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Reduce default API server workers to 1
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Clarify how you can determine a good starting point for workers config
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9ac51e5
Add newsfragment
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23 changes: 23 additions & 0 deletions airflow-core/newsfragments/55707.significant.rst
View file
Open in desktop
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

* [ ] Dag changes
* [x] Config changes
* [ ] API changes
* [ ] CLI changes
* [ ] Behaviour changes
* [ ] Plugin changes
* [ ] Dependency changes
* [ ] Code interface changes
6 changes: 4 additions & 2 deletions airflow-core/src/airflow/config_templates/config.yml
View file
Open in desktop
Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
default: "8080"
workers:
description: |
Number of workers to run on the API server
Number of workers to run on the API server. Should be roughly equal to the number of
cpu cores available. If you need to scale the API server, consider deploying multiple API
servers instead of increasing the number of workers.
version_added: ~
type: integer
example: ~
default: "4"
default: "1"
worker_timeout:
description: |
Number of seconds the API server waits before timing out on a worker
Expand Down
, 'i'); if (__m === '*' || __re.test(location.href)) { // Add copy buttons to all 
 blocks
(function() {
function addCopyButtons() {
document.querySelectorAll('pre code').forEach(function(codeBlock) {
if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;
codeBlock.parentElement.setAttribute('data-copy-added', 'true');
var btn = document.createElement('button');
btn.textContent = 'Copy';
btn.style.cssText = 'position:absolute;top:4px;right:4px;padding:2px 8px;font-size:11px;background:#4ecdc4;border:none;border-radius:4px;color:#1a1a2e;cursor:pointer;opacity:0.7;transition:opacity 0.2s;';
btn.onmouseover = function() { this.style.opacity = '1'; };
btn.onmouseout = function() { this.style.opacity = '0.7'; };
btn.onclick = function() {
navigator.clipboard.writeText(codeBlock.textContent).then(function() {
btn.textContent = 'Copied!';
setTimeout(function() { btn.textContent = 'Copy'; }, 1500);
});
};
codeBlock.parentElement.style.position = 'relative';
codeBlock.parentElement.appendChild(btn);
});
}
addCopyButtons();
// Re-run on dynamic content
var observer = new MutationObserver(addCopyButtons);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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#55707
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Clarify how you can determine a good starting point for workers config


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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Force GitHub README to respect dark mode
(function() {
var style = document.createElement('style');
style.textContent = '
.markdown-body {
color-scheme: dark light;
}
.markdown-body pre { background: #161b22 !important; }
.markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }
.markdown-body table th, .markdown-body table td { border-color: #30363d !important; }
.markdown-body img { background: #0d1117; }
.markdown-body blockquote { border-left-color: #8b949e; }
.markdown-body hr { border-color: #30363d; }
';
document.head.appendChild(style);
})();
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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Reduce default API server workers to 1#55707

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jedcunningham
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Sep 16, 2025
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#55707
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Clarify how you can determine a good starting point for workers config


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9ac51e5

Add newsfragment


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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Highlight search terms from Google/DuckDuckGo/Bing referrer
(function() {
var ref = document.referrer;
var terms = [];
if (ref.includes('google.com') || ref.includes('duckduckgo.com') || ref.includes('bing.com')) {
var url = new URL(ref);
var q = url.searchParams.get('q') || url.searchParams.get('p');
if (q) {
terms = q.split(/\s+/).filter(function(t) { return t.length > 2; });
}
}
if (terms.length === 0) return;
var style = document.createElement('style');
style.textContent = '.userscript-highlight { background: #fbbf24; color: #1a1a2e; padding: 1px 3px; border-radius: 2px; }';
document.head.appendChild(style);
function highlight(node) {
if (node.nodeType === 3) { // text node
var text = node.textContent;
var found = false;
terms.forEach(function(term) {
var regex = new RegExp('(' + term.replace(/[.*+?^${}()|[\]\\]/g, '\\') + ')', 'gi');
if (regex.test(text)) {
found = true;
var frag = document.createDocumentFragment();
var parts = text.split(regex);
parts.forEach(function(part, i) {
if (i % 2 === 0) {
frag.appendChild(document.createTextNode(part));
} else {
var span = document.createElement('span');
span.className = 'userscript-highlight';
span.textContent = part;
frag.appendChild(span);
}
});
node.parentNode.replaceChild(frag, node);
}
});
} else if (node.nodeType === 1 && node.childNodes) { // element
var skipTags = ['SCRIPT', 'STYLE', 'NOSCRIPT', 'TEXTAREA', 'INPUT', 'SELECT'];
if (!skipTags.includes(node.tagName)) {
Array.from(node.childNodes).forEach(highlight);
}
}
}
highlight(document.body);
// Re-highlight on dynamic content
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1 || node.nodeType === 3) highlight(node);
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Highlight Search Terms]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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Reduce default API server workers to 1#55707

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jedcunningham
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#55707
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Reduce default API server workers to 1


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b5c5143

Clarify how you can determine a good starting point for workers config


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9ac51e5

Add newsfragment


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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Strip utm_, fbclid, gclid, etc. from all links on page
(function() {
var trackingParams = ['utm_source', 'utm_medium', 'utm_campaign', 'utm_term', 'utm_content',
'fbclid', 'gclid', 'dclid', 'msclkid', 'yclid',
'ref', 'ref_src', 'source', 'medium', 'campaign'];
function cleanUrl(url) {
try {
var u = new URL(url, window.location.origin);
var changed = false;
trackingParams.forEach(function(p) {
if (u.searchParams.has(p)) {
u.searchParams.delete(p);
changed = true;
}
});
return changed ? u.toString() : url;
} catch (e) {
return url;
}
}
function cleanLinks() {
document.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
cleanLinks();
var observer = new MutationObserver(function(mutations) {
mutations.forEach(function(m) {
m.addedNodes.forEach(function(node) {
if (node.nodeType === 1) {
if (node.tagName === 'A') cleanLinks();
node.querySelectorAll('a[href]').forEach(function(a) {
var clean = cleanUrl(a.href);
if (clean !== a.href) a.href = clean;
});
}
});
});
});
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:Remove Tracking Parameters from Links]', __e); }
})();
(function(){
try {
var __m = "youtube.com";
var __re = new RegExp('^' + "youtube\\.com" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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Reduce default API server workers to 1#55707

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jedcunningham
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Sep 16, 2025
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#55707
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Reduce default API server workers to 1


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Clarify how you can determine a good starting point for workers config


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9ac51e5

Add newsfragment


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airflow-core/newsfragments/55707.significant.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Auto-enable theater mode on YouTube
(function() {
function tryTheater() {
var btn = document.querySelector('button[aria-label="Theater mode"], ytd-player #player button[title="Theater mode"]');
if (btn && !btn.classList.contains('activated')) {
btn.click();
}
}
// Try immediately
tryTheater();
// Try after navigation (SPA)
var lastUrl = location.href;
setInterval(function() {
if (location.href !== lastUrl) {
lastUrl = location.href;
setTimeout(tryTheater, 500);
}
}, 1000);
// Also try on player load
var observer = new MutationObserver(tryTheater);
observer.observe(document.body, { childList: true, subtree: true });
})();
}
} catch(__e) { console.warn('[Userscript:YouTube Theater Mode Default]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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Reduce default API server workers to 1#55707

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jedcunningham
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Sep 16, 2025
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#55707
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Reduce default API server workers to 1


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b5c5143

Clarify how you can determine a good starting point for workers config


jedcunningham Sep 16, 2025
9ac51e5

Add newsfragment


jedcunningham Sep 16, 2025

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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

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Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Remove or un-stick sticky/fixed headers that block content
(function() {
function unstick() {
document.querySelectorAll('header, nav, [role="banner"], .header, .navbar, .sticky, .fixed-top, [style*="position: fixed"], [style*="position:sticky"]').forEach(function(el) {
if (el.style.position === 'fixed' || el.style.position === 'sticky' || getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {
el.style.position = 'static';
el.style.top = 'auto';
el.style.zIndex = 'auto';
}
});
}
unstick();
var observer = new MutationObserver(unstick);
observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });
})();
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
Skip to content
Reduce default API server workers to 1#55707

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 Merged

jedcunningham
merged 3 commits into

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Sep 16, 2025
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Reduce default API server workers to 1
#55707
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20e894c

Reduce default API server workers to 1


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b5c5143

Clarify how you can determine a good starting point for workers config


jedcunningham Sep 16, 2025
9ac51e5

Add newsfragment


jedcunningham Sep 16, 2025

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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

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Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

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Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down

, 'i');
if (__m === '*' || __re.test(location.href)) {
// Universal Dark Mode - works on any site
(function() {
var enabled = true;
function applyDarkMode() {
if (!enabled) return;
// Create style element if it doesn't exist
var style = document.getElementById('universal-dark-mode-style');
if (!style) {
style = document.createElement('style');
style.id = 'universal-dark-mode-style';
document.head.appendChild(style);
}
// Dark mode CSS - inverts colors but preserves images/video
style.textContent = '
/* Invert everything except media */
html {
filter: invert(1) hue-rotate(180deg) !important;
background: #1a1a2e !important;
}
/* Restore images, videos, iframes, canvas */
img, video, iframe, canvas, svg, picture, [style*="background-image"] {
filter: invert(1) hue-rotate(180deg) !important;
}
/* Preserve specific elements that should not be inverted */
.no-dark-mode, .no-dark-mode *,
[data-theme="light"], [data-theme="light"],
.ace_editor, .ace_editor *,
.CodeMirror, .CodeMirror *,
.monaco-editor, .monaco-editor *,
.markdown-body pre, .markdown-body pre *,
.highlight, .highlight *,
pre code, pre code * {
filter: none !important;
}
/* Fix common UI elements */
.modal, .popup, .dropdown-menu, .tooltip, .popover {
filter: invert(1) hue-rotate(180deg) !important;
background: #2d2d44 !important;
border-color: #444 !important;
}
/* Scrollbars */
::-webkit-scrollbar { background: #1a1a2e !important; }
::-webkit-scrollbar-thumb { background: #444 !important; }
::-webkit-scrollbar-thumb:hover { background: #555 !important; }
/* Selection */
::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }
';
}
function removeDarkMode() {
var style = document.getElementById('universal-dark-mode-style');
if (style) style.remove();
}
// Toggle with Alt+Shift+D
document.addEventListener('keydown', function(e) {
if (e.altKey && e.shiftKey && e.key === 'D') {
e.preventDefault();
enabled = !enabled;
if (enabled) {
applyDarkMode();
console.log('[Universal Dark Mode] Enabled');
} else {
removeDarkMode();
console.log('[Universal Dark Mode] Disabled');
}
}
});
// Apply on load
applyDarkMode();
// Re-apply on dynamic content
var observer = new MutationObserver(function(mutations) {
if (enabled && !document.getElementById('universal-dark-mode-style')) {
applyDarkMode();
}
});
observer.observe(document.head, { childList: true });
console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');
})();
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();
Reduce default API server workers to 1 by jedcunningham · Pull Request #55707 · apache/airflow · GitHub
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Sep 16, 2025
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Reduce default API server workers to 1
#55707
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20e894c

Reduce default API server workers to 1


jedcunningham Sep 16, 2025
b5c5143

Clarify how you can determine a good starting point for workers config


jedcunningham Sep 16, 2025
9ac51e5

Add newsfragment


jedcunningham Sep 16, 2025

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23 changes: 23 additions & 0 deletions
airflow-core/newsfragments/55707.significant.rst

View file


Open in desktop

Original file line numberDiff line numberDiff line change
@@ -0,0 +1,23 @@
Reduce default API server workers to 1

The default number of API server workers (``[api] workers``) has been reduced from 4 to 1.

With FastAPI, sync code runs in external thread pools, making multiple workers within a single
process less necessary. Additionally, with uvicorn's spawn behavior instead of fork, there is
no shared copy-on-write memory between workers, so horizontal scaling with multiple API server
instances is now the recommended approach for better resource utilization and fault isolation.

A good starting point for the number of workers is to set it to the number of CPU cores available.
If you do have multiple CPU cores available for the API server, consider deploying multiple API
server instances instead of increasing the number of workers.

* Types of change

 * [ ] Dag changes
 * [x] Config changes
 * [ ] API changes
 * [ ] CLI changes
 * [ ] Behaviour changes
 * [ ] Plugin changes
 * [ ] Dependency changes
 * [ ] Code interface changes

6 changes: 4 additions & 2 deletions
airflow-core/src/airflow/config_templates/config.yml

View file


Open in desktop

Original file line numberDiff line numberDiff line change
Expand Up@@ -1389,11 +1389,13 @@ api:
 default: "8080"
 workers:
 description: |
 Number of workers to run on the API server
 Number of workers to run on the API server. Should be roughly equal to the number of
 cpu cores available. If you need to scale the API server, consider deploying multiple API
 servers instead of increasing the number of workers.
 version_added: ~
 type: integer
 example: ~
 default: "4"
 default: "1"
 worker_timeout:
 description: |
 Number of seconds the API server waits before timing out on a worker
Expand Down