{"id":35542,"date":"2024-10-31T08:27:08","date_gmt":"2024-10-31T07:27:08","guid":{"rendered":"https:\/\/www.dbi-services.com\/blog\/?p=35542"},"modified":"2024-10-31T08:27:08","modified_gmt":"2024-10-31T07:27:08","slug":"postgresql-delaying-authentication-to-debug-a-process","status":"publish","type":"post","link":"https:\/\/www.dbi-services.com\/blog\/postgresql-delaying-authentication-to-debug-a-process\/","title":{"rendered":"PostgreSQL: Delaying authentication to debug a process"},"content":{"rendered":"\n<p class=\"wp-block-paragraph\">While investigating a customer issue (details <a href=\"https:\/\/www.postgresql.org\/message-id\/flat\/GV0P278MB0419EB5885DF99C5354804A9D24B2%40GV0P278MB0419.CHEP278.PROD.OUTLOOK.COM\">here<\/a>) one of the replies suggested to use <a href=\"https:\/\/www.postgresql.org\/docs\/17\/runtime-config-developer.html#GUC-PRE-AUTH-DELAY\" target=\"_blank\" rel=\"noreferrer noopener\">pre_auth_delay<\/a> to add a delay before a session is authenticated. Even if this was not useful for the actual issue, this can be very useful for other scenarios, and this is the reason for this short blog post.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">Let&#8217;s assume you know that some of your sessions are doing something unexpected and you want to <a href=\"https:\/\/man7.org\/linux\/man-pages\/man1\/strace.1.html\" target=\"_blank\" rel=\"noreferrer noopener\">strace<\/a> that process from the operating system. The issue is, that those session are very short living and it is hard to know beforehand which session is causing issues. What you can do using <a href=\"https:\/\/www.postgresql.org\/docs\/17\/runtime-config-developer.html#GUC-PRE-AUTH-DELAY\" target=\"_blank\" rel=\"noreferrer noopener\">pre_auth_delay<\/a> is to add a delay before the session is authenticated so you&#8217;re able to identify the process and then attach strace to it. Another use case would be to troubleshoot authentication itself.<\/p>\n\n\n\n<p class=\"wp-block-paragraph\">The parameter can be changed online (context=sighup), so let&#8217;s change it to 20 seconds:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: sql; highlight: [1,7,9,14]; title: ; notranslate\" title=\"\">\npostgres=# \\dconfig+ pre_auth_delay\n                List of configuration parameters\n   Parameter    | Value |  Type   | Context | Access privileges \n----------------+-------+---------+---------+-------------------\n pre_auth_delay | 10s   | integer | sighup  | \n(1 row)\npostgres=# alter system set pre_auth_delay = &#039;10s&#039;;\nALTER SYSTEM\npostgres=# select pg_reload_conf();\n pg_reload_conf \n----------------\n t\n(1 row)\npostgres=# \\q\n<\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">In another session identify the current psql sessions (as we&#8217;re going to use psql to connect), which returns nothing in my case:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: bash; highlight: [1]; title: ; notranslate\" title=\"\">\npostgres@debian12-pg:\/home\/postgres\/ &#x5B;pgdev] ps -ef | grep psql | grep -v grep\npostgres@debian12-pg:\/home\/postgres\/ &#x5B;pgdev] \n<\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">Start a new psql session, which will block because of the delay we&#8217;ve set:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: bash; highlight: [1]; title: ; notranslate\" title=\"\">\npostgres@debian12-pg:\/home\/postgres\/ &#x5B;pgdev] psql\n<\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">In the other session identify the connection:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: bash; highlight: [1]; title: ; notranslate\" title=\"\">\npostgres@debian12-pg:\/home\/postgres\/ &#x5B;pgdev] ps -ef | grep psql | grep -v grep\npostgres    9750    8637  0 16:57 pts\/1    00:00:00 psql\n<\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">&#8230; and then attach strace to it:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: bash; highlight: [1]; title: ; notranslate\" title=\"\">\npostgres@debian12-pg:\/home\/postgres\/ &#x5B;pgdev] strace -fp 9750\nstrace: Process 9750 attached\npselect6(1, &#x5B;0], NULL, NULL, NULL, {sigmask=&#x5B;], sigsetsize=8}\n<\/pre><\/div>\n\n\n<p class=\"wp-block-paragraph\">Done. For completeness, there is also <a href=\"https:\/\/www.postgresql.org\/docs\/17\/runtime-config-developer.html#GUC-POST-AUTH-DELAY\" target=\"_blank\" rel=\"noreferrer noopener\">post_auth_delay<\/a>:<\/p>\n\n\n<div class=\"wp-block-syntaxhighlighter-code \"><pre class=\"brush: sql; highlight: [1]; title: ; notranslate\" title=\"\">\n\npostgres=# \\dconfig+ post_auth_delay\n                List of configuration parameters\n    Parameter    | Value |  Type   | Context | Access privileges \n-----------------+-------+---------+---------+-------------------\n post_auth_delay | 0     | integer | backend | \n(1 row)\n\n<\/pre><\/div>","protected":false},"excerpt":{"rendered":"<p>While investigating a customer issue (details here) one of the replies suggested to use pre_auth_delay to add a delay before a session is authenticated. Even if this was not useful for the actual issue, this can be very useful for other scenarios, and this is the reason for this short blog post. Let&#8217;s assume you&hellip;&nbsp;<\/p>\n","protected":false},"author":28,"featured_media":0,"comment_status":"open","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"neve_meta_sidebar":"","neve_meta_container":"","neve_meta_enable_content_width":"","neve_meta_content_width":0,"neve_meta_title_alignment":"","neve_meta_author_avatar":"","neve_post_elements_order":"","neve_meta_disable_header":"","neve_meta_disable_footer":"","neve_meta_disable_title":"","neve_meta_reading_time":"","_themeisle_gutenberg_block_has_review":false,"footnotes":""},"categories":[4133],"tags":[],"class_list":["post-35542","post","type-post","status-publish","format-standard","hentry","category-database"],"yoast_head":"<!-- This site is optimized with the Yoast SEO Premium plugin v28.8 (Yoast SEO v28.8) - https:\/\/yoast.com\/product\/yoast-seo-premium-wordpress\/ -->\n<title>PostgreSQL: Delaying authentication to debug a process - dbi services | Blog<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.dbi-services.com\/blog\/postgresql-delaying-authentication-to-debug-a-process\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"PostgreSQL: Delaying authentication to debug a process\" \/>\n<meta property=\"og:description\" content=\"While investigating a customer issue (details here) one of the replies suggested to use pre_auth_delay to add a delay before a session is authenticated. 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