Yay! We've needed this for a while. Looks good.
s/columsn/columns
Ethan
On Tue, Mar 27, 2012 at 17:00, Ben Pfaff <b...@nicira.com> wrote:
> Signed-off-by: Ben Pfaff <b...@nicira.com>
> ---
> lib/ovsdb-idl.c | 126
> ++++++++++++++++++++++++++++++++++++++++++++++++--
> lib/ovsdb-idl.h | 51 ++++++++++++++++++++-
> python/ovs/db/idl.py | 116 ++++++++++++++++++++++++++++++++++++++++++---
> 3 files changed, 280 insertions(+), 13 deletions(-)
>
> diff --git a/lib/ovsdb-idl.c b/lib/ovsdb-idl.c
> index 5019c43..81f1548 100644
> --- a/lib/ovsdb-idl.c
> +++ b/lib/ovsdb-idl.c
> @@ -357,8 +357,23 @@ ovsdb_idl_wait(struct ovsdb_idl *idl)
> jsonrpc_session_recv_wait(idl->session);
> }
>
> -/* Returns a number that represents the state of 'idl'. When 'idl' is
> updated
> - * (by ovsdb_idl_run()), the return value changes. */
> +/* Returns a "sequence number" that represents the state of 'idl'. When
> + * ovsdb_idl_run() changes the database, the sequence number changes. The
> + * initial fetch of the entire contents of the remote database is considered
> to
> + * be one kind of change. Successfully acquiring a lock, if one has been
> + * configured with ovsdb_idl_set_lock(), is also considered to be a change.
> + *
> + * As long as the sequence number does not change, the client may continue to
> + * use any data structures it obtains from 'idl'. But when it changes, the
> + * client must not access any of these data structures again, because they
> + * could have freed or reused for other purposes.
> + *
> + * The sequence number can occasionally change even if the database does not.
> + * This happens if the connection to the database drops and reconnects, which
> + * causes the database contents to be reloaded even if they didn't change.
> (It
> + * could also happen if the database server sends out a "change" that
> reflects
> + * what the IDL already thought was in the database. The database server is
> + * not supposed to do that, but bugs could in theory cause it to do so.) */
> unsigned int
> ovsdb_idl_get_seqno(const struct ovsdb_idl *idl)
> {
> @@ -992,6 +1007,7 @@ ovsdb_idl_table_from_class(const struct ovsdb_idl *idl,
> return &idl->tables[table_class - idl->class->tables];
> }
>
> +/* Called by ovsdb-idlc generated code. */
> struct ovsdb_idl_row *
> ovsdb_idl_get_row_arc(struct ovsdb_idl_row *src,
> struct ovsdb_idl_table_class *dst_table_class,
> @@ -1036,6 +1052,8 @@ ovsdb_idl_get_row_arc(struct ovsdb_idl_row *src,
> }
> }
>
> +/* Searches 'tc''s table in 'idl' for a row with UUID 'uuid'. Returns a
> + * pointer to the row if there is one, otherwise a null pointer. */
> const struct ovsdb_idl_row *
> ovsdb_idl_get_row_for_uuid(const struct ovsdb_idl *idl,
> const struct ovsdb_idl_table_class *tc,
> @@ -1058,6 +1076,12 @@ next_real_row(struct ovsdb_idl_table *table, struct
> hmap_node *node)
> return NULL;
> }
>
> +/* Returns a row in 'table_class''s table in 'idl', or a null pointer if that
> + * table is empty.
> + *
> + * Database tables are internally maintained as hash tables, so adding or
> + * removing rows while traversing the same table can cause some rows to be
> + * visited twice or not at apply. */
> const struct ovsdb_idl_row *
> ovsdb_idl_first_row(const struct ovsdb_idl *idl,
> const struct ovsdb_idl_table_class *table_class)
> @@ -1067,6 +1091,8 @@ ovsdb_idl_first_row(const struct ovsdb_idl *idl,
> return next_real_row(table, hmap_first(&table->rows));
> }
>
> +/* Returns a row following 'row' within its table, or a null pointer if 'row'
> + * is the last row in its table. */
> const struct ovsdb_idl_row *
> ovsdb_idl_next_row(const struct ovsdb_idl_row *row)
> {
> @@ -1143,6 +1169,11 @@ ovsdb_idl_row_is_synthetic(const struct ovsdb_idl_row
> *row)
> static void ovsdb_idl_txn_complete(struct ovsdb_idl_txn *txn,
> enum ovsdb_idl_txn_status);
>
> +/* Returns a string representation of 'status'. The caller must not modify
> or
> + * free the returned string.
> + *
> + * The return value is probably useful only for debug log messages and unit
> + * tests. */
> const char *
> ovsdb_idl_txn_status_to_string(enum ovsdb_idl_txn_status status)
> {
> @@ -1167,6 +1198,9 @@ ovsdb_idl_txn_status_to_string(enum
> ovsdb_idl_txn_status status)
> return "<unknown>";
> }
>
> +/* Starts a new transaction on 'idl'. A given ovsdb_idl may only have a
> single
> + * active transaction at a time. See the large comment in ovsdb-idl.h for
> + * general information on transactions. */
> struct ovsdb_idl_txn *
> ovsdb_idl_txn_create(struct ovsdb_idl *idl)
> {
> @@ -1185,7 +1219,6 @@ ovsdb_idl_txn_create(struct ovsdb_idl *idl)
>
> txn->inc_table = NULL;
> txn->inc_column = NULL;
> - txn->inc_where = NULL;
>
> hmap_init(&txn->inserted_rows);
>
> @@ -1210,6 +1243,13 @@ ovsdb_idl_txn_add_comment(struct ovsdb_idl_txn *txn,
> const char *s, ...)
> va_end(args);
> }
>
> +/* Marks 'txn' as a transaction that will not actually modify the database.
> In
> + * almost every way, the transaction is treated like other transactions. It
> + * must be committed or aborted like other transactions, it will be sent to
> the
> + * database server like other transactions, and so on. The only difference
> is
> + * that the operations sent to the database server will include, as the last
> + * step, an "abort" operation, so that any changes made by the transaction
> will
> + * not actually take effect. */
> void
> ovsdb_idl_txn_set_dry_run(struct ovsdb_idl_txn *txn)
> {
> @@ -1242,6 +1282,11 @@ ovsdb_idl_txn_increment(struct ovsdb_idl_txn *txn,
> txn->inc_row = row->uuid;
> }
>
> +/* Destroys 'txn' and frees all associated memory. If ovsdb_idl_txn_commit()
> + * has been called for 'txn' but the commit is still incomplete (that is, the
> + * last call returned TXN_INCOMPLETE) then the transaction may or may not
> still
> + * end up committing at the database server, but the client will not be able
> to
> + * get any further status information back. */
> void
> ovsdb_idl_txn_destroy(struct ovsdb_idl_txn *txn)
> {
> @@ -1261,6 +1306,7 @@ ovsdb_idl_txn_destroy(struct ovsdb_idl_txn *txn)
> free(txn);
> }
>
> +/* Causes poll_block() to wake up if 'txn' has completed committing. */
> void
> ovsdb_idl_txn_wait(const struct ovsdb_idl_txn *txn)
> {
> @@ -1391,6 +1437,55 @@ ovsdb_idl_txn_disassemble(struct ovsdb_idl_txn *txn)
> hmap_init(&txn->txn_rows);
> }
>
> +/* Attempts to commit 'txn'. Returns the status of the commit operation, one
> + * of the following TXN_* constants:
> + *
> + * TXN_INCOMPLETE:
> + *
> + * The transaction is in progress, but not yet complete. The caller
> + * should call again later, after calling ovsdb_idl_run() to let the
> IDL
> + * do OVSDB protocol processing.
> + *
> + * TXN_UNCHANGED:
> + *
> + * The transaction is complete. (It didn't actually change the
> database,
> + * so the IDL didn't send any request to the database server.)
> + *
> + * TXN_ABORTED:
> + *
> + * The caller previously called ovsdb_idl_txn_abort().
> + *
> + * TXN_SUCCESS:
> + *
> + * The transaction was successful. The update made by the transaction
> + * (and possibly other changes made by other database clients) should
> + * already be visible in the IDL.
> + *
> + * TXN_TRY_AGAIN:
> + *
> + * The transaction failed for some transient reason, e.g. because a
> + * "verify" operation reported an inconsistency or due to a network
> + * problem. The caller should wait for a change to the database, then
> + * compose a new transaction, and commit the new transaction.
> + *
> + * Use the return value of ovsdb_idl_get_seqno() to wait for a change
> in
> + * the database. It is important to use its return value *before* the
> + * initial call to ovsdb_idl_txn_commit() as the baseline for this
> + * purpose, because the change that one should wait for can happen
> after
> + * the initial call but before the call that returns TXN_TRY_AGAIN, and
> + * using some other baseline value in that situation could cause an
> + * indefinite wait if the database rarely changes.
> + *
> + * TXN_NOT_LOCKED:
> + *
> + * The transaction failed because the IDL has been configured to
> require
> + * a database lock (with ovsdb_idl_set_lock()) but didn't get it yet or
> + * has already lost it.
> + *
> + * Committing a transaction rolls back all of the changes that it made to the
> + * IDL's copy of the database. If the transaction commits successfully, then
> + * the database server will send an update and, thus, the IDL will be updated
> + * with the committed changes. */
> enum ovsdb_idl_txn_status
> ovsdb_idl_txn_commit(struct ovsdb_idl_txn *txn)
> {
> @@ -1596,7 +1691,10 @@ ovsdb_idl_txn_commit(struct ovsdb_idl_txn *txn)
>
> /* Attempts to commit 'txn', blocking until the commit either succeeds or
> * fails. Returns the final commit status, which may be any TXN_* value other
> - * than TXN_INCOMPLETE. */
> + * than TXN_INCOMPLETE.
> + *
> + * This function calls ovsdb_idl_run() on 'txn''s IDL, so it may cause the
> + * return value of ovsdb_idl_get_seqno() to change. */
> enum ovsdb_idl_txn_status
> ovsdb_idl_txn_commit_block(struct ovsdb_idl_txn *txn)
> {
> @@ -1612,6 +1710,9 @@ ovsdb_idl_txn_commit_block(struct ovsdb_idl_txn *txn)
> return status;
> }
>
> +/* Returns the final (incremented) value of the column in 'txn' that was set
> to
> + * be incremented by ovsdb_idl_txn_increment(). 'txn' must have committed
> + * successfully. */
> int64_t
> ovsdb_idl_txn_get_increment_new_value(const struct ovsdb_idl_txn *txn)
> {
> @@ -1619,6 +1720,12 @@ ovsdb_idl_txn_get_increment_new_value(const struct
> ovsdb_idl_txn *txn)
> return txn->inc_new_value;
> }
>
> +/* Aborts 'txn' without sending it to the database server. This is effective
> + * only if ovsdb_idl_txn_commit() has not yet been called for 'txn'.
> + * Otherwise, it has no effect.
> + *
> + * Aborting a transaction doesn't free its memory. Use
> + * ovsdb_idl_txn_destroy() to do that. */
> void
> ovsdb_idl_txn_abort(struct ovsdb_idl_txn *txn)
> {
> @@ -1628,6 +1735,14 @@ ovsdb_idl_txn_abort(struct ovsdb_idl_txn *txn)
> }
> }
>
> +/* Returns a string that reports the error status for 'txn'. The caller must
> + * not modify or free the returned string. A call to ovsdb_idl_txn_destroy()
> + * for 'txn' may free the returned string.
> + *
> + * The return value is ordinarily one of the strings that
> + * ovsdb_idl_txn_status_to_string() would return, but if the transaction
> failed
> + * due to an error reported by the database server, the return value is that
> + * error. */
> const char *
> ovsdb_idl_txn_get_error(const struct ovsdb_idl_txn *txn)
> {
> @@ -2101,6 +2216,8 @@ ovsdb_idl_txn_process_reply(struct ovsdb_idl *idl,
> return true;
> }
>
> +/* Returns the transaction currently active for 'row''s IDL. A transaction
> + * must currently be active. */
> struct ovsdb_idl_txn *
> ovsdb_idl_txn_get(const struct ovsdb_idl_row *row)
> {
> @@ -2109,6 +2226,7 @@ ovsdb_idl_txn_get(const struct ovsdb_idl_row *row)
> return txn;
> }
>
> +/* Returns the IDL on which 'txn' acts. */
> struct ovsdb_idl *
> ovsdb_idl_txn_get_idl (struct ovsdb_idl_txn *txn)
> {
> diff --git a/lib/ovsdb-idl.h b/lib/ovsdb-idl.h
> index 34ccf06..b7beccc 100644
> --- a/lib/ovsdb-idl.h
> +++ b/lib/ovsdb-idl.h
> @@ -112,7 +112,56 @@ const struct ovsdb_datum *ovsdb_idl_get(const struct
> ovsdb_idl_row *,
>
> bool ovsdb_idl_row_is_synthetic(const struct ovsdb_idl_row *);
>
> -/* Transactions. */
> +/* Transactions.
> + *
> + * A transaction may modify the contents of a database by modifying the
> values
> + * of columns, deleting rows, inserting rows, or adding checks that columns
> in
> + * the database have not changed ("verify" operations), through
> + * ovsdb_idl_txn_*() functions. (The OVSDB IDL code generator produces
> helper
> + * functions that internally call the ovsdb_idl_txn_*() functions. These are
> + * likely to be more convenient.)
> + *
> + * Reading and writing columsn and inserting and deleting rows are all
> + * straightforward. The reasons to verify columns are less obvious.
> + * Verification is the key to maintaining transactional integrity. Because
> + * OVSDB handles multiple clients, it can happen that between the time that
> + * OVSDB client A reads a column and writes a new value, OVSDB client B has
> + * written that column. Client A's write should not ordinarily overwrite
> + * client B's, especially if the column in question is a "map" column that
> + * contains several more or less independent data items. If client A adds a
> + * "verify" operation before it writes the column, then the transaction fails
> + * in case client B modifies it first. Client A will then see the new value
> of
> + * the column and compose a new transaction based on the new contents written
> + * by client B.
> + *
> + * When a transaction is complete, which must be before the next call to
> + * ovsdb_idl_run() on 'idl', call ovsdb_idl_txn_commit() or
> + * ovsdb_idl_txn_abort().
> + *
> + * The life-cycle of a transaction looks like this:
> + *
> + * 1. Create the transaction and record the initial sequence number:
> + *
> + * seqno = ovsdb_idl_get_seqno(idl);
> + * txn = ovsdb_idl_txn_create(idl);
> + *
> + * 2. Modify the database with ovsdb_idl_txn_*() functions directly or
> + * indirectly.
> + *
> + * 3. Commit the transaction by calling ovsdb_idl_txn_commit(). The first
> call
> + * to this function probably returns TXN_INCOMPLETE. The client must keep
> + * calling again along as this remains true, calling ovsdb_idl_run() in
> + * between to let the IDL do protocol processing. (If the client doesn't
> + * have anything else to do in the meantime, it can use
> + * ovsdb_idl_txn_commit_block() to avoid having to loop itself.)
> + *
> + * 4. If the final status is TXN_TRY_AGAIN, wait for ovsdb_idl_get_seqno() to
> + * change from the saved 'seqno' (it's possible that it's already changed,
> + * in which case the client should not wait at all), then start over from
> + * step 1. Only a call to ovsdb_idl_run() will change the return value of
> + * ovsdb_idl_get_seqno(). (ovsdb_idl_txn_commit_block() calls
> + * ovsdb_idl_run().)
> + */
>
> enum ovsdb_idl_txn_status {
> TXN_UNCOMMITTED, /* Not yet committed or aborted. */
> diff --git a/python/ovs/db/idl.py b/python/ovs/db/idl.py
> index f36ab03..4c11499 100644
> --- a/python/ovs/db/idl.py
> +++ b/python/ovs/db/idl.py
> @@ -52,7 +52,13 @@ class Idl:
> 'rows' map values. Refer to Row for more details.
>
> - 'change_seqno': A number that represents the IDL's state. When the IDL
> - is updated (by Idl.run()), its value changes.
> + is updated (by Idl.run()), its value changes. The sequence number can
> + occasionally change even if the database does not. This happens if the
> + connection to the database drops and reconnects, which causes the
> + database contents to be reloaded even if they didn't change. (It could
> + also happen if the database server sends out a "change" that reflects
> + what the IDL already thought was in the database. The database server
> is
> + not supposed to do that, but bugs could in theory cause it to do so.)
>
> - 'lock_name': The name of the lock configured with Idl.set_lock(), or
> None
> if no lock is configured.
> @@ -635,6 +641,49 @@ class _InsertedRow(object):
>
>
> class Transaction(object):
> + """A transaction may modify the contents of a database by modifying the
> + values of columns, deleting rows, inserting rows, or adding checks that
> + columns in the database have not changed ("verify" operations), through
> + Row methods.
> +
> + Reading and writing columsn and inserting and deleting rows are all
> + straightforward. The reasons to verify columns are less obvious.
> + Verification is the key to maintaining transactional integrity. Because
> + OVSDB handles multiple clients, it can happen that between the time that
> + OVSDB client A reads a column and writes a new value, OVSDB client B has
> + written that column. Client A's write should not ordinarily overwrite
> + client B's, especially if the column in question is a "map" column that
> + contains several more or less independent data items. If client A adds a
> + "verify" operation before it writes the column, then the transaction
> fails
> + in case client B modifies it first. Client A will then see the new value
> + of the column and compose a new transaction based on the new contents
> + written by client B.
> +
> + When a transaction is complete, which must be before the next call to
> + Idl.run(), call Transaction.commit() or Transaction.abort().
> +
> + The life-cycle of a transaction looks like this:
> +
> + 1. Create the transaction and record the initial sequence number:
> +
> + seqno = idl.change_seqno(idl)
> + txn = Transaction(idl)
> +
> + 2. Modify the database with Row and Transaction methods.
> +
> + 3. Commit the transaction by calling Transaction.commit(). The first
> call
> + to this function probably returns Transaction.INCOMPLETE. The client
> + must keep calling again along as this remains true, calling Idl.run()
> in
> + between to let the IDL do protocol processing. (If the client doesn't
> + have anything else to do in the meantime, it can use
> + Transaction.commit_block() to avoid having to loop itself.)
> +
> + 4. If the final status is Transaction.TRY_AGAIN, wait for
> Idl.change_seqno
> + to change from the saved 'seqno' (it's possible that it's already
> + changed, in which case the client should not wait at all), then start
> + over from step 1. Only a call to Idl.run() will change the return
> value
> + of Idl.change_seqno. (Transaction.commit_block() calls Idl.run().)"""
> +
> # Status values that Transaction.commit() can return.
> UNCOMMITTED = "uncommitted" # Not yet committed or aborted.
> UNCHANGED = "unchanged" # Transaction didn't include any changes.
> @@ -694,6 +743,8 @@ class Transaction(object):
> self._comments.append(comment)
>
> def wait(self, poller):
> + """Causes poll_block() to wake up if this transaction has completed
> + committing."""
> if self._status not in (Transaction.UNCOMMITTED,
> Transaction.INCOMPLETE):
> poller.immediate_wake()
> @@ -722,16 +773,56 @@ class Transaction(object):
> self._txn_rows = {}
>
> def commit(self):
> - """Attempts to commit this transaction and returns the status of the
> - commit operation, one of the constants declared as class attributes.
> - If the return value is Transaction.INCOMPLETE, then the transaction
> is
> - not yet complete and the caller should try calling again later, after
> - calling Idl.run() to run the Idl.
> + """Attempts to commit 'txn'. Returns the status of the commit
> + operation, one of the following constants:
> +
> + Transaction.INCOMPLETE:
> +
> + The transaction is in progress, but not yet complete. The
> caller
> + should call again later, after calling Idl.run() to let the
> + IDL do OVSDB protocol processing.
> +
> + Transaction.UNCHANGED:
> +
> + The transaction is complete. (It didn't actually change the
> + database, so the IDL didn't send any request to the database
> + server.)
> +
> + Transaction.ABORTED:
> +
> + The caller previously called Transaction.abort().
> +
> + Transaction.SUCCESS:
> +
> + The transaction was successful. The update made by the
> + transaction (and possibly other changes made by other database
> + clients) should already be visible in the IDL.
> +
> + Transaction.TRY_AGAIN:
> +
> + The transaction failed for some transient reason, e.g. because
> a
> + "verify" operation reported an inconsistency or due to a
> network
> + problem. The caller should wait for a change to the database,
> + then compose a new transaction, and commit the new transaction.
> +
> + Use Idl.change_seqno to wait for a change in the database. It
> is
> + important to use its value *before* the initial call to
> + Transaction.commit() as the baseline for this purpose, because
> + the change that one should wait for can happen after the
> initial
> + call but before the call that returns Transaction.TRY_AGAIN,
> and
> + using some other baseline value in that situation could cause
> an
> + indefinite wait if the database rarely changes.
> +
> + Transaction.NOT_LOCKED:
> +
> + The transaction failed because the IDL has been configured to
> + require a database lock (with Idl.set_lock()) but didn't
> + get it yet or has already lost it.
>
> Committing a transaction rolls back all of the changes that it made to
> - the Idl's copy of the database. If the transaction commits
> + the IDL's copy of the database. If the transaction commits
> successfully, then the database server will send an update and, thus,
> - the Idl will be updated with the committed changes."""
> + the IDL will be updated with the committed changes."""
> # The status can only change if we're the active transaction.
> # (Otherwise, our status will change only in Idl.run().)
> if self != self.idl.txn:
> @@ -849,6 +940,12 @@ class Transaction(object):
> return self._status
>
> def commit_block(self):
> + """Attempts to commit this transaction, blocking until the commit
> + either succeeds or fails. Returns the final commit status, which may
> + be any Transaction.* value other than Transaction.INCOMPLETE.
> +
> + This function calls Idl.run() on this transaction'ss IDL, so it may
> + cause Idl.change_seqno to change."""
> while True:
> status = self.commit()
> if status != Transaction.INCOMPLETE:
> @@ -862,6 +959,9 @@ class Transaction(object):
> poller.block()
>
> def get_increment_new_value(self):
> + """Returns the final (incremented) value of the column in this
> + transaction that was set to be incremented by Row.increment. This
> + transaction must have committed successfully."""
> assert self._status == Transaction.SUCCESS
> return self._inc_new_value
>
> --
> 1.7.2.5
>
> _______________________________________________
> dev mailing list
> dev@openvswitch.org
> http://openvswitch.org/mailman/listinfo/dev
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