README

This is a read-only subtree split of https://github.com/open-telemetry/opentelemetry-php-contrib.

OpenTelemetry curl auto-instrumentation

Please read https://opentelemetry.io/docs/instrumentation/php/automatic/ for instructions on how to install and configure the extension and SDK.

Overview

Auto-instrumentation hooks are registered via composer, and client kind spans will automatically be created when calling curl_exec or curl_multi_exec functions. Additionally, distributed tracing is supported by setting the traceparent header.

Limitations

The curl_multi instrumentation is not resilient to shortcomings in the application and requires proper implementation. If the application does not call the curl_multi_info_read function, the instrumentation will be unable to measure the execution time for individual requests-time will be aggregated for all transfers. Similarly, error detection will be impacted, as the error code information will be missing in this case. In case of encountered issues, it is recommended to review the application code and adjust it to match example #1 provided in curl_multi_exec documentation.

To ensure the stability of the monitored application, capturing request headers sent to the server works only if the application does not use the CURLOPT_VERBOSE option.

Configuration

Disabling curl instrumentation

The extension can be disabled via runtime configuration:

OTEL_PHP_DISABLED_INSTRUMENTATIONS=curl

Request and response headers capturing

Curl auto-instrumentation enables capturing headers from both requests and responses. This feature is disabled by default and be enabled through environment variables or array directives in the php.ini configuration file.

To enable response header capture from the server, specify the required headers as shown in the example below. In this case, the "Content-Type" and "Server" headers will be captured. These options values are case-insensitive:

Environment variables configuration

OTEL_PHP_INSTRUMENTATION_HTTP_RESPONSE_HEADERS=content-type,server
OTEL_PHP_INSTRUMENTATION_HTTP_REQUEST_HEADERS=host,accept

php.ini configuration

OTEL_PHP_INSTRUMENTATION_HTTP_RESPONSE_HEADERS=content-type,server
; or
otel.instrumentation.http.response_headers[]=content-type
otel.instrumentation.http.response_headers[]=server

Similarly, to capture headers sent in a request to the server, use the following configuration:

OTEL_PHP_INSTRUMENTATION_HTTP_REQUEST_HEADERS=host,accept
; or
otel.instrumentation.http.request_headers[]=host
otel.instrumentation.http.request_headers[]=accept