.log_metrics({
            "train_accuracy": train_acc,
            "val_accuracy": val_acc
        }, step=epoch)

    # Log final metrics (no step)
    mlflow.log_metric("final_accuracy", final_acc)

4. Logging Artifacts

with mlflow.start_run():
    # Log file
    model.save('model.pkl')
    mlflow.log_artifact('model.pkl')

    # Log directory
    os.makedirs('plots', exist_ok=True)
    plt.savefig('plots/loss_curve.png')
    mlflow.log_artifacts('plots')

    # Log text
    with open('config.txt', 'w') as f:
        f.write(str(config))
    mlflow.log_artifact('config.txt')

    # Log dict as JSON
    mlflow.log_dict({'config': config}, 'config.json')

5. Logging Models

# PyTorch
import mlflow.pytorch

with mlflow.start_run():
    model = train_pytorch_model()
    mlflow.pytorch.log_model(model, "model")

# Scikit-learn
import mlflow.sklearn

with mlflow.start_run():
    model = train_sklearn_model()
    mlflow.sklearn.log_model(model, "model")

# Keras/TensorFlow
import mlflow.keras

with mlflow.start_run():
    model = train_keras_model()
    mlflow.keras.log_model(model, "model")

# HuggingFace Transformers
import mlflow.transformers

with mlflow.start_run():
    mlflow.transformers.log_model(
        transformers_model={
            "model": model,
            "tokenizer": tokenizer
        },
        artifact_path="model"
    )

Autologging

Automatically log metrics, parameters, and models for popular frameworks.

Enable Autologging

import mlflow

# Enable for all supported frameworks
mlflow.autolog()

# Or enable for specific framework
mlflow.sklearn.autolog()
mlflow.pytorch.autolog()
mlflow.keras.autolog()
mlflow.xgboost.autolog()

Autologging with Scikit-learn

import mlflow
from sklearn.ensemble import RandomForestClassifier
from sklearn.model_selection import train_test_split

# Enable autologging
mlflow.sklearn.autolog()

# Split data
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)

# Train (automatically logs params, metrics, model)
with mlflow.start_run():
    model = RandomForestClassifier(n_estimators=100, max_depth=5, random_state=42)
    model.fit(X_train, y_train)

    # Metrics like accuracy, f1_score logged automatically
    # Model logged automatically
    # Training duration logged

Autologging with PyTorch Lightning

import mlflow
import pytorch_lightning as pl

# Enable autologging
mlflow.pytorch.autolog()

# Train
with mlflow.start_run():
    trainer = pl.Trainer(max_epochs=10)
    trainer.fit(model, datamodule=dm)

    # Hyperparameters logged
    # Training metrics logged
    # Best model checkpoint logged

Model Registry

Manage model lifecycle with versioning and stage transitions.

Register Model

import mlflow

# Log and register model
with mlflow.start_run():
    model = train_model()

    # Log model
    mlflow.sklearn.log_model(
        model,
        "model",
        registered_model_name="my-classifier"  # Register immediately
    )

# Or register later
run_id = "abc123"
model_uri = f"runs:/{run_id}/model"
mlflow.register_model(model_uri, "my-classifier")

Model Stages

Transition models between stages: None → Staging → Production → Archived

from mlflow.tracking import MlflowClient

client = MlflowClient()

# Promote to staging
client.transition_model_version_stage(
    name="my-classifier",
    version=3,
    stage="Staging"
)

# Promote to production
client.transition_model_version_stage(
    name="my-classifier",
    version=3,
    stage="Production",
    archive_existing_versions=True  # Archive old production versions
)

# Archive model
client.transition_model_version_stage(
    name="my-classifier",
    version=2,
    stage="Archived"
)

Load Model from Registry

import mlflow.pyfunc

# Load latest production model
model = mlflow.pyfunc.load_model("models:/my-classifier/Production")

# Load specific version
model = mlflow.pyfunc.load_model("models:/my-classifier/3")

# Load from staging
model = mlflow.pyfunc.load_model("models:/my-classifier/Staging")

# Use model
predictions = model.predict(X_test)

Model Versioning

client = MlflowClient()

# List all versions
versions = client.search_model_versions("name='my-classifier'")

for v in versions:
    print(f"Version {v.version}: {v.current_stage}")

# Get latest version by stage
latest_prod = client.get_latest_versions("my-classifier", stages=["Production"])
latest_staging = client.get_latest_versions("my-classifier", stages=["Staging"])

# Get model version details
version_info = client.get_model_version(name="my-classifier", version="3")
print(f"Run ID: {version_info.run_id}")
print(f"Stage: {version_info.current_stage}")
print(f"Tags: {version_info.tags}")

Model Annotations

client = MlflowClient()

# Add description
client.update_model_version(
    name="my-classifier",
    version="3",
    description="ResNet50 classifier trained on 1M images with 95% accuracy"
)

# Add tags
client.set_model_version_tag(
    name="my-classifier",
    version="3",
    key="validation_status",
    value="approved"
)

client.set_model_version_tag(
    name="my-classifier",
    version="3",
    key="deployed_date",
    value="2025-01-15"
)

Searching Runs

Find runs programmatically.

from mlflow.tracking import MlflowClient

client = MlflowClient()

# Search all runs in experiment
experiment_id = client.get_experiment_by_name("my-experiment").experiment_id
runs = client.search_runs(
    experiment_ids=[experiment_id],
    filter_string="metrics.accuracy > 0.9",
    order_by=["metrics.accuracy DESC"],
    max_results=10
)

for run in runs:
    print(f"Run ID: {run.info.run_id}")
    print(f"Accuracy: {run.data.metrics['accuracy']}")
    print(f"Params: {run.data.params}")

# Search with complex filters
runs = client.search_runs(
    experiment_ids=[experiment_id],
    filter_string="""
        metrics.accuracy > 0.9 AND
        params.model = 'ResNet50' AND
        tags.dataset = 'ImageNet'
    """,
    order_by=["metrics.f1_score DESC"]
)

Integration Examples

PyTorch

import mlflow
import torch
import torch.nn as nn

# Enable autologging
mlflow.pytorch.autolog()

with mlflow.start_run():
    # Log config
    config = {
        "lr": 0.001,
        "epochs": 10,
        "batch_size": 32
    }
    mlflow.log_params(config)

    # Train
    model = create_model()
    optimizer = torch.optim.Adam(model.parameters(), lr=config["lr"])

    for epoch in range(config["epochs"]):
        train_loss = train_epoch(model, optimizer, train_loader)
        val_loss, val_acc = validate(model, val_loader)

        # Log metrics
        mlflow.log_metrics({
            "train_loss": train_loss,
            "val_loss": val_loss,
            "val_accuracy": val_acc
        }, step=epoch)

    # Log model
    mlflow.pytorch.log_model(model, "model")

HuggingFace Transformers

import mlflow
from transformers import Trainer, TrainingArguments

# Enable autologging
mlflow.transformers.autolog()

training_args = TrainingArguments(
    output_dir="./results",
    num_train_epochs=3,
    per_device_train_batch_size=16,
    evaluation_strategy="epoch",
    save_strategy="epoch",
    load_best_model_at_end=True
)

# Start MLflow run
with mlflow.start_run():
    trainer = Trainer(
        model=model,
        args=training_args,
        train_dataset=train_dataset,
        eval_dataset=eval_dataset
    )

    # Train (automatically logged)
    trainer.train()

    # Log final model to registry
    mlflow.transformers.log_model(
        transformers_model={
            "model": trainer.model,
            "tokenizer": tokenizer
        },
        artifact_path="model",
        registered_model_name="hf-classifier"
    )

XGBoost

import mlflow
import xgboost as xgb

# Enable autologging
mlflow.xgboost.autolog()

with mlflow.start_run():
    dtrain = xgb.DMatrix(X_train, label=y_train)
    dval = xgb.DMatrix(X_val, label=y_val)

    params = {
        'max_depth': 6,
        'learning_rate': 0.1,
        'objective': 'binary:logistic',
        'eval_metric': ['logloss', 'auc']
    }

    # Train (automatically logged)
    model = xgb.train(
        params,
        dtrain,
        num_boost_round=100,
        evals=[(dtrain, 'train'), (dval, 'val')],
        early_stopping_rounds=10
    )

    # Model and metrics logged automatically

Best Practices

1. Organize with Experiments

# ✅ Good: Separate experiments for different tasks
mlflow.set_experiment("sentiment-analysis")
mlflow.set_experiment("image-classification")
mlflow.set_experiment("recommendation-system")

# ❌ Bad: Everything in one experiment
mlflow.set_experiment("all-models")

2. Use Descriptive Run Names

# ✅ Good: Descriptive names
with mlflow.start_run(run_name="resnet50-imagenet-lr0.001-bs32"):
    train()

# ❌ Bad: No name (auto-generated UUID)
with mlflow.start_run():
    train()

3. Log Comprehensive Metadata

with mlflow.start_run():
    # Log hyperparameters
    mlflow.log_params({
        "learning_rate": 0.001,
        "batch_size": 32,
        "epochs": 50
    })

    # Log system info
    mlflow.set_tags({
        "dataset": "ImageNet",
        "framework": "PyTorch 2.0",
        "gpu": "A100",
        "git_commit": get_git_commit()
    })

    # Log data info
    mlflow.log_param("train_samples", len(train_dataset))
    mlflow.log_param("val_samples", len(val_dataset))

4. Track Model Lineage

# Link runs to understand lineage
with mlflow.start_run(run_name="preprocessing"):
    data = preprocess()
    mlflow.log_artifact("data.csv")
    preprocessing_run_id = mlflow.active_run().info.run_id

with mlflow.start_run(run_name="training"):
    # Reference parent run
    mlflow.set_tag("preprocessing_run_id", preprocessing_run_id)
    model = train(data)

5. Use Model Registry for Deployment

# ✅ Good: Use registry for production
model_uri = "models:/my-classifier/Production"
model = mlflow.pyfunc.load_model(model_uri)

# ❌ Bad: Hard-code run IDs
model_uri = "runs:/abc123/model"
model = mlflow.pyfunc.load_model(model_uri)

Deployment

Serve Model Locally

# Serve registered model
mlflow models serve -m "models:/my-classifier/Production" -p 5001

# Serve from run
mlflow models serve -m "runs:/<RUN_ID>/model" -p 5001

# Test endpoint
curl http://127.0.0.1:5001/invocations -H 'Content-Type: application/json' -d '{
  "inputs": [[1.0, 2.0, 3.0, 4.0]]
}'

Deploy to Cloud

# Deploy to AWS SageMaker
mlflow sagemaker deploy -m "models:/my-classifier/Production" --region-name us-west-2

# Deploy to Azure ML
mlflow azureml deploy -m "models:/my-classifier/Production"

Configuration

Tracking Server

# Start tracking server with backend store
mlflow server \
  --backend-store-uri postgresql://user:password@localhost/mlflow \
  --default-artifact-root s3://my-bucket/mlflow \
  --host 0.0.0.0 \
  --port 5000

Client Configuration

import mlflow

# Set tracking URI
mlflow.set_tracking_uri("http://localhost:5000")

# Or use environment variable
# export MLFLOW_TRACKING_URI=http://localhost:5000

Resources

Documentation: https://mlflow.org/docs/latest
GitHub: https://github.com/mlflow/mlflow (23k+ stars)
Examples: https://github.com/mlflow/mlflow/tree/master/examples
Community: https://mlflow.org/community