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Server diagnostics for Azure Cosmos DB for Apache Cassandra

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APPLIES TO: Cassandra

Log Analytics is a tool in the Azure portal that helps you run server diagnostics on your API for Cassandra account. Run log queries from data collected by Azure Monitor Logs and interactively analyze their results. Records retrieved from Log Analytics queries help provide various insights into your data.

Prerequisites

Use Log Analytics

After you've completed the log analytics setup, you can begin to explore your logs to gain more insights.

Explore Data Plane Operations

Use the CDBCassandraRequests table to see data plane operations specifically for your API for Cassandra account. A sample query to see the topN(10) consuming request and get detailed information on each request made.

CDBCassandraRequests
| where RequestCharge  > 0
| project DatabaseName, CollectionName, DurationMs, OperationName, ActivityId, ErrorCode, RequestCharge, PIICommandText 
| order by RequestCharge
| take 10

Error Codes and Possible Solutions

Status Code Error Code Description
200 -1 Successful
400 8704 The query is correct but an invalid syntax.
400 8192 The submitted query has a syntax error. Review your query.
400 8960 The query is invalid because of some configuration issue.
401 8448 The logged user does not have the right permissions to perform the query.
403 8448 Forbidden response as the user may not have the necessary permissions to carry out the request.
404 5376 A non-timeout exception during a write request as a result of response not found.
405 0 Server-side Cassandra error. The error rarely occurs, open a support ticket.
408 4608 Timeout during a read request.
408 4352 Timeout exception during a write serviceRequest.
409 9216 Attempting to create a keyspace or table that already exist.
412 5376 Precondition failure. To ensure data integrity, we ensure that the write request based on the read response is true. A non-timeout write request exception is returned.
413 5376 This non-timeout exception during a write request is because of payload maybe too large. Currently, there is a limit of 2MB per row.
417 9472 The exception is thrown when a prepared statement is not cached on the server node. It should be transient/non-blocking.
423 5376 There is a lock because a write request that is currently processing.
429 4097 Overload exception is as a result of RU shortage or high request rate. Probably need more RU to handle the higher volume request. In, native Cassandra this can be interpreted as one of the VMs not having enough CPU. We advise reviewing current data model to ensure that you do not have excessive skews that might be causing hot partitions.
449 5376 Concurrent execution exception. This occurs to ensure only one write update at a time for a given row.
500 0 Server cassandraError: something unexpected happened. This indicates a server-side bug.
503 4096 Service unavailable.
256 This may be because of invalid connection credentials. Please check your connection credentials.
10 A client message triggered protocol violation. An example is query message sent before a startup one has been sent.

Troubleshoot Query Consumption

The CDBPartitionKeyRUConsumption table contains details on request unit (RU) consumption for logical keys in each region within each of their physical partitions.

CDBPartitionKeyRUConsumption 
| summarize sum(todouble(RequestCharge)) by PartitionKey, PartitionKeyRangeId
| render columnchart

Explore Control Plane Operations

The CBDControlPlaneRequests table contains details on control plane operations, specifically for API for Cassandra accounts.

CDBControlPlaneRequests
| where TimeGenerated > now(-6h)
| where  ApiKind == "Cassandra"
| where OperationName in ("Create", "Upsert", "Delete", "Execute")
| summarize by OperationName

Next steps