Add proxy concurrency post: ATS, HAProxy, Envoy architecture#38
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singhsanjay12 merged 16 commits intomainfrom Mar 10, 2026
Merged
Add proxy concurrency post: ATS, HAProxy, Envoy architecture#38singhsanjay12 merged 16 commits intomainfrom
singhsanjay12 merged 16 commits intomainfrom
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New post covering how reverse proxies handle concurrent connections at scale: the thin layer constraint, event loop model, and the concurrency architecture of Apache Traffic Server (continuation system), HAProxy (single-process nbthread), and Envoy (thread-per-core isolation). Includes 5 SVG diagrams: hero, thread-models comparison, ATS event thread architecture, HAProxy process model, and Envoy worker isolation. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- thread-models.svg: bold VS divider, proper arrow markers, larger event loop box with arc icon centered, clean fan-in lines from connection dots - ats-arch.svg: bezier dispatch curves with arrowheads, compact ET_NET column with arc icons, continuation model panel with plugin warning - haproxy-arch.svg: fixed epoll arc+arrowhead icons, SO_REUSEPORT dispatch arrows, hot-reload callout, shared-state annotation inside process box - envoy-arch.svg: 2×2 worker grid with isolated badges, bold NO SHARED STATE barriers with pill labels, xDS arrows from control plane box - hero.svg: column separators, arrow markers, load bars on backends, arc loop icon and ~10K badge in proxy box Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Always verify singhsanjay12 is the active gh account before creating PRs — ssingh1_LinkedIn (Enterprise Managed User) cannot create PRs on this repo. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
…ribute Duplicate XML attributes are invalid and prevent SVG parsing entirely. Merged into a single font-family value. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
tests/svg_test.rb: new test_no_duplicate_attributes scans every opening tag for repeated attribute names — the class of bug that silently broke haproxy-arch.svg and envoy-arch.svg (two font-family= on one element). envoy-arch.svg: same copy-paste duplicate font-family= fixed, caught immediately by the new test. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Adds {: file="haproxy.cfg" } and nginx syntax highlighting to the
configuration snippet so it renders as a named code box in the theme.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
The blog disables Rouge (syntax_highlighter: disable: true), so Chirpy's
{: file="..." } IAL and language specifiers do not produce styled output —
they only added broken attributes to <pre>. Replaced with a custom HTML
block: dark #1e293b background, file icon + label header, monospace code,
and greyed-out inline comments. Renders correctly regardless of theme processing.
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Two Python examples illustrate the concurrency model contrast: - Thread model: recv() blocks the OS thread; 10k clients = 10k threads - Event loop: await yields control; one thread serves thousands Both use the same dark HTML code box as the HAProxy config snippet, with keywords, literals, and comments lightly syntax-coloured. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Three issues fixed: - Dispatch arrows to W2 and W3 were passing through W0 and W1 boxes. W2 arrow now routes above the grid (y=16), W3 routes below (y=320), so both arc cleanly around the outside without crossing any box. - Horizontal NO SHARED STATE barrier was at y=162, inside W0/W2 (which end at y=165). Moved W1/W3 down to y=175, creating a proper 10px gap; barrier now sits at y=170 between the rows. - xDS second arrow was a raw diagonal line. Replaced both xDS arrows with smooth curves routing from xDS box bottom to each worker's right-centre edge. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Replace the 2×2 grid with a vertical stack of 4 workers so dispatch arrows can fan out cleanly from the listener through a dedicated 76-px lane (x=254–328) without any crossing. Key changes: - Workers now stacked vertically (W0–W3, each 190×62 px, 16-px gaps) - Listener Thread centred vertically alongside the worker column (y=167) - Dispatch S-curves all confined to x=254–328, control points at x=292 - xDS arrows confined to x=520–580, control points at x=555 - Three horizontal NO SHARED STATE barriers (y=90, 168, 246); centre barrier is labelled with the red pill - All text baselines ≤385 px (within viewBox bounds); passes SVG tests Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Link section headers to official docs: Apache Traffic Server, HAProxy, Envoy - Link body terms: Apache HTTPd, C10K problem, epoll, kqueue, TSAPI plugin interface, libevent, xDS protocol, Istio - Add HAProxy User Spotlight talk at the bottom: Modernizing LinkedIn's Traffic Stack Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
Two issues fixed: 1. Arc loop icon inside the event loop box was r=16 (~50px wide), whose right side extended into the text label zone. Text like "socket becomes readable" (centred at x=635, left edge ~x=574) overlapped the arc polygon (x≤579). Fix: shrink arc to r=10, reposition to top-left corner (x≈548-569, y≈118-133), shift all box text and badge from centre x=635 to x=648, giving ≥15 px clearance. 2. "idle" label (x=455, y=173, light-grey fill) sat directly on a fan-in line that passes through (455, ~175) in the same grey tone, making the label invisible. Fix: add opaque white background rect and darken label fill from #94a3b8 to #64748b. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- thread-models.svg: move '⋯ thousands' label above the green
annotation box (y=303→289) so it is not covered
- hero.svg: right-align backend load labels ('3 req', '5 req', 'idle')
at x=775 with text-anchor=end so they don't bleed into the box border
- ats-arch.svg: expand ET_NET 2 box height 52→64 and split the long
sublabel into two lines; reposition arc icon and dispatch arrow to
match the new box centre
Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
test_em_dash_count_in_post_sources caps em dashes at 3; the post had 32. Replaced all prose em dashes with colons, semicolons, commas, or parentheses as appropriate. Also updated code-label spans and inline code comments (thread-per-connection · Python, yields; other ...). Front-matter description is exempt from the check so its em dash is left as-is. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
- Move conn dots from cy=192 to cy=206 so they sit on a distinct row below the title instead of overlapping 'ET_NET 2 ⚠ overloaded' - Shift sublabel text down (y=210/223 → y=219/231) to match the new row spacing in the taller 64px box - Fix orange annotation line: extend from x=557→555 (box right edge) and x=578→580 (callout box left edge) to eliminate the floating gap - Add indigo pill background behind 'round-robin' label so it reads clearly over the crossing dispatch curves Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Summary
Testing Done
ruby tests/svg_test.rb— 8 runs, 965 assertions, 0 failures