Bugs/PluginAPISpec

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Launchpad Help > Bugs > Plugin API

Overview

We want Launchpad to share bug reports, comments, statuses and other information with as many bug trackers as possible. We've already produced plugins that enable Bugzilla and Trac to communicate directly with Launchpad.

Here you can find the details of Launchpad bug tracker plugin API. This gives you all the information you need to write a Launchpad plugin for your preferred bug tracker.

Authentication

When pushing information to a remote bug tracker, Launchpad needs to authenticate with that bug tracker.

An account should automatically be created for Launchpad to use. The user name need not be the same on all bug trackers the API gets installed in, however we recommend that the default be "launchpad" with email address "noreply-$bugtracker@launchpad.net".

Launchpad can authenticate with a remote tracker using any number of mechanisms, depending on the underlying protocols chosen for the API. The goal is simply to ensure that the remote bug tracker knows that it really is Launchpad that is making these calls. An example authentication protocol is given below.

The authentication shouldn't be made using a password. Instead Launchpad should authenticate like this:

  1. Launchpad gives the remote tracker a random token, $token. For example, it might call an unauthenticated API passing it that value as a parameter. Before it replies:
  2. The remote tracker checks if https://launchpad.net/tokens/$token exists (200 HTTP reply status)

  3. If the URL above exists, the remote tracker knows that it's Launchpad talking to it.
  4. The remote tracker returns a cookie, or similar, for Launchpad to use as authentication in the next few numbers of requests.

$token is a list of characters in the set of {a-z,A-z,0-9}. The client should URL encode the token when checking whether the token exists on Launchpad. This is to prevent someone passing in a token like "../+index" and be able to log in with that.

Each token will only be used once. After the initial authentication, Launchpad should be able to do a number of requests without authenticating using the method above again. Instead the returned cookie should be sufficient to authenticate.

In some cases, Launchpad will be passing information to the remote tracker which was contributed by a Launchpad user, either through the web interface at launchpad.net or through email or an API. Launchpad will add information about who initiated the action to the content itself, for example in the comment or bug text. So, if user Joe comments on a bug, and Launchpad wants to forward that comment to the remote tracker, it will add text identifying Joe as the commenter to the comment before passing it to the remote tracker.

API protocol

It's not that important whether the APIs can be accessed via XML-RPC, a REST interface or some other interface as long as it's structured, stable, and easy to parse. Using a protocol built on top of HTTP is preferred. Possible alternatives include:

XML-RPC is the preferred method if no API exists already.

General assumptions

We make some general assumptions when we're interacting with remote bug trackers:

  1. Time and time zone accuracy. We assume that the bug tracker knows what time it is. Specifically, we assume that the bug tracker knows what time its database thinks it is when it starts trying to answer the question we have asked it. Each reply from the bug tracker should also include that time, so that we can keep track of the "window" that has been covered since we spoke to it last. We want to know the time that the queries started, not the time that they finished, because things might be changing in other transactions during the course of this one, and next time we come along we want to pick up those changes. If we were told the time the queries finished, we should risk missing changes that happened during our query the next time we come along. We also assume that the bug tracker knows what time zone it is in, and each API should document whether times are given in local time or UTC.

  2. Bugs have unique IDs. We assume that every bug has a unique ID, and that the ID is immutable. A given ID refers to a given bug all the time. Note - we DO NOT assume that the title and description of a bug are immutable. Thus, a bug with ID "qwerty" may have a title "foo" today, and a title "bar" tomorrow.

  3. Bugs are ordinal. We assume that Bug ID's have some ordinality that is immutable. This means that we assume bugs can be ordered in a given sequence which does not change. We allow for bugs to be *inserted into that sequence* because of issues with database transactions. We use bug ID's to specify ranges of bugs, and we ask the bugtracker to specify ranges using bug id's. In other words, imagine we have been told about two bugs, with ID's "xyz" and "abc", and we have been told that bug "xyz" precedes "abc". We can ask questions like "tell us about the statuses of all bugs between xyz and abc". Today, there might be three bugs between "xyz" and "abc", and tomorrow there might be four bugs in that range, but we assume that "xyz" will *always* precede "abc", and any bug which lies in the range from "xyz" to "abc" today will always lie in that range. Note, we do not assume that bugs have integer ID's. The bug ID can be something like "issue56" or "ticket2576", or literally "abc" or "qwe". Note that we don't assume we can always see a particular ID - bugs in the bugtracker can be deleted or marked confidential after Launchpad has previously seen them. Also, we don't assume that we can see a bug which looks like it logically should exist - if we have been told about a bug "90" and another bug "100", and we ask for information about bugs between them, it's fine for us to be told that there are bugs "90", "93" and "100" only. Tomorrow, we might see but "96" because it is no longer confidential. This "belated insertion" happens in real life. Say I start a transaction to file a bug which will have ID X. For whatever reason, the transaction to do so takes a minute. A second after my transaction starts, someone files a bug with ID X+1. A second later, Launchpad asks for the top bug and is told X+1 (which has been filed). But at this stage, bug X is still in its transaction. If Launchpad asks for Bug X, it does not yet actually exist in the database, it's still in its transaction. So, while the bugs are ordered, bug X can show up after bug X+1, which is why I say we assume ordinality but allow for insertions.

  4. Bugs can be specified in ranges. We assume that we can refer to sets of bugs by the range between two bug ID's. We might have to limit this to the idea that bugs have a "date filed". We want this so that we can talk to big bugtrackers in sets of queries rather than in huge ones. We would prefer to be able to assume unique integer ID's on bugs with the ability to express ranges of them, i.e. "from bug '100000' to bug '200000'".

  5. Launchpad can push and pull information. By enabling this API in the remote tracker, the admin of the instance trusts Launchpad to pull and push information, and to relay information to users in Launchpad.

General API Methods

bugtracker_version(): Retrieve the version of the bug tracker

We will need to verify that the bug tracker version is one that we can talk to, and also to know if there are any version-specific quirks we should be aware of. There should be an API to establish:

For example, we might want to know that we are talking to a Bugzilla installation that is version 3.1 running version 1.2 of the Launchpad API.

time_snapshot(): Get current database time

In order to avoid issues where there's a skew between the time in Launchpad, and the time in the remote tracker, there should be a call to get the current time in the database. For example, if a new bug is filed, what timestamp will be used for its creation time.

It may seem unusual to ask for all three pieces of information, but doing so allows us to make sure that we have EXACTLY the same understanding about relevant time zones and current time as the remote bug tracker. Therefor, we want to be able to verify that the bug tracker is doing "sane" things w.r.t. time, and the only way to be sure is to ask for all three pieces of information.

Pulling information

We need to keep the bugs we're watching in sync regularly. This can be a great number of bugs, sometimes all bugs in the bug tracker. The API for pulling new information about these bugs need to be efficient enough, in order not to put too much load on the remote server. The less requests that are needed to get the information, the better. However, that doesn't mean that there has to be one request to get all information. The API that gives us information about a bug should be able to return multiple bugs at once; issuing one request per bug isn't scalable.

These sections describes only what APIs we need. Several of the sections could be combined into one API method.

The information we need to know for each bug is:

The current database time when the call started (see above) should be included in the output for all the API calls to avoid time skew issues.

get_bugs(): Get information about a set of bugs

Given a set of bug ids, return information about the bug. It should be possible to specify how much information should be returned. Possible levels should be 'bug ids only', 'metadata about the bug only', 'metadata + comment ids', and 'metadata plus full comment information'.

Note: It may be possible to overload get_bugs() to include the functionality of get_all_bugs(), get_bugs_changed_since() and get_new_bugs_since(), below.

get_all_bugs(): Get all bugs in the bug tracker

This will be used in order to do an initial import of a bug tracker. It will only be used for bug trackers with a small amount of bugs, or partial imports.

An error may be raised if the limit is too high, i.e. if the bug tracker doesn't want to return too many bugs at once due to performance reasons.

get_bugs_changed_since(): Get all bugs that have changed since a given timestamp

This will be used when we update bugs that we're watching. If possible (and easy), only the things that have changed since the given timestamp should be returned, but returning the current state of the bug is acceptable.

product/component:

get_new_bugs_since(): Get new bugs that were filed since a given timestamp

This could be combined with the API call above.

get_bug_count(): How many bugs are currently in the bug tracker

Simple count of the number of bugs the bug tracker contains.

last_modified_date(): Last modified

When was any bug last modified? This is a query about the last time the database was touched rather than referring to any specific bug.

latest_bug_id(): ID of latest bug

What's the ID of the latest bug filed in the bug tracker?

status_list(): Get the set of statuses

What are the possible status values a bug can have?

Synchronising comments

For a comment we need to know:

The comment id is important, so that we can identify the comment. It should be unique across the bug tracker.

Assumptions

When synchronising comments with remote bug trackers, Launchpad makes the following assumptions:

  1. Unique comment ID's. Every comment has a unique ID, so that we can talk to the bug tracker about sets of comments using only the unique ID. The ID can be a compound ID (i.e. bugnumber+commentnum or bug+timestamp+commenter) but it must be unique... we should be able to have APIs which pass a comment ID and the bug tracker should know exactly which comment we are referring to. Similarly, the bug tracker needs to be able to provide a list of comment ID's, and we should be able to know if we have the comment or not. The documentation for the API should define the format of a comment ID. For example, the documentation could say that "Comment ID's take the form of a positive integer, and reflect the database primary key on the BugComment table."

  2. Immutable comments. We assume that comments are immutable. I.e., the comment text and title never change. So, as long as we know we have the comment corresponding to a particular ID on their side, we don't need to ask for that comment again.

  3. Comment on one and only one bug. We assume that a particular comment applies to a particular bug, and that each comment applies to only one bug, and that comments do not move from one bug to another. In other words, if we have been told that comment with ID "xyz" is for bug "qwerty", we never expect to see a comment with id "xyz" on any other bug.

  4. There is a "Launchpad" user in the remote bug tracker. We assume that there will be a "user" in the remote bug tracker which denotes "Launchpad". That user may have an email address assigned to it. We do not assume any particular value for the email address, but we recommend that it either be noreply-$bugtracker@launchpad.net (which may or may not get human attention), or noreply-launchpad@domain.com in the case where the email address is required to be at a specific domain. The admins of that domain may in turn choose to forward email sent to that address to noreply-$bugtracker@launchpad.net, or feedback@launchpad.net. The user of Launchpad in that bugtracker is generally used as the "user" who makes comments on bugs, or files new bugs.

Required API Methods

These are the methods that we expect the remote API to provide for comment syncing. In order to be able to do syncing reliably we'll also need the time_snapshot() and get_bugs() methods described above to be implemented.

add_comment(): Add a comment to an existing bug

It's important to have some kind of unique non-changing id for comments, so we can identify them and avoid importing the same comment twice.

get_comment(): Get comments by comment id

When getting information about bugs using the API above, we will mostly only include the comment ids to save bandwidth. After deciding which new comments we need to import, we want to fetch them separately, in a single method call.

Pushing information

We want to make it easy for users to forward bugs to remote bug trackers from within Launchpad. A Launchpad user will initiate the action and Launchpad will execute it for the user. The user initiating the action might not have an account on the remote tracker.

The special Launchpad user is the one that actually files the bug or adds a comment in the remote tracker, not the person requesting the action from within Launchpad. Launchpad won't give the remote tracker the person's e-mail address due to privacy reasons. This is fine, though, the remote tracker users can ask the real reporter questions. Launchpad will relay all communication about the bug to/from the person in Launchpad. This imples that the remote tracker trusts Launchpad to relay comments back and forth.

Each API below has a recommended name (like "report_bug") but the name can be varied if needed.

report_bug(): File a new bug

set_launchpad_bug(): Set the corresponding Launchpad bug

In order to improve collaboration between the two bug trackers, we'd like the remote tracker bug to "know" what the corresponding bug is in Launchpad. The remote tracker will need to be able to store the Launchpad bug ID as an integer, for each bug in its database, and this API would be used to set the value stored for any particular bug.

The can be only one link to a bug in Launchpad per bug in the remote tracker.

The Launchpad bug id passed could be null, which means that this information is getting "unset".

The corresponding Launchpad bug should be displayed on the remote bug page, as a number linked to the relevant bug at Launchpad.net, for example:

It may also be appropriate to display the corresponding Launchpad bug number in other reports and pages. It should be possible for users of the remote tracker to update the corresponding Launchpad bug number for any given bug in the remote tracker directly.

get_launchpad_bug(): Retrieve the current Launchpad bug id for a given bugtracker bug

This is the read operation that matches set_launchpad_bug.

Next steps

You can find the Launchpad team in Freenode's #launchpad channel. We'd love to hear your experiences.

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Bugs/PluginAPISpec (last edited 2008-12-04 16:19:16 by matthew.revell)