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| author | William A. Rowe Jr <wrowe@apache.org> | 2010-08-02 03:48:08 +0000 |
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| committer | William A. Rowe Jr <wrowe@apache.org> | 2010-08-02 03:48:08 +0000 |
| commit | 41c2aed7da00d38b8b091cb8294af5ef32f9f456 (patch) | |
| tree | 493b02e8c2fbb43760293ecc49ee9b2b65970259 /docs/manual/mod/mod_unique_id.html.en | |
| parent | 45709f3f4fcfd4a805f75b4c7f56637897dc163f (diff) | |
| download | httpd-41c2aed7da00d38b8b091cb8294af5ef32f9f456.tar.gz | |
It seems we haven't built in some time
git-svn-id: https://svn.apache.org/repos/asf/httpd/httpd/trunk@981360 13f79535-47bb-0310-9956-ffa450edef68
Diffstat (limited to 'docs/manual/mod/mod_unique_id.html.en')
| -rw-r--r-- | docs/manual/mod/mod_unique_id.html.en | 16 |
1 files changed, 10 insertions, 6 deletions
diff --git a/docs/manual/mod/mod_unique_id.html.en b/docs/manual/mod/mod_unique_id.html.en index e5c17f3ff6..f59c758759 100644 --- a/docs/manual/mod/mod_unique_id.html.en +++ b/docs/manual/mod/mod_unique_id.html.en @@ -93,7 +93,10 @@ identifier for each request</td></tr> <p>Given those assumptions, at a single point in time we can identify any httpd process on any machine in the cluster from all other httpd processes. The machine's IP address and the pid - of the httpd process are sufficient to do this. So in order to + of the httpd process are sufficient to do this. A httpd process + can handle multiple requests simultaneously if you use a + multi-threaded MPM. In order to identify threads, we use a thread + index Apache httpd uses internally. So in order to generate unique identifiers for requests we need only distinguish between different points in time.</p> @@ -163,11 +166,13 @@ identifier for each request</td></tr> even still, if you're running NTP then your UTC time will be correct very shortly after reboot.</p> + <p>The <code>UNIQUE_ID</code> environment variable is - constructed by encoding the 112-bit (32-bit IP address, 32 bit - pid, 32 bit time stamp, 16 bit counter) quadruple using the + constructed by encoding the 144-bit (32-bit IP address, 32 bit + pid, 32 bit time stamp, 16 bit counter, 32 bit thread index) + quadruple using the alphabet <code>[A-Za-z0-9@-]</code> in a manner similar to MIME - base64 encoding, producing 19 characters. The MIME base64 + base64 encoding, producing 24 characters. The MIME base64 alphabet is actually <code>[A-Za-z0-9+/]</code> however <code>+</code> and <code>/</code> need to be specially encoded in URLs, which makes them less desirable. All values are @@ -193,8 +198,7 @@ identifier for each request</td></tr> issuing the new encodings.</p> <p>This we believe is a relatively portable solution to this - problem. It can be extended to multithreaded systems like - Windows NT, and can grow with future needs. The identifiers + problem. The identifiers generated have essentially an infinite life-time because future identifiers can be made longer as required. Essentially no communication is required between machines in the cluster (only |