Add long polling diagramssh-add-polling-images

[ci skip]

3 files changed, 48 insertions, 0 deletions

diff --git a/doc/development/img/cache-hit.svg b/doc/development/img/cache-hit.svg
new file mode 100644
index 00000000000..1c37693df2d
--- /dev/null
+++ b/doc/development/img/cache-hit.svg
@@ -0,0 +1,21 @@
+<svg version="1.1" id="mscgen_js-svg-__svg" class="mscgen_js-svg-__svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="976" height="310" viewBox="0 0 976 310"><desc>
+
+# Generated by mscgen_js - https://sverweij.github.io/mscgen_js
+msc {
+  # options
+  hscale="1.5";
+
+  # entities
+  c [label="Client", textbgcolor="lime"],
+  rails [label="Rails", textbgcolor="cyan"],
+  etag [label="EtagCaching", textbgcolor="orange"],
+  redis [label="Redis", textbgcolor="white"];
+
+  # arcs
+  c =&gt; rails [label="GET /projects/5/pipelines"];
+  rails =&gt; etag [label="GET /projects/5/pipelines"];
+  etag =&gt; redis [label="read(key = 'GET &lt;Etag&gt;')"];
+  redis =&gt; etag [label="cache hit", linecolor="green", textcolor="green"];
+    |||;
+  etag =&gt; c [label="304 Not Modified", linecolor="blue", textcolor="blue"];
+}</desc><defs><style type="text/css">svg.mscgen_js-svg-__svg{font-family:Helvetica,sans-serif;font-size:12px;font-weight:normal;font-style:normal;text-decoration:none;background-color:white;stroke:black;stroke-width:2;color:black}.mscgen_js-svg-__svg path, .mscgen_js-svg-__svg rect{fill:none;color:black;stroke:black}.mscgen_js-svg-__svg .label-text-background{fill:white;stroke:white;stroke-width:0}.mscgen_js-svg-__svg .bglayer{fill:white;stroke:white;stroke-width:0}.mscgen_js-svg-__svg line{stroke:black}.mscgen_js-svg-__svg .return, .mscgen_js-svg-__svg .comment{stroke-dasharray:5,3}.mscgen_js-svg-__svg .inline_expression_divider{stroke-dasharray:10,5}.mscgen_js-svg-__svg text{color:inherit;stroke:none;text-anchor:middle}.mscgen_js-svg-__svg text.entity-text{text-decoration:underline}.mscgen_js-svg-__svg text.anchor-start{text-anchor:start}.mscgen_js-svg-__svg .arrow-marker{overflow:visible}.mscgen_js-svg-__svg .arrow-style{stroke-width:1}.mscgen_js-svg-__svg .arcrow, .mscgen_js-svg-__svg .arcrowomit, .mscgen_js-svg-__svg .emphasised{stroke-linecap:butt}.mscgen_js-svg-__svg .arcrowomit{stroke-dasharray:2,2;}.mscgen_js-svg-__svg .box, .mscgen_js-svg-__svg .entity{fill:white;stroke-linejoin:round}.mscgen_js-svg-__svg .inherit{stroke:inherit;color:inherit}.mscgen_js-svg-__svg .inherit-fill{fill:inherit}.mscgen_js-svg-__svg .watermark{stroke:black;color:black;fill:black;font-size:48pt;font-weight:bold;opacity:0.14}</style><marker orient="auto" id="mscgen_js-svg-__svgmethod-black" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="black" fill="black"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-black" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="black" fill="black"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-blue" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="blue" fill="blue"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-blue" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="blue" fill="blue"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-green" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="green" fill="green"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-green" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="green" fill="green"></polygon></marker></defs><g id="mscgen_js-svg-__svg__body" transform="translate(53,3) scale(1,1)"><g id="mscgen_js-svg-__svg__background"><rect width="976" height="310" x="-53" y="-3" class="bglayer"></rect></g><g id="mscgen_js-svg-__svg__arcspanlayer"></g><g id="mscgen_js-svg-__svg__lifelinelayer"><line x1="75" y1="38" x2="75" y2="76" class="arcrow"></line><line x1="315" y1="38" x2="315" y2="76" class="arcrow"></line><line x1="555" y1="38" x2="555" y2="76" class="arcrow"></line><line x1="795" y1="38" x2="795" y2="76" class="arcrow"></line><line x1="75" y1="76" x2="75" y2="114" class="arcrow"></line><line x1="315" y1="76" x2="315" y2="114" class="arcrow"></line><line x1="555" y1="76" x2="555" y2="114" class="arcrow"></line><line x1="795" y1="76" x2="795" y2="114" class="arcrow"></line><line x1="75" y1="114" x2="75" y2="152" class="arcrow"></line><line x1="315" y1="114" x2="315" y2="152" class="arcrow"></line><line x1="555" y1="114" x2="555" y2="152" class="arcrow"></line><line x1="795" y1="114" x2="795" y2="152" class="arcrow"></line><line x1="75" y1="152" x2="75" y2="190" class="arcrow"></line><line x1="315" y1="152" x2="315" y2="190" class="arcrow"></line><line x1="555" y1="152" x2="555" y2="190" class="arcrow"></line><line x1="795" y1="152" x2="795" y2="190" class="arcrow"></line><line x1="75" y1="190" x2="75" y2="228" class="arcrow"></line><line x1="315" y1="190" x2="315" y2="228" class="arcrow"></line><line x1="555" y1="190" x2="555" y2="228" class="arcrow"></line><line x1="795" y1="190" x2="795" y2="228" class="arcrow"></line><line x1="75" y1="228" x2="75" y2="266" class="arcrow"></line><line x1="315" y1="228" x2="315" y2="266" class="arcrow"></line><line x1="555" y1="228" x2="555" y2="266" class="arcrow"></line><line x1="795" y1="228" x2="795" y2="266" class="arcrow"></line><line x1="75" y1="266" x2="75" y2="304" class="arcrow"></line><line x1="315" y1="266" x2="315" y2="304" class="arcrow"></line><line x1="555" y1="266" x2="555" y2="304" class="arcrow"></line><line x1="795" y1="266" x2="795" y2="304" class="arcrow"></line></g><g id="mscgen_js-svg-__svg__sequencelayer"><g id="mscgen_js-svg-__svgentities"><g><rect width="150" height="38" class="entity" style="fill:lime;"></rect><g><text x="75" y="22.5" class="entity-text "><tspan>Client</tspan></text></g></g><g><rect width="150" height="38" x="240" class="entity" style="fill:cyan;"></rect><g><text x="315" y="22.5" class="entity-text "><tspan>Rails</tspan></text></g></g><g><rect width="150" height="38" x="480" class="entity" style="fill:orange;"></rect><g><text x="555" y="22.5" class="entity-text "><tspan>EtagCaching</tspan></text></g></g><g><rect width="150" height="38" x="720" class="entity" style="fill:white;"></rect><g><text x="795" y="22.5" class="entity-text "><tspan>Redis</tspan></text></g></g></g><g><line x1="75" y1="95" x2="315" y2="95" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="134.06" height="14" x="127.97" y="79.5" class="label-text-background"></rect><text x="195" y="90.5" class="directional-text method-text "><tspan>GET /projects/5/pipelines</tspan></text></g></g><g><line x1="315" y1="133" x2="555" y2="133" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="134.06" height="14" x="367.97" y="117.5" class="label-text-background"></rect><text x="435" y="128.5" class="directional-text method-text "><tspan>GET /projects/5/pipelines</tspan></text></g></g><g><line x1="555" y1="171" x2="795" y2="171" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="135.64" height="14" x="607.17" y="155.5" class="label-text-background"></rect><text x="675" y="166.5" class="directional-text method-text "><tspan>read(key = 'GET &lt;Etag&gt;')</tspan></text></g></g><g><line x1="795" y1="209" x2="555" y2="209" class="arc directional method" style="stroke:green" marker-end="url(#mscgen_js-svg-__svgmethod-green)"></line><g><rect width="48.02" height="14" x="650.98" y="193.5" class="label-text-background"></rect><text x="675" y="204.5" class="directional-text method-text " style="fill:green;"><tspan>cache hit</tspan></text></g></g><g></g><g><line x1="555" y1="285" x2="75" y2="285" class="arc directional method" style="stroke:blue" marker-end="url(#mscgen_js-svg-__svgmethod-blue)"></line><g><rect width="90.72" height="14" x="269.63" y="269.5" class="label-text-background"></rect><text x="315" y="280.5" class="directional-text method-text " style="fill:blue;"><tspan>304 Not Modified</tspan></text></g></g></g><g id="mscgen_js-svg-__svg__notelayer"></g><g id="mscgen_js-svg-__svg__watermark"></g></g></svg>
\ No newline at end of file
diff --git a/doc/development/img/cache-miss.svg b/doc/development/img/cache-miss.svg
new file mode 100644
index 00000000000..8429e6a1918
--- /dev/null
+++ b/doc/development/img/cache-miss.svg
@@ -0,0 +1,24 @@
+<svg version="1.1" id="mscgen_js-svg-__svg" class="mscgen_js-svg-__svg" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="976" height="386" viewBox="0 0 976 386"><desc>
+
+# Generated by mscgen_js - https://sverweij.github.io/mscgen_js
+msc {
+  # options
+  hscale="1.5";
+
+  # entities
+  c [label="Client", textbgcolor="lime"],
+  rails [label="Rails", textbgcolor="cyan"],
+  etag [label="EtagCaching", textbgcolor="orange"],
+  redis [label="Redis", textbgcolor="white"];
+
+  # arcs
+  c =&gt; rails [label="GET /projects/5/pipelines"];
+  rails =&gt; etag [label="GET /projects/5/pipelines"];
+  etag =&gt; redis [label="read(key = 'GET &lt;Etag&gt;')"];
+  redis =&gt; etag [label="cache miss", linecolor="red", textcolor="red"];
+  |||;
+  etag =&gt; redis [label="write('&lt;New Etag&gt;')"];
+  etag =&gt; rails [label="GET /projects/5/pipelines"];
+  rails =&gt; c [label="JSON response w/ ETag", linecolor="blue", textcolor="blue"];
+}
+</desc><defs><style type="text/css">svg.mscgen_js-svg-__svg{font-family:Helvetica,sans-serif;font-size:12px;font-weight:normal;font-style:normal;text-decoration:none;background-color:white;stroke:black;stroke-width:2}.mscgen_js-svg-__svg path, .mscgen_js-svg-__svg rect{fill:none}.mscgen_js-svg-__svg .label-text-background{fill:white;stroke:white;stroke-width:0}.mscgen_js-svg-__svg .bglayer{fill:white;stroke:white;stroke-width:0}.mscgen_js-svg-__svg line{}.mscgen_js-svg-__svg .return, .mscgen_js-svg-__svg .comment{stroke-dasharray:5,3}.mscgen_js-svg-__svg .inline_expression_divider{stroke-dasharray:10,5}.mscgen_js-svg-__svg text{color:inherit;stroke:none;text-anchor:middle}.mscgen_js-svg-__svg text.entity-text{text-decoration:underline}.mscgen_js-svg-__svg text.anchor-start{text-anchor:start}.mscgen_js-svg-__svg .arrow-marker{overflow:visible}.mscgen_js-svg-__svg .arrow-style{stroke-width:1}.mscgen_js-svg-__svg .arcrow, .mscgen_js-svg-__svg .arcrowomit, .mscgen_js-svg-__svg .emphasised{stroke-linecap:butt}.mscgen_js-svg-__svg .arcrowomit{stroke-dasharray:2,2}.mscgen_js-svg-__svg .box, .mscgen_js-svg-__svg .entity{fill:white;stroke-linejoin:round}.mscgen_js-svg-__svg .inherit{stroke:inherit;color:inherit}.mscgen_js-svg-__svg .inherit-fill{fill:inherit}.mscgen_js-svg-__svg .watermark{font-size:48pt;font-weight:bold;opacity:0.14}</style><marker orient="auto" id="mscgen_js-svg-__svgmethod-black" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="black" fill="black"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-black" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="black" fill="black"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-blue" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="blue" fill="blue"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-blue" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="blue" fill="blue"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-red" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="1,1  9,3  1,5" class="arrow-style" stroke="red" fill="red"></polygon></marker><marker orient="auto" id="mscgen_js-svg-__svgmethod-l-red" class="arrow-marker" viewBox="0 0 10 10" refX="9" refY="3" markerUnits="strokeWidth" markerWidth="10" markerHeight="10"><polygon points="17,1 9,3 17,5" class="arrow-style" stroke="red" fill="red"></polygon></marker></defs><g id="mscgen_js-svg-__svg__body" transform="translate(53,3) scale(1,1)"><g id="mscgen_js-svg-__svg__background"><rect width="976" height="386" x="-53" y="-3" class="bglayer"></rect></g><g id="mscgen_js-svg-__svg__arcspanlayer"></g><g id="mscgen_js-svg-__svg__lifelinelayer"><line x1="75" y1="38" x2="75" y2="76" class="arcrow"></line><line x1="315" y1="38" x2="315" y2="76" class="arcrow"></line><line x1="555" y1="38" x2="555" y2="76" class="arcrow"></line><line x1="795" y1="38" x2="795" y2="76" class="arcrow"></line><line x1="75" y1="76" x2="75" y2="114" class="arcrow"></line><line x1="315" y1="76" x2="315" y2="114" class="arcrow"></line><line x1="555" y1="76" x2="555" y2="114" class="arcrow"></line><line x1="795" y1="76" x2="795" y2="114" class="arcrow"></line><line x1="75" y1="114" x2="75" y2="152" class="arcrow"></line><line x1="315" y1="114" x2="315" y2="152" class="arcrow"></line><line x1="555" y1="114" x2="555" y2="152" class="arcrow"></line><line x1="795" y1="114" x2="795" y2="152" class="arcrow"></line><line x1="75" y1="152" x2="75" y2="190" class="arcrow"></line><line x1="315" y1="152" x2="315" y2="190" class="arcrow"></line><line x1="555" y1="152" x2="555" y2="190" class="arcrow"></line><line x1="795" y1="152" x2="795" y2="190" class="arcrow"></line><line x1="75" y1="190" x2="75" y2="228" class="arcrow"></line><line x1="315" y1="190" x2="315" y2="228" class="arcrow"></line><line x1="555" y1="190" x2="555" y2="228" class="arcrow"></line><line x1="795" y1="190" x2="795" y2="228" class="arcrow"></line><line x1="75" y1="228" x2="75" y2="266" class="arcrow"></line><line x1="315" y1="228" x2="315" y2="266" class="arcrow"></line><line x1="555" y1="228" x2="555" y2="266" class="arcrow"></line><line x1="795" y1="228" x2="795" y2="266" class="arcrow"></line><line x1="75" y1="266" x2="75" y2="304" class="arcrow"></line><line x1="315" y1="266" x2="315" y2="304" class="arcrow"></line><line x1="555" y1="266" x2="555" y2="304" class="arcrow"></line><line x1="795" y1="266" x2="795" y2="304" class="arcrow"></line><line x1="75" y1="304" x2="75" y2="342" class="arcrow"></line><line x1="315" y1="304" x2="315" y2="342" class="arcrow"></line><line x1="555" y1="304" x2="555" y2="342" class="arcrow"></line><line x1="795" y1="304" x2="795" y2="342" class="arcrow"></line><line x1="75" y1="342" x2="75" y2="380" class="arcrow"></line><line x1="315" y1="342" x2="315" y2="380" class="arcrow"></line><line x1="555" y1="342" x2="555" y2="380" class="arcrow"></line><line x1="795" y1="342" x2="795" y2="380" class="arcrow"></line></g><g id="mscgen_js-svg-__svg__sequencelayer"><g id="mscgen_js-svg-__svgentities"><g><rect width="150" height="38" class="entity" style="fill:lime;"></rect><g><text x="75" y="22.5" class="entity-text "><tspan>Client</tspan></text></g></g><g><rect width="150" height="38" x="240" class="entity" style="fill:cyan;"></rect><g><text x="315" y="22.5" class="entity-text "><tspan>Rails</tspan></text></g></g><g><rect width="150" height="38" x="480" class="entity" style="fill:orange;"></rect><g><text x="555" y="22.5" class="entity-text "><tspan>EtagCaching</tspan></text></g></g><g><rect width="150" height="38" x="720" class="entity" style="fill:white;"></rect><g><text x="795" y="22.5" class="entity-text "><tspan>Redis</tspan></text></g></g></g><g><line x1="75" y1="95" x2="315" y2="95" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="134.06" height="14" x="127.97" y="79.5" class="label-text-background"></rect><text x="195" y="90.5" class="directional-text method-text "><tspan>GET /projects/5/pipelines</tspan></text></g></g><g><line x1="315" y1="133" x2="555" y2="133" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="134.06" height="14" x="367.97" y="117.5" class="label-text-background"></rect><text x="435" y="128.5" class="directional-text method-text "><tspan>GET /projects/5/pipelines</tspan></text></g></g><g><line x1="555" y1="171" x2="795" y2="171" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="135.64" height="14" x="607.17" y="155.5" class="label-text-background"></rect><text x="675" y="166.5" class="directional-text method-text "><tspan>read(key = 'GET &lt;Etag&gt;')</tspan></text></g></g><g><line x1="795" y1="209" x2="555" y2="209" class="arc directional method" style="stroke:red" marker-end="url(#mscgen_js-svg-__svgmethod-red)"></line><g><rect width="60.02" height="14" x="644.98" y="193.5" class="label-text-background"></rect><text x="675" y="204.5" class="directional-text method-text " style="fill:red;"><tspan>cache miss</tspan></text></g></g><g></g><g><line x1="555" y1="285" x2="795" y2="285" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="103.94" height="14" x="623.02" y="269.5" class="label-text-background"></rect><text x="675" y="280.5" class="directional-text method-text "><tspan>write('&lt;New Etag&gt;')</tspan></text></g></g><g><line x1="555" y1="323" x2="315" y2="323" class="arc directional method" style="stroke:black" marker-end="url(#mscgen_js-svg-__svgmethod-black)"></line><g><rect width="134.06" height="14" x="367.97" y="307.5" class="label-text-background"></rect><text x="435" y="318.5" class="directional-text method-text "><tspan>GET /projects/5/pipelines</tspan></text></g></g><g><line x1="315" y1="361" x2="75" y2="361" class="arc directional method" style="stroke:blue" marker-end="url(#mscgen_js-svg-__svgmethod-blue)"></line><g><rect width="130.72" height="14" x="129.63" y="345.5" class="label-text-background"></rect><text x="195" y="356.5" class="directional-text method-text " style="fill:blue;"><tspan>JSON response w/ ETag</tspan></text></g></g></g><g id="mscgen_js-svg-__svg__notelayer"></g><g id="mscgen_js-svg-__svg__watermark"></g></g></svg>
\ No newline at end of file
diff --git a/doc/development/polling.md b/doc/development/polling.md
index a7f2962acf0..e5a717f712b 100644
--- a/doc/development/polling.md
+++ b/doc/development/polling.md
@@ -22,6 +22,9 @@ Instead you should use polling mechanism with ETag caching in Redis.
 
 ## How it works
 
+![Cache miss](img/cache-miss.svg)
+![Cache hit](img/cache-hit.svg)
+
 1. Whenever a resource changes we generate a random value and store it in
    Redis.
 1. When a client makes a request we set the `ETag` response header to the value