Fix Upgrade Preview or Upgrade Monitor loading timeout showing socket closed errorIssue <!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } When you open Upgrade Preview or Upgrade Monitor, the page may display only a loading screen before timing out after approximately five minutes. The system generates an error message, "[ERROR CODE: -1 ] Socket closed". This issue occurs due to invalid Remote Instance configurations in the Update Source table. Example localhost logs: 2020-12-29 19:11:04 (909) glide.quota.manager Quota exceeded for UI Transactions, requesting cancel2020-12-29 19:11:04 (909) glide.quota.manager WARNING *** WARNING *** Transaction: Cancelling transaction #914670 /angular.do (maximum execution time exceeded): Thread Default-thread-4 (vaibhav.sethi@snc, 2D1D6AC31B596C101F5884415B4BCB05), after 298511ms2020-12-29 19:11:04 (915) glide.quota.manager SYSTEM Doing HttpCancel for thread Default-thread-42020-12-29 19:11:04 (922) glide.quota.manager SYSTEM Cancelled 0 child transactions2020-12-29 19:11:04 (923) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 OUTBOUND_HTTP: protocol=HTTP/1.1 response_status=-1 response_time=295362 request_length=350 response_length=-1 app_scope=global session_id=2D1D6AC31B596C101F5884415B4BCB05 transaction_name="#914670 /angular.do" transaction_id=4b1fe2c71b596c101f5884415b4bcb11 user_name=vaibhav.sethi@snc mid_server= source_table= source_record= system_id=<APP_NODE> method=POST log_level=Basic scheme=http hostname=<REMOTE_INSTANCE_NAME> path=/sys_upgrade_history.do url=<REMOTE_INSTANCE_URL>/sys_upgrade_history.do response_body="[ERROR CODE: -1 ] Socket closed"2020-12-29 19:11:04 (924) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 WARNING *** WARNING *** Socket error2020-12-29 19:11:04 (924) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 SEVERE *** ERROR *** getRecords failed (Socket error)2020-12-29 19:11:04 (924) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 WARNING *** WARNING *** Long Transaction started at 12/29/20 19:06:06.398, Memory at start was 515, Memory is 330, SQL count is 84, BR count is now 0.2020-12-29 19:11:04 (931) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 WARNING *** WARNING *** Transaction cancelled: maximum execution time exceeded2020-12-29 19:11:04 (933) Default-thread-4 2D1D6AC31B596C101F5884415B4BCB05 txid=4b1fe2c71b59 EXCESSIVE *** End #914670 /angular.do, user: vaibhav.sethi@snc, total time: 0:04:58.534, processing time: 0:04:58.533, total wait: 0:00:00.001, session wait: 0:00:00.001, SQL time: 0:00:00.206 (count: 84), Cache build time: 0:00:00.204, source: 103.23.64.60 Release<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } Beginning with Paris release Cause<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } This issue is caused by an invalid entry in the Update Source [sys_update_set_source] table. The logs show a problematic URL where you see <REMOTE_INSTANCE_URL> in the previous example logs. This URL exists in one of your sys_update_set_source records. The system uses Remote Instance records [sys_update_set_source] to fetch Upgrade History records [sys_upgrade_history] from all configured remote instances. This data helps estimate upgrade duration based on similar upgrades that ran on other remote instances. The information appears on the Scheduled Upgrade card in the Upgrade Preview and Upgrade Monitor pages. Resolution<!-- /*NS Branding Styles*/ --> .ns-kb-css-body-editor-container { p { font-size: 12pt; font-family: Lato; color: #000000; } span { font-size: 12pt; font-family: Lato; color: #000000; } h2 { font-size: 24pt; font-family: Lato; color: black; } h3 { font-size: 18pt; font-family: Lato; color: black; } h4 { font-size: 14pt; font-family: Lato; color: black; } a { font-size: 12pt; font-family: Lato; color: #00718F; } a:hover { font-size: 12pt; color: #024F69; } a:target { font-size: 12pt; color: #032D42; } a:visited { font-size: 12pt; color: #00718f; } ul { font-size: 12pt; font-family: Lato; } li { font-size: 12pt; font-family: Lato; } img { display: ; max-width: ; width: ; height: ; } } To resolve the issue, deactivate the Remote Instance record [sys_update_set_source] with the URL: "<REMOTE_INSTANCE_URL>" found in your localhost logs. If you don't have access to logs, you can try the following: Deactivate all records in the sys_update_set_source table.Check if this resolves the issue.If resolved, deactivate records one by one to identify the record causing the issue.