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From Acácio Centeno <>
Subject Question about developing plugins using the C++ API
Date Tue, 01 Apr 2014 13:36:05 GMT

We're creating a plugin that blocks/redirects some requests based on its
properties. We're using the C++ API, and created a RemapPlugin because we
need different configurations for different mappings.

On the DoRemap method, if we figure we need to block the request, we create
a TransactionPlugin instance, in order to intercept the
SEND_RESPONSE_HEADERS hook and do some modifications to the response, such
as changing the status code and adding headers.

When we did this, ATS would segfault when we tried to set a header. Then we
decided to create a global plugin to do some testing and found out that
just by adding the GlobalPlugin the TransactionPlugin was able to perform
the modification with no errors.

We found out that the reason for this behavior is that the GlobalPlugin
initialization calls a series of methods that end up calling
initTransactionClientResponse before the plugin developers' hooks are

Notice that a GlobalPlugin + Transaction alone wouldn't do because we need
these different configuration files. Of course we could have just one file
and have a different sections in it for each remap, but we don't like this
approach as the plugin's configuration file would have to be kept in sync
with the remap file, that is, whenever a new mapping was added, we would
have to add another section to the plugin configuration, and given the
dynamic nature of our configurations, we find it to be too error prone.

Given this, are we doing the right thing, that is, creating a Remap +
Transaction + Global plugin or there would be an easier way?

Best regards,
Acácio Centeno

Porto Alegre, Brasil + 55 51 3012 3005
Miami, USA + 1 305 704 8816

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