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A survey on Machine Learning In Production

730ee3af6c8be2f704bae5b17b27103d?s=47 Arnab Biswas
July 01, 2018
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A survey on Machine Learning In Production

What does Machine Learning In Production mean? What are the challenges? How organizations like Uber, Amazon, Google have built their Machine Learning Pipeline? A survey of the Machine Learning In Production Landscape as of July 2018

730ee3af6c8be2f704bae5b17b27103d?s=128

Arnab Biswas

July 01, 2018
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  1. A survey on Machine Learning In Production Arnab Biswas July

    2018
  2. Model Development != Software Development • The moment a model

    is in production it starts degrading • Same model rarely gets deployed twice • It's hard to know how well the model is doing • Often, the real modeling work only starts in production Source : https://www.slideshare.net/DavidTalby/when-models-go-rogue-hard-earned-lessons-about-using- machine-learning-in-production
  3. Learning & Prediction • Learning • Offline • Model trained

    with historical data. Re-train to keep it fresh. • Online • Model is constantly being updated as new data arrives. • Predictions • Batch • Based on its input data, generates a table of predictions. Schedule a service to run regularly & output predictions to DB. • On demand • Predictions being made in real-time using input data that is available at time prediction. Web Service, Real Time Streaming Analytics.
  4. ML E2E Work Flow 1. Generate Data 1. Fetch Data

    2. Clean Data 3. Prepare/Transform Data 2. Train Model 1. Train Model 2. Evaluate Model 3. Deploy Model Source : https://docs.aws.amazon.com/sagemaker/latest/dg/how-it-works-mlconcepts.html
  5. ML Work Flow - 1 Source : https://www.slideshare.net/fridiculo us/managing-and-versioning- machine-learning-models-in-python

  6. ML Work Flow - 2 Source : https://www.slideshare.net/fridiculo us/managing-and-versioning- machine-learning-models-in-python

  7. ML Work Flow - 3

  8. ML Work Flow - 4

  9. ML Work Flow - 5

  10. ML Work Flow - 7

  11. Amazon Sagemaker : ML Work Flow - JupyterNotebook is used

    for data exploration, preprocessing, training and evaluation - Model is deployed independent, decoupled from app code (As a service) - After model deployment - Monitor predictions, collect "ground truth" - Evaluate model to identify drift - Update training data to include newly collected ground truth - Retrain the model with the new dataset (Increased accuracy).
  12. Amazon Sagemaker - Two components - Model Training - Model

    Deployment - Training - Post training model artifact will be saved in S3 - Validation - Offline Testing - Deploy the trained model to alpha endpoint - Use historical data to test - Online Testing - Candidate model is actually deployed - 10% of live traffic goes to the model - Deployment - Create model using artifact in S3 (trained model) - Model for inference becomes available over HTTP - Endpoint can be configured to elastically scale the deployed ML compute instances - Append user’s input data & ground truth (if available) to already existing training data - Multiple variants of same model may get deployed Source : https://docs.aws.amazon.com/sagemaker/latest/dg/sagemaker-dg.pdf
  13. Uber - Michelangelo - Provides scalable, reliable, reproducible, easy-to-use, and

    automated tools to address - Manage data - Train models - Evaluate models - Deploy models - Make predictions - Monitor predictions - Tech Stack - HDFS, Spark, Samza, Cassandra, MLLib, XGBoost& TensorFlow https://eng.uber.com/michelangelo/
  14. Michelangelo : Get Data - Data Pipeline - Generates feature

    & label (outcome) data sets for (re)training - Generates feature-only data sets for predicting - Monitor for data quality - Offline Pipeline - Batch model training & prediction - Transactional & log data into HDFS data lake - Regular Spark, SQL jobs compute features & published to feature store - Online Pipeline - Online, low latency prediction - Online models can’t access HDFS - Batch pre-compute: load historical features from HDFS to Cassandra (few hours/ once a day) - Near Real Time compute : Store low latency features to Cassandra & logged back to HDFS - Same data generation/preparation process during training and predicting
  15. • Allows teams to share, discover, use a highly curated

    set of features • Reduces duplicity & increase data quality • Users can add a feature with metadata (owner, description, SLA) • Feature can be invoked by model using canonical names • System handles joining in the correct HDFS data sets for model training or batch prediction and fetching the right value from Cassandra for online predictions • Feature Store are automatically calculated and updated daily • Custom DSL has been created for feature selection and transformation • Filling missing values, normalization • Create different features from time-stamp Michelangelo : Feature Store
  16. Michelangelo : Train Models - Offline, large-scale, distributed training -

    DT, GLM, K-Means, ARIMA, DL - SparkMLib, XGBoost, Café, Tensorflow - Model identified by Model Configuration - Model Type - Hyper Parameter - Data Source - Feature DSL expression - Compute resource - Training Job run on Yarn or Mesos cluster - Trained model is evaluated based on error metrics - Performance metrics saved in evaluation report - Save model to repository - Model configuration - Learned parameters - Evaluation report - (re)Training Job can be configured/managed using WebUI or API (Using Jupyter Notebooks)
  17. Michelangelo : Evaluate Models - Hundreds of models are trained

    before deciding on the final model - Each model is versioned and stored in Cassandra - Owner’s name - Start/End time of training - Model configuration - Reference to training & test data set - Distribution of relative importance of each feature - Full Learned Parameters - Accuracy Metrics - Standard Charts for each model type (ROC Curve, PR Curve, Confusion Matrix) - Multiple models should be comparable over WebUI, API
  18. Michelangelo : Deploy Models - Model deployment using UI/API -

    Offline Deployment - Deployed to offline container. Used for batch prediction - Online Deployment - Used by online prediction service - Library Deployment - Used by Java App as library - Model artifacts (metadata files, model parameter files, compiled DSL expressions) are packaged in a ZIP archive and copied to the relevant hosts - The prediction containers automatically load the new models from disk and start handling prediction requests.
  19. Michelangelo : Make Predictions - Make predictions based on feature

    data loaded from pipeline or from client service - Raw features passes through DSL expressions to modify raw features, fetch additional features - Final feature vector is passed to the model for scoring - Online models return predictions to client - Offline models write back predictions to hive and kafka
  20. Michelangelo : Monitor Predictions - Monitoring ensures - Pipelines are

    sending accurate data - Production data has not changed much from training data - Live measurement of accuracy - Holds back a certain percentage of prediction - Later join these predictions to observed outcomes generated by pipeline - Calculate error metrics (R-Squared, RMSLE, RMSE etc)
  21. Michelangelo : Partitioned Models - One model per city. -

    Hierarchy of models : city, country, global - When one level has insufficient data to train a model, it will fall back to it’s parent or ancestor node.
  22. Michelangelo : Referencing Models • More than one model can

    be deployed on a serving container • Transition from old to new models, side by side A/B Testing • A model is specified by UUID & tag (optional) during deployment • Online Model • Client sends feature vector along with model UUID or tag • For tag, model most recently deployed to that tag will make prediction • Batch Model • All deployed models are used to score each batch data set • Prediction records contain the model UUID and optional tag • User can replace an old model with a new model without changing tag • Model gets updated without changing client code • User can upload a new model (new UUID) • Traffic can be gradually switched from old model to new one • A/B testing of models • Users deploy competing models either via UUIDs or tags • Send portions of the traffic to each model • Track performance metrics
  23. Michelangelo : Scaling • ML Models are stateless • Online

    Models • Add more nodes to cluster • Offline Models • Add more Spark executors
  24. Michelangelo : Learnings • There could be failure at every

    stage. Debuggability is important. • Fault tolerance is important • Abstract Machine Learning libraries • Ease of Use : Automating ML WorkFlow through UI. Ability to train, test, deploy models with mouse clicks • ML Systems must be extensible & easy for other systems to interact with programmatically (REST).
  25. Best Practices By Google • TensorFlow Extended (TFX), a TensorFlow

    based general-purpose machine learning platform implemented at Google [KDD : 2017] • Challenges of building Machine Learning Platforms • One machine learning platform for many different learning tasks (in terms of data representation, storage infrastructure, and machine learning tasks) • Continuous Training and Serving • Continuous training over evolving data (e.g. a moving window over the latest n days) • Human in loop • Simple interface for deployment and monitoring • Production-level reliability and scalability • Resilient to inconsistent data, failures in underlying execution environment • Should be able to handle high data volume during training • Should be able to handle increase in traffic in serving system http://www.kdd.org/kdd2017/papers/view/tfx-a-tensorflow-based-production-scale-machine-learning-platform
  26. TFX : Pipeline

  27. • Models are only as good as their training data

    • Understanding data and finding anomalies early is critical for preventing data errors downstream • Rigorous checks for data quality should be a part of any long running development of a machine learning platform • Small bugs in the data can significantly degrade model quality over a period of time in a way that is hard to detect and diagnose TFX : Data Analysis, Transformation & Validation
  28. TFX : Data Analysis • Component processes each dataset fed

    to the system and generates a set of descriptive statistics on the included features • Statistics about presence of each feature in the data • Number of examples with and without the feature • Distribution of the number of values per example • Statistics over feature values • For continuous features, quantiles, equi-width histograms, mean, standard deviation • For discrete features, top-K values by frequency • Statistics about slices of data (e.g., negative and positive classes) • Cross-feature statistics (correlation and covariance between features)
  29. TFX : Data Transformation • A suite of data transformations

    to allow feature wrangling for model training and serving • Transformation logic must be consistent during training and serving
  30. TFX : Data Validation • Is the data healthy or

    are there anomalies to be flagged? • Validation is done using a versioned schema • Features present in the data • Expected type of each feature • Expected presence of each feature (minimum count & fraction of examples that must contain feature) • Expected valency of the feature in each example (minimum and maximum number of values) • Expected domain of a feature (Values for a string feature or range for an integer feature) • Validate the properties of specific (training and serving) datasets, flag any deviations from the schema as potential anomalies • Provide actionable suggestions to fix the anomaly • Teams are responsible for maintaining the schema • Users should treat data issues as bugs • Different versions of the schema shows the evolution of the data
  31. TFX : Model Training • Automate and streamline training of

    production quality models • Often training needs huge datasets (Time & Resource intensive) • Training dataset of 100B data points. Takes several days to train • Warm Starting (Continuous Training) • High Level Model Specification API • Higher level abstraction layer that hides implementation
  32. TFX : Model Evaluation & Validation • A reusable component

    that automatically evaluates and validates models to ensure that they are "good" before serving them to users • Can help prevent unexpected degradations in the user experience • Avoids real issue in production • Definition of A Good Model • Model is safe to serve • Model should not crash, cause errors in the serving system when being loaded or when sent unexpected inputs • Model shouldn't use too many resources (CPU, RAM) • Has desired production quality • User satisfaction and product health on live traffic • Better measure than the objective function on the training data
  33. TFX : Model Evaluation • Evaluation : Human Facing Metrics

    of model quality • A/B testing on live traffic is costly and time consuming • Models are evaluated offline on held-out data to determine if they are promising enough to start an online A/B testing • Provides AUC or cost-weighted error • Once satisfied with models' offline performance, A/B testing can be performed with live traffic
  34. • Validation : Machine Facing judgment of model goodness •

    Once model is launched in production, automated validation is used to ensure updated model is good • Updated Model receives a small amount of traffic (canary process) • Prediction quality is evaluated by comparing the model quality against a fixed threshold as well as against a baseline model (e.g., the current production model) • Any new model failing these checks is not pushed to serving • Challenges • Canary process will not catch all potential errors. • With changing training data, some variation in models behavior is expected, but is hard to distinguish • Slicing • Useful in both evaluating and validating models • Metrics is computed on a small slice of data with particular feature value (e.g., country=="US") • Metrics on the entire dataset can fail to reflect performance on small slices TFX : Model Validation
  35. • TensorFlow Serving provides a complete serving solution for machine-

    learned models to be deployed in production environments • Serving systems for production environments require low latency, high efficiency, horizontal scalability, reliability & robustness • Multitenancy • A single instance of the server to serve multiple machine-learned models concurrently • Performance characteristics of one model has minimal impact on other models TFX : Model Serving
  36. Other ML Tools (As of July, 2018) • Google DataLabs

    • TensorFlow Serving • Azure ML Service (Not Azure ML Studio) • Azure ML Experimentation • Azure ML Model Management • Azure ML Workbench • MLFlow by Databricks • prediction.io • clipper.ai • SKIL - deeplearning4j • & More…
  37. Model Management (As of July, 2018) • ML : Rapid

    experimentation + iteration • Model History tracks the progress • Versioning, Management, Monitoring, Deployment, Hosting • Reproducibility, Rollback • Open Source • ModelDB • MLFlow - E2E ML • Pachyderm • H2O Steam (No active development) • comet.ml (Cloud Service) • Do it yourself • Source Code • SW/HW Environment • Data • Visualizations/Reports • Weight Files (Trained Models) • Configurations (Model Type, Hyperparameters, Features) • Performance Metrics • …..
  38. Best Practices • Separate training and prediction/serving pipeline • Automate

    model re-training. Keep the model fresh. • Save actual data used at prediction time to DB. Keep expanding it. • Use this data for retraining • Evaluate a trained model before deployment • Verify the model crosses a threshold error score on a predefined dataset • Post deployment • Monitor the performance of the model • Business Objective • Error Metrics • Identify cases where the model is struggling • Check if those use cases are needed? • Improve data collection? • Monitor customer feedback to identify cases to improve upon • Monitor distribution of features fed into model at training/prediction time • Identify errors at the data extractors • Nature of the data may be eventually changing • A/B Testing • Between training and deployment, there should be staging environment
  39. Questions to Ask • What kind of business problem are

    we going to solve? • Description • What kind of ML (Batch/Online)? • Scalability? • How to ensure quality of labeled data? • How do I find out the effectiveness of the model? • What do we need? • Complete ML pipeline covering the whole lifecycle OR • Just separate model training from prediction using existing frameworks • How do we want to use ML (As a service or as a library)? • How important is reproducibility & interpretation? • How to handle customer specific data/behavior?
  40. Questions?