[role="xpack"]
[testenv="basic"]
[[update-lifecycle-policy]]
== Update lifecycle policy
++++
<titleabbrev>Update policy</titleabbrev>
++++

You can update an existing lifecycle policy to fix mistakes or change
strategies for newly created indices. It is possible to update policy definitions
and an index's `index.lifecycle.name` settings independently. To prevent the situation
that phase definitions are modified while currently being executed on an index, each index
will keep the version of the current phase definition it began execution with until it completes.
This also means that changes to `min_age` will not be propagated. If a new policy is set that
introduces a later `min_age` for the currently executing phase, that new `min_age` will not
be picked up by the update.

There are three scenarios for examining the behavior updating policies and
their effects on policy execution on indices.

=== Updates to policies not managing indices

Indices not referencing an existing policy that is updated will not be affected.
If an index is assigned to the policy, it will be assigned the latest version of that policy

To show this, let's create a policy `my_policy`.

[source,console]
------------------------
PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_size": "25GB"
          }
        }
      },
      "delete": {
        "min_age": "30d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
------------------------

This newly defined policy will be created and assigned to have a version equal
to 1. Since we haven't assigned any indices to this policy, any updates that
occur will be reflected completely on indices that are newly set to be managed
by this policy.

Updating the Delete phase's minimum age can be done in an update request.

[source,console]
------------------------
PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_size": "25GB"
          }
        }
      },
      "delete": {
        "min_age": "10d", <1>
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
------------------------
// TEST[continued]

<1> update `min_age` to 10 days

//////////
[source,console]
--------------------------------------------------
GET _ilm/policy/my_policy
--------------------------------------------------
// TEST[continued]
//////////

When we get the policy, we will see it reflect our latest changes, but
with its version bumped to 2.

[source,console-result]
--------------------------------------------------
{
  "my_policy": {
    "version": 2, <1>
    "modified_date": 82392349, <2>
    "policy": {
      "phases": {
        "hot": {
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_size": "25gb"
            }
          }
        },
        "delete": {
          "min_age": "10d",
          "actions": {
            "delete": {
              "delete_searchable_snapshot": true
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[s/"modified_date": 82392349/"modified_date": $body.my_policy.modified_date/]

<1> The updated version value
<2> The timestamp when this policy was updated last.

Afterwords, any indices set to `my_policy` will execute against version 2 of
the policy.

=== Updates to executing policies

Indices preserve the phase definition from the latest policy version that existed
at the time that it entered that phase. Changes to the currently-executing phase within policy updates will
not be reflected during execution. This means that updates to the `hot` phase, for example, will not affect
indices that are currently executing the corresponding `hot` phase.

Let's say we have an index `my_index` managed by the below `my_executing_policy` definition.

[source,console]
------------------------
PUT _ilm/policy/my_executing_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_docs": 1
          }
        }
      },
      "delete": {
        "min_age": "10d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
------------------------

////
[source,console]
------------------------
PUT my_index
{
  "settings": {
    "index.lifecycle.name": "my_executing_policy"
  }
}
------------------------
// TEST[continued]
////

The <<ilm-explain-lifecycle,Explain API>> is useful to introspect managed indices to see which phase definition they are currently executing.
Using this API, we can find out that `my_index` is currently checking if it is ready to be rolled over.

[source,console]
--------------------------------------------------
GET my_index/_ilm/explain
--------------------------------------------------
// TEST[continued]

[source,console-result]
--------------------------------------------------
{
  "indices": {
    "my_index": {
      "index": "my_index",
      "managed": true,
      "policy": "my_executing_policy",
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "step": "check-rollover-ready",
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "my_executing_policy",
        "modified_date_in_millis": 1538475653317,
        "version": 1,
        "phase_definition": {
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_docs": 1
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[skip:no way to know if we will get this response immediately]

We can update `my_executing_policy` to enter the hot phase after one day.

[source,console]
------------------------
PUT _ilm/policy/my_executing_policy
{
  "policy": {
    "phases": {
      "hot": {
        "min_age": "1d", <1>
        "actions": {
          "rollover": {
            "max_docs": 1
          }
        }
      },
      "delete": {
        "min_age": "10d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
------------------------
// TEST[continued]

<1> updated `min_age` from "0ms" to "1d"

The index `my_index` has already entered the hot phase, so it will still
use version 1 of the policy until it completes the hot phase.

////
[source,console]
--------------------------------------------------
GET my_index/_ilm/explain
--------------------------------------------------
// TEST[continued]
////

[source,console-result]
--------------------------------------------------
{
  "indices": {
    "my_index": {
      "index": "my_index",
      "managed": true,
      "policy": "my_executing_policy",
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "step": "check-rollover-ready",
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "my_executing_policy",
        "modified_date_in_millis": 1538475653317,
        "version": 1, <1>
        "phase_definition": {
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_docs": 1
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[skip:no way to know if we will get this response immediately]

<1> the version of the policy used for executing the hot phase

We can also update `my_executing_policy` to have no rollover action and,
instead, go directly into a newly introduced `warm` phase.

[source,console]
------------------------
PUT _ilm/policy/my_executing_policy
{
  "policy": {
    "phases": {
      "warm": {
        "min_age": "1d",
        "actions": {
          "forcemerge": {
            "max_num_segments": 1
          }
        }
      },
      "delete": {
        "min_age": "10d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}
------------------------
// TEST[continued]

Now, version 3 of this policy has no `hot` phase, but if we run the
Explain API again, we will see that nothing has changed. The index
`my_index` is still executing version 1 of the policy.

////
[source,console]
--------------------------------------------------
GET my_index/_ilm/explain
--------------------------------------------------
// TEST[continued]
////

[source,console-result]
--------------------------------------------------
{
  "indices": {
    "my_index": {
      "index": "my_index",
      "managed": true,
      "policy": "my_executing_policy",
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",
      "phase": "hot",
      "phase_time_millis": 1538475653317,
      "action": "rollover",
      "action_time_millis": 1538475653317,
      "step": "check-rollover-ready",
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "my_executing_policy",
        "modified_date_in_millis": 1538475653317,
        "version": 1, <1>
        "phase_definition": {
          "min_age": "0ms",
          "actions": {
            "rollover": {
              "max_docs": 1
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[skip:no way to know if we will get this response immediately]

<1> the version of the policy used for executing the hot phase

After indexing one document into `my_index` so that rollover succeeds and
moves onto the next phase, we will notice something new. The index will
move into the next phase in the updated version 3 of its policy.

////
[source,console]
--------------------------------------------------
PUT my_index/_doc/1
{
  "foo": "bar"
}

GET my_index/_ilm/explain
--------------------------------------------------
// TEST[continued]
////

[source,console-result]
--------------------------------------------------
{
  "indices": {
    "my_index": {
      "index": "my_index",
      "managed": true,
      "policy": "my_executing_policy",
      "lifecycle_date_millis": 1538475653281,
      "age": "30s",
      "phase": "warm",
      "phase_time_millis": 1538475653317,
      "action": "forcemerge",
      "action_time_millis": 1538475653317,
      "step": "forcemerge",
      "step_time_millis": 1538475653317,
      "phase_execution": {
        "policy": "my_executing_policy",
        "modified_date_in_millis": 1538475653317,
        "version": 3, <1>
        "phase_definition": {
          "min_age": "1d",
          "actions": {
            "forcemerge": {
              "max_num_segments": 1
            }
          }
        }
      }
    }
  }
}
--------------------------------------------------
// TESTRESPONSE[skip:There is no way to force the index to move to the next step in a timely manner]

<1> The index has moved to using version 3 of the policy

`my_index` will move to the next phase in the latest policy definition, which is the newly added `warm` phase.

=== Switching policies for an index

Setting `index.lifecycle.name` to a different policy behaves much like a policy update, but instead of just
switching to a different version, it switches to a different policy.

After setting a policy for an index, we can switch out `my_policy` with
`my_other_policy` by just updating the index's `index.lifecycle.name`
setting to the new policy. After completing its currently executed phase,
it will move on to the next phase in `my_other_policy`. So if it was on the
`hot` phase before, it will move to the `delete` phase after the `hot` phase concluded.

////
[source,console]
------------------------
PUT _ilm/policy/my_policy
{
  "policy": {
    "phases": {
      "hot": {
        "actions": {
          "rollover": {
            "max_size": "25GB"
          }
        }
      },
      "delete": {
        "min_age": "10d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

PUT _ilm/policy/my_other_policy
{
  "policy": {
    "phases": {
      "delete": {
        "min_age": "1d",
        "actions": {
          "delete": {}
        }
      }
    }
  }
}

PUT my_index
{
  "settings": {
    "index.lifecycle.name": "my_policy"
  }
}
------------------------

////

[source,console]
--------------------------------------------------
PUT my_index/_settings
{
  "lifecycle.name": "my_other_policy"
}
--------------------------------------------------
// TEST[continued]

The change to the new policy will not happen immediately. The currently executing phase
of the existing policy for `my_index` will continue to execute until it completes. Once
completed, `my_index` will move to being managed by the `my_other_policy`.