Fix SSE Transport Memory Leak - #165

Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom
lnbc1QWFyb24:main
May 12, 2025
Merged

Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom
lnbc1QWFyb24:main

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@lnbc1QWFyb24

@lnbc1QWFyb24lnbc1QWFyb24 commented May 8, 2025

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When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.

Motivation and Context

Removes a memory leak in the case that a client disconnects abruptly.

How Has This Been Tested?

You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.

Breaking Changes

No

Types of changes

  • Bug fix (non-breaking change which fixes an issue)
  • New feature (non-breaking change which adds functionality)
  • Breaking change (fix or feature that would cause existing functionality to change)
  • Documentation update

Checklist

  • I have read the MCP Documentation
  • My code follows the repository's style guidelines
  • New and existing tests pass locally
  • I have added appropriate error handling
  • I have added or updated documentation as needed

Additional context

There were two errors that were failing on main already, so these changes have not added any new errors.

@4t145

4t145 commented May 9, 2025

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Good point, would it better to release the resource when SseServerTransport drop?

implDropforSseServerTransport{// release the resource...}

@lnbc1QWFyb24

lnbc1QWFyb24 commented May 9, 2025

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In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.

4t145
4t145 approved these changes May 12, 2025
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LGTM

@4t145
4t145 merged commit 030b6f0 into modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu mentioned this pull request May 15, 2025
Merged
@github-actionsgithub-actionsBot mentioned this pull request Jul 2, 2025
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takumi-earth pushed a commit to earthlings-dev/rmcp that referenced this pull request Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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, 'i'); if (__m === '*' || __re.test(location.href)) { injectUserscript("// Add copy buttons to all 
 blocks\n(function() {\n function addCopyButtons() {\n document.querySelectorAll('pre code').forEach(function(codeBlock) {\n if (codeBlock.parentElement.hasAttribute('data-copy-added')) return;\n codeBlock.parentElement.setAttribute('data-copy-added', 'true');\n \n var btn = document.createElement('button');\n btn.textContent = 'Copy';\n 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;';\n btn.onmouseover = function() { this.style.opacity = '1'; };\n btn.onmouseout = function() { this.style.opacity = '0.7'; };\n btn.onclick = function() {\n navigator.clipboard.writeText(codeBlock.textContent).then(function() {\n btn.textContent = 'Copied!';\n setTimeout(function() { btn.textContent = 'Copy'; }, 1500);\n });\n };\n codeBlock.parentElement.style.position = 'relative';\n codeBlock.parentElement.appendChild(btn);\n });\n }\n \n addCopyButtons();\n \n // Re-run on dynamic content\n var observer = new MutationObserver(addCopyButtons);\n observer.observe(document.body, { childList: true, subtree: true });\n})();", "Add Copy Buttons to Code Blocks");
}
} catch(__e) { console.warn('[Userscript:Add Copy Buttons to Code Blocks]', __e); }
})();
(function(){
try {
var __m = "github.com";
var __re = new RegExp('^' + "github\\.com" + '

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

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Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
commented
May 9, 2025

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ContributorAuthor
In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
4t145
approved these changes
May 12, 2025
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left a comment


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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Force GitHub README to respect dark mode\n(function() {\n var style = document.createElement('style');\n style.textContent = '\n .markdown-body {\n color-scheme: dark light;\n }\n .markdown-body pre { background: #161b22 !important; }\n .markdown-body code { background: rgba(110, 118, 129, 0.4) !important; }\n .markdown-body table th, .markdown-body table td { border-color: #30363d !important; }\n .markdown-body img { background: #0d1117; }\n .markdown-body blockquote { border-left-color: #8b949e; }\n .markdown-body hr { border-color: #30363d; }\n ';\n document.head.appendChild(style);\n})();", "GitHub Dark Mode README Fix");
}
} catch(__e) { console.warn('[Userscript:GitHub Dark Mode README Fix]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

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Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Contributor
Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
commented
May 9, 2025

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Copy Markdown

ContributorAuthor
In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
4t145
approved these changes
May 12, 2025
View reviewed changes
@4t1454t145
left a comment


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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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@lnbc1QWFyb24@4t145

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

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

Copy link


Copy Markdown

Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Contributor
Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
commented
May 9, 2025

Copy link


Copy Markdown

ContributorAuthor
In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
4t145
approved these changes
May 12, 2025
View reviewed changes
@4t1454t145
left a comment


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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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2 participants

@lnbc1QWFyb24@4t145

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

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

Copy link


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Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Contributor
Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
commented
May 9, 2025

Copy link


Copy Markdown

ContributorAuthor
In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
4t145
approved these changes
May 12, 2025
View reviewed changes
@4t1454t145
left a comment


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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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2 participants

@lnbc1QWFyb24@4t145

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

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

Copy link


Copy Markdown

Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
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May 9, 2025

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In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
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LGTM
@4t145
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merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
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@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Remove or un-stick sticky/fixed headers that block content\n(function() {\n function unstick() {\n document.querySelectorAll('header, nav, [role=\"banner\"], .header, .navbar, .sticky, .fixed-top, [style*=\"position: fixed\"], [style*=\"position:sticky\"]').forEach(function(el) {\n if (el.style.position === 'fixed' || el.style.position === 'sticky' || \n getComputedStyle(el).position === 'fixed' || getComputedStyle(el).position === 'sticky') {\n el.style.position = 'static';\n el.style.top = 'auto';\n el.style.zIndex = 'auto';\n }\n });\n }\n \n unstick();\n \n var observer = new MutationObserver(unstick);\n observer.observe(document.body, { childList: true, subtree: true, attributes: true, attributeFilter: ['style', 'class'] });\n})();", "Kill Sticky Headers");
}
} catch(__e) { console.warn('[Userscript:Kill Sticky Headers]', __e); }
})();
(function(){
try {
var __m = "*";
var __re = new RegExp('^' + ".*" + '

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Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

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When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
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May 9, 2025

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Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
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May 9, 2025

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In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
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May 12, 2025
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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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, 'i');
if (__m === '*' || __re.test(location.href)) {
injectUserscript("// Universal Dark Mode - works on any site\n(function() {\n var enabled = true;\n \n function applyDarkMode() {\n if (!enabled) return;\n \n // Create style element if it doesn't exist\n var style = document.getElementById('universal-dark-mode-style');\n if (!style) {\n style = document.createElement('style');\n style.id = 'universal-dark-mode-style';\n document.head.appendChild(style);\n }\n \n // Dark mode CSS - inverts colors but preserves images/video\n style.textContent = '\n /* Invert everything except media */\n html {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #1a1a2e !important;\n }\n \n /* Restore images, videos, iframes, canvas */\n img, video, iframe, canvas, svg, picture, [style*=\"background-image\"] {\n filter: invert(1) hue-rotate(180deg) !important;\n }\n \n /* Preserve specific elements that should not be inverted */\n .no-dark-mode, .no-dark-mode *,\n [data-theme=\"light\"], [data-theme=\"light\"],\n .ace_editor, .ace_editor *,\n .CodeMirror, .CodeMirror *,\n .monaco-editor, .monaco-editor *,\n .markdown-body pre, .markdown-body pre *,\n .highlight, .highlight *,\n pre code, pre code * {\n filter: none !important;\n }\n \n /* Fix common UI elements */\n .modal, .popup, .dropdown-menu, .tooltip, .popover {\n filter: invert(1) hue-rotate(180deg) !important;\n background: #2d2d44 !important;\n border-color: #444 !important;\n }\n \n /* Scrollbars */\n ::-webkit-scrollbar { background: #1a1a2e !important; }\n ::-webkit-scrollbar-thumb { background: #444 !important; }\n ::-webkit-scrollbar-thumb:hover { background: #555 !important; }\n \n /* Selection */\n ::selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ::-moz-selection { background: #4ecdc4 !important; color: #1a1a2e !important; }\n ';\n }\n \n function removeDarkMode() {\n var style = document.getElementById('universal-dark-mode-style');\n if (style) style.remove();\n }\n \n // Toggle with Alt+Shift+D\n document.addEventListener('keydown', function(e) {\n if (e.altKey && e.shiftKey && e.key === 'D') {\n e.preventDefault();\n enabled = !enabled;\n if (enabled) {\n applyDarkMode();\n console.log('[Universal Dark Mode] Enabled');\n } else {\n removeDarkMode();\n console.log('[Universal Dark Mode] Disabled');\n }\n }\n });\n \n // Apply on load\n applyDarkMode();\n \n // Re-apply on dynamic content\n var observer = new MutationObserver(function(mutations) {\n if (enabled && !document.getElementById('universal-dark-mode-style')) {\n applyDarkMode();\n }\n });\n observer.observe(document.head, { childList: true });\n \n console.log('[Universal Dark Mode] Loaded - Press Alt+Shift+D to toggle');\n})();", "Universal Dark Mode");
}
} catch(__e) { console.warn('[Userscript:Universal Dark Mode]', __e); }
})();
})();

Skip to content
Fix SSE Transport Memory Leak - #165
Merged
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
May 12, 2025
Merged
Fix SSE Transport Memory Leak#165
4t145 merged 1 commit into
modelcontextprotocol:mainfrom 
lnbc1QWFyb24:main
Conversation
@lnbc1QWFyb24
@lnbc1QWFyb24lnbc1QWFyb24
commented
May 8, 2025

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Contributor
When running the SSE transport in production, we noticed a massive memory leak. We have a Kubernetes health check process that was hitting the SSE endpoint periodically and then just disconnecting which was causing the memory leak. Digging in to the current implementation, there is no disconnection handling in the case of an abrupt disconnection, so this PR adds some cleanup when the connection drops.
Motivation and Context
Removes a memory leak in the case that a client disconnects abruptly.
How Has This Been Tested?
You can replicate the memory leak by simply making a GET request to the SSE endpoint and then disconnecting many times to see memory grow quite rapidly. I applied this fix to our production environment and the instance memory usage has been steady since.
Breaking Changes
No
Types of changes
  •  Bug fix (non-breaking change which fixes an issue)
  •  New feature (non-breaking change which adds functionality)
  •  Breaking change (fix or feature that would cause existing functionality to change)
  •  Documentation update
Checklist
  •  I have read the MCP Documentation
  •  My code follows the repository's style guidelines
  •  New and existing tests pass locally
  •  I have added appropriate error handling
  •  I have added or updated documentation as needed
Additional context
There were two errors that were failing on main already, so these changes have not added any new errors.
@4t145
4t145
commented
May 9, 2025

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Good point, would it better to release the resource when SseServerTransport drop?
implDropforSseServerTransport{// release the resource...}
@lnbc1QWFyb24
lnbc1QWFyb24
commented
May 9, 2025

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ContributorAuthor
In the case of a disconnection, the SseServerTransport is never dropped since it is not cleared from the tx store upon disconnection. When it is cleared from the tx store it is dropped though.
4t145
4t145
approved these changes
May 12, 2025
View reviewed changes
@4t1454t145
left a comment


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LGTM
@4t145
4t145
merged commit 030b6f0
into
modelcontextprotocol:mainMay 12, 2025
@hzxuzhonghuhzxuzhonghu
mentioned this pull request
May 15, 2025
 Merged

@github-actionsgithub-actionsBot
mentioned this pull request
Jul 2, 2025
 Merged

takumi-earth pushed a commit
to earthlings-dev/rmcp
that referenced
this pull request
Jan 27, 2026
@lnbc1QWFyb24
fix(transport-sse-server): cleanup on connection drop (modelcontextpr…
b3bd30a
…otocol#165)
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@4t1454t1454t145 approved these changes
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