Yesod app on keter with read-only access to DB
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I have couple yesod apps deployed using keter with PostgreSQL. The thing I really like about them is the automatic DB migration that happens on deployment.
But, now I have faced a small problem: I set up DB replica on another virtual machine; the second DB is slave and thus read-only. When I start keter with my apps deployed, the apps cannot start because they cannot successfully execute migration script. There are dummy changes only, no real change of table, but the app fails to start with
"cannot execute ALTER TABLE in a read-only transaction"
.
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
haskell yesod keter
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up vote
1
down vote
favorite
I have couple yesod apps deployed using keter with PostgreSQL. The thing I really like about them is the automatic DB migration that happens on deployment.
But, now I have faced a small problem: I set up DB replica on another virtual machine; the second DB is slave and thus read-only. When I start keter with my apps deployed, the apps cannot start because they cannot successfully execute migration script. There are dummy changes only, no real change of table, but the app fails to start with
"cannot execute ALTER TABLE in a read-only transaction"
.
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
haskell yesod keter
add a comment |
up vote
1
down vote
favorite
up vote
1
down vote
favorite
I have couple yesod apps deployed using keter with PostgreSQL. The thing I really like about them is the automatic DB migration that happens on deployment.
But, now I have faced a small problem: I set up DB replica on another virtual machine; the second DB is slave and thus read-only. When I start keter with my apps deployed, the apps cannot start because they cannot successfully execute migration script. There are dummy changes only, no real change of table, but the app fails to start with
"cannot execute ALTER TABLE in a read-only transaction"
.
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
haskell yesod keter
I have couple yesod apps deployed using keter with PostgreSQL. The thing I really like about them is the automatic DB migration that happens on deployment.
But, now I have faced a small problem: I set up DB replica on another virtual machine; the second DB is slave and thus read-only. When I start keter with my apps deployed, the apps cannot start because they cannot successfully execute migration script. There are dummy changes only, no real change of table, but the app fails to start with
"cannot execute ALTER TABLE in a read-only transaction"
.
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
haskell yesod keter
haskell yesod keter
asked Nov 12 at 8:03
artem
24219
24219
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Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
Yes, it's possible. The simplest way to do is using environment variables in my opinion.
If you are using yesod's scaffolding site, then you have to make the changes in the makeFoundation
function which runs the migration. Note the the function named runMigration
is used to perform it. You need to add a appropriate conditional to make it work.
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in therunMigration
function to not run any migration. But for that to work, you have to patchpersistent
library and modify some code!
– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
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1 Answer
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1 Answer
1
active
oldest
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active
oldest
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active
oldest
votes
up vote
0
down vote
accepted
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
Yes, it's possible. The simplest way to do is using environment variables in my opinion.
If you are using yesod's scaffolding site, then you have to make the changes in the makeFoundation
function which runs the migration. Note the the function named runMigration
is used to perform it. You need to add a appropriate conditional to make it work.
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in therunMigration
function to not run any migration. But for that to work, you have to patchpersistent
library and modify some code!
– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
add a comment |
up vote
0
down vote
accepted
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
Yes, it's possible. The simplest way to do is using environment variables in my opinion.
If you are using yesod's scaffolding site, then you have to make the changes in the makeFoundation
function which runs the migration. Note the the function named runMigration
is used to perform it. You need to add a appropriate conditional to make it work.
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in therunMigration
function to not run any migration. But for that to work, you have to patchpersistent
library and modify some code!
– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
add a comment |
up vote
0
down vote
accepted
up vote
0
down vote
accepted
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
Yes, it's possible. The simplest way to do is using environment variables in my opinion.
If you are using yesod's scaffolding site, then you have to make the changes in the makeFoundation
function which runs the migration. Note the the function named runMigration
is used to perform it. You need to add a appropriate conditional to make it work.
Is it possible to temporarily disable migration scripts at startup via keter or app configs or ENV variables?
Yes, it's possible. The simplest way to do is using environment variables in my opinion.
If you are using yesod's scaffolding site, then you have to make the changes in the makeFoundation
function which runs the migration. Note the the function named runMigration
is used to perform it. You need to add a appropriate conditional to make it work.
answered Nov 13 at 5:09
Sibi
29.8k965124
29.8k965124
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in therunMigration
function to not run any migration. But for that to work, you have to patchpersistent
library and modify some code!
– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
add a comment |
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in therunMigration
function to not run any migration. But for that to work, you have to patchpersistent
library and modify some code!
– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
Thanks, but I meant to do it without modifying the code of the app.
– artem
Nov 13 at 9:05
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in the
runMigration
function to not run any migration. But for that to work, you have to patch persistent
library and modify some code!– Sibi
Nov 13 at 15:52
@artem I don't see any way of doing it without modifying the code. One hypothetical thing I can image is to see if postgres provides any query for checking if it's in read only mode. You can then use that information in the
runMigration
function to not run any migration. But for that to work, you have to patch persistent
library and modify some code!– Sibi
Nov 13 at 15:52
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
Yep, so I take this as an answer "not possible"
– artem
Nov 14 at 10:41
add a comment |
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