client: fix gc deadlock when ar.prerun errors #5861
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I can take over this one! This is quite related to #5890 . One issue I noticed and added a test for is that if |
notnoop
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Jun 29, 2019
When an alloc runner prestart hook fails, the task runners aren't invoked and they remain in a pending state. This leads to terrible results, some of which are: * Lockup in GC process as reported in #5861 * Lockup in shutdown process as TR.Shutdown() waits for WaitCh to be closed * Alloc not being restarted/rescheduled to another node (as it's still in pending state) * Unexpected restart of alloc on a client restart, potentially days/weeks after alloc expected start time! Here, we treat all tasks to have failed if alloc runner prestart hook fails. This fixes the lockups, and permits the alloc to be rescheduled on another node. While it's desirable to retry alloc runner in such failures, I opted to treat it out of scope. I'm afraid of some subtles about alloc and task runners and their idempotency that's better handled in a follow up PR. This might be one of the root causes for #5840 .
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I made an alternative way to address this problem in #5905 . The issue is a more significant impacting issue than perceived here. |
notnoop
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Jul 2, 2019
When an alloc runner prestart hook fails, the task runners aren't invoked and they remain in a pending state. This leads to terrible results, some of which are: * Lockup in GC process as reported in #5861 * Lockup in shutdown process as TR.Shutdown() waits for WaitCh to be closed * Alloc not being restarted/rescheduled to another node (as it's still in pending state) * Unexpected restart of alloc on a client restart, potentially days/weeks after alloc expected start time! Here, we treat all tasks to have failed if alloc runner prestart hook fails. This fixes the lockups, and permits the alloc to be rescheduled on another node. While it's desirable to retry alloc runner in such failures, I opted to treat it out of scope. I'm afraid of some subtles about alloc and task runners and their idempotency that's better handled in a follow up PR. This might be one of the root causes for #5840 .
chrisboulton
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Jul 15, 2019
When an alloc runner prestart hook fails, the task runners aren't invoked and they remain in a pending state. This leads to terrible results, some of which are: * Lockup in GC process as reported in hashicorp#5861 * Lockup in shutdown process as TR.Shutdown() waits for WaitCh to be closed * Alloc not being restarted/rescheduled to another node (as it's still in pending state) * Unexpected restart of alloc on a client restart, potentially days/weeks after alloc expected start time! Here, we treat all tasks to have failed if alloc runner prestart hook fails. This fixes the lockups, and permits the alloc to be rescheduled on another node. While it's desirable to retry alloc runner in such failures, I opted to treat it out of scope. I'm afraid of some subtles about alloc and task runners and their idempotency that's better handled in a follow up PR. This might be one of the root causes for hashicorp#5840 .
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Repro by making
ar.prerunreturn an error. Without this patchar.killTasks(which is called by the client GC) blocks forever.