---
metadata:
  - name: generator
    content: Diplodoc Platform v5.50.4
alternate:
  - https://ydb.tech/docs/en/dev/timeouts.md
  - https://ydb.tech/docs/ru/dev/timeouts.md
sourcePath: en/core/dev/timeouts.md
---
> **Documentation Index:** Fetch the complete configuration index at https://ydb.tech/docs/en/llms.txt

# Using timeouts

This section describes available timeouts and provides examples of their usage in various programming languages.

## Prerequisites for using timeouts {#intro}

The timeout mechanism in YDB is designed to:

* Make sure the query execution time doesn't exceed a certain interval after which its result is not interesting for further use.
* Detect network connectivity issues.

Both of these use cases are important for ensuring the fault tolerance of the entire system. Let's take a closer look at timeouts.

## Operation timeout {#operational}

The ``operation_timeout`` value shows the time during which the query result is interesting to the user. If the operation fails during this time, the server returns an error with the ``Timeout`` code and tries to terminate the query, but its cancellation is not guaranteed. So the query that the user was returned the ``Timeout`` error for can be both successfully executed on the server and canceled.

## Timeout for canceling an operation {#cancel}

The ``cancel_after`` value shows the time after which the server will start canceling the query, if it can be canceled. If canceled, the server returns the ``Cancelled`` error code.

## Transport timeout {#transport}

The client must set a transport timeout for each query. This value lets you determine the amount of time that the client is ready to wait for a response from the server. If the server doesn't respond during this time, the client will get a transport error with the ``DeadlineExceeded`` code. Be sure to set such a client timeout value that won't trigger transport timeouts under the normal operation of the application and network.

## Using timeouts {#usage}

We recommend that you always set an operation timeout and transport timeout. The value of the transport timeout should be 50-100 milliseconds more than that of the operation timeout, that way there is some time left for the client to get a server error with the ``Timeout`` code.

Timeout usage example:

{% list tabs %}

- Python

  ```python
  import ydb

  def execute_in_tx(session, query):
    settings = ydb.BaseRequestSettings()
    settings = settings.with_timeout(0.5)  # transport timeout
    settings = settings.with_operation_timeout(0.4)  # operation timeout
    settings = settings.with_cancel_after(0.4)  # cancel after timeout
    session.transaction().execute(
        query,
        commit_tx=True,
        settings=settings,
    )
  ```


- C++

  ```cpp
  #include <ydb/public/sdk/cpp/client/ydb.h>
  #include <ydb/public/sdk/cpp/client/ydb_table.h>
  #include <ydb/public/sdk/cpp/client/ydb_value.h>

  using namespace NYdb;
  using namespace NYdb::NTable;

  TAsyncStatus ExecuteInTx(TSession& session, TString query, TParams params) {
    return session.ExecuteDataQuery(
        query
        , TTxControl::BeginTx(TTxSettings::SerializableRW()).CommitTx()
        , TExecDataQuerySettings()
        .OperationTimeout(TDuration::MilliSeconds(300))  // operation timeout
        .ClientTimeout(TDuration::MilliSeconds(400))   // transport timeout
        .CancelAfter(TDuration::MilliSeconds(300)));  // cancel after timeout
  }
  ```


- Go

  ```go
  import (
    "context"
    "time"

    ydb "github.com/ydb-platform/ydb-go-sdk/v3"
    "github.com/ydb-platform/ydb-go-sdk/v3/table"
  )

  func executeInTx(ctx context.Context, s table.Session, query string) {
  ctx, cancel := context.WithTimeout(ctx, time.Millisecond*500) // transport timeout
  defer cancel()
  ctx = ydb.WithOperationTimeout(ctx, time.Millisecond*400)     // operation timeout
  ctx = ydb.WithOperationCancelAfter(ctx, time.Millisecond*400) // cancel after timeout
  tx := table.TxControl(table.BeginTx(table.WithSerializableReadWrite()), table.CommitTx())
  _, res, err := s.Execute(ctx, tx, query, table.NewQueryParameters())
  }
  ```

{% endlist %}