Presto FAQs

  1. How is Presto different from Hive?
  2. How is Qubole’s Presto different from open-source Presto?
  3. Where do I find Presto logs?
  4. Why are new nodes not being used by my query during upscaling?
  5. Where can I find different Presto metrics for monitoring?
  6. How do I know if the query has failed due to a Spot loss?
  7. Where can I find the Presto Server Bootstrap logs?
  8. Does Qubole Presto support Hive ACID tables?

How is Presto different from Hive?

As a user, there are certain differences that you should be aware about Presto and Hive, even though they are able to execute SQL-like queries.

Presto:

  • Does not support User-defined functions (UDFs). However, Presto has a large number of built-in UDFs. Qubole provides additional UDFs, which can be added only before the cluster startup and runtime UDF additions such as Hive are not supported.
  • Does not support JOIN ordering. Ensure that a smaller table is to the right of the JOIN token.

How is Qubole’s Presto different from open-source Presto?

Note

Presto is supported on AWS, Azure, and GCP Cloud platforms; see QDS Components: Supported Versions and Cloud Platforms.

While Qubole’s Presto offering is heavily based on open-source Presto, there are a few differences. Qubole’s Presto:

  • Supports inserting data into Cloud Object Storage directories
  • Supports INSERT OVERWRITES
  • Supports autoscaling clusters
  • Supports Rubix to cache data from the Cloud on cluster storage, improving performance
  • Supports GZIP compression
  • Supports JDBC/ODBC through Qubole drivers
  • Supports Zeppelin and you can create Presto notebooks to run paragraphs as described in Using Different Types of Notebook.
  • Supports data traffic encryption among the Presto cluster nodes
  • Supports additional connectors such as Kinesis and SerDes such as AVRO and Openx JSON

Where do I find Presto logs?

  • The master cluster node’s logs are located at: DEFLOC/logs/presto/cluster_id/cluster_start_time/master/
  • The worker cluster node’s logs are located at: DEFLOC/logs/presto/cluster_id/cluster_start_time/nodeIP/node_start_time/

Where:

  • DEFLOC refers to the default location of an account.

  • cluster_id is the cluster ID.

  • cluster_start_time is the time you start the cluster. You can fetch Presto logs using the above log location using the approximate start time of the cluster.

    You can also get it by running a Presto command. When you run a Presto command, the log location is reported under the Logs tab.

    For example, on AWS you’ll see something like this:

    Log location: s3://mydata.com/trackdata/logs/logs/presto/910/2019-06-17_13-48-45/
    Started Query: 20190610_092450_00096_bucas Query Tracker
    Query: 20191060_092450_00096_bucas Progress: 0%
    Query: 20190610_092450_00096_bucas Progress: 0%
    

    2019-06-17_13-48-45 is the cluster start time; there are sub-directories for the master and worker nodes.

    However, for Azure blog storage and data lake, the log location is still in the cluster_instance_id. In Azure blob storage, the path would be something like wasb://mycontainer@myaccount.blob.core.windows.net/logs/presto/95907, and in Azure Data Lake storage (ADLS), the path would be something like adl://mydatalake.azuredatalakestore.net/logs/presto/95907.

Why are new nodes not being used by my query during upscaling?

New nodes are available only to certain operations (such as TableScans and Partial Aggregations) of queries already in progress when the nodes are added. For more information, see this explanation of how autoscaling works in a Presto cluster.

Where can I find different Presto metrics for monitoring?

Understanding the Presto Metrics for Monitoring describes the list of metrics that can be seen on the Datadog monitoring service. It also describes the abnormalities and actions that you can perform to handle abnormalities.

How do I know if the query has failed due to a Spot loss?

Whenever a node encounters Spot loss, the query info of all queries running on that node is updated with information about the spot node interruption. The query may or may not fail due to the spot interruption. The affected query’s query info displays the warning: Query may fail due to interruption of spot instance: <Instance ID> with private IP: <IP> by cloud provider at: <Spot Interruption Time> GMT.

The error about Query that has failed due to a Spot loss is displayed in the exception stack trace. This is an example of the Spot loss error in the stack trace.

../../../_images/SpotlossStacktrace1.png

Query failures due to Spot node interruptions are detected faster using information about the Spot interruption time from the Cloud Provider.

Where can I find the Presto Server Bootstrap logs?

An ec2-user can see the Presto Server Bootstrap logs in /media/ephemeral0/presto/var/log/bootstrap.log. The QDS account admin can see the Presto Server Bootstrap logs by logging into the cluster when the Customer Public SSH Key is configured in the cluster’s security settings. For more information, see modify-security-settings.

For information on how to log into the clusters, see:

Does Qubole Presto support Hive ACID tables?

Hive ACID tables is currently supported in Presto version 0.208 through a custom package. To know more, create a ticket with Qubole Support.