Add streaming TTFT (Time To First Token) support for LlamaIndex instrumentation#281
Open
Add streaming TTFT (Time To First Token) support for LlamaIndex instrumentation#281
Conversation
…umentation Introduces an EventHandler that listens to LlamaIndex instrumentation event system (LLMChatStartEvent/LLMChatInProgressEvent) to measure the time between an LLM request and the first streaming token. This metric is recorded as gen_ai.response.time_to_first_chunk on the LLM span. The implementation bridges two systems: - CallbackHandler (fires on_event_start/on_event_end with event_id) - EventHandler (fires per-token with span_id) A ContextVar correlates the callback event_id with the event span_id, and TTFTTracker calculates the delta. Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
2 participants
Add this suggestion to a batch that can be applied as a single commit.This suggestion is invalid because no changes were made to the code.Suggestions cannot be applied while the pull request is closed.Suggestions cannot be applied while viewing a subset of changes.Only one suggestion per line can be applied in a batch.Add this suggestion to a batch that can be applied as a single commit.Applying suggestions on deleted lines is not supported.You must change the existing code in this line in order to create a valid suggestion.Outdated suggestions cannot be applied.This suggestion has been applied or marked resolved.Suggestions cannot be applied from pending reviews.Suggestions cannot be applied on multi-line comments.Suggestions cannot be applied while the pull request is queued to merge.Suggestion cannot be applied right now. Please check back later.
Introduces an EventHandler that listens to LlamaIndex instrumentation event system (LLMChatStartEvent/LLMChatInProgressEvent) to measure the time between an LLM request and the first streaming token. This metric is recorded as gen_ai.response.time_to_first_chunk on the LLM span.
The implementation bridges two systems:
A ContextVar correlates the callback event_id with the event span_id, and TTFTTracker calculates the delta.
Parent PR #274