Profiling Amazon DocumentDB operations - Amazon DocumentDB
Supported operationsLimitationsEnabling the profilerDisabling the profilerDisabling profiler logs exportAccessing your profiler logsCommon queries

Profiling Amazon DocumentDB operations

You can use the profiler in Amazon DocumentDB (with MongoDB compatibility) to log the execution time and details of operations that were performed on your cluster. The profiler is useful for monitoring the slowest operations on your cluster to help you improve individual query performance and overall cluster performance.

By default, the profiler feature is disabled. When enabled, the profiler logs operations that are taking longer than a customer-defined threshold value (for example, 100 ms) to Amazon CloudWatch Logs. Logged details include the profiled command, time, plan summary, and client metadata. After the operations are logged to CloudWatch Logs, you can use CloudWatch Logs Insights to analyze, monitor, and archive your Amazon DocumentDB profiling data. Common queries are provided in the section Common queries.

When enabled, the profiler uses additional resources in your cluster. We recommend that you start with a high threshold value (for example, 500 ms) and gradually lower the value to identify slow operations. Starting with a threshold value of 50 ms can cause performance issues on your cluster for high throughput applications. The profiler is enabled at the cluster level and works on all instances and databases in a cluster. Amazon DocumentDB logs operations to Amazon CloudWatch Logs on a best-effort basis.

Although Amazon DocumentDB imposes no additional charge to enable the profiler, you are charged the standard rates for the usage of CloudWatch Logs. For information about CloudWatch Logs pricing, see Amazon CloudWatch pricing.

Supported operations

Amazon DocumentDB profiler supports the following operations:

  • aggregate

  • count

  • delete

  • distinct

  • find (OP_QUERY and command)

  • findAndModify

  • insert

  • update

Limitations

The slow query profiler is only able to emit profiler logs if the entire result set of the query is able to fit in one batch, and if the result set is under 16MB (maximum BSON size). Result sets greater than 16MB are automatically split into multiple batches.

Most drivers or shells may set a default batch size that is small. You can specify the batch size as part of your query. For the purpose of capturing slow query logs, we recommend a batch size that exceeds the size of your expected result set. If you are unsure of the result set size, or if it varies, you can also set the batch size to a large number (e.g., 100k).

However, using a larger batch size means more results will have to be retrieved from the database before a response is sent to the client. For some queries, that may create longer delays before you get results. If you do not plan to consume the entire result set, it is possible that you will spend more I/Os to process the query and throw away the result.

Enabling the Amazon DocumentDB profiler

Enabling the profiler on a cluster is a three-step process. Ensure that all steps are completed, or profiling logs will not be sent to CloudWatch Logs. Profiler is set at the cluster level and is performed on all of the cluster's databases and instances.

To enable the profiler on a cluster

  1. Because you can't modify a default cluster parameter group, ensure that you have an available custom cluster parameter group. For more information, see Creating Amazon DocumentDB cluster parameter groups.

  2. Using an available custom cluster parameter group, modify the following parameters: profiler, profiler_threshold_ms, and profiler_sampling_rate. For more information, see Modifying Amazon DocumentDB cluster parameter groups.

  3. Create or modify your cluster to use the custom cluster parameter group and to enable exporting profiler logs to CloudWatch Logs.

The following sections show how to implement these steps using the AWS Management Console and the AWS Command Line Interface (AWS CLI).

Using the AWS Management Console

  1. Before you begin, create a Amazon DocumentDB cluster and a custom cluster parameter group if you don't already have one. For more information, see Creating Amazon DocumentDB cluster parameter groups and Creating an Amazon DocumentDB cluster.

  2. Using an available custom cluster parameter group, modify the following parameters. For more information, see Modifying Amazon DocumentDB cluster parameter groups.

    • profiler — Enables or disables query profiling. Permitted values are enabled and disabled. The default value is disabled. To enable profiling, set the value to enabled.

    • profiler_threshold_ms — When profiler is set to enabled, all commands that are taking longer than profiler-threshold-ms are logged to CloudWatch. Permitted values are [50-INT_MAX]. The default value is 100.

    • profiler_sampling_rate — The fraction of slow operations that should be profiled or logged. Permitted values are [0.0-1.0]. The default value is 1.0.

  3. Modify your cluster to use the custom cluster parameter group and set the profiler log exports to publish to Amazon CloudWatch.

    1. In the navigation pane, choose Clusters to add your custom parameter group to a cluster.

    2. Choose the button to the left of the name of the cluster that you want to associate your parameter group with. Select Actions, and then Modify to modify your cluster.

    3. Under Cluster options, choose the custom parameter group from the step above to add it to your cluster.

    4. Under Log exports, select Profiler logs to publish to Amazon CloudWatch.

    5. Choose Continue to view a summary of your modifications.

    6. After verifying your changes, you can apply them immediately or during the next maintenance window under Scheduling of modifications .

    7. Choose Modify cluster to update your cluster with your new parameter group.

Using the AWS CLI

The following procedure enables the profiler on all supported operations for the cluster sample-cluster.

  1. Before you begin, ensure that you have an available custom cluster parameter group by running the following command, and reviewing the output for a cluster parameter group that doesn't have default in the name and has docdb3.6 as the parameter group family. If you don't have a non-default cluster parameter group, see Creating Amazon DocumentDB cluster parameter groups. 

    aws docdb describe-db-cluster-parameter-groups \
    --query 'DBClusterParameterGroups[*].[DBClusterParameterGroupName,DBParameterGroupFamily]'

    In the following output, only sample-parameter-group meets both criteria.

    [
       [
           "default.docdb3.6",
           "docdb3.6"
       ],
       [
           "sample-parameter-group",
           "docdb3.6"
       ]
]

  2. Using your custom cluster parameter group, modify the following parameters:

    • profiler — Enables or disables query profiling. Permitted values are enabled and disabled. The default value is disabled. To enable profiling, set the value to enabled.

    • profiler_threshold_ms — When profiler is set to enabled, all commands taking longer than profiler -threshold-ms are logged to CloudWatch. Permitted values are [0-INT_MAX]. Setting this value to 0 profiles all supported operations. The default value is 100.

    • profiler_sampling_rate — The fraction of slow operations that should be profiled or logged. Permitted values are [0.0-1.0]. The default value is 1.0.

    aws docdb modify-db-cluster-parameter-group \
    --db-cluster-parameter-group-name sample-parameter-group \
    --parameters ParameterName=profiler,ParameterValue=enabled,ApplyMethod=immediate \
                 ParameterName=profiler_threshold_ms,ParameterValue=100,ApplyMethod=immediate \
                 ParameterName=profiler_sampling_rate,ParameterValue=0.5,ApplyMethod=immediate

  3. Modify your Amazon DocumentDB cluster so that it uses the sample-parameter-group custom cluster parameter group from the previous step and sets the parameter --enable-cloudwatch-logs-exports to profiler.

    The following code modifies the cluster sample-cluster to use the sample-parameter-group from the previous step, and adds profiler to the enabled CloudWatch Logs exports.

    aws docdb modify-db-cluster \
       --db-cluster-identifier sample-cluster \
       --db-cluster-parameter-group-name sample-parameter-group \
       --cloudwatch-logs-export-configuration '{"EnableLogTypes":["profiler"]}'

    Output from this operation looks something like the following.

    {
    "DBCluster": {
        "AvailabilityZones": [
            "us-east-1c",
            "us-east-1b",
            "us-east-1a"
        ],
        "BackupRetentionPeriod": 1,
        "DBClusterIdentifier": "sample-cluster",
        "DBClusterParameterGroup": "sample-parameter-group",
        "DBSubnetGroup": "default",
        "Status": "available",
        "EarliestRestorableTime": "2020-04-07T02:05:12.479Z",
        "Endpoint": "sample-cluster.node.us-east-1.docdb.amazonaws.com",
        "ReaderEndpoint": "sample-cluster.node.us-east-1.docdb.amazonaws.com",
        "MultiAZ": false,
        "Engine": "docdb",
        "EngineVersion": "3.6.0",
        "LatestRestorableTime": "2020-04-08T22:08:59.317Z",
        "Port": 27017,
        "MasterUsername": "test",
        "PreferredBackupWindow": "02:00-02:30",
        "PreferredMaintenanceWindow": "tue:09:50-tue:10:20",
        "DBClusterMembers": [
            {
                "DBInstanceIdentifier": "sample-instance-1",
                "IsClusterWriter": true,
                "DBClusterParameterGroupStatus": "in-sync",
                "PromotionTier": 1
            },
            {
                "DBInstanceIdentifier": "sample-instance-2",
                "IsClusterWriter": true,
                "DBClusterParameterGroupStatus": "in-sync",
                "PromotionTier": 1
            }
        ],
        "VpcSecurityGroups": [
            {
                "VpcSecurityGroupId": "sg-abcd0123",
                "Status": "active"
            }
        ],
        "HostedZoneId": "ABCDEFGHIJKLM",
        "StorageEncrypted": true,
        "KmsKeyId": "arn:aws:kms:us-east-1:<accountID>:key/sample-key",
        "DbClusterResourceId": "cluster-ABCDEFGHIJKLMNOPQRSTUVWXYZ",
        "DBClusterArn": "arn:aws:rds:us-east-1:<accountID>:cluster:sample-cluster",
        "AssociatedRoles": [],
        "ClusterCreateTime": "2020-01-10T22:13:38.261Z",
        "EnabledCloudwatchLogsExports": [
            "profiler"
        ],
        "DeletionProtection": true
    }
}

Disabling the Amazon DocumentDB profiler

To disable the profiler, you disable both the profiler parameter and the export of profiler logs to CloudWatch Logs.

Disabling the Profiler

You can disable the profiler parameter using either the AWS Management Console or AWS CLI, as follows.

Using the AWS Management Console

The following procedure uses the AWS Management Console to disable Amazon DocumentDB profiler.

  1. Sign in to the AWS Management Console, and open the Amazon DocumentDB console at https://console.aws.amazon.com/docdb.

  2. In the navigation pane, choose Parameter groups. Then choose the name of the cluster parameter group that you want to disable the profiler on.

  3. In the resulting Cluster parameters page, select the button to the left of the profiler parameter and choose Edit.

  4. In the Modify profiler dialog box, choose disabled in the list.

  5. Choose Modify cluster parameter.

Using the AWS CLI

To disable profiler on a cluster using the AWS CLI, modify the cluster as follows.

aws docdb modify-db-cluster-parameter-group \
    --db-cluster-parameter-group-name sample-parameter-group \
    --parameters ParameterName=profiler,ParameterValue=disabled,ApplyMethod=immediate

Disabling profiler logs export

You can disable exporting profiler logs to CloudWatch Logs by using either the AWS Management Console or AWS CLI, as follows.

Using the AWS Management Console

The following procedure uses the AWS Management Console to disable Amazon DocumentDB exporting logs to CloudWatch.

  1. Open the Amazon DocumentDB console at https://console.aws.amazon.com/docdb.

  2. In the navigation pane, choose Clusters. Choose the button to the left of the name of the cluster for which you want to disable exporting logs.

  3. On the Actions menu, choose Modify.

  4. Scroll down to the Log exports section and unselect Profiler logs.

  5. Choose Continue.

  6. Review your changes, and then choose when you want this change applied to your cluster:

    • Apply during the next scheduled maintenance window

    • Apply immediately

  7. Choose Modify cluster.

Using the AWS CLI

The following code modifies the cluster sample-cluster and disables CloudWatch profiler logs.

For Linux, macOS, or Unix:

aws docdb modify-db-cluster \
   --db-cluster-identifier sample-cluster \
   --cloudwatch-logs-export-configuration '{"DisableLogTypes":["profiler"]}'

For Windows:

aws docdb modify-db-cluster ^
   --db-cluster-identifier sample-cluster ^
   --cloudwatch-logs-export-configuration '{"DisableLogTypes":["profiler"]}'

Output from this operation looks something like the following.

{
    "DBCluster": {
        "AvailabilityZones": [
            "us-east-1c",
            "us-east-1b",
            "us-east-1a"
        ],
        "BackupRetentionPeriod": 1,
        "DBClusterIdentifier": "sample-cluster",
        "DBClusterParameterGroup": "sample-parameter-group",
        "DBSubnetGroup": "default",
        "Status": "available",
        "EarliestRestorableTime": "2020-04-08T02:05:17.266Z",
        "Endpoint": "sample-cluster.node.us-east-1.docdb.amazonaws.com",
        "ReaderEndpoint": "sample-cluster.node.us-east-1.docdb.amazonaws.com",
        "MultiAZ": false,
        "Engine": "docdb",
        "EngineVersion": "3.6.0",
        "LatestRestorableTime": "2020-04-09T05:14:44.356Z",
        "Port": 27017,
        "MasterUsername": "test",
        "PreferredBackupWindow": "02:00-02:30",
        "PreferredMaintenanceWindow": "tue:09:50-tue:10:20",
        "DBClusterMembers": [
            {
                "DBInstanceIdentifier": "sample-instance-1",
                "IsClusterWriter": true,
                "DBClusterParameterGroupStatus": "in-sync",
                "PromotionTier": 1
            },
            {
                "DBInstanceIdentifier": "sample-instance-2",
                "IsClusterWriter": true,
                "DBClusterParameterGroupStatus": "in-sync",
                "PromotionTier": 1
            }
        ],
        "VpcSecurityGroups": [
            {
                "VpcSecurityGroupId": "sg-abcd0123",
                "Status": "active"
            }
        ],
        "HostedZoneId": "ABCDEFGHIJKLM",
        "StorageEncrypted": true,
        "KmsKeyId": "arn:aws:kms:us-east-1:<accountID>:key/sample-key",
        "DbClusterResourceId": "cluster-ABCDEFGHIJKLMNOPQRSTUVWXYZ",
        "DBClusterArn": "arn:aws:rds:us-east-1:<accountID>:cluster:sample-cluster",
        "AssociatedRoles": [],
        "ClusterCreateTime": "2020-01-10T22:13:38.261Z",
        "DeletionProtection": true
    }
}

Accessing your Amazon DocumentDB profiler logs

Follow these steps to access your profile logs on Amazon CloudWatch.

  1. Open the CloudWatch console at https://console.aws.amazon.com/cloudwatch/.

  2. Make sure that you are in the same Region as your Amazon DocumentDB cluster.

  3. In the navigation pane, choose Logs.

  4. To find the profiler logs for your cluster, in the list, choose /aws/docdb/yourClusterName/profiler.

    The profile logs for each of your instances are available under each of the respective instance names.

Common queries

The following are some common queries you can use to analyze your profiled commands. For more information about CloudWatch Logs Insights, see Analyzing Log Data with CloudWatch Logs Insights and Sample Queries.

Get the 10 slowest operations on a specified collection

filter ns="test.foo" | sort millis desc | limit 10

Get all the update operations on a collection that took more than 60 ms

filter millis > 60 and op = "update"

Get the 10 slowest operations in the last month

sort millis desc | limit 10

Get all the queries with a COLLSCAN plan summary

filter planSummary="COLLSCAN"