Expected Features

The following is a description of features that are commonly expected in Sentry SDKs. Make sure to also have read the unified API design documentation which explains the common API design.

Background Sending

Events should be transmitted in a background thread or similar system. This queue must be flushed when the application shuts down with a specific timeout. This feature is typically user facing and explained as part of shutdown and draining.

Uncaught Exception Handler

Ability for the SDK to be set as a hook to record any uncaught exceptions. At the language level this is typically a global hook provided by the language itself. For framework integrations this might be part of middleware or some other system.

This behavior is typically provided by a default integration that can be disabled.


Scopes should be provided by SDKs to set common attributes and context data on events sent to Sentry emitted from the current scope. They should be inherited to lower scopes so that they can be set "globally" on startup. Note that some attributes can only be set in the client options (release, environment) and not on scopes.

What scope means depends on the application, for a web framework it is most likely a single request/response cycle. For a mobile application there is often just one single scope that represents the single user and their actions. Scoping can be difficult to implement because it often has to deal with threads or concurrency and can involve deep integration with frameworks. See the scopes page for more information.

Automatic Context Data

Automatic addition of useful attributes such as tags or extra or specific contexts. Typically means the SDK hooks into a framework so that it can set attributes that are known to be useful for most users.

Manually record application events (into the current scope) during the lifecycle of an application. Implement a ring buffer so as not to grow indefinitely. The most recent breadcrumbs should be attached to events as they occur.

With deeper framework integration, the automatic recording of breadcrumbs is possible and recommended, for example:

  • UI Events: button clicks, touch events, etc.
  • System Events: low battery, low storage space, airplane mode started, memory warnings, device orientation changed, etc.
  • Outgoing HTTP requests

Check out the complete breadcrumb documentation for more types.

Event Sampling

SDKs should allow the user to configure what percentage of events are actually sent to the server (the rest should be silently ignored). For example:

sample_rate = options.get('sample_rate', 1.0)

# assuming random() returns a value between 0.0 (inclusive) and 1.0 (exclusive)
if random() < sample_rate:

Rate Limiting

Respect Sentry’s HTTP 429 Retry-After header, or, if the SDK supports multiple payload types (e.g. errors and transactions), the X-Sentry-Rate-Limits header. Outgoing SDK requests should be dropped during the backoff period.

See Rate Limiting for details.

In-App frames

Stack parsing can tell which frames should be identified as part of the user’s application (as opposed to part of the language, a library, or a framework), either automatically or by user configuration at startup, often declared as a package/module prefix.

Surrounding Source in Stack Trace

Lines of source code to provide context in stack traces. This is easier in interpreted languages, may be hard or impossible in compiled ones.

Local Variables

Local variable names and values for each stack frame, where possible. Restrictions apply on some platforms, for example it’s may only be possible to collect the values of parameters passed into each function, or it may be completely impossible to collect this information at all.


Turn compiled or obfuscated code/method names in stack traces back into the original. Desymbolication always requires Sentry backend support. Not necessary for many languages.

Retrieve Last Event ID

Ability to get the ID of the last event sent. Event IDs are useful for correlation, logging, customers rolling their own feedback forms, etc.

User Feedback

For all SDKs, it is strongly recommended to send the User Feedback as an envelope. Alternatively, the SDKs can use the User Feedback endpoint, which is not recommended.

User Facing Platforms

On user-facing platforms such as mobile, desktop, or browser this means first-class support for requesting User Feedback when an error or crash occurs. To see some examples of the API check out the user-facing docs for Apple and Java.

On mobile and desktop, it is common to prompt the user for feedback after a crash happened on the previous run of the application. Therefore the SDKs should implement the onCrashedLastRun callback on the options. This callback gets called shortly after the initialization of the SDK when the last program execution terminated with a crash. The SDK should execute the callback only once during the entire run of the program to avoid multiple callbacks if there are multiple crash events to send.

Backend Platforms

On backend platforms, SDKs should document how to use the last event ID to prompt the user for feedback themselves.

Example implementations

User Feedback class:

Envelope item:


Attachments are files stored alongside an event. To send an attachment, add it as an envelope item to the corresponding event.

We recommend implementing two types of attachments, one with a path and another with a byte array. If the programming language allows it, create one class with multiple constructors to keep things simple and guess the content type of the attachment via the filename.

The overload that takes a path should consider:

  • The SDK should read the file when an event gets captured and not when the user adds an attachment to the scope.
  • If reading the attachment fails, the SDK should not drop the whole envelope, but just the attachment's envelope item.
  • If the SDK is in debug mode log (debug=true) out errors to make debugging easier.

If the SDK supports transactions, the attachments should offer a flag addToTransactions, that specifies if SDK adds the attachment to every transaction or not. The default should be false.

Use the implementations of Java, Objective-C, or Python as a reference for the API.

Max Attachment Size

Alongside the implementation of attachments, add maxAttachmentSize to the options and set the default to 20 MiB. When converting an attachment to an envelope item, the SDK must discard items larger than the maxAttachmentSize. Especially on SDKs with offline caching, typical on mobile, this is useful because attachments could quickly eat up the users' disk space. Furthermore, Relay has a maximum size for attachments, and we want to reduce unnecessary requests.

Before-Send Hook

Hook called with the event (and on some platforms the hint) that allow the user to decide whether an event should be sent or not. This can also be used to further modify the event.

Before-Breadcrumb Hook

Hook called with the breadcrumb (and on some platforms the hint) that allow the user to decide whether and how a breadcrumb should be sent.

List Loaded Libraries

Include a list of loaded libraries (and versions) when sending an event.

Buffer to Disk

Write events to disk before attempting to send, so that they can be retried in the event of a temporary network failure. Needs to implement a cap on the number of stored events.

This is mostly useful on mobile clients where connectivity is often not available.

HTTP Proxy

Ability to use an HTTP proxy. Often easy to implement using the existing HTTP client. This should be picked up from the system config if possible or explicit config in the client options.

HTTP Client Integrations

Every HTTP client integration must exclude HTTP requests that match the configured DSN in the Options to exclude HTTP requests to Sentry.

Add a breadcrumb for each outgoing HTTP request after the request finishes:

  • type: http
  • category: http
  • data (all fields are optional but recommended):
    • url - The URL used in the HTTP request
    • method - uppercase HTTP method, i.e: GET, HEAD
    • status_code - Numeric status code such as 200 or 404
    • request_body_size Size in bytes
    • response_body_size Size in bytes

If Performance Monitoring is both supported by the SDK and enabled in the client application when the transaction is active a new Span must be created around the HTTP request:

Attaching Request Body in Server SDKs

Ability for the SDK to attach request body to events and triggered during the execution of request.

User should be able to set a configuration option maxRequestBodySize to instruct SDK how big requests bodies should be attached. SDK controls what is an actual size in bytes for each option:

  • none (default)
  • small - 1000 bytes
  • medium - 10000 bytes
  • always
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